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June Discussion Archive

June 30 2005 - 22:00

The main area of interest continues to be the tropical wave in the eastern Atlantic approaching 40 degrees longitude. Visible satellite imagery depicts a few low-level circluations, but a dominant one may be forming under a small area of deep convection slightly behind the wave's axis. The environment aloft is not completely unfavorable. Some moderate southwesterly shear is still noted due to the seasonal presence of the subtropical jet. That said, the heaviest concentration of shear is located well north of the circulation. This pattern is expected to continue over the next few days, and as the system moves further west, the jet to the north could even slightly aid in northerly outflow. However, the air is rather stable due to the presence of dry Saharan air being ushered westward by the subtropical ridge's flow. This is typical for late June and early July, and it will undoubtedly cap any significant intensification. The overall conditions taking everything into account should remain marginally favorable.

The models have not been in complete agreement on the future evolution of this system. The GFS has been one of the more bullish models in developing a tropical cyclone, but the 12Z run stands in contrast and barely shows anything more than a low pressure through the next seven days. However, this is only one run out of four per day, and therefore we do not take it to represent a trend unless future GFS runs echo its solution. Furthermore, it appears it may be under-initializing or simply missing the small but defined circulation mentioned above. This would explain the 12Z model's lack of developing the feature. Another scenario the GFS has been painting is recurving the system northward near 60 degrees longitude ahead of a digging trough in-between the subtropical ridge. First off, the GFS was notorious last season for having a significant rightward bias in storm tracks in this general area. Also, it is the only model that turns the system so soon. Given it is an outlier and the model's recent bias, very little weight is being given to its preferred track.

The ECMWF, a decent medium-range model, has been very consistent on development since 00Z June 26. The latest run, like the prior ones, takes a tropical cyclone west-northwestward just north of the Leeward Islands by the middle of next week. The CMC has been in good agreement with this solution. The UKMET is a little less aggressive on development, but still shows a system moving towards the northernmost Caribbean islands after Day Five. The 12Z NOGAPS, which has generally been the most conservative, just shows a weak low pressure moving westward and into the eastern Caribbean Sea, the first run out of any model that shows a movement south of the Leeward Islands. However, this motion is likely a direct result of the NOGAP's weaker strength, which would in turn cause the system to be steered by lower-level easterly flow. Moreover, it has seemingly been initializing the main circulation too far east, or alternatively is just picking up on a nonexistent or lesser circulation altogether. In any case, the NOGAPS, or its 12Z run at least, is not handling the system very well.

The aforementioned forecasted synoptic setup and model trends have not changed much since the chance of development was first mentioned on June 26. A tropical cyclone remains a distinct possibility from this tropical wave over the next few days. Conditions support a tropical storm, though no more, as most models have been indicating. The chance of this becoming a hurricane within the next six days is very small, mostly given the stability of the air ahead. If a tropical cyclone does form as forseen, it will follow the subtropical ridge on a west-northwestward motion, with a ever-so-slightly increasing bend towards the north with time as it feels the ridge's weakness in the central Atlantic. On this motion, the system will likely pass just north of the Leeward Islands. There is still a possibility it could impact the islands, particularly if it develops slower than forecasted and thus being steered by more easterly layers.

Beyond the standard six-day period, a lot more uncertainty arises. It was stated above the GFS is likely overdoing the trough and consequential recurvature. The CMC and ECMWF, models that have been more consistent and reasonable so far, indicate a weakness significant enough to have it moving in a more northwestward heading in the middle of next week. If these models have the precise handle on the synoptic pattern, any tropical cyclone just north of the Leeward Islands at the time will have a good chance of turning northward and out to sea due to the trough. One small possibility that cannot be ruled out yet is the trough bypasses too far north and misses the storm altogether. This would leave it under stronger ridging behind and therefore cause it to bend back to the west towards the Bahamas and southeast United States. Such a scenario is less likely than the former at the present time given the anticipated amplification and position of the weakness. Of course, all of this discussion regarding what may happen beyond a week's time is speculation at best.

Another more immediate area of disturbed weather is located in the southwestern Caribbean Sea. Convection is being fueled from the combination of a tropical wave near 75 degrees longitutde, intertropical convergence, and diffluence from an upper-level low to the west. Some mid-level cyclonic motion is noted, and a ridge aloft is aiding ventilation. However, the area is expected to move west-northwestward into the Yucatan Peninsula since it is under a large ridge of high pressure. This may allow convection to persist with the help of the upper-level low, but at the same time, strong shear will hinder any significant organization. Whatever part of this system emerges into the Gulf of Mexico in the next few days will not have a favorable environment either. A shortwave is progged to move into the central Gulf of Mexico into early next week, which will in turn enhance shear and usher dry air in the region. None of the reliable models have shown anything remotely resembling a tropical cyclone in this area since the ECMWF hinted in one on 00Z June 29. It will be monitored, but development is unlikely.

June 29 2005 - 21:00 UTC

Edited as of 22:00 UTC

Tropical Storm Bret has moved inland over southern Mexico. Further weakening is expected, though the threat of heavy rainfall and flash flooding near the coast will continue for another 24-36 hours.

Our medium range focal point is evolving in the deep Atlantic east of the Caribbean islands. A series of tropical waves associated with the inter-tropical convergence zone has initiated some mid to low-level cyclonic rotation in a large swath east of 40 degrees latitude. Westerly shear is not too strong, though the air remains dry and Saharan-laden. Global models are in agreement that this broad area of disorganized convection will become better organized over the next few days. The GFS has been showing tropical cyclone formation for the past 4 days. The last few runs, however, only show a weak storm and curve it ever so slightly northward near 60 degrees latitude by Day 6. These developments are in response to an upper trough that is progged to dig southward over the northwest Atlantic. If such a pattern simulated by the GFS were to evolve, then there would also be a noticeable increase in upper level shear shear. Thus, it is no surprise the model has backed off on intensity. However, the GFS is notorious for over-amplifying troughs in the central Atlantic, explaining its right-bias with tropical cyclones in the area. Further reason to believe the GFS solution is not viable is that no other model shows nearly as much an erosion of the subtropical ridge early next week. The 12Z NOGAPS, ECMWF, and CMC all show an intensifying system moving towards or just north of the Leeward Islands between Day 6 and 7. The ECMWF, a model we have found to be reliable for medium-range scenarios, has been calling for development for 8 consistent runs. The UKMET, similarly, picks up on a storm, but runs beyond Day 5 remain obscurred due to grid projection issues.

Given the model guidance and recent synoptic trends, tropical cyclone formation east of the Lesser Antilles later this weekend or early next week is becoming more likely. Thereafter, provided such occurs, conditions will permit gradual intensification on a west-northwest track. The strength and alignment of the ridge suggests that any tropical cyclone will pass very close to, if not over, the Leeward Islands in the middle of next week. After that point, there is a lot of uncertainty. There is very little doubt that the progged tropical cyclone will be steered north by a trough at some point, as all of the models agree on some sort of ridge weakness near the eastern United States around Day 7. If a tropical cyclone does form, it is not totally out of the question that there will be a southeast United States threat in the long run.

A tropical wave in the eastern Caribbean has become very active as a result of interaction with an upper low centered over Hispaniola. The wave will continue to move westward over the next several days. No development is expected in the Caribbean Sea, however, as upper level winds are highly unfavorable. In the medium range, the wave will enter the central Gulf of Mexico. Upper winds will likely remain unfavorable, but it will be monitored. The 00Z ECMWF did indicate some surface reflection near the Texas coast at 168 hours, but has since backed off.

June 28 2005 - 23:30 UTC

TPC Reconnaissance Aircraft flew into the disturbed area of weather in the southwest Gulf of Mexico and found sustained surface winds of 35mph, which warrants the classification of Tropical Depression Two. The TPC intensity forecast is calling for slight intensification into a classified tropical storm, but a landfalling depression is quite possible. The surface circulation will likely move inland within 12 hours. Furthermore, TD2 is approaching an upper trough over Mexico, and upper winds are not as favorable as they were in the Bay of Campeche. We anticipate a landfalling 35mph tropical depression, but the difference between 35-40mph is insignificant. The only concern with this system is the threat of heavy rainfall over the next 36-48 hours. Tropical Depression Two is no threat to the United States.

