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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Quoting tennisgirl08:
good evening guys, i have a question about the NHC mentioning unfavorable upper level winds. even if it does "develop" will those winds shred 94L or possible future TD apart? or can we still expect a rainmaker in the gulf?


Also, doesn't 94L have 40-50kts of shear in its path if it heads NW or WNW or even N?? Is this what the NHC is referring to?

My question is whether a mediocre system could survive this at all - or will it still bring us much needed rainfall??
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Quoting 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

Going by that bottom wind forecast, Nothing much is going to happen up to 156hrs. This thing could be there for the next week.
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Levi, looking to be so, i think the next or two cycle will seal the deal with TD status, Recon tomorrow here we come!
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1443. Patrap
The ATCF link thru that one works well most the time.
Member Since: July 3, 2005 Posts: 428 Comments: 129904
1442. beell
Quoting Patrap:
why there ya go..

Service wit a smile as its da sharing that makes it cool here


I think I got it from one of your previous posts a couple years ago.
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1441. Levi32
The new burst of convection could very well seal the development of a new surface low. Such a pattern is classic of developing broad systems.
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1440. pottery
Quoting wunderkidcayman:
I curently have the reformed center at 16.8N 77.6W right underneath the new blow up of convection

If it is confirmed that the center is relocated there, you got it right today!
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Leavin' on a Southern train....
Member Since: October 8, 2008 Posts: 14 Comments: 4553
good evening guys, i have a question about the NHC mentioning unfavorable upper level winds. even if it does "develop" will those winds shred 94L or possible future TD apart? or can we still expect a rainmaker in the gulf?
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Here is the latest 850 vorticity map. Pass the Aleve please LOL

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Quoting KoritheMan:

Speak for yourself. I'm getting a headache just tracking it. Seriously. :P


pottery, this thing has been thru twists and turns and ups and downs many times.

KoritheMan, to think that the season is only in it's first days tracking this disturbance of moonsonal origin.Will the season have more systems like these?
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Quoting HurricaneDean07:
Quoting TWC:
That is BS, The latest Tropical Update states that the low is in too strong of Shear to form, My !*^(sorry for being fed up with TWC's Consevative act as always)
Latest Shear, Although the anticyclone is displaced to the SW it still in 5 to 10 knots of shear

Shut you mouth weather channel and do some research for once... *sighs* okay... back to the MOST LIKELY FORMATION of 94L.
LOL

TWC amazes me, I can never understand how you can have that much staffing and enough money to maintain a website and a 24 hr weather channel and still be so bad at forecasting and analyzing.

Granite, they aren't horrible, but for the amount of effort, time, and money they invest in their system, the net product is pretty bad.
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1434. xcool


00z
Member Since: September 26, 2009 Posts: 2 Comments: 15684
xcool, looks to be that the dry air has been put at bay, and even the dry air to the north is not really much trouble for 94L, so moistening up nicely.
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1432. Patrap
why there ya go..

Service wit a smile as its da sharing that makes it cool here
Member Since: July 3, 2005 Posts: 428 Comments: 129904
1431. beell
Quoting sammywammybamy:


Patrap, If its not too much.

May i have a link for those Black model plots..

You gave it to me last year.. but i got a new computer.. cause my old one bit the dust


raleighwx.americanwx.com
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1430. xcool





Member Since: September 26, 2009 Posts: 2 Comments: 15684
1429. mbjjm
I have a powerpoint of the radar images out of Jamaica. click download this file andopen powerpoint press f5 to view the loop, It was between the hours of 5pm-10pm edt this evening.

Radar loop June 5
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Its fun to vent, especially about how conservative TWC, theyre 100 times more conservative than the NHC, and even when they use the NHC for most of all of their hurricane information(that is if there is a named storm out in the basin)
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1427. EricSFL
Quoting HurricaneDean07:
Quoting TWC:
That is BS, The latest Tropical Update states that the low is in too strong of Shear to form, My !*^(sorry for being fed up with TWC's Consevative act as always)
Latest Shear, Although the anticyclone is displaced to the SW it still in 5 to 10 knots of shear

Shut you mouth weather channel and do some research for once... *sighs* okay... back to the MOST LIKELY FORMATION of 94L.


