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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Yea your right Levi, some reason the NOGAPS on that site is not working right and I didn't loop it. But it does indeed show two systems.
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Quoting MiamiHurricanes09:
Sounds great. Let me know.
miami does it look like the center SW of jamaica is reforming closer to the midlevel center i see a band of convection begining to wrap around what appears to be a new center
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Quoting charlottefl:
Levi-


Doing this from memory, so the locations are rough, is this basically what you're seeing?
Photobucket


The center of the broad surface circulation is farther west, though the center of greatest low-level vorticity is probably closer to 79.5W.
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Tampa NWS:

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY)...MID/UPPER
LEVEL RIDGING WILL HOLD OVER THE SOUTHEAST U.S DURING MIDWEEK THEN
WEAKEN LATE IN THE WEEK INTO NEXT WEEKEND AS A LOW SETS UP OVER
THE GULF OF MEXICO. MEANWHILE AT THE SURFACE THE RIDGE AXIS WILL
REMAIN JUST NORTH OF THE REGION WITH AN INVERTED TROUGH/WEAK AREA
OF LOW PRESSURE EXPECTED TO DRIFT NORTHWESTWARD FROM THE CARIBBEAN
INTO THE SOUTHEAST GULF. THIS WILL BRING AN INCREASE IN MOISTURE
LATE IN THE WEEK INTO NEXT WEEKEND LEADING TO A BETTER CHANCE OF
AFTERNOON AND EVENING THUNDERSTORMS.
FOR NOW HAVE LEFT THE SLIGHT
CHANCE POPS FOR WEDNESDAY THROUGH FRIDAY AND GONE WITH CHANCE POPS
FOR THE CENTRAL AND SOUTH ON SATURDAY. TEMPERATURES WILL REMAIN
NEAR TO SLIGHTLY ABOVE NORMAL THROUGH THE PERIOD.
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Quoting kmanislander:


Correct. All a matter of nuance LOL.

The point I was making, somewhat in shorthand, was that yes there is a spin in the middle levels but that overall the circulation was fairly well stacked.


Fair enough. It certainly looks stacked from top to bottom on the vort maps.
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Quoting Grothar:


You're OK, 09. So, you've been following my coverage of this event for the past few days? I nailed it. Right to the location and timing and all. Even got it in right before Dr. Masters new post. The only thing is my arm hurts for patting myself on the back. LOL

I would do a video-blog but I don't think any of you would like my accent. I'll give you a sample and you let me know.
Sounds great. Let me know.
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Quoting CybrTeddy:


NOGAPS appears to be the same system.
Link

Same with the CMC though kills it off once it reaches the GOMEX.


NOGAPS shows two separate systems, with 94L moving into the Gulf of Mexico.
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Getting some nice rain here now. I hope it lasts the rest of the day :-)
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Quoting pottery:

That is an Incredible loop.
Look at the thunderstorms at the bottom of the image, especially bottom left and over eastern Maracaibo.
Lightening is clearly visible.


That is the reflection of the sun moving across.
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Quoting caneswatch:


That looked like a Cat. 1 to me. A Cat. 2-3 is very unlikely, yes. But, a Cat. 1 isn't out of the question.


Hmm, it was an awful lot of low pressure lines. I guess as cat 1 is very slightly acheivable, though I would still have my doubts.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting MississippiWx:


I think we pretty much agree. Lol. The mid-level spin (or gyre) is making the system look better than it really is, like always.


Correct. All a matter of nuance LOL.

The point I was making, somewhat in shorthand, was that yes there is a spin in the middle levels but that overall the circulation was fairly well stacked.
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Quoting Hugo7:
I know the Atlantic is exciting and all, but Does no one care that models on 91 put it at being a TS storm strenght in 24hours? Also to note it suggest that it will move up along the coast to gulf of cali.


NHC delayed updating on it and I was thinking maybe they were on the verge of initiating advisories, but the 18Z update still has it as a disturbance (DB). Normally they change to a low (LO) before they start advisories. You are right, SHIPS has it a hurricane in 48 hours, and the rapid intensification index is at 64% for a 25 kt increase.

