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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..were back in Drak,..

And I'm beatin' the flak
Nobody's gonna get me on another rap
Member Since: July 3, 2005 Posts: 415 Comments: 125715
796. xcool
Drakoen heyyyyyyyyyyyyyy
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Quoting Drakoen:
Satellite imagery shows a strong mid level rotation south of Jamaica. The RGB imagery is really good for seeing the distinction between the low level cloud movements and the mid to upper level clouds. Notice that the surface flow is southwesterly underneath the mid level center. Going to be interesting to see whether or not this mid level low can better align itself with the surface center.The upper level anticyclone is not directly overhead 94L judging from the CIMSS Wind shear maps. The clockwise flow around the high is producing marginally favorable upper level conditions. Water vapor imagery shows sinking air in the vicinity of the system which is helping to inhibit convection on the western side of the system. Global computer models show that this upper high may move more to the north and position itself better with the system over the next couple of days.


DRAK! You're back. I hope you don't mind me calling you Drak?
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94L Multiplatform Satellite Surface Wind Analysis 1800
Member Since: July 3, 2005 Posts: 415 Comments: 125715
Precipitable water

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Quoting stormpetrol:
Link

The more I look at this loop, the more I'm thinking that COC has relocated to near 17.1N/77W, it is becoming more pronounced all time and I just don't see the spin at 16.2/79 anymore?



SSD has the low at 17.1N 79.1W

I do see a spin there and it is now covered.
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Quoting WeatherNerdPR:
94L looks very impressive to me.
Yeah. I bet it looks impressive to a lot of people. 70% by tonight!
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Quoting charlottefl:
Im there with you, theres a lot of vorticity due s of the island. And if you look close enough you can almost see inflow coming from the sw into that convective cluster.


I am glad I am not the only one. That certainly doesn't look like a mid-level to me. I know that even the pros think it is further out there, but I really do think the Center of Circulation is where I have said it is all day. If anyone can give a good argument (in the literal sense) as to why this may not be the case I am listening. If not I will do a blog on this whole thing.
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Quoting CyclonicVoyage:


Getting there, that's for sure. 94L should make a solid run tonight..

I'd be shocked if it isn't a TD by Tuesday.
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Satellite imagery shows a strong mid level rotation south of Jamaica. The RGB imagery is really good for seeing the distinction between the low level cloud movements and the mid to upper level clouds. Notice that the surface flow is southwesterly underneath the mid level center. Going to be interesting to see whether or not this mid level low can better align itself with the surface center.The upper level anticyclone is not directly overhead 94L judging from the CIMSS Wind shear maps. The clockwise flow around the high is producing marginally favorable upper level conditions. Water vapor imagery shows sinking air in the vicinity of the system which is helping to inhibit convection on the western side of the system. Global computer models show that this upper high may move more to the north and position itself better with the system over the next couple of days.
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Quoting stormpetrol:
Link

The more I look at this loop, the more I'm thinking that COC has relocated to near 17.1N/77W, it is becoming more pronounced all time and I just don't see the spin at 16.2/79 anymore?


That's still mid-level. Look at 79.5W-80W and 17.4N. That's where the most pronounced low-level spin is in the low-level cumulus.
Member Since: November 24, 2005 Posts: 628 Comments: 26460
Quoting WeatherNerdPR:
94L looks very impressive to me.


Getting there, that's for sure. 94L should make a solid run tonight..
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Quoting sunlinepr:
COC
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Quoting Mrsenseofhumor:


You can call me Randrewl, if you want?


So mrsenseofhumor, what do you think of 94L?
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Link

The more I look at this loop, the more I'm thinking that COC has relocated to near 17.1N/77W, it is becoming more pronounced all time and I just don't see the spin at 16.2/79 anymore?
Member Since: April 29, 2007 Posts: 0 Comments: 7506
I think it will take at least 24 hours to see anything form out of 94L. needs a couple more diurnal cycles to get going
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Hey I noticed that the high pressure over the Southeastern United States right now that is giving them the heat wave was responsible for steering all the systems away from the U.S last year...is that going to be the case this hurricane season again and do you think that we will go another year without a U.S hurricane landfall?
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Gulf Of Mexico - Rainbow Loop
Member Since: July 3, 2005 Posts: 415 Comments: 125715
94L looks very impressive to me.
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Quoting KEEPEROFTHEGATE:
ok sure randrewl
A new day a new troll?
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This is One Spectacular Evening here!
Golden sunlight slanting in from the west, and a big black Monster cloud rumbling away in the East.
Incredible sky overhead
Tropical Bliss.!

aaaaahhhhhh!
Member Since: October 24, 2005 Posts: 0 Comments: 23105
I'm not yet convinced that there isn't a circulation under the convection.
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770. 7544
if and when 94l makes it to td1 the cone should be interestring to see from the nhc the way the models are showing now espeacialy the tvcn one looks tricky wait watch and see for now
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Quoting Patrap:
YOU are the devil!
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Quoting Levi32:


Every single tropical cyclone in the world needs those conditions met. It is not an Atlantic thing. Atlantic storms have land to deal with when they develop, which often makes it more difficult. The EPAC has the monsoon trough, which has SW winds meeting NE trade winds out of the Caribbean. This setup is much more conducive for cyclonic vorticity than the normal ITCZ that the Atlantic usually has, consisting of NE trades meeting SE trades.