Meanwhile, the 18Z run of the GFS model continues to suggest that tropical development could occur in the central Atlantic in three to seven days. GFS run to run consistency has been a major plus over the last several days. One thing that should be noted, is that the 06Z and 18Z runs of the GFS should not be discounted simply because those runs are initiallized by some observations that already went into the 00Z and 12Z runs, especially when all we are dealing with is a disorganized African wave that would not develop until the medium range. The 18Z NOGAPS is still struggling to pick up the feature. Better model agreement is needed in order to become too concerned about development. The wave could impact the Lesser Antilles' weather in around six days.

Another thing that should be noted about the GFS, is the model hinted at surface low development in the Bay of Campeche several days ago. I must say that our general ideas starting on the 19th regarding the Caribbean wave split, with one piece traveling north and dissipating, and the southern end needing to be monitored once in the Gulf was correct. Yes, we did back off on the Gulf threat but the general idea was accurate, not to mention no more than a depression or minimal tropical storm will come out of this system.

June 28 2005 - 19:00 UTC

A surface low pressure in the southern Bay of Campeche is extremely well-organized, with sufficient banding and convection. An aircraft reconnaissance is flying into the system this afternoon and will determine how strong this truely is. Based on satellite imagery alone, it appears to be at least a 30-knot tropical depression, perhaps a tropical storm. The only problem is that it will be moving inland Mexico within the next 18 hours or so. Therefore, time is extremely limited and it is nto expected to strengthen much more than what it already may be now.

Development is still a possibility east of the Lesser Antilles next week. The GFS has continued to indicate a weak tropical cyclone developing around Day 4 and clipping the northern Caribbean islands by Day 7. The ECMWF has been surprisingly consistent on the idea of development and a similar track as well. In fact, the 12Z run is more bullish than previous runs, bringing a strong tropical storm into the Virgin Islands on Day 7 similar to the GFS. The UKMET output beyond Day 5 has not been available recently and so we cannot make any inferences with that model at this time. The 12Z CMC and NOGAPS both finally pick up on the feature and show at least a weak low pressure area. It is typical of both the CMC and NOGAPS to be slow in catching on to low-level tropical features, and the fact that they now pick up on the system holds value. This will be a feature to watch closely later in the week and into next week. The model trends explained above lead us to believe development is possible.

In the East Pacific, Tropical Storm Calvin is slowly weakening as it pulls westward away from the Mexican coast. Dissipation should commence within the next few days.

June 27 2005 - 23:00 UTC

Shower and thunderstorm activity over the central and eastern Gulf of Mexico is related with a surface trough. Some of this moisture is also related to the Caribbean wave that was first mentioned here on the 19th. A mid level circulation is present along the trough axis in the Bay of Campeche. If this feature were to hang around over open waters for several days, then there would be some concern for development. That scenario appears unlikely this time around. All global model guidance suggests that the broad area of low pressure will remain weak, and then move into northern Mexico and southern Texas within the next couple days. The two main inhibitors for development are lack of time over water and moderate shear, which is associated with an upper trough near the coast of Texas. Tropical development is not expected.

The remainder of the Atlantic Basin is quiet. Looking into the medium range, the ECMWF and GFS have wanted to develop a tropical wave in the central Atlantic. However, the GFS has been delaying development a couple days for the last several runs, the ECMWF just began to pick up on this progged wave yesterday, no other model shows development, and the possibility of development is still several days away. Therefore, tropical development is unlikely. But the models may be hinting on a more active ITCZ and Atlantic next month. The 2005 IWIC seasonal forecast is calling for two to three named storms during the month of July.

Tropical Storm Calvin, while still producing heavy rainfall along coastal Mexico, is beginning to move west-northwest and away from land. Calvin may strengthen slightly due to some upper ridging aloft, but conditions are only marginally conducive for development. Calvin is not expected to reach hurricane status.

A few global models want to develop another tropical cyclone south of Mexico in three to six days. The potential for another EPAC tropical storm within the next week or so is being considered slight for now.

June 26 2005 - 18:00 UTC

The hybrid surface trough moved inland in northern North Carolina this morning, not as a classified storm, but nonetheless a very nasty weathermaker. Development was never expected from this system in the first place, but it did come close just prior to landfall when a weak low developed.

The slight potential for Gulf of Mexico development from the southern end of the wave we mentioned a few days ago has vanished. A tropical system is forming off Mexico as this discussion is being written, and will likely achieve the name Calvin before heading west into cooler waters. Furthermore, models are coming into agreement on developing yet another East Pacific tropical cyclone further south later this week. The combination of these two systems, plus the energy that was already transferred on the northern piece of the wave greatly diminishes the chance of a healthy incipient disturbance or favorable conditions in the Gulf of Mexico. With this being said and nothing else imminent, development is not expected in the Atlantic Basin for the remainder 5 days of June.

Now we shift our attention to the long-range, to the week of July 3. Early indications suggest that the deep Atlantic mid-way between the Lesser Antilles and the Coast of Africa will be a region to watch very closely for possible development. The 06Z and 12Z runs of the long-range GFS both develop a tropical cyclone around Day 7 or so and take it westward just north of the Caribbean and the Bahamas on Day 16. Earlier runs did not show this exact solution, but the model has been trying to develop various lows around this general period and area for a few days now. It is too far out to worry about specifics of the track and intensity, and it would not be surprising to see a totally different scenario next run. However, the consistent idea of development in general is what attracts our attention. In fact, the latest ECWMF develops a weak tropical cyclone in the same area on Day 7 as well, one of our favored models for medium-range situations. None of the other models are truely showing development yet, though the 12Z NOGAPS indicates a probable weak low. The lack of other model support besides GFS and ECWMF at this time is not a concern since they only run out to Day 6. Further evidence to this possibility is referring back to our seasonal hurricane forecast. The years that best match the early season pattern based upon the ENSO trend and ATC are 1966, 1995, and 2003. All of these years had a storm form near or east of the Lesser Antilles during the first half of July. Two other analog years in general, 1989 and 1996, did as well. Climatology alone is not enough to call for development, but the past few runs of the GFS are intriguing, especially since the ECWMF agrees. Future model runs from those and others may totally eliminate the possibility, but at this point development east of the Caribbean islands before July 10 cannot be ruled out.

June 24 2005 - 21:00 UTC

The main focus today is on the complex situation evolving in the Bahamas and off the southeast coast. A wide area of convection is present with the system, and this is in association with a tropical wave, surface trough, series of low-level circulations, and an upper-level low. The upper-level low is enhancing convection via divergence, and an anticyclone aloft is allowing for an outflow pattern and ventilation to the north and east of the "center". Models have not changed significantly from their solutions yesterday. The CMC and GFS are both the most bullish, but even so have backed off a bit. On the other hand, the UKMET and NOGAPS are still calling for weak surface reflection.

In last night's discussion, we mentioned the likelihood of a hybrid-type low arising, and this is what is happening now. There is no doubt that this will never become a purely tropical system, though even hybrid storms have earned names in the past (Allison, Gustav, Bill, etc) if enough barotropic features are present to warrant so. So the major question is, how tropical will this become before landfall? With an upper-level ridge building over the system more than what the GFS and other models had in mind earlier, there is a greater chance of becoming a classified tropical system than we originally thought. If enough convection fires over the main low, and that is possible going into diurnal maximum, then the result would be more surface vorticity reflection and thus the system would become more of a tropical feature. On the other hand, the upper-level low is still driving a lot of dry, stable air in the region. It does not take much more than a glance at the latest water vapor loop to notice the system is already inhaling dry air from the south and west.

Right now we still think an unclassified storm is slightly more likely than a tropical depression or tropical storm, but the chance is certainly there. However, two things are certain, regardless of the classification. This will remain predominantly hybrid in nature, and coastal regions of the Carolinas (particularly Charleston to Wilmington) will be in for extremely rough seas and gusty weather over the weekend. Residents in these areas should turn to local National Weather Service statements and other official sources for more details on the severity of the weather impact from this storm.