91E 18Z SHIPS
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Quoting NICycloneChaser:


I really can't see a cat 2/3 hurricane landfalling on the GoM coast in 5 days. I guess I could be wrong, but I don't think it's a possibility.


That looked like a Cat. 1 to me. A Cat. 2-3 is very unlikely, yes. But, a Cat. 1 isn't out of the question.
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Quoting Levi32:
The surface low is broad, which means it could focus itself in many different places by developing a vort max on the edge of the circulation. Looking at visible loops, it is possible that the low is forming one such vort max just to the southwest of the Jamaican island, which makes sense given that the low pressure should tend to strengthen as close to the convection as possible.


I don't think there is any question the east side of the elongated surface low is where the focus of convergence is.

Thanks for the update.
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Quoting Levi32:


That's not model support. That's an entirely separate entity that they develop.


I would think it is more important to note that the models are now developing something

I mean for those who end up being affected by whatever happens; whether it be just beneficial rains or more; I really do not think they care less whether its from 94L or something else
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Quoting Levi32:
The surface low is broad, which means it could focus itself in many different places by developing a vort max on the edge of the circulation. Looking at visible loops, it is possible that the low is forming one such vort max just to the southwest of the Jamaican island, which makes sense given that the low pressure should tend to strengthen as close to the convection as possible.


That is an Incredible loop. POST 263.
Look at the thunderstorms at the bottom of the image, especially bottom left and over eastern Maracaibo.
Lightening is clearly visible.
Member Since: October 24, 2005 Posts: 0 Comments: 24874
Quoting kmanislander:


Ah, here is what I posted in response to your post. A gyre is a spin.

The circulation is pretty much aligned all the way from the surface to 500 mbs if you look at the maps. .There is a spin slightly off to the ENE of the main circulation but it is not really interfering with the system apparently and may just be a temporary gyre within the overall circulation itself


I think we pretty much agree. Lol. The mid-level spin (or gyre) is making the system look better than it really is, like always.
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Quoting charlottefl:
Levi-


Doing this from memory, so the locations are rough, is this basically what you're seeing?
Photobucket
that looks about right
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Quoting sammywammybamy:
I wouldn't blame them hoping for a weak TS.... The current setup is not allowing the desperately needed rainy season to begin for south and central Florida.
I'm here and just praying for rain..lawn dead!
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Quoting Levi32:


That's not model support. That's an entirely separate entity that they develop.


NOGAPS appears to be the same system.
Link

Same with the CMC though kills it off once it reaches the GOMEX.
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looks like the midlevel circulation south of jamaica is trying to merge with the main circulation off SW jamaica and i have noticed that convections continues to increase over the circulation off SW jamaica
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Quoting Levi32:


That's not model support. That's an entirely separate entity that they develop.


Nevertheless, the CMC, NOGAPS, GFDL and HWRF all now show at least a tropical storm.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Levi-


Doing this from memory, so the locations are rough, is this basically what you're seeing?
Photobucket
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Quoting CybrTeddy:


Model support has actually increased today, CMC & NOGAPS. GFS develops 'something' perhaps from energy related to 94L into a cyclone N of Puerto Rico.


That's not model support. That's an entirely separate entity that they develop.
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Quoting MississippiWx:


LOL...So you agreed with Levi, but not me when I said the same thing? All I was trying to say in my original post was that the circulation in the middle of the convection is mid-level. I wasn't really talking about a stacked low. :-)


Ah, here is what I posted in response to your post. A gyre is a spin.

The circulation is pretty much aligned all the way from the surface to 500 mbs if you look at the maps. .There is a spin slightly off to the ENE of the main circulation but it is not really interfering with the system apparently and may just be a temporary gyre within the overall circulation itself
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One problem 94L has is that its not vertically stacked and this is inhibiting rapid development. That's why we're not seeing it develop as quickly as some people might have expected it too.
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Quoting caneswatch:


5 days out. If that shear up in the GOM moves out, that's a possibility.


I really can't see a cat 2/3 hurricane landfalling on the GoM coast in 5 days. I guess I could be wrong, but I don't think it's a possibility.
Member Since: August 10, 2010 Posts: 2 Comments: 1971
Quoting IKE:

lol.

