Caribbean disturbance 94L dumping heavy rains on Jamaica

By: Dr. Jeff Masters , 4:44 PM GMT en Junio 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 Seflhurricane:
looking at visible images it appears the midlevel center is taking over look closely as convection is refiring up and how convection is wraping around the west side , what it appears to me is that the circulation off the SW jamaica may be weak and the new center getting stronger

I agree with you it seem this way
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Looks like we have a little action out there.

I made it safely to Iraq...

Just wanted to say "Hi", and let you all know I may be in and out a lot this season. I'll post as the internet and situation permits!
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Quoting kmanislander:


I don't think so. That mid level low would have to work its way all the way down to the surface and then compete with the well established surface low for domination. All of the vort maps show the surface low to the West as being dominant at this time and in fact none of the maps show a seperate or elongated vorticity signature in the mid levels that would be associated with the feature you are referring to.

In the image below you will see the heavy cluster of storms that are beginning to cover the surface low. For now I do not see that mid level feature taking over but as always things can change.

thanks kman as always. i am trying to find the dominant low center but it is hard tofind on visible but i do see what you mean SW of jamaica
Member Since: Julio 14, 2009 Posts: 0 Comments: 3022
I would think bloggers would be used to the fact that most storms in June to July are Monsoonal in nature. But I guess they just remember how quick storms form in August onward...
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Quoting Seflhurricane:
Kman it appears to me the center is reforming near the midlevel low to the SE of jamaica look at the visible that convective band you are talking about is wraping around the western side .


I don't think so. That mid level low would have to work its way all the way down to the surface and then compete with the well established surface low for domination. All of the vort maps show the surface low to the West as being dominant at this time and in fact none of the maps show a separate or elongated vorticity signature in the mid levels that would be associated with the feature you are referring to.

In the image below you will see the heavy cluster of storms that are beginning to cover the surface low. For now I do not see that mid level feature taking over but as always things can change.

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Quoting BadHurricane:
First run the GFDL develops 94L...
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Quoting Levi32:


Indeed. I really do miss QuickSCAT.
levi does it look like the midlevel center Se of jamaica is trying to become the dominant center
Member Since: Julio 14, 2009 Posts: 0 Comments: 3022
Regarding discussion of Gulfcoast temps and drought, SE LA has been having August temps in June. Slight drizzle today for a bit but still way behind in rainfall and unusually high temps here also.
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Quoting Skyepony:


It would have been nice if the ASCAT pass was a little more to the west to point it right out. That spin at the surface ASCAT picked up on yesterday, is still pretty easy to see on RGB west of the blow up. Kinda at that critical spot of wait & see if these couple & draw about all the energy into one storm like the cmc or if the broad low & tropical wave goes their separate wave in two weaker storms or blobs.


Indeed. I really do miss QuickSCAT.
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Evening all, Can someone tell me what affect 94l is having on sea temp's underneath it does such a system remove heat from the ocean at all??
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Definite gradual organization today...

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Quoting kmanislander:
The deepening convection immediately South of the Western tip of Jamaica is immediately East of the surface low center which I would estimate is close to 16.5 N and 79 W. It may in fact be covering the eastern half of the low. What is interesting is that the convection referred to is starting to " come over the top " of the low. Put another way, it is trying to wrap around from the North for the first time.

The fact that very high cold cloud tops are being generated at this time of day is an indication of a strengthening system.

Kman it appears to me the center is reforming near the midlevel low to the SE of jamaica look at the visible that convective band you are talking about is wraping around the western side .
Member Since: Julio 14, 2009 Posts: 0 Comments: 3022
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334. Skyepony (Mod)
Quoting Levi32:


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


It would have been nice if the ASCAT pass was a little more to the west to point it right out. That spin at the surface ASCAT picked up on yesterday, is still pretty easy to see on RGB west of the blow up. Kinda at that critical spot of wait & see if these couple & draw about all the energy into one storm like the cmc or if the broad low & tropical wave goes their separate wave in two weaker storms or blobs.
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We need 94L to follow Stephanie Abram's worst-case scenario hurricane track (just the track) in order to erradicate the drought across the South.
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Quoting Levi32:


It looks like they are waiting until tomorrow.