Lately, they have been blaming all sorts of lack of tropical development to shear.
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Quoting TWC:
That is BS, The latest Tropical Update states that the low is in too strong of Shear to form, My !*^(sorry for being fed up with TWC's Consevative act as always)
Latest Shear, Although the anticyclone is displaced to the SW it still in 5 to 10 knots of shear

Shut you mouth weather channel and do some research for once... *sighs* okay... back to the MOST LIKELY FORMATION of 94L.
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@ TexasGulf

Man, I bet that rain was nice! Things are dry and toasty here in north central florida. We need some relief soon. I hope 94L moves north and gives peninsula Florida some soaking rains.
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Quoting Patrap:
I had 17.3 N 78.8 W Kman by the last 5 frames
yes sir.
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1421. pottery
'
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1418. pottery
Quoting kmanislander:


Yeah, he lives half a mile away from me LMAO

Ah !
I had no idea...
This blog can be a place filled with Dangers for the unaware LOLOL!
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Quoting Patrap:
I had 17.3 N 78.8 W Kman by the last 5 frames


Close enough
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I curently have the reformed center at 16.8N 77.6W right underneath the new blow up of convection
Member Since: June 13, 2009 Posts: 2 Comments: 12719

Quoting TexasGulf:
A nice storm cell moved through Kingwood, Texas (NE of Houston) about 7:00pm. We just got power restored about 10:00pm.

There was some marble sized hail and about 1" of welcome rain in the span of 1/2 an hour. The wind was outrageous, though. Wind gusts at a neighborhood level were every bit as high as those I saw in the eye-wall of Hurricane Ike. My rough guesstimate would be winds in the 70-80 mph range, pretty much constant for about 15-minutes. Several trees went down in the neighborhood, trash cans blowing down the street... the usual stuff. It was quite a powerful little storm cell. At one point, from the swirling and change in wind direction, I could swear it was trying to produce a vortex.

Anyway, that was impressive for such a small, isolated storm cell.
I wish I could have been there. :(
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Quoting tropicfreak:


And blobfest continues off the east coast, another one off the coast of the OBX.
And don't forget Haiti. They are getting way too much rain.
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1412. Patrap
I had 17.3 N 78.8 W Kman by the last 5 frames
Member Since: July 3, 2005 Posts: 428 Comments: 129904
Quoting pottery:

LOL to that!


Yeah, he lives half a mile away from me LMAO
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Quoting pottery:

I didnt doubt that the Low was around 80W, but it seemed that it was not sustainable there to me.
I find this a most interesting system, monsoonal or not, it's filled with surprises!


Very true.
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1409. pottery
Quoting stormpetrol:


I felt like saying this earlier, but didn't, but you have to be careful of word on the street :)

LOL to that!
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A nice storm cell moved through Kingwood, Texas (NE of Houston) about 7:00pm. We just got power restored about 10:00pm.

There was some marble sized hail and about 1" of welcome rain in the span of 1/2 an hour. The wind was outrageous, though. Wind gusts at a neighborhood level were every bit as high as those I saw in the eye-wall of Hurricane Ike. My rough guesstimate would be winds in the 70-80 mph range, pretty much constant for about 15-minutes. Several trees went down in the neighborhood, trash cans blowing down the street... the usual stuff. It was quite a powerful little storm cell. At one point, from the swirling and change in wind direction, I could swear it was trying to produce a vortex.

Anyway, that was impressive for such a small, isolated storm cell.
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Quoting pottery:

I find this a most interesting system, monsoonal or not, it's filled with surprises!
Speak for yourself. I'm getting a headache just tracking it. Seriously. :P
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Here you go. 45 minutes later than the post I just put up at 1400

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1404. pottery
Quoting kmanislander:


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.


I didnt doubt that the Low was around 80W, but it seemed that it was not sustainable there to me.
I find this a most interesting system, monsoonal or not, it's filled with surprises!
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Well Goodnight everyone, we'll see what tomorrow brings. Take care.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
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.

Agreed. I think by morning we will be watching 17 79.

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Check out another blob off the east coast, probably from the thunderstorms that rolled through here in VA early this morning, which was one heck of a line of loud storms, now it's out in the atlantic, maybe development???
Member Since: September 2, 2006 Posts: 110 Comments: 6878
17 N 78 W. The focal point for the next round of intense thunderstorm activity which is commencing now.

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Quoting CyclonicVoyage:
ULAC is moving SW away from 94L


also I said earler that ove the MLC there is 5-10kt shear you zoomed in and that shows it prefectly
Member Since: June 13, 2009 Posts: 2 Comments: 12719
1397. Patrap
Member Since: July 3, 2005 Posts: 428 Comments: 129904

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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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