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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1497. pottery
Quoting kmanislander:


A riddle within an enigma. Time to turn in. The convection is steadily expanding tonight so let's see where we stand tomorrow. We know that an intense cluster of thunderstorms has the capability to create a new area of lowest pressure underneath it.

Back in the morning.

Good night all.

Seen.
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1496. Levi32
Quoting pottery:

Well, What the BEEEP !??
I think I will have to go to bed.
This one is Crazy...

Stay Safe all.
It's tomorrow already here.


It actually kinda makes sense. The surface low was far too well-defined this afternoon to have been replaced already. It would be a slow process. The new burst of convection may prompt a relocation, or not, depending on how long it lasts.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
Seems there is an upper level low organizing to the south of 94L. Also visible in WV.

200mb

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1494. pottery
Quoting beell:


Normally, in the absence of a monsoon, the vorticity of a single circulation is apparent. A basin wide circulation is another story. The vorticity dances around quite a bit.

Here it is at 700mb stretching to the Pacific on the west side of the monsoon.

Link

Thanks!
I will study that in the AM.
I'm out>>>>>>
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Quoting pottery:

Looking forward to your thoughts.....
On this one, I have no idea!


A riddle within an enigma. Time to turn in. The convection is steadily expanding tonight so let's see where we stand tomorrow. We know that an intense cluster of thunderstorms has the capability to create a new area of lowest pressure underneath it.

Back in the morning.

Good night all.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
I really like that the NHC is conservative. This system has more negatives in its path than positives -and designating a system a TD (when it will only dissipate or be a rainmaker) can unnecessarily cause too much negative media attention and affect insurance, closings, etc. This system could maybe be a TD now - but too much shear (30-50kts) in its path for any further development so not really a threat to people. Right now it is just going to soak Florida.

In summary, I would be really surprised if they ever even declare it a TD - because of what i stated above.

I am not a "downcaster," but am really starting to understand the reasonings behind the NHC forecasts sometimes.
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Quoting Drakoen:
The low level center is still well west of that new burst of convection and the upper level high remains in an unfavorable position south of the LLC.

Hey Drak. good to see ya again. How was your off season?
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1489. pottery
Quoting Levi32:
As fresh as they come:

It would seem that the low remains broad and has not relocated yet.


Well, What the BEEEP !??
I think I will have to go to bed.
This one is Crazy...

Stay Safe all.
It's tomorrow already here.
Member Since: Posts: Comments:
1488. beell
Quoting pottery:

I didnt know that. Thanks!


Normally, in the absence of a monsoon, the vorticity of a single circulation is apparent. A basin wide circulation is another story. The vorticity dances around quite a bit.

Here it is at 700mb stretching to the Pacific on the west side of the monsoon.

Link
Member Since: September 11, 2007 Posts: 137 Comments: 15330
1487. JLPR2
So 94L looks prettier but it is just appearances?
I just wish it would move out of the Caribbean.
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1486. Drakoen
The low level center is still well west of that new burst of convection and the upper level high remains in an unfavorable position south of the LLC.
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The longer 94L remains a large but disorganized area of disturbed weather, the sooner this blog will become disorganized and disturbed. The window of opportunity for 94L is closing soon.
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Quoting Levi32:
As fresh as they come:

It would seem that the low remains broad and has not relocated yet.

Well that explains a lot.
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1483. pottery
Quoting kmanislander:


We have conflicting maps. The 925 mb map shows the vorticity back where the convection is now firing. That is 2500 feet up. The cold cloud tops I just posted are around 50,000 feet. The 850 vort map is 5000 feet. I have to think about this one.

Looking forward to your thoughts.....
On this one, I have no idea!
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1482. Patrap
Member Since: July 3, 2005 Posts: 415 Comments: 125628
1481. Levi32
As fresh as they come:

It would seem that the low remains broad and has not relocated yet.

Member Since: November 24, 2005 Posts: 628 Comments: 26455
Quoting Levi32:


Latest 925mb shows an elongated vorticity region.



Surface pressure has spread out as well. I think I will leave this until tomorrow.

Interesting feature, this 94L
Member Since: August 19, 2006 Posts: 0 Comments: 15671
Aussie, seems that the afternoon isnt too friendly to 94L(PM Heating)
94L status:
12AM to 1PM: good convection
1PM to 10PM: Dissipating Convection
10PM to 12AM: Refire, and Restart
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Quoting Levi32:


Latest 925mb shows an elongated vorticity region.

Perhaps indicative of a transitioning center location?
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1477. Patrap
Most of the tourist flourish here in the Vieux Carre at Night easily.

Most fizzle after dawn as well.
Member Since: July 3, 2005 Posts: 415 Comments: 125628
1476. Levi32
Quoting AussieStorm:

I guess for the NHC to take it seriously. meaning to send the HHers to it. 94L needs to maintains it's convection during the day and not just fire up at night.


