Caribbean disturbance 94L dumping heavy rains on Jamaica

By: Dr. Jeff Masters , 4:44 PM GMT on June 05, 2011

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A large, wet, and disorganized tropical disturbance (Invest 94L) continues to spread heavy rain to the Central Caribbean near Jamaica. Rain has fallen continuously at Jamaica's Kingston Norman Manley Airport since midnight, with 1.89" having fallen from midnight to noon local time. Sustained winds of 24 mph also affected Kingston between 7am and 8am this morning. Satellite-estimated rainfall amounts of 1.4" per hour occurred in ocean regions 100 miles to the southeast of Kingston this morning, and heavy rains of up to 1/2" per hour are probably affecting portions of Jamaica early this afternoon, judging by the recent increase in heavy thunderstorm activity seen on visible satellite loops. This imagery also shows a slow increase in organization of 94L in recent hours, with spiral bands beginning to develop to the southeast of the center. There is a broad, poorly-defined circulation apparent that is not well enough defined to make 94L a tropical depression. Water vapor satellite loops show a region of dry air on the west side of 94L, and this dry air is interfering with the storm's organization. However, upper air balloon soundings from Kingston and the Cayman Islands taken at 8am EDT this morning show much moister air at mid levels of the atmosphere compared to Saturday (2% humidity at 500 mb on Saturday, compared to 49% this morning at Grand Cayman), and 94L appears to be gradually overcoming its dry air issues. Wind shear remains in the moderate range, 15 - 20 knots, and is predicted by the SHIPS model to remain below 20 knots through Tuesday morning. Water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm.


Figure 1. Rainfall rates of up to 1.4" per hour (pink colors) were estimated by the F-15 satellite for 94L at 6:02am EDT Jun 5, 2011.

Since 94L is so large and is battling dry air, it is taking its sweet time to develop, and today's mission by the Hurricane Hunters has been cancelled. A new mission is scheduled for Monday afternoon at 2pm EDT. This morning's 06Z model runs are pretty unimpressed with 94L, with most of them showing little or no development. At 2pm EDT on Sunday, NHC gave the disturbance a 40% of developing into a tropical depression by Tuesday. If 94L stays to the south, its chances of development are greater, since a band of very high wind shear of 30 - 50 knots lies over Cuba and the southern Bahama Islands. The disturbance is expected to meander slowly westward or northward over the next two days, with Jamaica and southeastern Cuba being the primary targets for very heavy rains of 4 - 8 inches through Tuesday. Haiti and Central Cuba can expect somewhat lesser rains of 3 - 6 inches. If 94L does develop into a tropical depression and moves northwards over Cuba by Wednesday, I don't see the storm attaining hurricane strength, due to the high wind shear. The primary threat from 94L will be very heavy rains, capable of causing life-threatening flash flooding.


Figure 2. Afternoon satellite image of the Central Caribbean disturbance 94L.

Jeff Masters

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1397. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127810
Quoting pottery:

And I feel vindicated. I was saying that at about 4:00 pm. or earlier.
I heard all the explanations, but was having real difficulty agreeing with them.


I felt like saying this earlier, but didn't, but you have to be careful of word on the street :)
Member Since: April 29, 2007 Posts: 0 Comments: 7833
Quoting wunderkidcayman:
so how many of you are agreeing that we are/will have/having a COC Reformation

say I


I
Member Since: September 2, 2006 Posts: 110 Comments: 6876
1394. Patrap
..its right dere Moe!!

94L Floater - Rainbow Color Infrared Loop
Member Since: July 3, 2005 Posts: 423 Comments: 127810
Quoting alfabob:
Jamaica is going to have problems


And blobfest continues off the east coast, another one off the coast of the OBX.
Member Since: September 2, 2006 Posts: 110 Comments: 6876
I sure hope it looks good in the morning so they can send recon. out and settle this debate!
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Quoting pottery:

And I feel vindicated. I was saying that at about 4:00 pm. or earlier.
I heard all the explanations, but was having real difficulty agreeing with them.


