Tropical Tidbits from the Tundra

A quiet June wraps up for the tropics; A peek into July

By: Levi32, 5:28 PM GMT on June 29, 2009

Tropical Tidbit from 12:00pm EDT Monday, June 29, 2009:

No video today. There's nothing going on in the tropics.

The system that looked like it had a great chance at becoming our first named storm in the Atlantic is dead and is not a threat to develop anymore, although the surface trough should not be ignored while it's still in the gulf. The reason this didn't develop was the energy didn't get consolidated. Energy was taken to the NE out of the system and the upper low to the west finished it off. The energy is now bundling in the east Pacific again. You can see though how this pattern that I stressed so much since the beginning of June has brought the moisture north from the east Pacific into the western Caribbean and the Bay of Campeche, where a disturbance formed in each of those areas that I lined out.

Elsewhere....there are currently no imminent threats of tropical development in the Atlantic Basin. A tropical wave south of the Cape Verde Islands continues to show cyclonic turning but has no convection and is not likely to develop, but will have an eye kept on it.


A quiet June:

It's been a very quiet June in the tropics. We managed to eek out 3 named storms worldwide, with 2 in the west Pacific and 1 in the east Pacific. El Nino is continuing to do its thing and getting the MJO locked down in this pattern of upward motion in the central and eastern Pacific with downward motion in the west Pacific and north Indian Ocean.



This pattern completely shut down the Indian Monsoon during the month of June, which although expected to recover in July, will likely remain below normal. The Indian Meteorological Department reports that the cumulative seasonal rainfall for the country of India as a whole during this year’s monsoon has so far been 54% below the long period average (LPA), with 30 out of 36 meteorological sub-divisions receiving scanty precipitation.




Tropical Outlook for the next 2 weeks:

In the month of July average tropical cyclone tracks shift a little farther to the east, with storms more likely to form and travel through the eastern Caribbean and western Atlantic. A little over half of all hurricane seasons see their first named storm by July 10th.



The tropical Atlantic is forecast to be in a mostly downward phase of the MJO for the first 2 weeks of July, which suppresses upward motion and usually puts a damper on tropical activity. El Nino tends to disrupt the MJO, which means this isn't going to be a very strong pulse of downward motion like the one in the Indian Ocean that crippled the Indian monsoon. We will probably see a lot of this sort of thing throughout the of the hurricane season, with the MJO in the tropical Atlantic staying near neutral or in the negative (downward motion). One should keep in mind that the MJO, just like ENSO, is not a magic wand that kills storms or makes them form. A tropical cyclone can still form during a downward MJO pulse, it just makes it a bit harder to do.

The TUTT is forecast to be dipping into central and eastern Caribbean quite a bit during the first half of July, causing unfavorable high wind shear in these areas and the SW Atlantic during most of this time. Higher than normal trade winds through the central/east Caribbean will also be unfavorable for development.

There are 2 areas I am watching for tropical trouble during the next 2 weeks. The first one is off the Carolinas and SE US coast during the 2nd week of July between the 6th and the 13th.

The sub-tropical ridge over Texas is pretty much staying put for the next 2 weeks thanks to the El Nino pattern, but it does go through cycles of oscillating west and east. It's currently going west which is why the upper trough currently coming in will be digging so far west over the SE states. Later this week the ridge is forecasted to start pushing east again, forcing the trough back near the eastern seaboard.



The long-wave upper pattern over North America has been becoming more zonal (flatter) and that trend is expected to continue into next week. This less-amplified pattern does not produce as many trough-splits over the Gulf of Mexico. However, this sets up a pattern where fronts associated with low pressure systems off the US east coast like to hang back near the Carolinas or down near Florida and be slow to drag out. Mischief between the SW side of the upper trough and the upper ridge to the west can occur in this situation with cyclogenesis at the tail-end of those fronts. This type of situation may occur sometime in the next 7-14 days.

The 2nd area that I think has the greatest chance of seeing a tropical disturbance during the next 2 weeks is the western Caribbean. This is basically for the same reasons I called on it to see a tropical disturbance in June. The pattern we have right now with the MJO and El Nino supports periodic advection of moisture north out of the eastern Pacific and into the western Caribbean and Bay of Campeche. We are currently seeing a retreat of the moisture after a surge northward that produced a tropical disturbance in the Bay of Campeche and 93L in the western Caribbean. Moisture will again be trying to invade these areas during the next 2 weeks, predominantly the western Caribbean. Timing of these bursts will be crucial in determining whether we get tropical disturbances, as upper-level conditions will be alternating from unfavorable to marginally favorable in the western Caribbean. Although we are much more likely to see development in the east Pacific than the Caribbean, it is still in my opinion the 2nd best area to watch for the next 2 weeks.



So overall things are expected to be pretty quiet in the Atlantic, but may be a couple areas to watch during the next 2 weeks. The 2nd half of July, as you might expect due to the time of year, probably has a greater chance of seeing a named storm than the first half of the month. The eastern Pacific may also see a shot at another named storm in 3-8 days from the area of bundling energy south of central America that will be creeping NW.

The heart of the hurricane season is fast approaching. I hope everyone is prepared.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Updated: 4:34 PM GMT on July 01, 2009

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Invest 93L hanging by a thread

By: Levi32, 5:30 PM GMT on June 28, 2009

Tropical Tidbit from 1:00pm EDT Sunday, June 28, 2009:

As usual it is Sunday meaning I don't have time for a video.

Invest 93L has gotten pretty beat up overnight, taking heavy hits from the upper low in the western Gulf of Mexico, which didn't move SW as forecasted by the models several days ago. This is shearing 93L and cutting off its moisture supply, which is leaving all the convection east of the main low-level circulation which is now north of the Yucatan. Ok so it got sheared to death? Not really....it's still like I said yesterday shear was not what prevented this from developing. It is now, but that's only because the system was divided to begin with. The mid-level low that started this whole thing in the western Caribbean didn't interact well with the tropical wave, and continued north while the wave continued west. This divided up the energy, and you must get energy consolidated and bundled into a compact area before you can get development. You can still see the division with at least 4 or 5 different low to mid-level swirls on visible satellite imagery this morning.

Is there any hope for 93L? I have to say yes. It's going to get downplayed to death, and I agree that the odds are very much in favor of this just fizzling away, but I must stress the importance of watching things like this in the Gulf of Mexico. There is still a strong area of low-level vorticity, and as the upper low to the west moves over Mexico there will be about a 48-hour window from Monday to Wednesday of marginally favorable upper-level conditions before shear increases in the northern gulf due to a front. There is some dry air in the western gulf associated with the upper low which could end up being the last deciding factor in 93L's death, but do not write this off yet. You can't underestimate what can happen with troughs in the Gulf of Mexico. It always means trouble, and just because something doesn't develop doesn't mean it didn't mean to cause trouble. These things are always looking for ways to cause mischief.

Ok so I've got nothing really exciting to track but where will it go anyway? Well the track forecast in the gulf got all messed up because of a couple things. For one, my forecast was based on the upper low in the western gulf backing SW and being out of the picture by now. Two, I didn't expect 93L to be so weak right now. The forecast for this getting north of the Yucatan near 90W verified nicely, but now we have a very uncertain future in the gulf. If the system remains weak and dissipates, it will likely continue WNW, and some models even take it WSW into the Bay of Campeche. If somehow 93L reorganizes to the east like Alberto in 2006 did, a more northerly component to its movement is likely, and the stronger the system is the more towards the north it goes. The first front coming down into the SE US now won't be able to pick this up, but due to weak steering currents 93L may still be around in 3-5 days, when a 2nd front might, depending on where 93L is at that time and how strong it is, if it's even alive. Hypothetically at this time 93L could end up anywhere from Mexico to Florida if it survives.

So the bottom line here is we have a very weak and possibly dissipating disturbance entering the Gulf of Mexico, that could go nearly anywhere depending on how the situation evolves. Watch it, really. Don't let this go. If for nothing else watch it for a chance of rain in your area.

Elsewhere....still monitoring tropical waves coming off Africa in the eastern Atlantic. Some of the models continue to try to develop some of these, and they should be watched due to marginally favorable conditions.

We shall see what happens!

Invest 93L Visible Satellite: (click image for loop)



Invest 93L model tracks:





Updated: 5:35 PM GMT on June 28, 2009

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93L to threaten eastern Gulf of Mexico

By: Levi32, 4:46 PM GMT on June 27, 2009

Update 8pm eastern time:

During the course of the afternoon, a new area of convection has developed near and east of Cozumel, Mexico in association with Invest 93L. Visible imagery indicates that the tropical wave axis has become more amplified near or over the coast of the Yucatan Peninsula. The loops are also showing rotation with the area of convection but it looks mostly mid-level, and CIMSS maps show the 850mb vorticity maximum to already be well inland continuing on a NW course over the NE Yucatan. The upper low over the Bay of Campeche is backing away slower than expected and this is causing problems for 93L. The proximity of the upper low is causing the mid-upper steering flow to be towards the north, while the low-level flow is still to the NW. This is causing the mid-level circulation to try to run north but the surface center wants to deviate more to the west. That's a fancy way of saying 93L is getting severely inhibited by vertical wind shear, and is vertically skewed because of it. The new mid-level circulation may attempt to pull in the surface trough but only if convection persists, which it may not, and surface-feature domination seems to have been the rule so far with this system.

So for now we still have a very disorganized tropical disturbance that will be emerging in the southern Gulf of Mexico tomorrow, where there will be a more favorable environment for organization as the upper low gets out of the way. I will continue to monitor the situation.

Tropical Tidbit from 12:30pm EDT Saturday, June 27, 2009:

Turn up the volume, and click HD if quality is too low:



Invest 93L remains disorganized this morning without a closed low-level circulation. The location of the center was previously thought to be south of western Cuba earlier this morning before visible imagery came out, but it is just the mid-level circulation that came from the east Pacific and started this whole thing. The low-level center is actually somewhere south of Cozumel, Mexico, just east of the Yucatan if not already over the coast. The reason this didn't develop yesterday was because the energy didn't get bundled and consolidated because the mid-level low didn't interact very well with the tropical wave. So today as the mid-level circulation starts to weaken and move north the low-level center will have a chance to organize. We'll see convection try to cluster around it today, but it likely won't be able to do much while it moves over the NE Yucatan today and tonight.

