Tropical Tidbits from the Tundra

Tropical Tidbit for Wednesday, April 28th

By: Levi32, 4:34 PM GMT on April 28, 2010

An area of disturbed weather continues to persist in the eastern Pacific. The somewhat organized low-mid vorticity max that we were tracking yesterday has fallen apart overnight and lost all its convection. This is because the system took an unprecedented jog to the northwest near 12N, 94W, where it ran into dry air and ended up well-removed from the area of greatest favorability for tropical development, which right now is south of 10N and east of 95W. The whole area has now lost any organization that it had, and this now has to start from scratch again.

What we should start to see today is a refocusing of the heat to the east, probably east of 90W, back under the upper-level ridge where the high moisture content and greatest surface convergence is. We are now back to a broad area of multiple vort maxes, and it will take time to consolidate everything into a compact disturbance that is capable of developing into a tropical depression. This will be difficult with the upper-level environment being less than ideal, as although there is a 200mb ridge extending over the area, there are easterlies on its south side which are inflicting 20 knots of easterly shear over the area.

The GFS continues to be the only model that really plays with this, and still tries to develop a tropical cyclone in about 4 days. After losing its first battle, my confidence in this disturbance is much less than it was, but it still has 3-4 days to work with before upper-level conditions become too unfavorable. The MJO upward-motion pulse will also be moving on to the east by that time, withdrawing some of its support from the east Pacific. At the very least, this feature will continue to spread scattered areas of locally heavy rains to the coastal areas of Panama, Costa Rica, Nicaragua, and El Salvador. Overall, this is an area of disturbed tropical weather that has potential for development, but any development will be slow, and the area will continue to be watched over the next few days.

We shall see what happens!

Visible RGB Satellite: (click image for loop)



CIMSS 850mb vorticity (left) and 700mb vorticity (right):

   

Satellite-derived upper-level winds:



200mb vertical velocity: (green areas represent upward motion associated with the MJO)






Updated: 4:48 PM GMT on April 28, 2010

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Tropical Tidbit for Tuesday, April 27th

By: Levi32, 4:05 PM GMT on April 27, 2010

Heat continues to build in the eastern Pacific as convergence caused by a Kelvin Wave and a MJO upward-motion pulse enhance thunderstorm activity in the area. Convection has become better consolidated overnight, focused more toward the west, with little convection left near Panama. An area of low-mid-level turning is observed on visible RGB satellite imagery centered around 8N, 88.5W. This is confirmed by CIMSS 850mb and 700mb vorticity analysis. The vorticity field remains rather elongated, especially off to the west, but less so than yesterday. The area has not moved much over the past 48 hours, as steering currents are very weak over the eastern Pacific. There is an upper ridge extending over the system, providing a decent environment, but 10-20 knots of easterly shear still exist over the area.

Most of the models seem to have lost touch with this feature since yesterday, with the GFS being the only global model left which really plays with this. Despite the lack of model support, the pattern is just about as favorable as you can want it to be in early May with the Kelvin Wave and MJO pulse coming across together, and the potential for the formation of a tropical depression is definitely there. As this feature has been proving over the last couple days, it will take time to organize into a consolidated area of low pressure, and I expect slow development of this area will continue over the next couple days, with little change in position as it meanders about the same general area.

On Friday, a longwave trough digging into the central US will draw a strong low-level southerly flow out of the Gulf of Mexico in association with a severe weather outbreak in the plains. Regardless of whether or not we have a tropical cyclone sitting down in the eastern Pacific at this time, this flow will likely pull some moisture northward over Central America, bringing heavy rains to areas of Honduras, El Salvador, Belize, Guatemala, and Mexico. With the southerly flow expected to stay in place for 3-4 days, this moisture may eventually affect the north gulf coast sometime early next week.

We shall see what happens!

Visible RGB Satellite: (click image for loop)



CIMSS 850mb vorticity (left) and 700mb vorticity (right):

   

Satellite-derived upper-level winds:



200mb vertical velocity: (green areas represent upward motion associated with the MJO)






Updated: 4:35 PM GMT on April 28, 2010

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Possible tropical mischief in the East Pacific?

By: Levi32, 4:27 PM GMT on April 26, 2010

A broad area of moderate convection continues to flare in the eastern Pacific, associated with convergence along the ITCZ, which is being enhanced both by a Kelvin Wave moving eastward across the far eastern Pacific and a positive MJO upward motion pulse currently moving over the area as well.

The whole area continues to be broad and disorganized, with no one area of convection persisting for more than 12 hours so far. Most of the convection has shifted northwestward overnight, with the deep convection previously observed south of Panama yesterday now mostly dissipated. The area of greatest low to mid-level turning is found near 8N, 88W, in association with a weak 850-700mb vorticity maximum west of Costa Rica. However, the overall vorticity field remains scattered around and spread out, and no consolidated system appears to be forming yet. This was expected with this kind of situation, and any organization of a low in this area will be slow to occur. The models, especially the GFS, continue to play around with this, and the GFS develops a weak tropical cyclone in 3-4 days west of Costa Rica. Given the pattern of fairly low wind shear associated with an upper high over the area, as well as a favorable pattern for heat buildup, the area will continue to be watched for mischief over the next several days.

Looking at the bigger picture, the next longwave trough to dig into the central US is going to draw a strong southerly flow out of the Gulf of Mexico and western Caribbean during the 4-7 day period. Regardless of whether or not there is a tropical cyclone sitting down in the eastern Pacific during this time, deep tropical moisture will likely be pulled northward over Central America and the western Caribbean, bringing heavy rains to these areas. This moisture may eventually affect the gulf coast.

We shall see what happens!

Visible RGB Satellite: (click image for loop)



CIMSS 850mb vorticity (left) and 700mb vorticity (right)



Satellite-derived upper-level winds:



200mb vertical velocity: (green areas represent upward motion associated with the MJO)










Updated: 4:28 PM GMT on April 26, 2010

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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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