The second half of the tropical wave will still be moving into the Western Caribbean Sea and then into the Gulf of Mexico in the next few days. The prospects of development from this area have always been low, but today it is even less of a threat. First off, far more energy than was originally expected has been transported to the Bahaman region via the northern end of the wave. This leaves less moisture for the southern half to work with. Second, models are, if anything, slightly more aggressive on developing an East Pacific tropical cyclone this weekend off Mexico. Thirdly, a shortwave trough is still progged to move into the Gulf of Mexico, which will help induce strong shear over the region at about the same time as the disturbance arrives. Fourthly, global models are now coming into agreement on developing yet another East Pacific tropical cyclone after Day 5 or so behind the heels of the other one. We have deduced from all of this that there is going to be very little energy in only a marginally favorable environment at best as far as the Gulf of Mexico disturbance is concerned. Too much moisture has already been spent from the northern end, and most energy, according to the models, will be concentrated in the East Pacific in the forecast period. Such tropical cyclones would only add to the unfavorable conditions in the Gulf of Mexico. It remains worth watching, but tropical cyclone development is not expected here, aside from the East Pacific areas.

Elsewhere across the globe, the tropics are quiet at the present time.

June 23 2005 - 23:00 UTC

There are two areas of interest in the Atlantic Basin this evening, as has been expected for the past several days.

A tropical wave is currently located in the central Caribbean Sea. Convection is being divergently enhanced by an upper-level low situated to the west, over the Florida Straits. The tropical wave will soon break into two pieces, with the northern end moving northwest into the Bahamas. Some models continue to develop this system over the next few days. The CMC, by far the most aggressive, has been indicating a formidable low pressure moving northwestward into the Carolinas for several consistent runs. However, it is interesting to note it also shows cyclonic flow in the 200 millibar-level of the atmosphere over the progged surface low, the opposite of what a true tropical cyclone should harbor. The CMC solution as a whole seems skewed; it moves the upper-level low over the southeast on top of the surface low and fuses the two together to form an unreasonably strong hybrid storm. The CMC has had a history of overdoing baroclinic interaction, the dynamics of this particular scenario does not match other models at all, and so the model is dismissed.

The GFS is the next most bullish model on this low, ten steps down from the CMC. However, the GFS does not depict a purely tropical feature either, but rather suggests the upper-level low will be close enough to keep convection well to the north and east of the surface low. This in mind, the GFS is likely too strong with the low since it is not taking the strong shear that would also come into play under such a situation. Furthermore, it still may be suffering from its common case of convective feedback. The NOGAPS, UKMET, and ECMWF all pick up on low-level vorticity, but for the most part show something more along the lines of an inverted trough. The upper-level low to the west will stay in the same general area over the next few days, which will continue to fuel convection by divergence. Simultaneously, shear will remain strong and unfavorable for development. If a low does form as some models suggest, it will likely remain lopsided, possibly bearing more resemblence of a hybrid than tropical low. The model consensus for the track is just to the east of Florida and into the Carolinas by Day 4, owing to the southerly flow likely to setup in the region. This area will be monitored, but tropical development is not expected.

Meanwhile, an impressive area of disturbed weather has developed just off the coast of Honduras as we anticipated yesterday. Mid-level cyclonic turning is very evident in the area of deep convection, and there are even signs of anticyclonic flow aloft in the southern quadrant. The southern end of the tropical wave mentioned above will move into this area within the next 24 hours, adding even more fuel to the system. That said, there is a sharp cutoff on the northern edge of its upper regime, courtesy of the upper-level low over the Florida Straits. The associated stable air and shear decrease any chance of tropical cyclone development over the next day or so. Furthermore, the system is located under a surface ridge of high pressure which is inducing easterly steering currents over the region. This brings the issue of land interaction into the equation. A general westward motion with no development is anticipated, though there will likely be enough moisture to maintain heavy spurts of convection and possibly the mid-level center.

It is when the system emerges into the southern Gulf of Mexico around Day 4 or so when the picture becomes slightly more blurry. Yesterday's afternoon run of the ECMWF, as well as a few prior runs of the NOGAPS did indicate what appeared to be a tropical depression at the weakest in the western Gulf of Mexico. Since those runs, the models have backed off and now just show an area of lower vorticity running into the Mexican coast south of Texas. The 18Z GFS, which was earlier not showing anything at all, agrees with this scenario, as does the latest UKMET. The CMC is the only model that does not pick up on anything, however this is likely due to the fact that it is significantly over-intensifying the system in the Bahamas. Generally when nearly all models are picking up on a feature, regardless of how strong they portray it, it is something to pay a very close eye on for more significant tropical development. Further reason to believe a stronger system than what the models show is the fact that none picked up as strong of a mid-level reflection as what is present now in the western Caribbean Sea. The 18Z lead time GFS, for instance, barely even depicts the disturbance. To put it simply, the models as a whole may be underestimating the amount of energy in this system.

Having said that, the environment upon entrance into the Gulf of Mexico will not be all that conducive. Many models, notably the GFS and CMC, prog a sharp shortwave to move from Texas into the western Gulf of Mexico around Day 3. This feature will help stimulate a more stable environment and strong shear aloft in the region. The timing of the shortwave's and tropical disturbance's appearances into the Gulf of Mexico will be key to the chances of tropical development. A faster shortwave and slower disturbance will equate to more favorable conditions and vice-versa. But yet another caveat to strengthening is the likelihood of another East Pacific tropical cyclone offshore Mexico around the same general time. All of the models, again excluding the problematic CMC, support development from the incipient area of disturbed weather south of the Gulf of Tehuantepec. A tropical cyclone in the East Pacific would undoubtedly induce stronger shear into the Gulf of Mexico via its poleward outflow channel, as well as possibly robbing any nearby weaker system of low-level energy. This and the shortwave will be the two main variables. Regardless of whether a tropical cyclone develops or not, it will be just to the right of the southwestward flank of the subtropical ridge. This supports a track westward into either Texas or Mexico, and right now more models suggest the latter. At this time, tropical development in the Gulf of Mexico is not expected due to the aforementioned problems, but it is a situation worth watching.

Tropical Storm Beatriz in the East Pacific is weakening out in the open waters. A continued decline in strength is expected as it slowly moves westward. Dissipation should occur sometime late in the forecast period. Another tropical cyclone, mentioned above, may develop on its heels within the next few days.

June 23 2005 - 02:00 UTC

There is not all that much to add this evening...

The tropical wave that has been given much attention over the last three days is now located in the central Caribbean Sea. Upper level winds are highly unfavorable for development in the short term. The main headline over the next few days will be the heavy downpours being encountered by the Greater Antilles.

The northern end of the wave axis is still forecast to shift northward into the western Atlantic. This track is now evident in the 18Z tropical model suite and several of the global models. But conditions are not going to be favorable for tropical cyclone formation along the East Coast over the next several days. Tropical development in the western Atlantic is not forecast.

The southern end of the wave axis will have to be monitored for tropical cyclone development in the medium range. All global model guidance indicate that the wave axis will add fuel to the fire of an already active western Caribbean. A mid-level low is progged to form east east of Honduras and Nicaragua as the wave begins to interact with the activity already in place over the southwest Caribbean. That's the easy part of the forecast. Within three to five days, the low is forecast to move across the Yucatan Peninsula, entering the southern or central gulf of Mexico by day six at the latest. Again, upper level conditions will remain unfavorable in the Caribbean Sea, and development is nearly out of the question until the feature moves into the Gulf. This is where a lot of the variability between the guidance begins. the 12Z CMC, 18Z UKMET, and 18Z GFS show a very weak surface low moving into the Bay of Campeche or southern Gulf by day six, leaving little or no time for development. The 12Z ECMWF model is more northerly, showing the low moving into the central Gulf after passing Cancun between 144-168hrs. The European is also the most bullish model (surprisingly) in terms of intensity, showing a tropical storm aiming for the Texas coast beyond 168hrs. The 18Z NOGAPS remains conservative, showing only a broad low moving into southeast Louisiana at 144hrs.

It seems as if the greatest disparity between the models is the upper level pattern, which is going to determine the potential for development and track thereafter. After analyzing several different model runs, it is relatively unlikely that enough upper level ridging will be in place over the central gulf of Mexico to sustain tropical cyclone development. It is interesting to note that the GFS and NOGAPS show a decrease in shear beyond 144 hours, but the timing may be too late. Note that the ECMWF is the slowest model since it does not suggest a landfall until day eight, and that may explain why the model is so aggressive.

In conclusion, the Caribbean wave will have little to no chance of development until it enters the western Gulf of Mexico or Bay of Campeche. There is a slight chance of development as long as the wave does not move well into Central America due to land interaction. Once in the central or western Gulf, timing will become key. If the wave moves inland along the western Gulf Coast or eastern Mexico within six days, then the potential for development is extremely low. If the wave meanders for an addition one to three days, then upper level conditions may become more favorable for slow development as an upper level ridge begins to build over the western Gulf.