Darn!
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Sprouts!
Bean sprouts might be responsible for bacteria: officials
(AFP) HANOVER, Germany — Bean sprouts are suspected of being at the root of a deadly E. coli outbreak which has killed 22 people, mainly in Germany, the agriculture minister from the German state of Lower-Saxony said Sunday.

Bon appetit from Germany! And have a nice week with 94L everybody. Hope those who are longing for it, will get some rain.

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Quoting weathermanwannabe:
In looking at the "big" loop of the Atlantic basic, it is pretty obvious that the northern quadrant of 94L, just north of the islands, is still "attached" to the clouds being blown away into the mid-atlantic as a result of the "squeeze" play, and presure gradient, between the sub-tropical jet streaming just north of the islands, and, that strong mid-atlantic ULL also diving southward (it almost looks like the sub-tropial jet and polar jet have merged out in the mid-atlantic).....I think that 94L will not fully blossom until it "seperates" from that sheer line to the north.....The growing anti-cyclone and nearly stationary location is why she is still here with us............It is a very tough call and a watch and wait to see what happens just to the North of the disturbance. Either way, the poor folks in Jamaica/Hispanola are being hammered by rain and flooding.......It's already a no win for them.


Good call!
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Quoting IKE:
Shear is low near 94L......high pressure helping it...




Darn 20 kt shear won't leave 94L.
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328. ackee
Quoting jlp09550:
Nice spin!

Looks like the centre has relocated SE of jamaica on that Loop
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Quoting tropicfreak:
Afternoon, looks like the NHC upped it to 40% for 94L, good call. It has really come together since yesterday evening.

Can someone give me a update on recon? Where are they?


It looks like they are waiting until tomorrow.
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Quoting tropicfreak:
Afternoon, looks like the NHC upped it to 40% for 94L, good call. It has really come together since yesterday evening.

Can someone give me a update on recon? Where are they?


They didn't go, today's and tonight's got cancelled. Going in tomorrow if necessary, leaving 1030 EST
Member Since: Agosto 10, 2010 Posts: 2 Comments: 1971
The deepening convection immediately South of the Western tip of Jamaica is immediately East of the surface low center which I would estimate is close to 16.5 N and 79 W. It may in fact be covering the eastern half of the low. What is interesting is that the convection referred to is starting to " come over the top " of the low. Put another way, it is trying to wrap around from the North for the first time.

The fact that very high cold cloud tops are being generated at this time of day is an indication of a strengthening system.

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Quoting tropicfreak:
Afternoon, looks like the NHC upped it to 40% for 94L, good call. It has really come together since yesterday evening.

Can someone give me a update on recon? Where are they?


Cancelled for the day.
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Quoting charlottefl:
Thx trying. It's always hard sorting of the COC on these systems in the formative stages, especially when you factor in the mid levels. There can be so many vorticies revolving within a broad low.

This may sound crazy but I've heard a similiar explanation regarding some tornados. Instead of a single vortex, many small ones circulating around a center point looking as though it was a single one. Something like that I think. Anyway thanks again.
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Afternoon, looks like the NHC upped it to 40% for 94L, good call. It has really come together since yesterday evening.

Can someone give me a update on recon? Where are they?
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Sorry, but I see the system moving more NW than WNW at this time. Depending on the strength and the position of the ridge to the North, this will most likely move over Western or central Cuba first. Just take a slow look at it now.

Link
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Quoting IKE:
Yes...if you live in the peninsula of Florida.....maybe the pattern is about to be broken.


We need the pattern to break too. Today is the 5th consecutive day we hit 100 degrees or higher. Yesterday, the high was 103. It's supposed to hit 100 tomorrow as well. The longer we stay dry, the easier it is for temps to soar over 100. The crazy thing is that we never hit 100 this many days in a row. We normally have a heat index of 110 in the summer, but the actual temp is usually around 95. It's normally our humidity that's unbearable, not the actual temp. Crazy stuff.
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In looking at the "big" loop of the Atlantic basic, it is pretty obvious that the northern quadrant of 94L, just north of the islands, is still "attached" to the clouds being blown away into the mid-atlantic as a result of the "squeeze" play, and presure gradient, between the sub-tropical jet streaming just north of the islands, and, that strong mid-atlantic ULL also diving southward (it almost looks like the sub-tropial jet and polar jet have merged out in the mid-atlantic).....I think that 94L will not fully blossom until it "seperates" from that sheer line to the north.....The growing anti-cyclone and nearly stationary location is why she is still here with us............It is a very tough call and a watch and wait to see what happens just to the North of the disturbance. Either way, the poor folks in Jamaica/Hispanola are being hammered by rain and flooding.......It's already a no win for them.
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Nice spin!

