Tropical Tidbits from the Tundra

SW Caribbean disturbance still disorganized, will be watched for rainfall potential

By: Levi32, 2:04 PM GMT on May 31, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



Due to some lengthly issues during the video-making process this morning, I didn't have enough time left to write up a written portion to this blog. Please refer to the video. I apologize for any inconvenience.

We shall see what happens!



Caribbean/East Pacific Visible/IR2 Satellite (click image for loop):



Central Atlantic Visible/IR2 Satellite (click image for loop):



Atlantic Tropical Surface Analysis:



200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






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Continuing to watch the SW Caribbean for possible development

By: Levi32, 5:52 PM GMT on May 30, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



There's not much change to the area of interest in the southwest Caribbean this afternoon. Most of the convection with it died off overnight, though we do now have a new blob developing just east of Nicaragua. 12z surface analysis actually has a new low in that area, which makes sense given the weak inflow into that region apparent on visible satellite imagery. There is still 30-40 knots of shear over the system out of the WSW based on CIMSS analysis, and this shear is likely to remain strong for at least the next 48 hours. By Thursday, however, an upper trough backing westward over the Gulf of Mexico will allow the subtropical jetstream to retreat northward a bit, allowing upper ridging and lighter wind shear to develop over much of the central Caribbean. This is when we will have to start monitoring for possible tropical development.

The track of this system appears to be the biggest determining factor of whether it will develop and how strong it will get. The models have been all over the place with this system over the last couple days. There are two main solutions that seem to be going around right now. The one that nearly all the models have gravitated toward this morning features the upper trough in the western Atlantic tugging the Caribbean low northeastward, dragging it back under the jetstream where the area of low pressure becomes elongated, and it eventually scoots out to sea without ever really developing. The other solution, which was shown more yesterday, has the low getting trapped south of the U.S. ridge, sitting in the NW Caribbean for several days, waiting for a weakness to develop somewhere in the steering pattern. Eventually the longwave pattern over the U.S. flattens out, allowing the low to make a move towards the Gulf of Mexico. The model runs that showed this solution generally showed a low of at least tropical storm intensity.

Right now, it's still too far out to really pick one of these solutions. It is clear that the low will be feeling a tug in multiple directions, and it's simply too fragile for us to know right now which solution is correct. It's best to wait for this to develop, if it does at all, and then evaluate the situation again when we are closer to the fork in the road. Meanwhile, the NW Caribbean and the U.S. gulf coast can continue to hope for some rainfall from this if it drifts far enough north. It shouldn't be too strong of a storm in any event. It's still going to be like pulling teeth to get this to develop at all, and it may never amount to much. Patience is necessary in these kind of forecasting situations. Development chances for this low during the next 48 hours are about nil. I will continue to monitor the situation as it evolves.

We shall see what happens!



Caribbean/East Pacific Visible/IR2 Satellite (click image for loop):



Central Atlantic Visible/IR2 Satellite (click image for loop):



Atlantic Tropical Surface Analysis:



200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






Updated: 6:24 PM GMT on May 30, 2011

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Watching the SW Caribbean for possible development later this week

By: Levi32, 6:17 PM GMT on May 29, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



Our first real tropical disturbance of the season continues to fester in the southwest Caribbean this afternoon. Scattered moderate showers/thunderstorms have been developing with it in a disorganized fashion. There is a surface trough lying north of Panama, but surface winds are all still easterly for the most part. There is broad cyclonic turning noted with the system, which can be noted in TPW imagery. Wind shear remains above 30 knots out of the WSW over this entire region, and this system will be under unfavorable upper-level conditions for the next 3 days or so. By Thursday, however, an upper-level trough retrograding westward over the Gulf of Mexico will be allowing the upper ridge over the Caribbean to balloon northward, reducing wind shear and setting up a more favorable environment for potential development of this broad low. With the upper trough over the GOM shoving dry air towards the western side of the system, it is likely to be a typical eastern-weighted storm which is very common in the early season. As a result, don't expect this storm to become too strong right away. It will be like pulling teeth to get this to develop into anything significant, which is again typical of these early-season systems. Regardless, it will be looked forward to as a prospect of rainfall for the northwest Caribbean islands and nations which need it badly.

Regarding the potential track of this system, it has a few possible ways to go, go figure. One possibility is that the trough in the SW Atlantic picks it up and draws it northeast over Cuba and then out to sea. The GFS has liked this scenario the most, and the 6z NOGAPS leaned toward that as well. However, the models and ensemble means have been trending farther east with this trough, and if that trend turns out to be correct, which I think it may, it will be less likely to pull our tropical system out of the Caribbean. It would instead become stuck directly south of the eastern U.S. ridge, with nowhere to go very fast. It would be at the mercy of the cut-off upper low over the Gulf of Mexico, which is a very unpredictable feature on the models. The system could move right away towards central America and likely die slowly, or it could continue to sit over the western Caribbean for many days. If it is still there by next week, the longwave pattern over North America will be becoming flatter by that time, opening up the possibility for the tropical system to get drawn northward into the Gulf of Mexico, potentially providing some much-needed rainfall. This is a long way off, however, and will require the system to survive for an entire week over the Caribbean. Regardless, it is a great thing to hope for for those who need the rain.