Or are you serious? You think it's going to Florida too?


I hope it comes here.
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Quoting AllStar17:


Is it not possible for that circulation to overtake the other one?


That mid-level rotation appears insignificant, as it looks like one of those features left behind from collapsing thunderstorms, and a portion of that complex did collapse within the last several hours. Such mid-level rotations rarely have significant impact. It should dissipate within the next several hours.
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Greetings all! Such divergent models, it's crazy and confounding. Just a waiting game I guess. Thanks ya'll for all the great graphics. Much appreciated.
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265. IKE

Quoting EricSFL:


If shear is low, then what is keeping the low level coc dislocated from the convection?
The convection is a lot closer this afternoon. I'm not an expert but it appears to be aligning itself better.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting charlottefl:
then we have more than one vort. I see the second on the W edge of the convective mass.


I dont think that goes to the surface though.
It is pretty well stacked, but not entirely.
See KMan's earlier post with the vorts at different levels.
Member Since: October 24, 2005 Posts: 0 Comments: 24874
The surface low is broad, which means it could focus itself in many different places by developing a vort max on the edge of the circulation. Looking at visible loops, it is possible that the low is forming one such vort max just to the southwest of the Jamaican island, which makes sense given that the low pressure should tend to strengthen as close to the convection as possible.

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will it hit Florida?


just kidding!!! I couldn't resist.
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Quoting IKE:

Not according to the latest CMC bomber....




5 days out. If that shear up in the GOM moves out, that's a possibility.
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Quoting IKE:
Shear is low near 94L......high pressure helping it...




If shear is low, then what is keeping the low level coc dislocated from the convection?
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Quoting kmanislander:


Agreed


LOL...So you agreed with Levi, but not me when I said the same thing? All I was trying to say in my original post was that the circulation in the middle of the convection is mid-level. I wasn't really talking about a stacked low. :-)
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258. Hugo7
I know the Atlantic is exciting and all, but Does no one care that models on 91 put it at being a TS storm strenght in 24hours? Also to note it suggest that it will move up along the coast to gulf of cali.
Member Since: June 1, 2011 Posts: 0 Comments: 64
Quoting Levi32:
Despite lack of model support, there is still a chance for 94L. We will have to see if it can make any progress today. Pressures at this buoy west of the center should be watched to see if they get below 1007mb today. The latest diurnal peak ringed in a bit lower than previous peaks.


Model support has actually increased today, CMC & NOGAPS. GFS develops 'something' perhaps from energy related to 94L into a cyclone N of Puerto Rico.
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256. IKE

Quoting Grothar:


Hey, one must keep the "will it hit South Florida' casters happy, too!
I'm surprised there aren't more of them on yet.

Bastardi said this 14 hours ago via Tweeter......

Joe Bastardi




94L slowly getting better
organized.Heavy rain still the main story next few days,rather than
this moving north(think it will late next wk)

Member Since: June 9, 2005 Posts: 23 Comments: 37860
Levi: In your tropical tidbit, you paint the circle where the COC is located. Through RGB satellite, I honestly thought the COC is south of western Jamaica. Not closer to the Nicaraguan / Honduran border. Thanks for the clarification.

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then we have more than one vort. I see the second on the W edge of the convective mass.

Quoting pottery:

Too far East, I think...
By a long way.
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253. IKE
Shear is low near 94L......high pressure helping it...


Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting Levi32:


That would be a mid-level rotation that you are seeing on the satellite loop. The surface circulation is west of the convection.


Is it not possible for that circulation to overtake the other one?
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Quoting IKE:

lol.

Or are you serious? You think it's going to Florida too?


Hey, one must keep the "will it hit South Florida' casters happy, too!
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Quoting Levi32:


That would be a mid-level rotation that you are seeing on the satellite loop. The surface circulation is west of the convection.


Agreed
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Quoting PcolaDan:


Don't forget to post your recipes too.


Very Good!!
heheheheheh
Member Since: October 24, 2005 Posts: 0 Comments: 24874
248. xcool
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Surface



2500 feet

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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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