We will know soon enough whether we have a center relocation. There was no doubt in my mind earlier that the area of lowest pressure was off near 80 W. Tonight I am seeing something else based not just on the satellite imagery, which can be deceiving at the best of time, but based upon the much weaker 850 vort signature, the surface low pressure obs and the 925 mb vorticity.

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Quoting wunderkidcayman:
so how many of you are agreeing that we are/will have/having a COC Reformation

say I
I'm not completely sold on it yet, as I don't think there's quite enough evidence just yet. I'll just say maybe. :P
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Quoting 1992Andrew:
How strong will shear be to its north and west?

Both the SHIPS and GFS bring it to at least 30 kt as early as Tuesday afternoon and/or evening. The former actually goes as high as 49 kt (rounded to 50 kt) by 60 hours.
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1388. Patrap
00z Early Cycle NHC model tracks
Invest94
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)






Dynamic Models (More sophisticated models)




Early Model Wind Forecasts
Member Since: July 3, 2005 Posts: 423 Comments: 127810
so how many of you are agreeing that we are/will have/having a COC Reformation

say I
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1386. beell
498. beell 8:38 PM GMT on June 05, 2011

If 17.5N 76.5W is mid level it sure is hard to ignore what appears to be a feeder band SW of this point working its way to the east
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1385. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127810
1384. Levi32
Quoting kmanislander:


You should be studying law LOL


LOL
Member Since: November 24, 2005 Posts: 635 Comments: 26600
1383. pottery
Quoting KoritheMan:
I'm beginning to agree with kman et al about a possible center relocation. While the current surface low is still evident, there is very little evidence of a well-defined circulation in that vicinity based on shortwave IR imagery.

And I feel vindicated. I was saying that at about 4:00 pm. or earlier.
I heard all the explanations, but was having real difficulty agreeing with them.
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1382. Levi32
Quoting KoritheMan:
I'm beginning to agree with kman et al about a possible center relocation. While the current surface low is still evident, there is very little evidence of a well-defined circulation in that vicinity based on shortwave IR imagery.


IR2 isn't proving too useful tonight, but based on sunset visible images, the original surface low was in the process of slowly weakening. I doubt an entirely new surface low has formed yet, but it may later tonight if convection can develop consistently.
Member Since: November 24, 2005 Posts: 635 Comments: 26600
Quoting 1992Andrew:
Not that the invest will become a hurricane (hardly that), but here's a revealing fact about the formation of hurricanes in the month of June:

"Since 1960, or in the past 50 years, only eight Atlantic basin hurricanes have formed in June or earlier. That’s an average of one every 6.25 years." -Suntinel website.


I wonder how strong this system will become before it is destroyed by shear in the northern caribbean / Gulf of Mexico. How strong will shear be to its north and west?



It's also a matter of how strong the anticyclone will be so it can fend off that shear and also a question of how strong the shear will be, oh well, guess we will cross that bridge when we get there.
Member Since: September 2, 2006 Posts: 110 Comments: 6876
Be gone 94L! You're just a monsoon low. You may be interfering with or blocking the normal flow of moisture to the US. We need afternoon thunderstorms, not your deluges!
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Quoting Levi32:


The only thing is I don't know what those isobars are generated from. If it's directly from in situ surface obs then that's questionable, since they are scattered. If from model input, then also questionable. It will be interesting to see if buoy 42057 shows a pressure min tonight due to the first low center passing.
just wondering that myself...
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Quoting hurricanehunter27:
Convection is blowing up again S of jamaica


This is exactly what we expected, a lull from 94L then BAM!
Member Since: September 2, 2006 Posts: 110 Comments: 6876
I swear didn't we see this episode with Alex last yr.? I mean COC racing off to the Southwest away from the MLC leading to a reformation that's coalescing with the deepest convection.
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Not that the invest will become a hurricane (hardly that), but here's a revealing fact about the formation of hurricanes in the month of June:

"Since 1960, or in the past 50 years, only eight Atlantic basin hurricanes have formed in June or earlier. That’s an average of one every 6.25 years." -Suntinel website.


I wonder how strong this system will become before it is destroyed by shear in the northern caribbean / Gulf of Mexico. How strong will shear be to its north and west?