Tropical Storm Beatriz is no threat to any landmasses. Beatriz is expected to peak as a moderate tropical storm before dissipating in cooler waters in four to seven days.

A few of the global models developing a secondary cyclone in the eastern Pacific have backed off slightly. In addition, there are no concentrated areas of convection east of Beatriz. With that said, there is still some potential for development off the Mexican coast in a few days.



June 21 2005 - 23:00 UTC

Tropical Depression Two-E has developed in the East Pacific near 13.6ºN 101.7ºW, a few hundred miles south-southwest of Acapulco. This depression is moving westward and should continue to do so over the next few days, away from the Mexican coast. Outflow is fair, owing to the ridge of high pressure aloft over the system. However, dry subsidence, strong southeasterly shear, and cooler ocean temperatures are present just ahead. Therefore, the amount of time this has to intensify is limited, no more than 48 hours. Strengthening into a weak tropical storm seems likely, but anything more than that is doubtful due to the hostile conditions that it will encounter in the coming days.

There have not been any significant changes in our line of thinking in regards to the medium-range events we mentioned in yesterday’s discussion. A tropical wave moving into the eastern Caribbean has been the subject of a few interesting model runs today. The 00Z CMC was especially bullish on developing it into tropical cyclone northwest of the Bahamas around Day 3 and had it hit North Carolina head-on as a formidable system. The 12Z shows a much weaker scenario, and no other models have come even close to as aggressive. It is likely the CMC is overdoing the degree of baroclinic enhancement from the progged upper-level troughing off the southeast coast through means of divergence. The most recent GFS and ECWMF pick up on low level development in this area too, though much less robust. Furthermore, the low the GFS develops is purely cold-core as the 200MB GFS animation depicts cyclonic flow associated with an upper trough. It is probable that convection associated with this wave or a split piece of the wave will be aided by the divergence once in the western Atlantic. With so much energy, a surface low may in fact form. However, the environment will be highly baroclinic, and any low that does form will be sheared by the trough, strengthen as a non-tropical entity, or both. Tropical cyclone development from this area is not expected.

The wave we mentioned above will probably split into two parts before too long, with the northern end going into the western Atlantic, and the southern traveling into the western Caribbean and southern Gulf of Mexico by late in the week. Models are starting to agree that a large upper-level ridge will be present in this region around the same time. Such a feature would greatly help the chances of tropical low to develop, providing ventilation and an outflow regime. That said, no model has really shown any tropical cyclone in this area, sans the 12Z GFS which seems to show a weak depression in the Bay of Campeche around Day 6. We pointed out the issue with the models prior to Arlene, which did develop in a similar environment to what is being progged. A fly in the ointment remains the possibility of East Pacific development off the Mexican coast around this time. Models have not backed off on this notion from yesterday, and a consensus may be coming together for a storm there. If this happens, and model persistence and agreement has lead us to believe that it is looking more likely, the poleward outflow channel would inflict shear upon any storm that tries to develop in the southern Gulf or northwestern Caribbean. This whole situation will continue to be monitored. At the present time, development chances on the Atlantic side of Mexico are slim due to the much higher chance of an East Pacific storm and the lack of models latching onto anything. Best bet is June will exit without any additional tropical cyclones in the Atlantic Basin.

June 20 2005 - 23:00 UTC

The area of disturbed weather and associated 1006MB low pressure near 13ºN and 97ºW in the eastern Pacific has slowly organized over the last 24 hours. Satellite imagery depicts a developing outflow pattern in response to a ridge of high pressure aloft. There is some potential of further development into a tropical depression within the next couple days. However, even if the low develops into a classified tropical depression or minimal tropical storm, significant or rapid intensification is not likely. The main low center is still moving west at a faster rate than the upper ridge aloft, and an upper trough to the west of the approaching system has put a cap on convection in its path. In summary, there is about a 50/50 chance of classification, and a hurricane is nearly out of the question. The low will remain on a westerly or wnw course and the threat to Mexico is minimal.

Beyond day five, several models are indicating the development of another tropical cyclone in the same general area. Given an already converging model consensus in the medium range, development is worth considering. If a tropical cyclone does form, a track away from Mexico is most likely, but it is too early to be certain. Finally, the long-range GFS develops yet another East Pacific system late next week. Specifics in the GFS that far out are worthless, but adds to the point that it appears the East Pacific is finally becoming active after a month-long lull. Climatology does show this basin tends to become more active around this time of the year and into July.

As noted in the previous discussion, the Atlantic could become a bit more active in the medium range. Today, the 00Z and 12Z model guidance is depicting a very confusing pattern across much of the basin. None of the models develop a tropical cyclone over the next six days, but each model is hinting at falling surface pressures in either the northwest Caribbean Sea, southern Gulf of Mexico, or western Atlantic. We begin with a mention of the tropical wave producing gusty winds and heavy rainfall over the southern half of the Lesser Antilles. This will be the first wave of energy that will be monitored. The wave will probably split with one half continuing on a westerly path towards the Yucatan Peninsula, and the other spreading northward into the western Atlantic.

Conditions are very hostile in the western Caribbean due to the upper level troughing over Florida and the Gulf. However, the upper trough will slowly lift northward while an upper level ridge attempts to develop over the Yucatan Channel. The southern end of the wave would certainly bear watching once in the western Caribbean or southern Gulf of Mexico if conditions do become more favorable as some of the models suggest. One caveat in this line of thinking is the potential tropical cyclone in the eastern Pacific around day six. The aforementioned favorable environment applies to the west side of Mexico as well, and currently all of the models are far more bullish with this system than any in the Bay of Campeche or northwest Caribbean. If cyclogenesis does occur in the Pacific at the end of the forecast period, the cyclone's poleward outflow channel would induce strong shear into the Gulf and western Caribbean Sea and thus counter any conducive environment in that region. Tropical development is not expected at this time, but our thinking may change as the technicalities of the pattern are worked out by medium range model guidance. Keep in mind, tropical storm Arlene developed in a similar patten. Also, none of the models, barring the GFS, indicated tropical cyclone development until 12 hours prior to the first signs of developing low pressure north of Honduras.

Meanwhile, the northern end of the wave will lift northward due to mid level ridging north of Puerto Rico. The Canadian is the most bullish model pertaining to the northern scenario, with weak surface low formation occuring east of the Carolinas by day six. Currently, the southeast is being dominated by an upper trough, which is inhibiting development near the East Coast due to shear. the main upper level low centered near southeast Tennesse will retrograde eastward, and will eventually become quasi-stationary near the coast. Hereafter, the low level energy associated with the approaching wave will become entwined within the aformentioned mid-level circulation envelope. Thus, any surface low would be aided by baroclinic forcing. Furthermore, mid to upper level southwest winds will also remain high, so even if a weak low were to form east of the upper low, it would likely be sheared apart. No development is expected in the western Atlantic within the next six to seven days.

June 19 2005 - 10:00 UTC

A broad low located near 100ºW in the eastern Pacific has shown no signs of tropical development within the last 12-24 hours. While there is some upper level ridging in place, the anticyclone is not centered directly over the low, and some easterly wind shear is present. Dry, sinking air, may also become a problem for TC formation in a few days. In conclusion, conditions are marginal for slow development, but don't hold your breathe. If a tropical cyclone were to form, it would likely remain south of Mexico.

While there has been some mention of medium range tropical development in the Gulf of Mexico by a few local NWS offices, the chances appear fairly low. The only model that has progged a broad low anywhere near tropical depression strength has been the GFS. The GFS scenario is not supported by any of the remaining global models, and is likely being enhanced by its convective feedback problems. Tropical development in the Gulf of Mexico is not expected through the medium range.

Tropical development in the Atlantic Basin is not anticipated within the next six days. There are no disturbances that show any signs of development, and the global model runs through 120 hours are sluggish.

Beyond day five, the 00Z NOGAPS and GFS show a weak surface low trying to form along a wave axis near the Lesser Antilles. Neither model really shows TC development, but it could be considered the first "hint." Currently, there are no tropical waves that stand out in the eastern Atlantic. Most low level features between 20W-50W are generally void of convection, which is expected this time of the year. However, the NGP and GFS show the broad low at 144hrs originating from one of the features currently in the eastern Atlantic. If the models are correct, then it would be logical to assume that one of these systems will become more obvious on satellite imagery in a few days.