Once north of the Yucatan though, is when we really have to watch this. The upper low in the Bay of Campeche currently shearing 93L a little bit from the south is going to continue moving west and allowing the upper ridge to build over the system, ventilating it and providing a low wind shear environment. SSTs in the gulf are very warm, and the only inhibiting factor I can think of is the moderate amount of dry air present in the western gulf. I still think this has a decent shot at becoming a tropical depression sometime in the next 2 days and possibly TS Anna. Right now I'd like to see a closed circulation develop and get the system into the gulf before speculating any more on the potential intensity. Keep in mind this could also dissipate just as easily as it could get named.

The GFS, GFDL, and HWRF still take this through the Yucatan channel and into Florida but they are initialized too far east. This isn't going through the channel. My idea over the last few days has been for this to move over the Yucatan and end up north of it near 88W 23N, and the 12z GFS that just came out has caught on and shifted west more in line with this track. The track forecast after that becomes more tricky. The upper high over Texas will be retrograding westward over the next 3 days and won't be able to grab the system and pull it into the western gulf, so I'm not really concerned about that possibility. However anyone from eastern Louisiana to south Florida could be staring this one in the face early next week. I'm currently leaning towards a scenario where 93L drifts around north of the Yucatan under weak steering currents and then eventually gets pulled north or northeast by the upper trough over the eastern US. This new trough coming in is going to be much more zonal (flatter) than previous troughs, as the pattern isn't quite as amplified as it was. The exact movement will depend on several things such as the strength of the system, the timing of the trough, and how deep the trough gets.

So the bottom line is that we still have an unorganized tropical disturbance that will be moving into the eastern Gulf of Mexico over the next few days with favorable conditions for development. Until or if we get classified system we can't speculate too much on strength and exact landfall locations.

We shall see what happens!

Invest 93L Visible Satellite: (click image for loop)



Invest 93L model tracks:





Updated: 11:30 PM GMT on June 27, 2009

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Invest 93L in the western Caribbean

By: Levi32, 4:48 PM GMT on June 26, 2009

Tropical Tidbit from 12:30pm EDT Friday, June 26, 2009:

Turn up the volume, and click HD if quality is too low:



The main feature today is the area of disturbed weather in the western Caribbean that I've been watching since Wednesday. This area has now been designated "Invest 93L" by the NHC, which is nice because we can start to get some model runs on it today. What happened overnight is the mid-level circulation came north out of Honduras and into the western Caribbean, while the tropical wave to the east has moved in with the axis now just west of the Caymans. This has resulted in lots of convection going off in the area east of the mid-level low. The NHC is only talking about the tropical wave right now because they like to focus on surface features. Because of this they put the center of 93L on the wave axis NE of Honduras, where a buoy nearby registered a rapid pressure fall and a wind shift from S to NE earlier this morning. Pressure at the buoy has since risen almost as fast as it fell but just in the past hour has reported falling pressures again, which are pretty high to begin with at around 1013mb.

So, how strong is it going to get? Well with the trough-split over the western Yucatan backing SW it's setting up a nice upper high over the western Caribbean which is ventilating the disturbance, allowing it to breathe, as well as providing low wind shear. This, along with obviously warm SSTs in the area, means we could see some gradual organization of 93L over the next 24 hours. Within 36-48 hours 93L's northwestward motion is expected to carry it over the Yucatan, which will delay significant organization for a while. I don't expect anything big to come of this during its time in the Caribbean, as it still needs time to consolidate and get a surface low going before it can do anything. If a surface low does form it will likely initiate along the tropical wave axis. This wave is already amplifying so we will have to watch for for that today and tonight. Formation of a closed well-defined surface low will likely result in 93L getting upgraded Tropical Depression 2. For the moment there is nothing significant going on at the surface.

Ok, but where will it go? Will it threaten the north gulf coast? There is an upper weakness to the north over western Florida that is pulling north on 93L, but the trough-split to the west is acting as a westward pull on it, as well as trying to build a nosing ridge north of the system. These factors all combine to give a NW motion which should take 93L towards the NE Yucatan and eventually into the southern Gulf of Mexico. Thereafter is when things get tricky. As the trough-split feature leaves the area 93L will be left under an area of very weak steering currents, and the last several runs of the GFS have kept it in the Gulf of Mexico for up to 5 days before going anywhere. However the latest 12z run that just came out takes it through the channel and into SW Florida.

This is where I need to mention one of the things to remember about models is that they jump around a lot with the track. I expect they will be particularly jumpy in this situation because when you get weak steering currents there are usually many possible tracks. The main factor determining when 93L can move north again after getting into the GOM is the trough off the US east coast. If it digs far enough south, a track through the weakness to the NE like the latest GFS shows is possible. If the trough stays further to the north like most of the other models are showing, a more westward track would ensue under the pull of the westward flow on the south side of the subtropical high over the NW gulf coast. Right now it's still a bit too far out, and all we know for sure is that 93L will be moving NW in the vicinity of the Yucatan and eventually into the southern Gulf of Mexico.

The bottom line here is we're going to have a tropical disturbance moving into the southern Gulf of Mexico in 2-3 days that has a shot at developing, and everyone along the gulf coast should keep an eye on it. Hopefully if it gets drawn north it can provide some much-needed rain for somebody, which is not a bad thing at all.

There is another area to keep an eye on, and that is the tropical wave over the eastern Atlantic, which will probably be forgotten amongst the excitement close to home. The wave has mid-level turning with it with scattered moderate convection. Some organization is possible over the next few days as the TUTT lifts out and upper winds become marginally favorable. Don't write it off just because it's early in the year. Climatology is a poor excuse to ignore the current situation. At any rate this wave will not be affecting any land areas anytime soon.

We shall see what happens!

Invest 93L Visible Satellite: (click image for loop)



Invest 93L model tracks:





Updated: 5:26 PM GMT on June 26, 2009

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Western Caribbean and GOM to be watched for mischief

By: Levi32, 4:13 PM GMT on June 25, 2009

Tropical Tidbit from 12:00pm EDT Thursday, June 25, 2009:

Turn up the volume, and click HD if quality is too low:



There are a couple areas we need to keep an eye on. First I'll address the situation closest to home. The trough-split I've been talking and warning about is underway over the eastern Gulf of Mexico, and as the piece splits off it will drift SW into the Bay of Campeche over the next 3 days. The old frontal trough still draped across the eastern GOM, southern Florida, and the Bahamas hasn't spawned any organized areas of low pressure, but there is an area of low-level vorticity just SW of Tampa that you can see spinning on satellite imagery. I failed to mention this in the video, but as I said there is nothing really organized and most of the energy is going to start focusing to the south which I will talk about in a moment. Regardless of how it looks right now, surface troughs in the Gulf of Mexico ALWAYS mean trouble, especially with trough-splits, and no matter what we must watch them. The old frontal trough boundary will slowly dissipate over the next few days as the cut-off upper feature backs to the SW.

Now as the upper feature gets into the Bay of Campeche it will start interacting with a new system. There is a mid-to-low-level circulation near the border of Costa Rica and Nicaragua that I have been watching since yesterday. This circulation is going to be moving slowly NW towards the northern coast of Honduras during the next 2 days, then in the vicinity of the Yucatan, and eventually in about 4 days will get drawn up into the Bay of Campeche and southern Gulf of Mexico by the trough-split feature which will be backing SW out of the GOM into Mexico. During this time a tropical wave currently along 77W entering the western Caribbean will be combining with the mid-level circulation, and as this happens the GFS forms a surface low north of Honduras in 48 hours. Due to all the land in the way this is likely not a threat to significantly develop in the Caribbean, but I would watch this very closely as it gets into the Gulf of Mexico because when that trough-split pulls out it's going to get stuck there for several days under weak upper-level winds. If it sits long enough another tropical wave currently approaching the Antilles Islands may pile its energy into the mix as well. I will be watching this area closely for mischief over the next week.

Notice the pattern we have going here. Remember how in early June I talked about this period from the 20th through the 30th where moisture and heat would advect northward from the east Pacific into the western Caribbean and southern Gulf of Mexico. We had that disturbance in the Bay of Campeche a couple days ago. It came north over Mexico from the east Pacific. This disturbance I mentioned in the previous paragraph is also coming north out of the east Pacific where it was last night. Even if nothing develops it's not like there's nothing going on here. You can see the pattern that has developed with the MJO pulse and the big ridge over the southern US. The mean trough off the east coast as I also mentioned in early June is in a pattern prime for trough-splits into the Gulf of Mexico and NW Caribbean, which are one of the main causes of early-season tropical development. It is interesting to see how this is all coming together.

The 2nd area we need to watch is the big wave coming off west Africa. In my last blog I outlined all the pros and cons, and they still stand today. I know there's a lot of threatening-looking convection with this system but don't be surprised if it all falls apart when it moves over water tonight and tomorrow. I'd like to see this over water for 24 hours before I make a judgement on whether it may develop as the GFS has been insisting on. Don't discount it though, we do need to watch this one as it is the strongest wave to come off Africa yet this season.

We shall see what happens!



Caribbean Visible Satellite: (click image for loop)





Updated: 4:44 PM GMT on June 25, 2009

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Andres dies, but not before taking 1 life with him

By: Levi32, 4:05 PM GMT on June 24, 2009

Tropical Tidbit from 12:00pm EDT Wednesday, June 24, 2009:
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No video today. It's too quiet lol.
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As expected, Tropical Storm Andres failed to revive himself and is how completely void of convection. The storm will continue to weaken as it moves off to the WNW over cold SSTs away from the Mexican coast. Andres was declared a hurricane yesterday after hurricane hunters found hurricane-force winds with the SFMR instrument and a 65kt reading from a dropsonde. Based on Andres' bare satellite appearance at the time of these readings, it is likely that Andres had been stronger than this on Monday, possibly as strong as an 80-knot Cat 1, before ingestion of dry stable air severely weakened him.

Andres claimed one life in Mexico. This from a FOX News report:

"...rain caused flooding Monday in the resort of Acapulco that forced about 200 people to evacuate their homes. A fisherman drowned when choppy currents overturned his boat in a lagoon in Tecpan de Galeana, between Acapulco and Zihuatanejo, a state police report said." Click here to read full report

Atlantic:

It's another typical June day in the Atlantic, with no tropical disturbances to speak of. As usual we look to the forecasted pattern evolution and computer models to sniff out potential trouble spots. The first area we need to watch is the NW Caribbean and eastern Gulf of Mexico. An old frontal trough laying across the Bahamas extending over south Florida and the eastern GOM associated with a stationary upper trough off the eastern US is expected to spawn a couple areas of weak low pressure over the next couple days, with one of them near the north gulf coast. The upper trough that has been stuck off the east coast for days now is going to split and lift out leaving a piece behind in the SE Gulf of Mexico. We now have the two primary causes of early season tropical cyclones, trough-splits and old fronts.