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12z CMC


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Brush fires have begun in Miami-Dade County


SMOKE FROM A GRASS FIRE WILL AFFECT THE WESTERN MOST AREAS OF THE
MIAMI METRO AREA. THE FIRE IS ABOUT 3 MILES NORTH OF U.S. HIGHWAY
41 BETWEEN THE FLORIDA TURNPIKE AND KROME AVENUE. THERE IS A
MODERATE EAST TO NORTHEAST WIND FLOW ACROSS THE REGION...WITH
AREAS OF SMOKE POSSIBLY AFFECTING KROME AVENUE ABOUT 3 MILES TO
THE NORTH OF THE MICCOSUKEE RESORT. PORTIONS OF U.S. HIGHWAY 41
JUST TO THE WEST OF THE MICCOSUKEE RESORT MAY ALSO EXPERIENCE SOME
SMOKE. DRIVERS IN THESE AREAS OF THE WESTERN MIAMI METRO AREA
SHOULD EXERCISE CAUTION WITH REDUCED VISIBILITIES POSSIBLE.
Member Since: Julio 14, 2009 Posts: 0 Comments: 3022
Quoting IKE:
Yes...if you live in the peninsula of Florida.....maybe the pattern is about to be broken.
We can only hope. We truly one lit cigarette away from some major fires.
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looking at visible images it appears the midlevel center is taking over look closely as convection is refiring up and how convection is wraping around the west side , what it appears to me is that the circulation off the SW jamaica may be weak and the new center getting stronger
Member Since: Julio 14, 2009 Posts: 0 Comments: 3022
Quoting MiamiHurricanes09:
Yeah, but does the CMC develop a separate system that isn't 94L? Looks to me like that's what ends up in the GOM.


CMC 12z just develops 94L, nothing 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 big tail moving from the south will reach us tonight thru Monday, causing more rain that we dont need. PR is under a flash flood watch.
Member Since: Abril 29, 2009 Posts: 75 Comments: 14342
311. Hugo7
Quoting nrtiwlnvragn:


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 indes is at 64% fir a 25 kt increase.

91E 18Z SHIPS

Thank you for post. Most prolly don't care about this region because most tropical developement in this area goes out to sea and causes little to no damage, but this one has a pretty good chance according to models.
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310. IKE
Yes...if you live in the peninsula of Florida.....maybe the pattern is about to be broken.
Member Since: Junio 9, 2005 Posts: 23 Comments: 37858
309. ackee
THere is two spin with 94L one to the SW of jam and the other to the SE is it possible that 94L will weaken as a result of this
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HPC Extended Forecast Discussion

Excerpt:

DISCOUNTING THE 00 UTC ECMWF IN THIS MANNER ALSO SEEMS TO WORK
BETTER MUCH FARTHER SOUTH ACROSS THE SERN US/FL WHERE ITS
DEPICTION OF BRINGING MORE AMPLE TROPICAL ENERGY FARTHER NORTH
THAN THE GFS/GEFS DOES NOT FIT LATEST 17 UTC HOTLINE COORDINATION
GUIDANCE FROM NHC THAT ADVOCATES CONSISTENT WITH EXPECTED SHEAR
THE TRACK OF A WEAK LOW JUST INTO THE SERN GULF OF MEXICO IN ABOUT
A WEEK AS DEPICTED ON THE HPC FINAL PROGS.



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The models really struggle with the monsoon lows. I wouldn't put too much credence in them unless and until we actually get a TD classified from this.
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Thx trying. It's always hard sorting of the COC on these systems in the formative stages, especially when you factor in the mid levels. There can be so many vorticies revolving within a broad low.