The first sign of potential development will be if the models become repetitive. Since this progged low is relatively weak and six days out, it would not be surprising to see the feature dropped altogether in the 12Z guidance. But the main point is model consistency. Is development east of the Lesser Antilles during the last week of June really a possibility? Well, it is rather unlikely because only two named storms have ever formed east of the islands (1886-2004) during this month. But, the main focus is the potential for development beyond 144 hrs (June 25th). Once again, assuming the models are correct, a weak wave and associated broad low near the islands at TAU 144 could eventually move into the western Caribbean or western Atlantic by around July 1. Both regions are much more climatologically favored for tropical cyclogenesis. Therefore, July 1 and beyond is the most likely timeframe for development of the progged tropical wave. In addition, the enhancing phase of the Madden Julian Oscillation might move back into the basin by that period. This progged low probably does not deserve this much attention this far out, but it is the only system to speak of at this time.

June 18 2005 - 22:00 UTC

There are no areas of interest at this time. There are no signs of tropical development within the next few days.

June 16 2005 - 22:00 UTC

INVEST 93L, an area of convection and associated MLC in the Bay of Campeche, has spread primarily over the terrain of MX as expected. TC development will not occur over land, though heavy rain and flooding is possible.

An area of disturbed weather, associated w/ what was INVEST 92L, is now evident NE of the Bahamas. This increase in organization was anticipated yesterday as an UL ridge is currently situated just a little to the right of the main convection, aiding in ventilation. However, an UL trough is still present to the W, and this is inducing strong shear over the region. Furthermore, this is moving to the NE along flow ahead of an approaching LW trough. Shear will increase even more as the trough advances nearer, and the UL ridge will not move in tandem. The loss of ventilation and more shear in the near future highly argue against any TC development from this area.

Disturbances in the Atlantic Basin may be few and far between over the next few weeks w/ the upcoming presence of an unfavorable MJO. Climatological statistics presented in our hurricane season forecast also indicate the next named storm won't form until sometime in July. Elsewhere across the globe, two INVESTs are present in the WPAC. However, both are disorganized at this time and show no imminent signs of development.

June 15 2005 - 18:00 UTC

INVEST 92L, a surface trough in the vicinity of Haiti, Jamaica, and E Cuba, is showing no signs of organization. An ULL to the W is resulting in convection along the trough by means of divergent flow aloft. Simultaneously, it is inducing strong shear. The overall environment is baroclinic in nature and not conducive for TC development. A NNE movement into the Bahamas should begin soon as the steering flow shifts poleward ahead of a progressive trough. In 2 days or so, it should bend more to the NE as the flow becomes more zonal above of 25ºlat. Following shortly after, the system will gradually become intertwined w/ the mid-lat trough. The above in mind, the system only has about a day to organize. Development will be limited in the next 24hrs due to close proximity to land and the negative influence of the ULL. Conditions will improve once in the W Atlantic as a ridge aloft is progged by most models to develop near or just to the E of the system. This won’t make conditions perfect, though it’ll allow for ventilation on the right and counter any affect the ULL will still have. The window of opportunity for development will end once the system becomes caught in the aforementioned flow. Hence, the amount of time where conditions will be at least marginally favorable is small. Given this, the fact that only the GFS allows TC formation, and that an LLC has even yet to develop, development remains unlikely.

Another area of disturbed weather in the Bay of Campeche has just received INVEST 93L classification. Conditions aloft are conducive for TC formation in this area, as an UL ridge is present almost directly over the main area of convection. However, it is very close to the mountainous terrain of MX, which will act to disrupt surface inflow needed to stimulate a TC. Furthermore, it is located directly under a surface ridge, which is inducing an Erly steering flow over the area. Therefore, a slow but sure W movement is expected to continue, bringing the system inland MX before too long. The proximity to land, lack of time before being completely in land, and the lack of a low pressure are clear reasons why this should not develop as well. Even in the very improbable event that it lingers over water, Wrly shear will dramatically increase over the area w/in 2 days as the UL ridge slowly scoots S.

The rest of the Atlantic Basin and globe remains quiet, and no tropical systems are forecasted in the next several days.

June 14 2005 - 22:00 UTC

Conditions required for tropical cyclone formation are continuing to deteriorate in the central Caribbean Sea. The mid level disturbance near Haiti has not shown signs of organization, scatterometer wind imagery does not indicate suface convergence, and surface observations around the area are reporting no significant decreases in pressure. Water vapor imagery reveals that the upper level trough to the north of the disturbance is digging southward rather than retrograding to the north. An upper low has moved southwest into Cuba from the Bahamas, and its associated upper trough is now dominating the entire western Caribbean Sea. A strong southerly flow is setting up right over the broad low pressure area, and global model guidance suggests that these conditions will remain in place for the next several days. Conditions may even be worse once the system enters the southwest Atlantic Ocean. Tropical development appears highly unlikely.

A tropical wave previously over the Yucatan Peninsula has entered the Bay of Campeche. The low level steering level supports continued westerly movement into southern Mexico within the next 36 hours. Tropical development is not expected.

June 13 2005 - 23:00 UTC

This evening's area of interest is the central Caribbea Sea, which is where convection has been flaring periodically for the last 12-24 hours. A mid level low is located southwest of Hispaniola, but it has shown no signs of tropical development. The numerous shower and thunderstorm activity can be attributed to an upper level low and associated upper trough; it has enhanced upper level divergence over the low pressure area by means of vertical shear aloft. Upper level ridging would be a lot more conducive for tropical cyclogensis rather than an upper trough, a feature that is baroclinic. Furthermore, upper ridging is not forecast to build over the central Caribbean until the medium range, and all global model guidance depicts the 850-950MB vorticy center moving into the western Atlantic by that period. Meanwhile, the troughing over the Greater Antilles will simpy retrograde northward into the Bahamas in tandem with the low. Moderate southwest winds will not relax, and the feature being watched will remain in a marginally favorable environment at best. Not only will winds remain moderately high, but the system will also have to pass over eastern Cuba or Hispaniola. The chances of tropical storm development do not appear all that likely. If development does occur, then nothing more than a tropical depression or minimal tropical storm will come out of this. But development is not the main issue, its the heavy rainfall that will inundate most of the Greater Antilles, primarily Hispaniola. Residents should anticipate flash flooding and mudslides, especially in mountainous areas. The bulk of activity will pass east of central Cuba and west of the Lesser Antilles. Once in the western Atlantic, the low will turn northeast out to sea, eventually becoming extratropical within three to six days. The eastern Bahamas will probably see an increase in shower activity and winds will increase slightly, but some of the worst weather will remain to the east as a result of westerly shear.

A tropical wave is passing over the Yucatan Peninsula. Conditions are not favorable for development.

June 12 2005 - 23:00 UTC

Arlene's remnants are producing heavy rain over part of the OH Valley. As a tropical threat, however, it's out of the picture, and the Atlantic Basin has returned to tranquility.

A surface trough over the central Caribbean Sea is producing scattered areas of convection, w/ the help of strong diffluent flow from the ULL N of PR. Conditions in this area are not conducive for TC development. Furthermore, the only model that indicates anything resembling a TC in the forecast period is the MM5; the GFS has since backed off from yesterday. The GFS solution now shows just a few weak lows along the trough, and this makes more sense than a TC if the ULL moves W in tandem as we anticipate. Such a scenario would keep shear on the high side in the Caribbean as it is now. Given the lack of model support, disorganization, and a prevailing hostile upper environment, development is not expected in this area.

It is also interesting to note that in the past 2 runs (12Z and 18Z), the GFS has indicated TC development S of the CV islands starting on Day 3. This region is climatologically unfavorable at this time of the year, though weak systems do occasionally develop. So far the GFS is the only model that develops a system, and until other models join in, it is a scenario that is hard to accept. Moreover, if anything does develop, it would be short-lived. By Day 6, model guidance suggest increasing shear in the C Atlantic Basin ahead of a LW trough. This feature would also carve a large enough weakness in the subtropical ridge to curve any TC harmlessly to the N, assuming the shear doesn't destroy it beforehand. Chances of development are low in the first place, and they are even lower by a longshot for something surviving and threatening land.

The EPAC and WPAC remain quiet, and there are no signs of development in either of these basins over the next few days.