Precisely.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
1475. pottery
Quoting AussieStorm:

Going ok mate. you getting that concrete poured soon, any phone calls on it yet?

The crew called to say that the 2" of rain yesterday held them back on another site. Could not make it today.
Today we dried out real nice.
Hoping tomorrow works out...
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1474. Levi32
Quoting kmanislander:


We have conflicting maps. The 925 mb map shows the vorticity back where the convection is now firing. That is 2500 feet up. The cold cloud tops I just posted are around 50,000 feet. The 850 vort map is 5000 feet. I have to think about this one.


Latest 925mb shows an elongated vorticity region.

Member Since: November 24, 2005 Posts: 628 Comments: 26455
1473. 7544
im thinking if it does develope its going northward the same path fay took models will start to show that soon only my opinon . but seems to be trying to get its act together now again we should see another good dmax tonight .
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Quoting Levi32:


Diurnal cycles really do a number on most invests.

I guess for the NHC to take it seriously. meaning to send the HHers to it. 94L needs to maintains it's convection during the day and not just fire up at night.
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KORITHE MAN - nice blog post. it really answered some of my questions. why do we think the track will shift east? to me the models are still pretty spread at this point..
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Quoting AussieStorm:

Didn't it blow up last night? Seems it prefers the night life to day life. Awake at night and asleep during the day.


Tropical systems all prefer the cool of the night because that is when they flourish. No hot sun to interfere with the cold cloud tops.
Member Since: August 19, 2006 Posts: 0 Comments: 15671

Quoting HurricaneDean07:
94L should be 50% at the next TWO, 91E should be 70-80% chance because the DMIN hit it HARD.
91E should stay 90%. It has strong model support for development tomorrow, and it also has an excellent structure, which continues to improve.
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Quoting pottery:

Like Aussies!
LOL

How is it, Aussie?

Going ok mate. you getting that concrete poured soon, any phone calls on it yet?
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91E isnt looking so well 94L, Oh God it going to throw up! run 94L! Form into a Tropical Depression and run to florida! and change your name to Arlene!
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1465. pottery
Quoting beell:


CIMSS sees the larger scale vorticity associated with the monsoonal circulation.

I didnt know that. Thanks!
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Quoting pottery:

How do we explain that one?


We have conflicting maps. The 925 mb map shows the vorticity back where the convection is now firing. That is 2500 feet up. The cold cloud tops I just posted are around 50,000 feet. The 850 vort map is 5000 feet. I have to think about this one.
Member Since: August 19, 2006 Posts: 0 Comments: 15671
94L should be 50% at the next TWO, 91E should be 70-80% chance because the DMIN hit it HARD.
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1461. Levi32
Quoting AussieStorm:

Didn't it blow up last night? Seems it prefers the night life to day life. Awake at night and asleep during the day.


Diurnal cycles really do a number on most invests.
Member Since: November 24, 2005 Posts: 628 Comments: 26455
1459. pottery
Quoting AussieStorm:

Didn't it blow up last night? Seems it prefers the night life to day life. Awake at night and asleep during the day.

Like Aussies!
LOL

How is it, Aussie?
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1458. beell
Quoting pottery:

How do we explain that one?


CIMSS sees the larger scale vorticity associated with the monsoonal circulation.

ADDED: at 850mb (approx 5,000')
Member Since: September 11, 2007 Posts: 137 Comments: 15330
1457. Patrap
Indeed aussie,,these Big Monsoonal ones take some time to gather the momentum seems.



Member Since: July 3, 2005 Posts: 415 Comments: 125628
1456. KEEPEROFTHEGATE (Mod)
XX/INV/94L
MARK
16.89N/78.10W
Member Since: July 15, 2006 Posts: 165 Comments: 52265
Quoting kmanislander:
Here is the latest 850 vorticity map. Pass the Aleve please LOL



925 also decayed a bit.

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Quoting kmanislander:


4:01. Ramping up


Didn't it blow up last night? Seems it prefers the night life to day life. Awake at night and asleep during the day.
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1452. pottery
Quoting kmanislander:
Here is the latest 850 vorticity map. Pass the Aleve please LOL


How do we explain that one?
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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.



Well, they are most likely going with the documented COC (05/2345 UTC 17.0N 80.2W TOO WEAK 94L -- Atlantic ) which is sitting in 30kts of shear and doesn't look to improve. In that sense they are right. However, should the center reform east and is documented they may change there tune and rightly so because 5-10kts exists in that region.
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Quoting Tropicsweatherpr:


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?
Well, such systems are typical of June. Same with October/November systems.

I do not know if we will see more such systems. That is pretty much impossible to tell, but it will depend at least partially on how low sea level pressures get over a given region at any given time.
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Quoting 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.


4:01. Ramping up

Member Since: August 19, 2006 Posts: 0 Comments: 15671

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About JeffMasters

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