Quoting midgulfmom:
A wimpy little rainmaker would be nice here in S.E. LA but don't think 94L has any intention of being wimpy. Nice graphic charlottefl, you clarified what they were talking about for me.. thanks.
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Seems pretty odd that the GFDL, in a 6 hour period, went from doing nothing with 94L, to making it a strong TS nearing hurricane strength in 5 days time in the GoM.
Member Since: Agosto 10, 2010 Posts: 2 Comments: 1971
NWS MIAMI Discussion looks like South Florida will get rain FINALLY !!!


WEATHER CONDITIONS BEYOND WEDNESDAY WILL GREATLY DEPEND ON THE
EVOLUTION AND TRACK OF THE SURFACE LOW CURRENTLY OVER THE WESTERN
CARIBBEAN. MOST MODELS ARE NOW CONVERGING TOWARD A SIMILAR
SOLUTION WITH ECMWF BEING THE MOST PERSISTENT IN BRINGING THIS
SYSTEM SLOWLY NORTH THROUGH EXTREME WESTERN CUBA BY LATE
THURSDAY/EARLY FRIDAY AND INTO THE SOUTHEAST GULF OF MEX BY
SATURDAY. IN DOING SO...ECMWF SIGNIFICANTLY INCREASES THE CHANCES
FOR PRECIP ACROSS SOUTH FLORIDA FRIDAY AND SATURDAY. GFS,
LIKEWISE, INCREASES POPS FOR THIS PERIOD ALTHOUGH DOES NOT SEEM AS
AGGRESSIVE AS THE ECMWF. CURRENT FORECAST CALLS FOR A MODEST
INCREASE IN POPS FOR THIS PERIOD. THIS, HOWEVER, COULD INCREASE
FURTHER IF THE MODELS CONTINUE WITH THIS TREND.

Member Since: Julio 14, 2009 Posts: 0 Comments: 3022
Quoting PcolaDan:


Don't forget to post your recipes too.



Twit! LOL
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It's interesting though that the models that do develop 94L somewhat, do so in the Gulf of Mexico, as opposed to the Caribbean. There is some goofy work going on there in the upper-levels on the models that show that. It's basically 94L hijacking the upper trough by sneaking right underneath the jetstream into another pocket of light upper-level winds and reversing the cyclonic upper flow to anticyclonic.
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301. IKE
Miami discussion....

WEATHER CONDITIONS BEYOND WEDNESDAY WILL GREATLY DEPEND ON THE
EVOLUTION AND TRACK OF THE SURFACE LOW CURRENTLY OVER THE WESTERN
CARIBBEAN. MOST MODELS ARE NOW CONVERGING TOWARD A SIMILAR
SOLUTION WITH ECMWF BEING THE MOST PERSISTENT IN BRINGING THIS
SYSTEM SLOWLY NORTH THROUGH EXTREME WESTERN CUBA BY LATE
THURSDAY/EARLY FRIDAY AND INTO THE SOUTHEAST GULF OF MEX BY
SATURDAY. IN DOING SO...ECMWF SIGNIFICANTLY INCREASES THE CHANCES
FOR PRECIP ACROSS SOUTH FLORIDA FRIDAY AND SATURDAY. GFS,
LIKEWISE, INCREASES POPS FOR THIS PERIOD ALTHOUGH DOES NOT SEEM AS
AGGRESSIVE AS THE ECMWF. CURRENT FORECAST CALLS FOR A MODEST
INCREASE IN POPS FOR THIS PERIOD. THIS, HOWEVER, COULD INCREASE
FURTHER IF THE MODELS CONTINUE WITH THIS TREND.
Member Since: Junio 9, 2005 Posts: 23 Comments: 37858
A wimpy little rainmaker would be nice here in S.E. LA but don't think 94L has any intention of being wimpy. Nice graphic charlottefl, you clarified what they were talking about for me.. thanks.
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299. ackee
THE rain here in jamaica has not been heavy thow seem like tuesday wenesday before things will improve there have been flooding manily in st. thomas so far
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Quoting Levi32:


NOGAPS shows two separate systems, with 94L moving into the Gulf of Mexico.
Yeah, but does the CMC develop a separate system that isn't 94L? Looks to me like that's what ends up in the GOM.
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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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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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