As this is happening an upper high is forecast to be building northwestward in the western Caribbean as the TUTT lifts out, and the GFS is insisting that there will be some sort of disturbance coming out of the SW Caribbean during this time and trying to come north. I think most of what the model is seeing is the tropical wave currently along 67w that will be in the western Caribbean in 2-3 days. As this wave moves into the area of the trough split and old front in the Gulf of Mexico we will have to watch all of these features closely. One should also keep in mind that we remain in the upward phase of the MJO, where upward motion is enhanced in our part of the world. However, the latest forecast shows a burst of downward motion (orange colors) will finally make it across to our area in 5-10 days, which is unfavorable for tropical development. It is equally likely that nothing of interest will materialize, but situations like this should always be watched for mischief.

The 2nd area that we should keep an eye on is purely based on the GFS, which is forecasting a tropical wave to develop into a closed tropical cyclone in the central and eastern Atlantic in 3-6 days. This wave is currently over Africa at about 0E, and will exit the coast sometime on Friday. The factors in favor of development are that the African Easterly Jet is currently a little stronger than normal and is enhancing several strong tropical waves that will be coming off in a train next week. The TUTT which has been dominating the eastern Atlantic all season so far is forecasted to lift out allowing more favorable upper-level winds and low wind shear to develop over the tropical Atlantic. Also, the MJO will be keeping an area of upward motion over the central and eastern Atlantic for the next 5-10 days.

Factors against development are that the GFS develops the wave rather far south, near 5N, which is pretty unlikely. The GFS is likely having it follow the warm SSTs, as sub-26C water temps still extend all the way down to 10N. This leads to the 2nd factor which is that it is still very early in the year for Cape Verde-type developments, and because of this the warm SSTs are still found very far south in the east/central Atlantic. Another thing to consider is that the GFS has been very off its game so far this season, forecasting ghost storms and handling crucial patterns poorly. Therefore confidence in this model forecast is low, especially since there is no support from other models.

So, although unlikely, the potential is there, and this tropical wave will be watched closely as it comes off the African coast in 2 days.

We shall see what happens!



Caribbean Visible Satellite: (click image for loop)





Updated: 4:32 PM GMT on June 24, 2009

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Andres grazing Mexico; Atlantic trough-split to be watched

By: Levi32, 4:10 PM GMT on June 23, 2009

Update 5:30 eastern time:

Andres has been upgraded to a hurricane according to the latest advisory from the NHC. This is based on the 65kt surface winds found by a recon flight earlier this afternoon. This upgrade can be a bit deceiving because Andres is not strengthening. He is in fact, weakening, and has lost almost all of his deep convection, especially over and north of the center, due to dry air entrainment, proximity to land, and unfavorable upper-level conditions. What this tells us is that Andres was likely already a hurricane last night, and may have reached a peak intensity of around 80 knots - a solid Cat 1 hurricane. Since last night the hurricane has been weakening as it lost its convection and inner core structure, and is only barely a hurricane now. Andres has been able to efficiently hold off rapid weakening due to his impressive low-level structure, but he likely won't stay a hurricane for long. Gradual weakening should continue into tonight with more steady and rapid weakening by tomorrow as the system moves into a stable airmass over colder SSTs.

Tropical Tidbit from 12:00pm EDT Tuesday, June 23, 2009:

Video Discussion:

Turn up the volume, and click HD if the quality is too low:



Tropical Storm Andres:

Despite advisories from the NHC keeping Andres a 70mph tropical storm, he appears to have weakened overnight. Cloud tops within the CDO have warmed and the core structure is ragged and disorganized. The 3 main factors that have caused this weakening that I outlined yesterday are 1) Lack of poleward outflow 2) Proximity to land 3) Low ocean heat content and dry, stable air associated with low SSTs to the NW. On Satellite Imagery you can see the outflow boundary to Andres' northwest that is trying to expand north but is getting shunted southward by an upper low over central Mexico and the big upper ridge in the NW Gulf of Mexico. I believe this lack of favorable upper-level conditions to be the primary reason for Andres' decline. Proximity to land may also be playing a role here, and on its current track Andres will be passing very close to the Mexican coast in the next 24 hours, and may even make landfall briefly if his track deviates even a little to the NE.

Andres is being steered NW on the SW periphery of the sub-tropical high over the NW Gulf of Mexico, and this high is forecast to build westward over the next few days, eventually curving Andres to the west as he moves over cold SSTs and dissipates. Some of the track models now are indicating that the upper trough over California may be slow in lifting out and allowing the ridge to build west, which may take Andres closer to the Baja Peninsula than originally thought. If this verifies Baja will likely only get some light rain and nothing worse than that.

I do not expect Andres to significantly strengthen again, but he still has a 12-18 hour window to reach my forecasted intensity of a minimal Cat 1 hurricane. He was only 5mph short of it last night according to the NHC. The NHC has also been forecasting a maximum intensity of a border-line hurricane, and continues to do so this morning. A recon plane is en route to the system as I type, and will give a clearer picture of the strength and health of Andres. I do not expect Andres to reach hurricane intensity, and I think this is likely the start of a gradual weakening period that will continue for the rest of Andres' existence. A hurricane warning is still in effect for part of the Mexican coastline. Refer to the National Hurricane Center for official forecasts and information.

Atlantic:

The Atlantic basin is still quiet for the most part. The trough split that will be occurring in 2-3 days in the Gulf of Mexico will have to be watched as the old frontal boundary extending from east of Florida into the GOM will have to be watched for little lows forming along it. Right now nothing significant is being forecasted by the models but this type of a situation must always be watched. The GFS and NOGAPS try to form something in the western Caribbean in 4-6 days, likely from the tropical wave currently passing through the windward islands. This area will have to be watched as well as the TUTT lifts out and an upper anticyclone builds over the NW Caribbean during that time. The GFS is forecasting some development of an African wave that will exit the coast in 48 hours. With the eastern Atlantic TUTT also forecasted to lift out there may be some breathing room for development so I will keep an eye on that as well.

The disturbance in the Bay of Campeche has slightly increased thunderstorm activity but remains disorganized and I still don't see it as a threat to develop, as it will run out of time and water soon as it gets steered NW inland over Mexico.

We shall see what happens!

NASA High-Resolution Visible Loop of Andres and BOC disturbance

National Hurricane Center official Andres forecast track:



Andres Visible Satellite: (click image for loop)



Caribbean Visible Satellite: (click image for loop)





Updated: 9:37 PM GMT on June 23, 2009

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Tropical Storm Andres threatens Mexico; watching for Atlantic mischief

By: Levi32, 5:16 PM GMT on June 22, 2009

Andres Update 5:30pm eastern time:

High-resolution visible loop of Andres and BOC system

Andres doesn't seem to have changed much since this morning. Estimated overall forward motion is towards the NW at 4kts, but motion has been erratic since this morning due to weak steering currents between the upper high over the southern US and the upper trough over California. Andres has been trying to form an eye structure throughout the afternoon with little success, but the system exhibits a nice CDO with tight curved convective banding. Upper-level outflow remains well-established in the SW quadrant, and also in the SE quadrant with outflow being enhanced by the upper trough in the western Caribbean. Outflow is severely limited to the north due to Andres' proximity to an upper-level low over central Mexico. Andres is not over an area of particularly high ocean heat content and SSTs drop off rapidly west of 105W on Andres' current trajectory.

Due to these factors and Andres' forecasted proximity to the Mexican coast over the next 2 days, I don't expect more than a minimal Cat 1 hurricane at peak intensity. Hurricane warnings have been posted for portions of the Mexican coastline. A hurricane warning means hurricane conditions are expected within 24 hours.



Tropical Tidbit from 1:30pm EDT Monday, June 22, 2009:

Here's my 3rd video:

Turn up the volume, and click HD if the quality is too low:



Tropical Storm Andres:

The east Pacific finally has its first named storm of the season. Andres is sitting just SW of Guerrero, Mexico, and if he gets any closer to the coast it could limit his intensification. This would be good for Mexico as Andres is in an environment favorable for intensification into a Cat 1 hurricane. Andres is embedded in a weak steering flow on the SW side of the upper high sitting over Louisiana. This flow will take Andres slowly towards the NW and likely very close to the Mexican coast of Colima and Jalisco through Wednesday. This slow motion will mean lots of rainfall along the coastline, with the GFS forecasting a total of 6-10 inches as a general rule for these areas. The NHC forecasts Andres to become a minimal hurricane just off the coast of Jalisco in 36 hours before land interaction weakens it back to a tropical storm. I have doubts about this forecast if the track is as close to land as the NHC is forecasting. Regardless, rain will be the primary issue with this system, and for mountainous countries like Mexico slow-moving tropical cyclones near the coast can be nightmares.

Atlantic:

It's still pretty quiet in the Atlantic which is typical for June. Andres' competing circulation from last night has moved into the Bay of Campeche, and looks impressive for the moment but I doubt it will amount to much. When you have a strong system just to the SW of Mexico like Andres it's hard to get anything going near the Yucatan or BOC because the east Pacific system takes most of the energy. However, it is a fairly small system and wouldn't require very much energy to get a closed circulation going. If I were the NHC I would be mentioning this in the TWO today. I will be keeping a close eye on it.

I've seen some talk of a system near the Bahamas developing along the cold front east of Florida. A low will probably form, but it will not be tropical. Why? Because there's too much of a baroclinic zone, meaning that heat is being transported not consolidated. That is the basis of a cold-core system. There is no leeway for sub-tropical development either. For that you need a symmetric system, but this will be asymmetric.

The tail-end of the same front mentioned above is forecast to spawn an area of low pressure over the northern gulf coast during the next couple days, and as this happens the trough off the US east coast will be splitting, leaving a piece behind in the central Gulf of Mexico. This will try to pull the surface low SW over the gulf and we'll have to watch this to see if it tries to get something going. The GFS is still trying to bring a low NW out of the Caribbean in 4-5 days but as usual is too fast with it. We will have to watch for activity there though as the upper anticyclone builds over top of the area in 4-6 days. If anything these invasions into the GOM and Caribbean are signifying the northward push of moisture from the eastern Pacific in association with the MJO pulse that I've been talking about for several weeks, and if you remember I said there was a strong possibility of a tropical disturbance in the Bay of Campeche during this time, and today we have one =)

We shall see what happens!