We shall see what happens!



Caribbean/East Pacific Visible/IR2 Satellite (click image for loop):



Central Atlantic Visible/IR2 Satellite (click image for loop):



Atlantic Tropical Surface Analysis:



200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






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The tropics are bubbling into next week; Much-needed rainfall on the way for the western Caribbean

By: Levi32, 6:59 PM GMT on May 28, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



The tropics are starting to bubble for the first time as the official start of the season rapidly approaches. An area of deep convection has moved northward into the SW Caribbean, with an associated area of low-level vorticity indicating a surface trough. The subtropical jet is still pressed down quite far to the south over the Caribbean, which will limit the potential of this system for the next 2-3 days. This is, however, the precursor to the area of broad low pressure that the models unanimously forecast to develop within 5-6 days in the western or southwestern Caribbean as the jetstream lifts north enough to allow moderately favorable conditions. At this point, none of the models deepen this low significantly, as wind shear will still be an issue north of about 17N. However, with the upper low that will be ventilating the western Caribbean backing westward, the pattern will support the possibility of getting our first tropical depression of the season.

This system is unlikely to get very strong, and thus the main concern here is with the precipitation. There are many folks in the NW Caribbean and southern U.S. who want rainfall badly right now. Unfortunately, it will be difficult to get any rainfall far enough north to provide relief to the gulf coast. I show in the video how the pattern associated with the positive NAO is sending several shortwave troughs southeastward into New England, shaving off the northeast portion of the ridge that will be building into the central US. This will cause the ridge to retrograde slowly westward, continually blocking off the Gulf of Mexico from any invasion of tropical moisture. The two main choices our Caribbean system is likely to have are to either scoot northeast into the trough in the western Atlantic, or get trapped underneath the ridge for several days, which would probably force it into central America, and possibly the Bay of Campeche. The 0z ECMWF had the low still sitting west of Jamaica at Day 10, which is a long time. The longer the low waits, the more possibilities will open up, as the pattern will eventually become much flatter with time, which opens the door to any kind of weakness being able to pick up the tropical system and bring it towards the United States. However, it would take a lot to actually trap the system that long without letting it dissipate in the Caribbean, and unfortunately, it is more likely that it will avoid the U.S. for now.

Overall, we have the first potential tropical disturbance of the season developing in the SW Caribbean, and as conditions become more favorable over the next 5-6 days, there is a small possibility that a tropical depression may try to develop. The track forecast remains problematic, as every model is jumping around from run to run, and the pattern will be tugging the system in two different directions, but it is likely that it will avoid the United States, at least during the next 8-10 days. However, much-needed rainfall will have a good chance of coming to the islands and nations of the western Caribbean.

We shall see what happens!



Caribbean/East Pacific Visible/IR2 Satellite (click image for loop):



Central Atlantic Visible/IR2 Satellite (click image for loop):



Atlantic Tropical Surface Analysis:



200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






Updated: 7:11 PM GMT on May 28, 2011

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Tropical trouble in the western Caribbean next week

By: Levi32, 1:34 PM GMT on May 27, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



There's not much at all going on in the tropical Atlantic right now, but there are strong hints that things may be afoot next week. As I mentioned a couple days ago, the pattern coming up is one that is conducive for ventilating the Caribbean and lowering pressures there. A monster ridge is about to develop over the eastern United States in 3-5 days, and with lots of upper troughing over the central Atlantic, pieces of it are going to get dragged southwestward beneath the big ridge. One that the models are starting to lock onto moves over the Gulf of Mexico by 120 hours, taking air out of the Caribbean at the upper levels and causing surface pressures to lower. The ECMWF, GFS, CMC, and NOGAPS are all in agreement on a broad area of low pressure developing by 144 hours southwest of Jamaica.

As the upper low continues to retrograde westward over the Gulf of Mexico, a lower wind shear environment should develop near and southeast of Jamaica that could allow this low to develop further, but the subtropical jet will still be close by, likely limiting the potential of this system. It will be a typical eastern-weighted system that we usually get early in the season, with most of the convection and weather to the east and north of the center. The models are not getting too deep with this system yet, which makes sense given that this early pattern is still not that favorable, but the conditions necessary for development are there in this pattern, and it is very possible that we will be watching a potential invest trying to become a tropical depression on the first day of the hurricane season.

We shall see what happens!

200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






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Trough-splits possibly causing trouble in 7-10 days

By: Levi32, 2:07 PM GMT on May 25, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



We shall see what happens!

200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






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2011 Atlantic Hurricane Season Outlook

By: Levi32, 1:47 AM GMT on May 20, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



We shall see what happens!

200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






Updated: 1:49 AM GMT on May 20, 2011

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Continuing to watch for pre-season mischief

By: Levi32, 7:47 PM GMT on May 10, 2011

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems or questions about the video.



We shall see what happens!

200mb Vertical Velocity (green areas represent upward motion associated with the MJO):






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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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