June 11 2005 - 15:00 UTC

Tropical Storm Arlene is just a couple hours away from landfall. Convection has finally wrapped to the W of the center, however, it remains minimal overall. As was mentioned last evening, the UL trough is feeding in dry stable air into the circulation, keeping strong convective bursts from developing. This will not abait any today, and therefore Arlene should remain a TS. Landall will likely be little E of Mobile Bay. Heavy rain and flooding remain a likely issue, and if you are within the NHC's hurricane warning area, please refer to local NWS statements and the NHC for location specific details.

This has been a successful storm as far as our unofficial IWIC discussions go. Development potential was first hinted on June 1, and our consistent ideas of its landfall location and strength have been accurate. Continued accuracy through the remainder of the season is a priority.

Elsewhere, strong scattered convection, in part associated w/ a surface trough, is noted across the E Caribbean and to the NE of the Virgin Islands. The most recent 06Z run of the GFS is aggressive in developing a TC from this area, beginning on Day 3 near Jamaica and then getting pulled NE through the Bahamas and towards Bermuda by Day 7. However, the only other model that even remotely shows development from this is the NOGAPS, and it's solution is weaker than the GFS. Furthermore, this is the first run where the GFS really shows a true TC, rather than a series of weaker lows along a parent trough. More consistency in the GFS and agreement from other models is needed, as otherwise this is an unlikely scenario. No development is expected here or elsewhere across the globe in the next few days.

June 10 2005 - 21:00 UTC

Arlene has intensified over the past 24HR. Most recent recon data indicate that max sustained winds are now at 55KT w/ a min central pressure of 997MB. This makes the storm just 10KT shy of hurricane status. However, the satellite signature is unimpressive, and in fact, the storm may not be quite as organized as it was earlier this morning. Prominent outflow is evident to the N and E of the system, courtesy of the favorable UL ridge in the area. On the other hand, there is also an UL trough in the central GOM not too far to the left of Arlene. The SWrly flow and ushering of dry stable air associated w/ this trough is restricting both convection and outflow to the S and E of the center. This trough, albeit weakening very slowly, will remain in place. As Arlene gains latitude, the restriction should continue to shift further S as the dry air further undercuts rather than sidesweeps. Although blossoming of deep convection near the center later tonight is likely in tandem w/ diurnal maximum, we expect the circulation will remain predominantly exposed for the rest of the storm's lifetime over water due to the aforementioned stable air issues. Arlene is already showing signs of becoming more elgonated; if it doesn't become a hurricane soon, it won't at all. In fact, we would be less surprised if the system weakened some prior to landfall.

We have been calling for a landfall near Mobile, AL for several days. Latest data suggests that this will be very close. However, it is looking more like Arlene could hit slightly further east. So far Arlene has not bent to the NNW as the models have been insisting due to the progged Wward extension of the subtropical ridge. Furthermore, Arlene is a stronger storm than what most of the leftwardmost models, such as the ECMWF, depicted, therefore it is responding to more poleward higher-level flow. Upon analyzing the latest CIMSS 500-850MB steering layer map, a bend to the NNW is still probable. However, it will be a subtle one since the model consensus likely overdid the building of the ridge, and plus we're dealing w/ a sub-1000MB now. Landfall is about 24HR away, and based on the above, it should be between Mobile and Fort Walton. That being said, this a large-coverage storm, and heavy rains will extend well away from the center. The worst potential from Arlene remains flooding, more so than wind damage.

The remainder of the tropics across the globe are relatively quiet. No development elsewhere is expected in the next few days.

June 09 2005 - 14:00 UTC

A ship report of 35-40 KT winds has warranted the upgrade of Tropical Depression 1 to Tropical Storm Arlene, the first TS of the 2005 Atlantic Basin hurricane season. The satellite signature of the system is much more representative of a TS this morning. The center remains exposed to the W, but heavy convection now occupies the entire Ern side. Well-defined outflow to the E, courtesy of the UL ridge in place, is also noted. The problem that will continue to prevent convection from wrapping around the W side is the presence of a sharp UL trough over the central GOM. This is inducing mass dry air and SW shear, both hostile for convective development in a TC. On the other hand, the aforementioned UL ridge, not quite directly over Arlene itself, is helping to ventilate the system to the E and is having an opposite (favorable) influence. The net result of this UL pattern is a 2-faced storm: strong convection and outflow on the right, but barely nothing left of the circulation. Model guidance suggests that there will be little change in the positioning of the trough and ridge, and therefore Arlene is expected to remain heavily-weighted on the E. That being said, slight additional intensification is still likely as the storm moves closer to the lat of the trough axis, placing it in a slightly less hostile location relative to the SW shear. Moreover, most models still indicate some more strengthening in the next 48HR. A moderate TS, w/ max sustained winds at 45-50KT, remains the most probable, though some baroclinically-induced amplifcation is possible too if Arlene takes on more hybrid characteristics, enabling it to react to the shear differently. A hurricane seems unlikely at this point given the structure issues.

The future track of Arlene remains straightforward. The storm is being steered slowly Nward along the leftward periphery of the subtropical ridge. The progressing LW trough over the MS Valley is further stimulating southerly flow in the area. Model guidance is in tight agreement on a continued Nward track, w/ a slight Wward bend in the GOM due to extension in the ridge position. Most models are in agreement on a landfall somewhere along the N Gulf coast, and even a tighter cluster is expected later today w/ the help of the TPC surveillance jet. The leftmost of the consensus, the ECMWF, also shows the least development. On the other hand, the rightmost, CMC, indicates the most intensificaiton. The influence of their forecasted strengths is that a stronger storm would be subjected to be steered by higher layers of the atmosphere (in this case, such would pull it further N) and vice-versa for a weaker storm. The remaining GFS/NOGAPS/UKMET/MM5 indicate the most likely amount of strengthening, and consequencely agree more specifically between New Orleans and Panama City. These model solutions are preferred as we do not expect as strong of a storm as the CMC depicts, nor as weak of a one as the ECMWF shows. Mobile AL remains our favored target landfall, but anywhere between the 2 aforementioned cities should be closely following the progess of the storm. The main problem will be heavy rainfall and flooding, less so winds, since we're dealing w/ a generally weaker system. It should also be reminded that the worst weather will be to the E of where it's center actually makes landfall.

Elsewhere in the tropics, 91L INVEST has formed from a weak cyclonic spin near 27ºN/57ºW, well NE of PR. This is the other area we repeatedly discussed in addition to what became Arlene several days ago. Most models have significantly backed off on strengthening this into a TC, the exception being NOGAPS, though it does not seem to be grasping the strong shear very accurately. Atmospheric conditions are unfavorable and further development is not expected at this time. In the WPAC, Typhoon Dante/Nesat has continued to weaken as it moves E of Japan w/ little fanfare. Further weakening and extratropical transition is likely.

June 08 2005 - 23:00 UTC

TPC reconnaissance aircraft investigated the broad area of low pressure in the western Caribbean this afternoon. Reconnaissance observations depicted converging winds, sustained winds of 25MPH, and a 1004MB pressure, which was enough to warrant an upgrade to tropical depression status. This evening, shortwave infrared satellite imagery reveals a highly exposed surface circulation near 17.4ºN and 84.0ºW. Moderate southwest winds in the upper levels are still a major problem as far as development goes. CIMMS shear tendency maps indicate decreasing shear, but the LLC will still struggle for another 24 hours until the upper level ridge builds fully in place. Another concern for development is the dry air in the central and western Gulf of Mexico that is expanding over the Yucatan Peninsula. The possibility of dry air entrainment always has to be noted when convection has not consolidated around the center.

All model guidance still shows further development of upper ridging over the northwest Caribbean, which will help to ventilate TD1 and protect it from the sinking air to the west. But until that happens, further tropical cyclone development will not be 100% certain. However, the global models do seem to have initialized the correct upper level pattern correctly, and slow development will likely take place over the next 48 hours as conditions become more favorable. As long as the surface circulation maintains itself over the next 36 hours, development should transpire at a faster rate once in the eastern Gulf. The upper trough over the central Gulf will relax and settle to the west and the ridge should become more of an influence. Light to moderate southwest winds will still be present, however, and they should prevent rapid intensification. Initial expectations of a one sided tropical storm due to shear remain. The system is expected to come onshore as a moderate tropical storm with 50mph-60mph by Sunday evening and no earlier than mid-day Saturday.