Caribbean Visible Satellite: (click image for loop)





Updated: 10:02 PM GMT on June 22, 2009

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Tropical Tidbit for Sunday June 21st

By: Levi32, 5:40 PM GMT on June 21, 2009

Tropical Tidbit from 1:30pm EDT Sunday, June 21, 2009:

No video today as I usually don't have the time on weekends unless there's something big going on in the tropics, and I only have time for a very brief update this morning.

All is quiet in the Atlantic for now. There is one area of low pressure in the east Pacific now labeled Invest 93E that will be watched for development over the next few days. Tropical Storm Linfa in the west Pacific has made landfall in SE China bringing heavy rains to the area. Linfa achieved minimal typhoon status for a while before landfall but it was just that - minimal.

Right now King TUTT is shearing everything above 10N in the Caribbean, but we do need to watch the area in 3-6 days as a trough-split occurs over the Gulf of Mexico with the upper trough currently off the eastern US. With the old frontal boundary sitting over the Gulf of Mexico things like this have the potential to cause mischief. The GFS this morning is already hinting at a surface low trying to form in the NW Caribbean under an upper-level ridge that is forecasted to build northward when the TUTT temporarily lifts out in 3-4 days. The area will be monitored.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Updated: 5:42 PM GMT on June 21, 2009

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Tropical Tidbit for Sunday June 21st

By: Levi32, 5:38 PM GMT on June 21, 2009

Tropical Tidbit from 1:30pm EDT Sunday, June 21, 2009:

No video today as I usually don't have the time on weekends unless there's something big going on in the tropics, and I only have time for a very brief update this morning.

All is quiet in the Atlantic for now. There is one area of low pressure in the east Pacific now labeled Invest 93E that will be watched for development over the next few days. Tropical Storm Linfa in the west Pacific has made landfall in SE China bringing heavy rains to the area. Linfa achieved minimal typhoon status for a while before landfall but it was just that - minimal.

Right now King TUTT is shearing everything above 10N in the Caribbean, but we do need to watch the area in 3-6 days as a trough-split occurs over the Gulf of Mexico with the upper trough currently off the eastern US. With the old frontal boundary sitting over the Gulf of Mexico things like this have the potential to cause mischief. The GFS this morning is already hinting at a surface low trying to form in the NW Caribbean under an upper-level ridge that is forecasted to build northward when the TUTT temporarily lifts out in 3-4 days. The area will be monitored.

We shall see what happens!



Caribbean Visible Satellite: (click image for loop)





Tropical Tidbit from 1:00pm EDT Friday, June 19, 2009:

Here's my 2nd video. There may be a few pauses/blurps because my brothers got up earlier than I expected this morning and kept bursting into the computer room while I was recording LOL. I've decided to keep the written updates going as well for people who can't view the video or just prefer a written blog. Today's update is below the video.


Turn up the volume, and click HD if the quality is too low:



The main feature this morning is TD 01E in the east Pacific moving NE towards landfall in southern Sinaloa, Mexico. The system is getting affected by strong southerly shear being inflicted by an upper trough over the Gulf of California, and the low-level center is positioned under the southern edge of the convection. The NHC is still forecasting this to get named before landfall but I don't buy it. This system is small and vulnerable and will dissipate quickly after landfall over the mountains of Mexico. Rainfall amounts of generally 1-3 inches are expected in the states of Sinaloa, Nayarit, Durango, and Chihuahua with local amounts of 4-6 inches.

The two systems in the western Pacific continue to duke it out, with TS Linfa winning, but neither system is very healthy right now due to dry air to the north being punched into their circulations by an upper trough in close proximity. Linfa's current forecast track takes her between Taiwan and SE China. Due to the conditions she is expected to remain at TS intensity, and the main issue for these areas will be heavy rain, especially over mountainous Taiwan. There are no other areas of tropical interest around the globe.

In the Atlantic Basin, there is nothing to currently worry about, but we will be watching as a low-pressure system stalls off the US east coast in 4-6 days bringing a cold front down into the northern Gulf of Mexico. Fronts like these with possible trough-splits aloft have to be watched for trouble, and moisture from the Caribbean may be drawn into this situation as well. So far the models are having a difficult time narrowing down this situation and the exact behavior of the low off the eastern seaboard. I will be keeping an eye on it early next week.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Updated: 5:39 PM GMT on June 21, 2009

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TD 01-E nears landfall in Mexico; Atlantic still quiet

By: Levi32, 5:31 PM GMT on June 19, 2009

Tropical Tidbit from 1:00pm EDT Friday, June 19, 2009:

Here's my 2nd video. There may be a few pauses/blurps because my brothers got up earlier than I expected this morning and kept bursting into the computer room while I was recording LOL. I've decided to keep the written updates going as well for people who can't view the video or just prefer a written blog. Today's update is below the video.


Turn up the volume, and click HD if the quality is too low:



The main feature this morning is TD 01E in the east Pacific moving NE towards landfall in southern Sinaloa, Mexico. The system is getting affected by strong southerly shear being inflicted by an upper trough over the Gulf of California, and the low-level center is positioned under the southern edge of the convection. The NHC is still forecasting this to get named before landfall but I don't buy it. This system is small and vulnerable and will dissipate quickly after landfall over the mountains of Mexico. Rainfall amounts of generally 1-3 inches are expected in the states of Sinaloa, Nayarit, Durango, and Chihuahua with local amounts of 4-6 inches.

The two systems in the western Pacific continue to duke it out, with TS Linfa winning, but neither system is very healthy right now due to dry air to the north being punched into their circulations by an upper trough in close proximity. Linfa's current forecast track takes her between Taiwan and SE China. Due to the conditions she is expected to remain at TS intensity, and the main issue for these areas will be heavy rain, especially over mountainous Taiwan. There are no other areas of tropical interest around the globe.

In the Atlantic Basin, there is nothing to currently worry about, but we will be watching as a low-pressure system stalls off the US east coast in 4-6 days bringing a cold front down into the northern Gulf of Mexico. Fronts like these with possible trough-splits aloft have to be watched for trouble, and moisture from the Caribbean may be drawn into this situation as well. So far the models are having a difficult time narrowing down this situation and the exact behavior of the low off the eastern seaboard. I will be keeping an eye on it early next week.

We shall see what happens!



Caribbean Visible Satellite: (click image for loop)





Updated: 6:30 PM GMT on June 19, 2009

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Atlantic still quiet for the time being

By: Levi32, 4:25 PM GMT on June 18, 2009

Ok so I was feeling weird yesterday and I got this random idea to try an experiment. I have noticed how much people on this site value graphical illustration much more than just plain words, so I decided to try something very embarrassing for me but I hope beneficial to some of you. I have made a video of my computer screen with my voice recorded over it and drawing software to illustrate what I talk about in my update. Now I know I don't have the rosiest voice in the world but it's the only one I have =P Believe me no matter what you think it's nothing compared to what I'm going through hearing my own silly typical teenage voice on this lol. I've never recorded myself before so I had trouble being comfortable and getting my thoughts to flow fluently out loud. Hopefully if I practice it will get better in time. I'm definitely not a natural camera person. The drawing software is also a little quirky as I have to use keyboard buttons to make it work.

Anyway please bear with me and leave me some feedback! I know most of you pass through without leaving a comment and that's completely fine but I would really appreciate some thoughts on whether I should attempt to continue doing this. Or you can tell me I'm horrible and I'll go back to written updates, be honest lol. There's not much to talk about today but I prepared my usual written discussion in case I messed up with the video.

Turn up the volume, and click HD if the quality is too low:



Tropical Tidbit from 12:00pm EDT Wednesday, June 17, 2009:

There's really nothing new to talk about. There are currently no tropical disturbances in the Atlantic Ocean. The GFS for some silly reason is trying to turn the extratropical low forecast to move off the east coast in 3 days warm-core, which is ridiculous. The low south of North Carolina along the quasi-stationary frontal boundary won't develop, and trouble if any will probably be found in the western Caribbean or Gulf of Mexico late next week and into early July as moisture advects northward from the east Pacific and an upper anticyclone builds again over the area.

Invest 92E in the east Pacific has finally been upgraded to TD 1, snapping their quiet streak, and will move NNE towards the Gulf of California. It may get named later and help bolster the global count. We have one for June! Tropical Storm Linfa in the west Pacific just got named this morning and will head off NE towards Taiwan.

The GFS has shifted its area of potential trouble eastward for next week, focusing energy in the western Caribbean now, which is still within my bounds that I've lined out over the last couple weeks. The GFS continues to form a storm and bring it north into the Gulf of Mexico in 8-10 days. The pattern is there and the area will be watched for mischief down the road.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





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Atlantic quiet for now; other basins heat up

By: Levi32, 4:21 PM GMT on June 17, 2009

Tropical Tidbit from 12:00pm EDT Wednesday, June 17, 2009:

The surface trough and tropical wave complex we were tracking in the western Caribbean yesterday has moved inland over the Yucatan. The trough is already in the southern Bay of Campeche with the wave lingering behind. This is dividing the energy, most of which is staying inland over Central America anyway. Due to somewhat favorable conditions in the southern Bay of Campeche under an upper-level high, the system will be watched over the next 48 hours, but I do not expect significant development of this system.

A low forming off the Carolinas along a frontal boundary will be picked up by a mid-latitude low within 48 hours and swept off to the NE out to sea. Before that happens it may turn into one of those nasty hybrids with tight gales and convection that takes ships by surprise, but despite favorable conditions there is not enough time for this to turn into a sub-tropical system and I don't expect significant development.

Some good news is that behind the mid-latitude storm that will pick up the Carolinas low another shortwave trough will be swinging down from the Great Lakes into the NE US in 5 days. This trough is forecast to dig southward and sit over the eastern seaboard for a few days, dragging a cold front down all the way to Florida. This should provide some much-wanted relief in the form of rain and cooler temperatures to the southeastern states east of Louisiana.

The GFS is continuing to forecast increasing moisture to advect northward from the east Pacific into the western Caribbean and Gulf of Mexico during the 8-15 day time frame. There will be an upper-level weakness over the Gulf of Mexico between the upper high over Texas and the high over the SW Atlantic due to the mean upper trough over the eastern seaboard. We will need to watch the western Caribbean and Gulf of Mexico for tropical trouble trying to come north starting late next week and into early July.