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1373. Patrap
GFDL 10m Wind Speed & Sea Level Pressure

Member Since: July 3, 2005 Posts: 423 Comments: 127810
Quoting Levi32:


I did say I agreed with the position shown on the map. I did not comment on its accuracy as a product though.


You should be studying law LOL
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1370. Levi32
Quoting kmanislander:


Earlier when I posted them to support your conclusion of a low center farther West you didn't have a problem with it though. You have to be consistent Levi


I did say I agreed with the position shown on the map. I did not comment on its accuracy as a product though, or contribution as evidence. I spoke only of agreeing with its coordinates.
Member Since: November 24, 2005 Posts: 635 Comments: 26600
1369. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127810
1368. Levi32
Quoting spathy:


Excuse my ignorance.
Why does that analysis always look more organized that than Other info we see on a storm?


Because a broad, closed low consisting of mostly 10-knot winds is not really considered organized.
Member Since: November 24, 2005 Posts: 635 Comments: 26600
I'm beginning to agree with kman et al about a possible center relocation. While the current surface low is still evident, there is very little evidence of a well-defined circulation in that vicinity based on shortwave IR imagery.
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Quoting Levi32:


The only thing is I don't know what those isobars are generated from. If it's directly from in situ surface obs then that's questionable, since they are scattered. If from model input, then also questionable.


Earlier when I posted them to support your conclusion of a low center farther West you didn't have a problem with it though. You have to be consistent Levi
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One thing that everyone can agree upon is that 94L has been a very puzzling system.
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1364. Patrap
94L Enhanced Infrared (IR) Imagery (4 km Mercator) Loop
Member Since: July 3, 2005 Posts: 423 Comments: 127810
The 00z surface analysis shows the low stationary.

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1362. Levi32
One thing's for sure, a relocation would place 94L under a much better upper-level environment, more centered beneath the upper anticyclone. It would be in its best interest to relocate.
Member Since: November 24, 2005 Posts: 635 Comments: 26600
ULAC is moving SW away from 94L

Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting kmanislander:
Take a look at this. The area of lowest pressure is now much farther East near to the area I was just referring to.


You've been calling it all night...good job!
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1358. Levi32
Quoting kmanislander:
Take a look at this. The area of lowest pressure is now much farther East near to the area I was just referring to.



The only thing is I don't know what those isobars are generated from. If it's directly from in situ surface obs then that's questionable, since they are scattered. If from model input, then also questionable. It will be interesting to see if buoy 42057 shows a pressure min tonight due to the first low center passing.
Member Since: November 24, 2005 Posts: 635 Comments: 26600
925 mb vorticity is also back to the East

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Quoting kmanislander:


Maybe, but that area near 17 / 77 sure looks like a center relocation to me.

I have been saying this from when I saw it was developing a good MLC
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Take a look at this. The area of lowest pressure is now much farther East near to the area I was just referring to.

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To me it looks like the extremely broad "surface low" keeps drifting west while the other mid-level center just south of Jamaica is just sitting there and the two are getting farther and farther apart. I've said this before and I'll probably be wrong, but I am going to maintain my earlier prediction that the MLC will take over. Heck, what have I got to lose.
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Quoting Levi32:


We won't really know until daylight or a possible ASCAT pass coming up shortly.


If its at 77W then the invest hasn't gain much distance because it keeps relocating to its back. Sure will take advantage of Dmax.
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Quoting KanKunKid:


Yeah, well, we've all been there...eh Dewey?

There was a little more to it than that, but that will suffice. Some of us are just too darn funny for our own good, not Storm of course, but some of us..
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plus there is also a few spots of convection starting to increase near the MLC
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1349. Patrap
Member Since: July 3, 2005 Posts: 423 Comments: 127810
1348. Patrap
94L Multiplatform Satellite Surface Wind Analysis 00Z
Member Since: July 3, 2005 Posts: 423 Comments: 127810
1347. Levi32
Quoting kmanislander:


Maybe, but that area near 17 / 77 sure looks like a center relocation to me.


We won't really know until daylight or a possible ASCAT pass coming up shortly.
Member Since: November 24, 2005 Posts: 635 Comments: 26600

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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