There are no significant changes to our previous forecast track expectations. All of the global models have been rather consistent except for the Canadian model. The Canadian has been flip-flopping from turning a strong tropical storm or minimal hurricane into the west-central Florida peninsula or a track towards the panhandle. The GFS, ECMWF, NOGAPS, MM5, WRF, GFDL, and UKMET are all in relative agreement with a landfall between Grand Isle and Apalachicola. It is difficult to pinpoint an area much smaller than that this far out, but there are noteworthy trends in the model data. The available model guidance that supports a southeast Louisiana landfall initialized the depression a bit too far west. Furthermore, the deepening of the low as shown in the majority of model data would support more of a northerly track. The subtropical ridge over the western Atlantic and Florida will have a harder time expanding well into the central Gulf, which is what the ECMWF has been indicating for several runs. Meanwhile, the only global model supporting a track east of Pensacola is the Canadian. A track in the general direction of Mobile, Alabama seems most logical at this time.

As a side note, a landfall in Mississippi or points eastward would greatly diminish any significant flooding threat posed towards the vulnerable city of New Orleans. The only areas at flooding risk in Louisiana would be coastal areas, and I fully expect coastal flood advisories to be issued as the development of a strong easterly wind flow looks certain.

June 07 - 22:00 UTC

A broad area of low pressure has developed in the W Caribbean, as was correctly forseen in many of the computer models. Although the convection pattern is disorganized, this area is slowly consolidating and in fact is now being carried as INVEST 90L by the NRL, the first INVEST of the Atlantic Basin this season. There is enough concern from the TPC to schedule a reconnaissance aircraft to the system tomorrow afternoon, if necessary. The GFS still quickly develops a LLC w/in the next 12HR, and based on recent satellite trends, this is not all that unreasonable. The GFS has also been consistent for the past several runs on a N-ward track towards the MS/AL coastline by Day 5. A similar but slightly further W track is supported by the most recent ECMWF. The UKMET is even further W, and depicts a track more towards central LA. The NOGAPS is the furthest W of all of the global models, however, it continues to be the weakest and barely even depicts the low at all. The CMC was earlier showing a strong TC moving into the FL peninsula, but the latest 12Z run has shifted left and also a tad weaker, making it not too far off from the GFS in both strength and track.

Overall no major changes in the model suite, and our current thinking remains that this will probably develop into a TD or weak TS w/in the next 2-3 days. The UL ridge that has been progged by the models to develop over the area is already becoming evident in satellite imagery. This feature will aid in ventilation, particularly in the E side of the system. As the low/TC moves into the EGOM, exposure to increased shear from the W may result in a more hybrid appearance or all of the convection to the right of the circulation, depending on exactly how it interacts to the more baroclinic environment. We still favor the GFS solution of a landfall in the MS/AL vicinity since it's responding best to what's occurring in the Caribbean right now and has been, surprisingly, the most consistent. A significant TC is not likely, but regardless of its strength status, heavy rainfall and flooding will likely be an issue wherever it hits.

On another note, the global models have backed down slightly on developing the other area of interest currently in the E Caribbean. There is still the likelihood of a low pressure forming N of PR from this disturbance in the coming days, and conditions may become more conducive by this weekend. If a TC does develop down the road in this area, it is almost certainly bound to move NE out to sea in response to a large low-level weakness in the subtropical ridge.

June 7 2005 - 9:00 UTC

The potential for tropical cyclone development in the southeast Gulf of Mexico or northwest Caribbean Sea between the 10th and 15th of June (previous discussions can be found on this page) has been mentioned since June 1. The true threat is beginning to emerge in this morning's model guidance. The discussion will begin with an overview of today's 00Z model runs.

The 00Z run of the Global Forecast System (GFS) is projecting the rapid formation of a 996MB-1000MB surface low north of Honduras in 48-72 hours. By 84 hours, the surface low will have already entered the southeast Gulf of Mexico based on this run. The northwesterly steering is a result of a weakness of the subtropical ridge over the central Gulf Coast. By 144 hours, the GFS shows a moderate tropical storm making landfall in eastern Louisiana, southern Mississippi or Alabama. The ECMWF shows a similar path through day five, but it does not forecast a surface low nearly as strong as progged by the GFS. The Euro has been fluxing back and forth between little or no surface low formation for the last 48 hours. The UKMET has a slightly different feel of the pattern vs. that of the GFS. Rather than quickly developing a surface low in the northwest Caribbean, it shows a broad area of low pressure moving over the Yucatan Peninsula and eventually moving into the central Gulf of Mexico. By day six, the model shows what appears to be a broad wave axis moving inland near Lake Charles, Louisiana. The appearance of an open low pressure area is most evident on the UKMET forecast precipiation accumulation at the FSU tropical cyclogenesis model page. Nevertheless, this is the first run of the UKMET that even hints at the possibility of surface low development in the Gulf, and the the forecast is indicative of heavy rainfall along portions of the Gulf Coast if it verifies. The Canadian is by far the most aggressive and variant of the global model suite. First, it develops a massive upper level ridge of high pressure over the western Caribbean Sea. Such a ridge would be highly condusive for tropical cyclone formation, but the strength of the high is likely being exaggerated. With that being said, the model is trying to develop a tropical storm or hurricane underneath the progged mid to upper ridge. A tropical system of that magnitude would be steered by mid to upper level weaknesses. In this current patten, a track over the Florida peninsula would be most likely, and that is just what the Canadian is trying to do. The CMC shows a tropical storm or minimal hurricane landfall near Tampa early Sunday morning. But as mentioned, the Canadian is the overwhelming outlier, and there are no other indications that a hurricane developing out of this progged feature is even remotely possible so Floridians need not to worry about such a scenario just yet. A weaker tropical system (such as a broad low, depression, or storm) would be steered more by the low to mid levels (where the troughing is not as prominent), and that is why the majority of global models are more focused on the central Gulf Coast rather than the FL peninsula. For instance, the NOGAPS shows a more westerly track than any of the other global models, and it also happens to be the most conservative in terms of intensity.

The progged surface low already getting so much hype is nowhere to be seen on current satellite imagery. However, the origin of the low is evident in all of the model data. The tropical wave in the eastern Caribbean Sea is being heavily sheared by an upper level low over Hispaniola. Some of the energy associated with the wave will slide westward into the western Caribbean. In addition, a southerly fetch of moisture coming out of Central America will be present over the next several days. A consolidation of the two moisture channels will be necessary in order for tropical cyclogenesis to become possible. Such a scenario does seem logical. A mid to upper level trough is positioned over much of the Gulf of Mexico and southeast this morning. This trough will enhance the divergence and outflow over the Yucatan Channel, and a mid to upper level ridge is progged to form over the area. The ridge would equal less vertical shear and latent heat would become concentrated in this region, prime conditions for tropical development when sea surface temperatures are 86ºF.

The possibility of slow tropical development in the northwest Caribbean or eastern/central Gulf of Mexice over the next five days does exist. The likelyhood of any upcoming tropical entity becoming anything more than a tropical storm is considered highly unlikely. Any significant threat to the Gulf Coast would not solidify until a few more days, and nothing more than an increase in heavy tropical downpours along the Gulf Coast should be anticipated this far out. Nothing more than a close watch on the tropics is being called for.

The potential for tropical development in the central Atlantic still exists. None of the global models have backed off from previous runs, and a surface low is still progged to form north of the Virgin Islands. This low would be no threat to land, and it may not even be fully tropical in nature.

Typhoon Dante (04W) is beginning to acquire extratropical characteristics. The typhoon will likely be degenerate within 24-48 hours. There is no threat to land.

June 6 2005 - 19:00 UTC

There are 2 potential areas of interest to closely monitor this week in the Atlantic Basin.

The first is the tropical wave located near 70ºW, just S of the DR. Convection in association w/ this wave is being enhanced by an upper-level low to the W. This feature is expected to diminish over the next day or so, and as a result this may coincide w/ some decrease in convection for a limited time. However, time may be on the side for adjusting to a barotropically-sustained convective environment. The global models unanimously indicate a low pressure of some sort developing in this area in 2-4 days. All take it out of the Caribbean and NE-ward out to sea by Day 5 in response to a large weakness in the subtropical ridge. The CMC is the most agressive for intensity, the UKMET and ECMWF being the least. NOGAPS has trended towards a stronger solution, and GFS has been fluxing back and forth. The overall consistency of the idea gives the scenario of a low itself plausible merit. Whether or not the low becomes a TC is still an uncertainty. For one thing, the E Caribbean is a climatologically very unfavorable region for development, especially at this time of the year. There is almost no doubt strong easterly mid to upper-level shear from the subtropical jet will be present just N of PR and adjacent Caribbean islands, and therefore will likely become an issue at some point. If the models are correct, the low should develop over the E Caribbean, and it is during this time it'll be protected by favorable upper level ridging. Once it moves N, interaction w/ the jet may actually baroclinically strengthen it, possibly leading to a more hybrid-natured system. No significant development is anticipated in the near term while the upper low to the W weakens, but beyond 72HR or so or once a true low pressure forms, weak TC formation must be viewed as an option. Regardless if it becomes a TC or not, heavy rain and hazardous flooding are likely to occur in PR, Virgin Islands, and the DR for the rest of the week.