The world-wide tropics may be finally getting their act together. Invest 92E in the eastern Pacific which should be a tropical depression is gradually organizing and has a good shot at getting named. In the west Pacific Invest 98W has been upgraded to TD 03W and may get named as it drifts slowly NE. Invest 90W just to its east near the northern Philippines may develop as well if it gets far enough away from TD 03W. Despite large-scale downward motion due to the MJO, a monsoonal low is forming in the Bay of Bengal, and has been labeled Invest 92B. So while the rest of the world tries to heat up in the tropics, the Atlantic should be void of much activity for the next 5-7 days as the TUTT returns to set up shop in the NW Caribbean, bringing strong wind shear to most of the western Atlantic, Caribbean, and Gulf of Mexico. The Atlantic will see trouble soon enough, possibly as soon as a week from now, so make sure you're ready for the season!

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Another strong tropical wave is ready to exit the African coast. The GFS tries to develop this a little bit in the central Atlantic, but the window of opportunity would be small due to the sub-tropical jet enforcing shear everywhere west of 50W. It's still a bit too early to think much about these waves developing in the eastern Atlantic, but they do need to be watched as they get into the Caribbean down the road.



Updated: 4:39 PM GMT on June 17, 2009

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Mostly quiet in the tropics

By: Levi32, 4:06 PM GMT on June 16, 2009

Tropical Tidbit from 12:00pm EDT Tuesday, June 16, 2009:

Things remain quiet for the most part in the Atlantic; typical of June. The area of most interest is our persistent surface trough in the NW Caribbean, which has continued to slowly organize. Convection has become nice and consolidated, with a nice 850mb vort max just NE of Belize. As expected this system will not have enough time to get a closed circulation before moving inland over the Yucatan, and the primary issue will be rain. In 2-3 days this trough will move into the southern Bay of Campeche, where potential development is not out of the question, but most of the energy is going to the east Pacific and Mexico so development seems unlikely to me. I will keep an eye on it just in case.

The models have come into a decent consensus on a weak low forming along a frontal boundary off the coast of North Carolina tomorrow. This low should be picked up pretty fast by an upper shortwave trough and associated low pressure system dropping SE over New England in 48 hours. Conditions would be favorable during its time near North Carolina, but the low will initiate as cold-core and probably won't have enough time to become sub-tropical or tropical. I do not expect anything significant to develop in this area, but it will be watched.

Global tropical cyclone activity continues to stay at a minimum. There have been no named storms in the world so far this June, and there were only 3 in May. It is interesting to note that the Southern Hemisphere tropical cyclone season from October 2008 to April 2009 had the lowest ACE (107) in 30 years. The West Pacific has a few invests that could have a chance at developing, but we'll see how they do in the face of the downward motion starting to come in from the Indian Ocean to the west. The east Pacific has invest 92E which may also have a shot at getting named, but it remains to be seen. The east Pacific will continue to have most of the global tropical energy this week. Next week that energy will be moving north and east, and as I continue stressing we will have to watch the western Caribbean and southern/west/central Gulf of Mexico for potential trouble brewing. The return of hostile upper-level winds in the Caribbean and GOM this week should keep everything in check for the time being.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Updated: 4:15 PM GMT on June 16, 2009

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Tropics still deliver no storms

By: Levi32, 3:58 PM GMT on June 15, 2009

Tropical Tidbit from 12:00pm EDT Monday, June 15, 2009:

There is nothing remarkable to report in the tropics this morning. The pattern reversal in the western Caribbean has completed, with an upper anticyclone now situated over the surface trough as the old ULL retreats into the east Pacific. Convection has increased slightly in concentration, and will likely continue to do so under favorable upper-level conditions, but there is not enough time for anything significant to develop. The system will be inland over Belize and the southern Yucatan by 48 hours, and the energy will stay over central America and extreme southern Gulf of Mexico this week. Starting next week and through the end of June the western Caribbean and especially southern/western Gulf of Mexico will have to be watched again as this area of building heat advects northward.

Some of the global models are still hinting at a low or two forming along an old quasi-stationary frontal boundary draped across the NW Atlantic in 2-4 days, but model support is not near as strong as it was the last couple days. These lows would initiate as cold-core entities and would have to convert to sub-tropical, as some models were indicating. However, this usually takes a lot of time, and the position of the upper high over the GOM favors shortwaves plunging south over the eastern seaboard that should pick up anything sitting there rather quickly. I don't expect anything significant to unfold here. Nevertheless I will keep an eye on the area as wind shear will be low and Gulf Stream SSTs favorable.

Elsewhere....the African wave train is spitting out another probable tropical wave over the west coast of Africa. The GFS keeps trying to do something with these waves but it's still too early in the season. The sub-tropical jet is still south of 20N over the tropical Atlantic and is shearing everything. As these waves start to come off further north we will have to watch them down the road when they get in to the Caribbean.

Global tropical activity remains at a minimum. Invest 98W in the WPAC has no chance. 99W has a better shot but is poorly organized right now. The east Pacific should be the first to try to get something going later this week as heat continues to build in that area with the MJO upward motion pulse. Again we need to watch the western Caribbean and GOM next week as that heat moves northward and we get favorable upper-level conditions over the area. Threats are minimal this week with the sub-tropical jet coming back into the Caribbean and enforcing strong shear.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Updated: 8:19 PM GMT on June 15, 2009

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Tropical Tidbit for Sunday June 14

By: Levi32, 4:23 PM GMT on June 14, 2009

Tropical Tidbit from 12:30pm EDT Sunday, June 14, 2009:

The weather pattern over the Caribbean is finally starting to change this morning. The upper trough has moved out and the cut-off upper low that used to be its tail is backing SW near Belize. This has allowed the sub-equatorial ridge to start expanding northward over the west-central Caribbean, which is lowering wind shear values over the persistent surface trough in the area. This trough is not expected to significantly develop and will drift northwestward towards the Yucatan over the next 3 days, bringing rain to Jamaica, Honduras, Nicaragua, and western Cuba, enhanced by the divergent flow on the east side of the retreating upper low.

The models are forecasting a low to develop in 3 days near North Carolina along a quasi-stationary front draped across the NW Atlantic. The GFS quickly takes this feature out to sea as a cold-core entity, but the CMC, UKMET, and NOGAPS all try to do mischievous stuff with it, trying to trap it under the building ridge to the west and bringing it south towards Florida. This is a possibility that cannot be discounted, but any low that forms will be mostly cold-core in nature and have to convert to sub-tropical, and that takes time. The environment would be marginally favorable with low wind shear in the void between the sub-tropical and polar jetstreams. SSTs in the Gulf Stream off North Carolina are warm enough to support a sub-tropical cyclone or a weak tropical one. Old fronts are one of the primary causes of early-season tropical development, and therefore this area will be monitored over the next 3-5 days.

The worldwide slump in tropical activity continues. Invests 99W and 98W in the west Pacific are still not ready to develop as they are robbing each other of their own energy. The east Pacific still can't organize anything, and the western Caribbean is not in its game yet either. The east Pacific should be the first to get going here soon as the MJO is enhancing lots of convection there. In 10-15 days we need to watch the southern Gulf of Mexico as heat and moisture advect northward under the upper ridge. I believe we have a strong chance of getting a tropical disturbance in that area during that time.

We shall see what happens!

Caribbean Visible Satellite: (click image for loop)





Updated: 10:50 PM GMT on June 14, 2009

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Tropical Tidbit for Saturday June 13th

By: Levi32, 4:23 PM GMT on June 13, 2009

Tropical Tidbit from 12:30pm EDT Saturday, June 13, 2009:

The persistent upper trough is still sitting in the NW Caribbean this morning, causing atmospheric instability and diffluence aloft generating showers/thunderstorms in Jamaica, Cuba, Haiti, and the Caymans. The main trough energy has lifted out and can be seen as a shortwave trough northeast of the Bahamas. The tail part left behind over the NW Caribbean will start closing off into a cut-off ULL (upper-level low) today and tonight. Meanwhile, an equally persistent surface trough in the western Caribbean along 81W continues to enhance shower activity west and south of Jamaica. Looking at the satellite shot you can see the huge build-up of heat in the form of convection over the east Pacific and southern Caribbean (see figure 1).

None of the global models do much with the Caribbean trough anymore. The NOGAPS takes a very weak trough NW into the Gulf of Mexico, and the 06z GFS finally got its timing right and took a weak low into the southern Yucatan in 72 hours. The ECMWF also shows a very weak low east of Belize in 72 hours. The area of 30-knot wind shear still over the southern Caribbean will start to lift northward tonight as the ULL over the NW Caribbean closes off and starts to back SW towards Guatemala. By monday the ULL will be in the EPAC and an upper high will build over the western Caribbean, providing ventilation and a low-shear environment. A weak surface low may try to form along the trough axis during this time and move NW near Honduras and Belize, but significant development is not expected. I will continue to monitor the area for any changes.

Elsewhere....a tropical wave along 63W is moving through the windward islands bringing showers, mostly concentrated in Trinidad and Tobago. This wave has weakened since yesterday and is currently embedded within a dry air mass, but in 2-3 days it will be in the western Caribbean where the environment will be much more hospitable. With all the heat sitting in there all it takes is one wave to take advantage of it, and therefore I will keep an eye on it.

A cold front sitting off the eastern seaboard is expected to continue to sit there for the next several days. The GFS and CMC are forecasting a sub-tropical low to form along the tail-end of this front off North Carolina in 3-4 days in the low-shear void between the subtropical jet and the polar jet. This area will be watched for mischief as well.

We shall see what happens!


Figure 1. The IR satellite image from this morning shows a lot of convection over the EPAC and southern Caribbean, indicating the build-up of heat in this part of the tropics. A lot of this is due to the MJO upward motion pulse which is moving into this area right now. This heat and moisture will be slowly advancing northward into the western Caribbean and southern Gulf of Mexico over the next 2 weeks, and these areas will have to be watched for tropical trouble during that time.


Figure 2. GFS 72-hour forecasted total precipitation. The ULL and surface trough in the western Caribbean are expected to generate 1-3 inches of rain for Cuba, the Caymans, Jamaica, and central America over the next 3 days.

Caribbean Visible Satellite: (click image for loop)





Updated: 4:38 PM GMT on June 13, 2009

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Wet weather continues for the Caribbean

By: Levi32, 4:34 PM GMT on June 12, 2009

Tropical Tidbit from 12:30pm EDT June 12, 2009:
An upper trough centered over eastern Cuba and Jamaica has begun to make its move north and east preparing to lift out of the area. Along with it the area of showers and thunderstorms within the diffluent flow on the trough's east side has shifted east as well, bringing rain mostly to Hispaniola today, and giving Cuba and Jamaica a dry spell. This break will be short-lived though, as the tail-end of the upper trough is expected to split into a cut-off low in the NW Caribbean today as the main trough moves out, which will shift the diffluent zone back to the west over Jamaica and eastern Cuba tonight, once again bringing rain to the area. During the weekend the upper low will back away towards the SW over Guatemala, bringing showers and thunderstorms with it. This will allow an upper-level high pressure system to build over the western Caribbean in 48-72 hours.

At the surface this morning we still have a weak trough in the western Caribbean that extends from Panama to up west of Jamaica. The convection that was associated with it has all but disappeared today as it loses the support of the upper-level forcing provided by the upper trough. The area remains under 30 knots of wind shear. None of the global models are forecasting a closed low to form anymore, and it's starting to look like the ECMWF is going to win out in having the best solution for this system.

The surface trough will slowly drift northwest over the weekend as the cut-off upper low moves out of the way and allows wind shear to lower over the region. The ULL (upper-level low) will likely amplify the trough and enhance shower activity along its axis, but I do not expect any significant development. Regardless, I will keep an eye on the system early next week as sneaky things can always happen when an upper high builds over top with an ULL backing away. 1-3 inches of rain is expected for Honduras, Nicaragua, Cuba, and Hispaniola over the next 3 days, with a pocket of 3-6 inch amounts expected for Jamaica and the Caymans.

Elsewhere....a tropical wave along 58W with strong low-level turning will bring moisture through the Antilles Islands by tomorrow. The windwards should only get isolated showers with most of the moisture staying confined to Trinidad and Tobago. This wave is currently no threat to develop but should be watched in 3-4 days as it enters the western Caribbean and a more favorable environment.

In 4-7 days the GFS is forecasting a front to drop down from the NE US and drape itself across North Carolina and out into the Atlantic. The GFS forms a low along the tail-end of this front on the back-side of the upper trough that will be moving through to the north. I will keep an eye on this area next week.

So are our chances for a June named storm pretty much over? The answer is no. It will definitely seem unlikely in about a week if nothing has developed and the subtropical jet comes back down into the Caribbean, but it doesn't end there. The MJO is entering phase 8, which centers upward motion over the western Atlantic. The ECMWF/GFS 8-10 day comparison shows the mean upper high to continue to build over the north gulf coast and remain in that area. What this says to us is to watch under the high (by under I mean south of). Sure enough the GFS long-range has been consistently forecasting lots of moisture over the western Caribbean, Central America, and the southern Gulf of Mexico in the 10-15 day period. This is the area to watch for mischief during the last 2 weeks of June.

We shall see what happens!

GFS Forecasted Total Precipitation ending 2am local time June 15th:



Caribbean Visible Satellite: (click image for loop)





Updated: 4:53 PM GMT on June 12, 2009

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Disturbed weather continues in the Caribbean

By: Levi32, 3:52 PM GMT on June 11, 2009

Tropical Tidbit from 12:00pm EDT June 11, 2009:
An upper trough continues to linger over the western Caribbean this morning, producing showers and thunderstorms in the diffluent flow on its east side. This trough is starting to move east, as seen in satellite imagery evidenced by the diffluent zone shifting east over Haiti and extreme eastern Cuba. An area of surface low pressure continues to sit under the southeast flank of the upper trough, enhancing thunderstorms north of Columbia and Panama. This low is getting sheared by the upper trough, and is currently not expected to develop during the next 48 hours.

During the next 2 days the upper trough is expected to lift out of the area, getting replaced by a weaker shortwave that will close off into a cut-off low that will move SW over Mexico and into the east Pacific. The backing away of this upper low will ventilate the western Caribbean and allow a low-shear environment to develop in 72-96 hours. This time-frame may vary depending on the behavior of the upper trough, which is the main point on which the models have been disagreeing.

Meanwhile, the area of low pressure in the southern Caribbean will be drifting slowly northwest as the upper trough gives it room to do so. The models are coming into fair agreement on the evolution of this system. The CMC and NOGAPS depict a weaker system with a northwest track over the southern Yucatan Peninsula and into the western Gulf of Mexico. The GFS has completely dropped the low, but continues to handle the entire situation poorly, and thus I don't really care. The NAM has taken its rightful position as a terrible tropical forecaster and joined the GFS in its poor handling of the situation.

The ECMWF more or less agrees with the CMC and NOGAPS, forecasting a weak low to drift north of Honduras Monday through Wednesday of next week before advecting into the southern Gulf of Mexico under the influence of a deep-layer high over the north gulf coast. This has been my model of choice from the beginning, as it has been the only one properly handling the timing of this feature as the shear gradually relaxes in the western Caribbean.

Development of this low remains uncertain, as factors like land interaction with central America are hard to pinpoint right now. At this point I don't foresee significant development during the time that it will have in the Caribbean, but depending on how it looks in 5 days, it may try to develop in the Gulf of Mexico. Regardless of development, this system will continue to enhance rainfall over Jamaica, Hispaniola, eastern Cuba, and the Bahamas over the next couple days, with amounts of 1-3 inches generally expected. I will continue to monitor this system for any development as it drifts northwestward over the next few days.

Elsewhere in the Alantic....a strong tropical wave along 52W is generating an area of thunderstorms to the east of its axis. This wave has a strong low-level signature on visible satellite imagery and 850mb vorticity maps. The wave is about to enter an area of subsidence due to upper confluence associated with a ridge of high pressure, which should prevent the windward islands from getting much rain as the wave passes tomorrow. This wave is not a threat to develop at this time due to northerly wind shear, but it should be watched down the road in 5-7 days when it enters the western Caribbean, where the environment will be more conducive for development.

We shall see what happens!

West Caribbean Visible Satellite: (click image for loop)





Updated: 8:34 PM GMT on June 11, 2009

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Still watching the Caribbean for possible trouble this weekend

By: Levi32, 4:54 PM GMT on June 10, 2009

Tropical Tidbit from 12:30pm EDT June 10, 2009:
The weather in the Caribbean continues to be dominated by an upper trough extending from east of Florida down to Honduras. Divergence on the east flank of this trough is still sparking showers and thunderstorms over Jamaica, Haiti, eastern Cuba, and the Bahamas, although not as many as yesterday. A tropical wave along 82W just east of Nicaragua is enhancing thunderstorms over Panama and Columbia associated with a broad area of low pressure.

The GFS, NAM, and NOGAPS are forecasting a closed low to form in the SW Caribbean in the next 2 days within the moisture surge brought by the tropical wave. The upper trough is currently imparting 30+ knots of shear over the entire area, making conditions too hostile to allow any tropical development. However, the GFS and NAM forecast the upper trough to start lifting out by this weekend, getting replaced by a weaker shortwave dropping down from Florida. This shortwave will become a closed upper low and drift SW over Mexico, allowing an area of low shear to develop over the western Caribbean in 3-5 days as an upper ridge noses in.

Most of the models are still too fast in the formation and movement of the forecasted Caribbean low, and I am continuing to lean towards the ECMWF model, which has been very consistent in forming a weak low over the SW Caribbean this weekend and moving it slowly northwest next week. During this time frame the low would be under more favorable conditions, but at this point development is uncertain.

The pattern I've been talking about is almost here, with the MJO coming over and ridging building over the Caribbean and Gulf of Mexico. This may not be the only disturbance we track over the next 15 days, and the Caribbean and southern Gulf of Mexico need to be watched for trouble. A look into the future shows the next tropical wave in the central Atlantic bringing another moisture surge into the Caribbean in 6-8 days. I will continue to monitor the Caribbean for any changes.

We shall see what happens!

Forecasted Total Accumulated Precipitation during the next 72 hours:


Figure 1. GFS forecasted precipitaion. The GFS has QPF problems and the bomb of 10 inches of rain over Jamaica on this map should be ignored. These areas in the western Caribbean will be getting 1-3 inches of rain over the next 3 days, with isolated amounts of up to 6 inches.

West Caribbean Visible Satellite: (click image for loop)





Updated: 5:04 PM GMT on June 10, 2009

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Rain for the Caribbean, possible low development late this week

By: Levi32, 4:14 PM GMT on June 09, 2009

Tropical Tidbit from 12:00pm EDT June 9, 2009:
An upper trough still positioned over the western Caribbean is producing showers and thunderstorms in the divergent flow on its eastern side. Eastern central America, Jamaica, Haiti, eastern Cuba, and the Bahamas are all getting rain from the deep-layer moisture surge being brought northward by the upper trough. This will continue for the next 3 days as the upper trough lingers in the area. By Friday this upper trough will start to pull out of the Caribbean, but will leave behind a cut-off upper low. This low will drift southwest over Central America and allow an upper high to build into the Caribbean.

As this happens, a tropical wave currently south of Haiti along 74W will be interacting with the cut-off upper low. This will cause more showers and thunderstorms over the western Caribbean, and possibly form a surface low, as depicted by the GFS, NAM, ECMWF, and the NHC forecast. At this time it is unclear whether the low would have a good chance at becoming a tropical cyclone. The environment will be steadily improving from 72 hours onward with an upper high building in to ventilate the area and provide low wind shear. Right now it's best to wait until we actually have a low , and then we can make a proper assessment of the development potential.

I would like to once again point out that we are entering an activity pulse during the next 5-15 days, which I have explained in previous blog entries. This may not be the only disturbance we will track during that time, and the western Caribbean/southern Gulf of Mexico will have to be watched for trouble. For now all of this just means a lot of rain for people in the Caribbean.

We shall see what happens!



Figure 1. Notice the consolidated area of convection in the eastern Pacific around 100W. That's symbolizing the MJO pulse moving over, and now we notice that convection is becoming a little more consolidated in the SW Caribbean, and we may get a more organized Panamanian Low that can drift north and interact with the tropical wave coming in from the east. This area won't be able to develop for 3-5 days but it should be watched to see if it wants to be a trouble-maker.