If that isn't enough for the first week of the Atlantic Basin hurricane season, there is yet another area to watch. An upper-level trough is situated off the Yucatan Peninsula, helping to induce scattered conveciton in the W Caribbean. No direct feature w/ TC development potential is present in this area in the mean time, but this will not remain so per model guidance. All of the global models except ECMWF show a low pressure developing in the NW Caribbean in more or less 72HR. The GFS, NOGAPS, and UKMET all indicate a track through the Yucatan Peninsula and into the central GOM by Day 6. The CMC, on the other hand, shows the low moving NNE towards the FL straits. The reason for this solution is that the CMC develops another low pressure near the DR in the forecast period, and erodes the ridge enough to pull it in. Such a scenario is not indicated by any other models and is viewed doubtful. Therefore, a track along the lines of CMC, although not impossible, is considered unlikely. Movement into the central GOM is the favored solution, but details beyond that remain iffy. Early indications suggested by a few of the aforementioned models are that the steering currents will diminish in the GOM, which would result in a deceleration of forward speed at the least, possibly stalling. Too many uncertainties in the track remain to indicate when and which areas along the GOM coast are most likely to be directly affected by the low. That being said, conditions may become favorable enough to allow for intensification from this progged low pressure as well. Models agree on a broad upper level anticyclone developing over the W Caribbean and GOM after Day 4. If this feature situates itself over the low, it will help ventilation, but if it remains further S as some models are trying to hint, it will only increase shear once the system gains a certain latitude. Weak TC development from this area can't be ruled out down the road either, though again the main threat, wherever and whenever it comes ashore, will be rain.

Elsewhere in the tropics across the globe, Typhoon Dante/Nesat is slowly weakening. Now on a NNE heading, it is expected to bypass Japan not far to the E, but w/ little significant effect.

June 5 2005 - 19:00 UTC

The Atlantic Bain could become active within the next six days.

The tropical wave passing through the eastern Caribbean Sea has shown no signs of organization. A 200MB low near Hispaniola is responsible for 30 knot southwest winds in the mid to upper levels, which has been prohibiting the wave's associated convection from consolidating. As the upper low propogates westward along with the wave, the aforementioned upper level winds will create enough divergence to support further thunderstorm activity along the wave axis. Some upper level ridging has developed to the east of the wave in response to the divering winds aloft. Tropical development is unlikely, but the wave will be monitored.

The area of disturbed weather in the Yucatan Channel has not organized within the last 24 hours. Much of the activity is baroclinic in nature as an upper trough is still in place across the entire Gulf of Mexico. While a local buoy reported a surface pressure as low as 1009MB a couple days ago, recent observations suggest that the atmosphere is becoming more stable. Tropical development is not expected.

The global models are trying to develop a weak surface low in or around the Virgin Islands in the medium range. None of the models are projecting significant tropical development yet, but such a low would increase the potential for heavy rainfall in the Virgin Islands depending on the point of origination and how much it deepens. Tropical development in this area during the month of June is highly unlikely based on climatology, but there is the slightest chance of development if 12Z model guidance is correct. The initial motion once a surface signature is present is northeast due to an approaching upper trough over the western Atlantic.

Today's model runs are beginning to point out another area of interest. The 12Z runs of the GFS and NOGAPS show a southerly flow of low level moisture coming from the eastern Pacific and extending into the western Caribbean Sea and eastern Gulf of Mexico. Such a southerly flow is currently evident in the 700MB-850MB steering layer. Infrared satellite imagery as of 16:45 UTC shows a broad area of low pressure between 85ºW and 95ºW at 12ºN, which is the area of the eastern Pacific south of Central America. A bulk of this moisture should propogate northward. The western Caribbean is the most climatologically favored area for tropical development during the month of June, and the anticipated increase in convective activity will spell watchful eyes on this area in three to six days.

Typhoon Dante (codenamed Nesat for international use) is passing between the southern islands of Japan. While infrared imagery currently shows continued weakening, an approaching trough could temporarily enhance the poleward outflow channel, which would allow for some deepening. Luckily, a direct hit on any landmass is not forecast.

June 4 2005 - 20:00 UTC

Typhoon Nesat in the WPAC continues to fluctuate between a strong cat 3/weak cat 4. It's satellite presentation has detioriated over the past 24HR, and further weakening is expected as it completes its recurvature. Nesat is tracking along the westward periphery of the subtropical ridge, and should continue to move more poleward in the coming days. A path east of Japan and away from any landmasses is likely.

The EPAC continues to be quiet. Several strong areas of convection have developed in association w/ the ITCZ, but strong UL shear is preventing any from organizing. None of the global models show any development from this area in the next 5 days.

In the Atlantic, the UL trough and associated broad area of low pressure continues to produce rainfall over FL and adjacent regions. The convection, firing to the east of the trough axis, is of baroclinic origin, and tropical development is not a concern. The GFS continues to hint in another low pressure forming in this general area shortly after the June 10th timeframe, though it has been less robust in the past 2 days of runs. Right now, chances of anything developing in aforementioned area and time are slim, but not non-existent. The GFS and other global models are also picking up on one or more low pressures of some sort to develop not too far to the NW of the Lesser Antilles around the same time period. The precise location, strength, time of either of these systems, if they even ever do come to fruition, is still in question. IF (big if) the GFS is right, then there will be a moderate surge of disturbances coming in the middle 10 days of the month. With this comes an increased possibility of seeing a classified TC in the Atlantic Basin.

June 3 2005 - 00:00 UTC

In the Atlantic Basin, an upper-level trough is inducing divergence and convection over the eastern Gulf of Mexico, FL peninsula, and NW Caribbean. Some of the showers are heavy, and FL is certainly in for continued high amounts of rain over the next day or so. Tropical development is not anticipated due to the shearing environment and corresponding baroclinic origin of the convection. In the long range, about 10 days or so from now, the GFS continues to hint in a more organized low pressure in the eastern Gulf of Mexico. It has also been suggesting a broad low developing in the central ATL well away from land. It's too far in time to take such forecasts literally, but it's the overall consistent idea that's intriguing. Again, still nothing to be concerned about at this point in time.

The EPAC remains quiet since Adrian. In the WPAC, Typhoon Nesat has leveled off in intensity some. Fluctuations between a strong cat 3/weak cat 4 are expected over the next few days as it completes its slow recurvature well away from the Philippines or any other landmasses.

June 1 2005 - 21:00 UTC

Today is the first day of the Atlantic Basin hurricane season. There are no signs of tropical development within the next several days in this basin. However, the long-range GFS has been consistently hinting for several days in a low pressure developing in the NW Carib/E GOM in the June 10-15 timeframe. Interestingly, this time period may also closely correspond to the arrival of the favorable MJO currently over the WPAC. Although it would be foolish to take such long-term forecasts at face-value, the consistent idea is at least enough to merit mention in this discussion. Climatological statistics, as we outlined in our hurricane season forecast, do favor a named storm forming sometime this month. It's worth keeping note of, but many things can happen before then and so it's nothing to be concerned about at this point in time.

Elsewhere across the globe, the EPAC is quiet. The favorable MJO in the WPAC has helped spawn Typhoon Nesat, located several hundred miles east of the Philippines. This system has rapidly intensified over the past 24HR, and some further strengthening is likely given the very favorable upper level pattern, though a slight dose of impeding shear will likely slow or even stop the intensity trend soon. Model guidance shows that the weakness ahead of Nesat will be sufficient enough to recurve it well east of the Philippines. It also appears the storm will stay far away from Japan in the long-run due to a greater eastward component in the track beyond 5 days.

Independent Wx, 2005. All rights reserved.