West Caribbean Visible Satellite: (click image for loop)



Forecasted Precipitation during the next 72 hours:






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Updated: 1:47 AM GMT on June 10, 2009

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Monitoring the Caribbean

By: Levi32, 3:52 PM GMT on June 08, 2009

Tropical Tidbit from 12:00pm eastern time June 8, 2009:

Nothing has really changed today in the Atlantic. We are still watching a weak surface trough in the SW Caribbean associated with an area of thunderstorms. These are being enhanced by upper divergence on the eastern flank of a TUTT (tropical upper tropospheric trough) extending from the northern coast of Honduras to east of Florida. This same TUTT is also enforcing strong wind shear of 30 knots over the trough, which has hampered all attempts at development over the last couple days. QuikSCAT shows almost no surface reflection, but there is still some mid-level turning present.

The GFS has finally come to its senses and backed off a bit on development of this system. The 06z forms a low SW of Jamaica in 48 hours, and then kind of dissipates it by 120 hours as it moves NW. I still think 48 hours is too early, as the TUTT won't really start lifting out until 72-96 hours from now. Once that happens, some ridging will build into the Caribbean, shear will lower, and the overall environment will be much more favorable for development. By 72 hours a tropical wave currently along 68W moving south of the Dominican Republic will be in the western Caribbean, and may serve as a catalyst for cyclogenesis. I still like the European model's idea, developing a weak low in 3-4 days and moving it slowly northwestward into the NW Caribbean during the 5-8 day period. The only other model that even hints at a low is the NOGAPS, which lowers pressures in the region.

At this point confidence in the forecast is low, as the models, especially the GFS, have been jumping around a lot, and model support for this particular low is gradually decreasing. However, one must keep in mind that we are entering a pulse of activity with the MJO here and the upper pattern changing to more favorable over the Caribbean and western Gulf of Mexico. This is likely not the only disturbance we will have to watch over the next 5-15 days. Again I want to mention that regardless of what happens Florida should keep an eye out for tropical moisture getting pulled northward by the retreating TUTT in 5-10 days and possibly bringing more rain to the sunshine state. I will continue to monitor the Caribbean area for any changes.

We shall see what happens!

West Caribbean Visible Satellite: (click image for loop)







website hit counters unique people have been here =)

Updated: 4:14 PM GMT on June 08, 2009

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Tropical Tidbit from 11am EDT June 7, 2009

By: Levi32, 3:23 PM GMT on June 07, 2009

There is nothing particularly exciting on the weather map this morning. A tropical wave along 63w moving through the Windward Islands is bringing scattered showers to the NE coast of South America and the southern windwards.

A weak and broad trough of low pressure associated with a mid-level circulation in the SW Caribbean is producing an area of showers and thunderstorms extending from Panama to Jamaica, being enhanced by upper divergence on the eastern flank of a mid-upper trough extending from Florida down to the north coast of Honduras. This trough is also creating 20 knots of shear over the extreme southern Caribbean, with upwards of 30 knots just to the north covering the entire area. This trough will continue to impose this shear on the western Caribbean for the next 5-7 days before lifting out as the upper high in the east Pacific noses into the Gulf of Mexico.

A pattern pulse of tropical activity is on the way for the next 5-15 days. The MJO upward motion region has arrived in the western Caribbean, and as mentioned above, the TUTT over the area will start to lift in 5-7 days, relaxing the shear and providing favorable conditions for tropical development. The area of low pressure in the SW Caribbean is forecast by the GFS to be a trigger for a TD to form in 5 days, and the tropical wave at 63W which will be in the western Caribbean by that time may be a factor as well. The European model is predicting a TD to form 6 days. The rest of the models show lowering pressures in the western Caribbean but no lows.

The point is the western Caribbean and southern Gulf of Mexico are going to become favorable for tropical development during the next 5-15 days, and at the very least, tropical moisture advecting northward in 6-10 days may threaten Florida with more rain. The area will be continue to be monitored.

We shall see what happens!

West Atlantic Visible Satellite: (click image for loop)







website hit counters unique people have been here =)

Updated: 4:18 PM GMT on June 07, 2009

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Watching the Caribbean

By: Levi32, 4:10 PM GMT on June 06, 2009

Update 1:45pm eastern time: NHC is onboard.

000
ABNT20 KNHC 061727
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SAT JUN 6 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

CLOUDINESS...SHOWERS...AND THUNDERSTORMS OVER THE SOUTHWESTERN
CARIBBEAN SEA ARE ASSOCIATED WITH A BROAD AND WEAK AREA OF LOW
PRESSURE. ALTHOUGH SIGNIFICANT DEVELOPMENT IS NOT LIKELY AT THIS
TIME...THIS SYSTEM SHOULD BRING LOCALLY HEAVY RAINS TO PORTIONS OF
CENTRAL AMERICA OVER THE NEXT COUPLE OF DAYS. THERE IS A LOW
CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$
FORECASTER PASCH/BERG

Tropical Tidbit from 12:00pm eastern Time 6-6-09:

Not much has changed this morning. A broad area of low pressure spread out across the east Pacific, Central America, and SW Caribbean is still being jumped on by the GFS to turn into a tropical cyclone in the Caribbean within 4 days. A strong area of low-level turning and 850mb vorticity has formed just north of Panama and is moving northwest towards Nicaragua. Wind shear is still around 20 knots in this area, and becomes increasingly stronger within the sub-tropical jet just to the north. There are scattered areas of moderate convection north and south of the low.

I still think the GFS is rushing things forming a TS by 96 hours. The sub-tropical jetstream is still firmly entrenched in the Caribbean, and isn't forecasted to really start retreating to the north until 6 days from now. Until the upper-level environment improves, I expect slow development, if any, of the system near Panama. Land interaction will also be a hindering factor as the low will probably move right over Nicaragua and Honduras during the next 3 days before getting into the western Caribbean.

The only other models forecasting a low to form are the European and the NOGAPS. These two models move a weak low slowly up through the western Caribbean in 5-7 days. I am inclined to agree with this solution rather than the quick GFS. 5-7 days out the sub-tropical jet will start to lift north and relax the shear over the Caribbean, and the MJO upward-motion pulse will be in full swing. Also around that time the tropical wave along 59W right now will be moving into the western Caribbean, and may want to have its say in things, at least adding its heat to the area. Another reason I am skeptical of the GFS is that it hasn't had a good handle on this situation for a couple of days now. It has a problem handling the trough-split that will be helping to de-rail the sub-tropical jet, and it also has feedback issues, which makes it split the energy all over the place. This is the subject of today's Graphic of the Day:

Graphic of the Day:

Graphic of the Day: 06z GFS 144-hour 850mb Vorticity, showing how the GFS splits the Caribbean low into 4 different lows, spreading out the energy over a wide area. Interestingly, the GFS seems to spawn the two lows north of Hispaniola from a tropical wave that is currently in the central Atlantic near 59W, approaching the Antilles Islands. The GFS also forms these two lows right under 40 knots of shear associated with the sub-tropical jetstream, further reinforcing my point, that the GFS has serious issues.

So the bottom line here is that the western Caribbean will be becoming more favorable for tropical development in the 5-15 day period, and we may have a trigger already in place to start the process once the environment becomes favorable enough. Right now it's best to just watch and see how things evolve over the next couple of days. Regardless of any development of the system near Panama, it will be spreading heavy rains over Central America, and Florida should keep an eye out for tropical moisture moving north and dumping more rain on them in 6-10 days.

We shall see what happens!


NASA High-Resolution Visible Loop of the low near Panama

West Atlantic Visible Satellite: (click image for loop)







website hit counters unique people have been here =)

Updated: 8:37 PM GMT on June 06, 2009

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Eye on the Caribbean

By: Levi32, 6:41 PM GMT on June 05, 2009

Tropical Tidbit from 2:30pm eastern Time 6-5-09:

The GFS is continuing to develop a tropical cyclone in the western Caribbean early next week from an area of disturbed weather south of Panama and Costa Rica. A tropical wave in the eastern Pacific is helping to enhance thunderstorms in this area, as well as a strong monsoonal flow from the SW. An area of low pressure is forecasted to form in this region, and should drift very slowly towards the NNW over or near Nicaragua during the next few days.

The GFS seems to be rushing things a bit with cyclogenesis in the Caribbean, giving little time for the subtropical jetstream to lift far enough north to give some breathing room to the disturbance. Development seems more likely in 6-8 days, when environment becomes more favorable. I also feel that the model is mishandling the trough split getting ready to occur with the upper shortwave moving into the eastern Gulf of Mexico right now. We may get a sort of "double-split" with one piece of the trough digging southward towards the NW Caribbean and the other piece swinging out across Florida and planting itself south of the Carolinas. It will be interesting to see how the first piece interacts with the area of disturbed weather in the Caribbean. It is worth noting that all other models have dropped the low in recent runs, although most of them lower pressures in the area. It is possible that the GFS is getting plagued by its feedback and QPF issues, but it is hard to say.

We can't speculate on what might happen with this potential storm, but we can say with fair certainty that the environment is going to become more favorable for tropical cyclone formation in the Caribbean during the next 6-10 days. The models are forecasting the upper high in the east Pacific to nudge north into the southern Gulf of Mexico. Coupled with the trough split to the east, this should effectively split the subtropical jet and lift it to the north, allowing an area of lower wind shear to envelop the western Caribbean. Today's graphic of the day illustrates this with the 12z GFS shear forecast from this morning:

Graphic of the Day:


The MJO upward pulse is on the way as well, and should be in the western Caribbean in a few days. These factors will all make the environment more favorable in the western Caribbean, and that area will be monitored for development during the next 10 days. Regardless of development, please remember that this whole mess could be another big rain-maker for Florida if it migrates north in 6-10 days, so be aware. Countries in Central America may also get a lot of rain over the next few days.

We shall see what happens!


NW Atlantic Water-vapor Loop (to watch trough-split over north gulf coast)

West Atlantic Visible Satellite: (click image for loop)







website hit counters unique people have been here =)

Updated: 7:57 PM GMT on June 05, 2009

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Trouble may brew next week

By: Levi32, 5:18 PM GMT on June 04, 2009

Tropical Tidbit from 12:00pm eastern Time 6-5-09:

Most of my philosophy remains mostly the same so yesterdays analysis will remain below this update.

Model Update this morning:

The GFS is continuing to develop a strong tropical cyclone in the Caribbean within 2-4 days and move it through Cuba and up east of Florida in 6-10 days. The model seems to think the starting point will be a low south of Panama that crosses over into the Caribbean. In my opinion it's still a bit too far east with both the trough-split over Florida and consequentially, the low in the Caribbean. Any development of the convection in the east Pacific should move NNW over Nicaragua and Honduras for a while, and then get pulled into the NW Caribbean by the upper trough over Florida. In 4-6 days the tropical wave currently in the central Atlantic may get involved, and regardless of whether a low actually forms, I think it will definitely be getting messy down there next week.

The only models now developing a low are the GFS of course and the NOGAPS model. Regardless of development please remember that this whole mess could be another big rain-maker for Florida if it migrates north in 6-10 days, so be aware. I will continue to keep an eye on the situation.

We shall see what happens!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~

Tropical Tidbit from 1:20pm eastern time 6-4-09:

By the way, the trough set-up currently over the northern Gulf of Mexico is very similar to what we had with Invest 90L back in May, and the little low that moved onshore last night over Alabama is warm-core, at least at the low-to-mid levels. It's got banding features and convection at the center, not to mention its position in the warm-sector of the low to the west of it. If you don't believe me look at its inland radar signature this morning (see below). I'm not saying it should have been named. It didn't have nearly enough time for that, but it is very interesting to see these things spin up.



I'm still waiting for the trough split that I talked about yesterday. The low mentioned above will be merging with the extratropical low center over Mississippi today and tonight. The whole thing will get kicked out northeast and a piece of the shortwave will get squeezed off in the eastern gulf. The last few runs of the GFS are drifting too far to the east splitting the trough over or east of Florida. The GFS and Canadian models are also moving east with the surface low formation in the west Caribbean in 4-7 days. The GFS brings the low NE over Jamaica and the Canadian forms a low north of Cuba. In my mind both these solutions are too far east, and trouble, if any, should be watched for in the far western Caribbean. Most models have trouble seeing trough splits properly until they're right on top of them. It's worth mentioning that the 00z European last night has dropped the low almost entirely, but again we know that models jump around a lot forecasting stuff several days out.

So it's looking like a good possibility of some sort of low forming in the western Caribbean in 4-7 days. There are several ways this could happen. The GFS version forms a small low pressure area under the area of convection south of Panama right now, and moves it as a tropical cyclone north and then northeast towards Jamaica, partially phasing with the trough split over Florida by that time. Another possibility is that the well-defined tropical wave in the central Atlantic will pile into the western Caribbean interacting with the trough split feature. The point is there are a variety of ways that trouble can start here.

Conditions will be becoming progressively more favorable for tropical development in the Caribbean and southern/west Gulf of Mexico in 6-10 days. As I mentioned yesterday, the high in the east Pacific will be nosing north into the SW GOM, and combined with the trough split feature will effectively split the subtropical jetstream over the Caribbean, leaving an area of low shear. The MJO upward motion pulse will be moving into the Caribbean over the next 5-15 days, which would enhance any activity sitting down there. It could be an active last half of June, and I think we could get 1 or even 2 storms out of the pattern, but that doesn't necessarily mean the rest of the season will be as active.

I do want to mention that, named or not, a lot of tropical moisture will be trying to funnel northward out of the Caribbean in 6-10 days, and Florida should be prepared for yet more rain. I will continue to monitor the situation. We still have a lot of time.

We shall see what happens!

NW Atlantic Water-vapor Loop (to watch trough-split over north gulf coast)

West Atlantic Visible Satellite: (click image for loop)




Updated: 4:13 PM GMT on June 05, 2009

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Potential Trouble to Brew in the NW Caribbean

By: Levi32, 4:51 PM GMT on June 03, 2009

Tropical Tidbit from 12:30pm eastern time:

Across the Atlantic and Eastern Pacific things remain very quiet for the beginning of the hurricane season, but we may have a mischievous trouble-maker down the road here playing games in the Caribbean. I'll tell you why.

Right now the current situation is we have a weak area of low pressure (1013mb) near the mouth of the Mississippi River, which formed yesterday under a broad area of showers and thunderstorms in advance of an upper shortwave trough moving through eastern Texas, Arkansas, and western Louisiana. In about a day or so this weak low will move northeast and merge with a cold front which is currently moving through north Texas and NW Arkansas, forming one low pressure system over the SE states that will move NE off the eastern Seaboard in 60-72 hours.

The catch is that a piece of the shortwave trough is going to get left behind near the north gulf coast and split off from the westerlies, along with a surface remnant low. Events like this are called "trough-splits", and are one of the main causes of early-season tropical cyclones in the western Atlantic, especially the Gulf of Mexico and the Caribbean. I put together a little animation of this morning's 06z GFS 500mb 0-180 hours to show you how this occurs:



Now over the next 5-7 days this upper-level piece will drift southward into the NW Caribean, where the GFS forms a surface low at 120 hours. Yes it's shown as a shallow warm-core sub-tropical low, but that is typical of how trough-split systems begin, and it will be over SSTs of 28C. The environment doesn't look very favorable down there right now with the sub-tropical jetstream screaming through the area, but during the next 5 days the models are forecasting the upper high in the eastern Pacific to start moving north and bulging up into Mexico and the western GOM. This, coupled with the upper piece from the GOM moving south, will effectively split the sub-tropical jet over the Caribbean, leaving an area of lower shear for the low to deal with.

This is one of those things that will need to be watched carefully as it evolves. It may not happen at all and the split-off feature may dissipate all-together, but the GFS has been sniffing it out (on the new 12z run also), and it's a possibility worth investigating. Again, trough-splits are one of the main causes of early-season tropical storms, so they deserve attention. I will continue to monitor this area over the next several days.

We shall see what happens!



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Subtropical Storm in the NE Atlantic

By: Levi32, 7:45 PM GMT on June 01, 2009

UPDATE 8:15 EDT:

The NHC has recognized the system, but for some reason has not named it yet, despite clear evidence that the system meets STS criteria, and has met it for at least the 6-hour minimum that the NHC likes to see. They are inconsistent in this area so there is no way to know. The invest will not be able to maintain itself for much longer due to cold SSTs.

000
ABNT20 KNHC 012355
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT MON JUN 1 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A NON-TROPICAL AREA OF LOW PRESSURE LOCATED A COUPLE HUNDRED MILES
NORTH-NORTHEAST OF THE AZORES ISLANDS IS PRODUCING WINDS TO NEAR
GALE FORCE. SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE LOW HAVE
BECOME A LITTLE LESS ORGANIZED DURING THE PAST FEW HOURS. THIS
SYSTEM IS EXPECTED TO MOVE NORTHWARD OVER COOLER WATERS DURING THE
NEXT DAY OR TWO. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A SUBTROPICAL CYCLONE DURING THE NEXT 48
HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN
---------------------------------------------------------------------------------------


We got a surprise to start off the 2009 Atlantic Hurricane Season! The SSD just put up an "invest" floater on a 1002mb extratropical system in the NE Atlantic centered around 24W 40N, just north of the Azores. This system has become warm-secluded (part warm-core), as seen in the phase diagram and satellite image below:





You can see the sub-tropical characteristics associated with this system. Shallow thunderstorms have formed into symmetrical bands rotating inward towards a warm "eye" at the center of the system. QuikSCAT shows a well-defined secondary wind field at the center of the system with tropical storm-force winds. This system bears great resemblance as well as location to Hurricane Vince of the 2005 hurricane season, although Vince was fully tropical.

What precipitated this rare event was probably the system getting cut off from the main westerlies and becoming a closed upper low over the NE Atlantic with the frontal structures spread out quite far from the center of the storm. The system is over water temperatures less than 20C, and hence thunderstorm activity is shallow, but we've seen things like this happen before and we know that it is not impossible. The low will move slowly towards the north and then northeast during the next couple days before the GFS forecasts it to dissipate. This system, by all definition, deserves to be named Sub-tropical Storm Ana, but we'll see whether the NHC decides to be weird or not. Enjoy this awesome storm =)

We shall see what happens!



Visible Loop of the sub-tropical storm (click image for loop)

Updated: 12:17 AM GMT on June 02, 2009

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Here we go, Hurricane Season Begins

By: Levi32, 5:02 PM GMT on June 01, 2009

The 2009 Hurricane Season begins today. Hopefully everyone that lives in hurricane-prone areas are prepared for the potential threats to come.

We're getting off to a quiet start right now, with nothing of interest in the Atlantic, and nothing forecast to form by the models. This is fairly typical of the month of June, where only roughly 1 out of every 3 years sees a named storm during this month. Let's look at the historical tracks of all storms in June:



You can see that all but one of the storms in the past 150 years have formed as "home-brew" close to the coast in either the Caribbean, Gulf of Mexico, or off the Southeast US. These developments are most commonly triggered by trough splits or old fronts getting stranded and acting as trigger points for tropical formation. This is the case because African tropical waves are still mostly too far south at this time of year to form storms, and the SSTs in the tropical Atlantic are still too cool.

Right now the sub-tropical jetstream is sitting pretty far south over the Caribbean, Gulf of Mexico, and all of the tropical Atlantic, causing too much wind shear for anything to form south of 20N.



The GFS is forecasting this shear to start to lift in the Caribbean 2 weeks from now, which would open the door for possible development there. Until then the only area with low enough shear to allow development is off the Southeast US coast, which has been sitting between the sub-tropical jet and the polar jet, allowing lower than average winds in the upper atmosphere. This can be seen in this graph of wind shear compared to the climatological average (black line), which shows how wind shear off the eastern seaboard has been generally lower than normal during the month of May. This gap in the wind shear field is what allowed TD One and Invest 90L to form in May.



How are SSTs doing so far this year?

Well they're definitely much lower than the record year of 2005, and are pretty similar to last year. Generally they are about average, which is lower than the above-average temperatures we have been usually seeing during the past 10-15 years. SSTs may be cooler than normal in the tropical Atlantic MDR(Main Development Region) this year.



2009 Hurricane Season Outlook in a nutshell:

I'm also expecting an about average year number-wise, with 12 named storms, 7 of those hurricanes, and 2 of those major hurricanes. However, it only takes one storm to turn a "normal" season into one that's impossible to forget. I believe threats to the coast will be significant this year, with a quieter Cape Verde season, fewer long-track storms, and more developments close to home. El Nino will be a factor by the middle of the season, and will probably cause conditions to become less favorable in the MDR. With storms forming closer to the coast, everyone should be ready to act quickly in the event of something spinning up close to their area. The official 2009 NHC Hurricane Outlook can be found here.



Updated: 5:04 PM GMT on June 01, 2009

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About Levi32

Levi Cowan has been tracking tropical systems since 2002, and is currently working on his bachelor's degree in physics at UAF.

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