The EPAC also has somewhat less issues with dry air than the Atlantic does, as the semipermanent Texas ridge keeps mid-latitude troughs from invading and depositing dry air into the tropics. The Atlantic also has to deal with dry Saharan dust outbreaks that travel as far west as the Caribbean and Gulf of Mexico. The EPAC overall does have it easier, but there is no difference in the conditions that have to be met for tropical cyclones to form in either basin.
thanks levi.

Would less shear in the epac also be a reason? Shear seems to be a very frequently cited reason for lack of development in the Atlantic, but I usually don't see that being the case in the epac. Is my assumption true, or is shear about equal in both basins?

Also, why does the epac have ne winds meeting sw winds, while the Atlantic has se winds meeting ne winds?
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Quoting Mrsenseofhumor:


You can call me Randrewl, if you want?
ok sure randrewl
Member Since: July 15, 2006 Posts: 165 Comments: 52383
COC
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Im there with you, theres a lot of vorticity due s of the island. And if you look close enough you can almost see inflow coming from the sw into that convective cluster.
Quoting Grothar:
I just don't think the center is that far to the west. I still maintain that it is closer to the SW of Jamaica. Perhaps as far west as 79.5 but not much more. It will be a few hours before we know for sure.
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting Mrsenseofhumor:


You can call me Randrewl, if you want?

-I HIGHLY DOUBT THAT-

wumail me and PROVE it
Member Since: August 13, 2005 Posts: 163 Comments: 25512
Quoting Hurrykane:
My guess would be , that at maximum heating, the air is warmer, and easier to lift, allowing for pressure to lower in general%uFFFDaround%uFFFDan area. %uFFFDConvection at night%uFFFDincreases, or at Dmax in the early a.m., as the surrounding atmosphere cools, per se, basically increasing the DAR/WAR in relation to the ELR

DAR = Dry Adiabatic Lapse rate

WAR = Wet or Most Adiabatic Lapse Rate

ELR = Environmental Lapse Rate
It's a little more technical than that...but the basic principle
if the air is warmest during the day, causing the pressure over the ocean to be lowest during he day, then shouldn't the Convective dmax over the ocean be during the day?

But thats obviously not the case..
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Quoting congaline:
Another wishcaster for SFL landfall of TS Arlene the lawn looks like a nuke exploded on it! Rain, yes please!


We need to organize a statewide rain dance. Hey, and we even have real Indians here :-)
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Member Since: July 3, 2005 Posts: 415 Comments: 125715
Did everyone see 12z cmc. Can anyone say ridiculous?
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Quoting aquak9:


Bwwwhahaaaa-hahaaa!! and THAT was your FIRST post??

I am called many things, but definitely not anything with a cutesy avatar!


Obviously a person who has been here a while under a different name to know who TropicalAmanda is. ;)

Yep, your avatar is cute, but not cutesy.
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Quoting PcolaDan:


That's not weather or hurricane related.



HAHAHAHA Gotcha :)




LOL
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
I just don't think the center is that far to the west. I still maintain that it is closer to the SW of Jamaica. Perhaps as far west as 79.5 but not much more. It will be a few hours before we know for sure.
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Link

just click the camera, looks quite windy
Member Since: April 29, 2007 Posts: 0 Comments: 7506
Quoting Mrsenseofhumor:


And aquak9 is really just tropicalAmanda.


Bwwwhahaaaa-hahaaa!! and THAT was your FIRST post??

I am called many things, but definitely not anything with a cutesy avatar!
Member Since: August 13, 2005 Posts: 163 Comments: 25512
752. txjac
Quoting gulfscout:
kemah, tx

102 F




Houston, Texas

Temperature
106.0 °F
Feels Like 113 °F
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Quoting Tazmanian:
i am all most at 102.000 commets


remember this is an active time period for posting so please no meaningless posts lol
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Quoting Grothar:



Don't get so Mobey on us. It is too late in the day. They call me Yosarian. See if you catch that.


:(
Had to look it up. Never read that book.
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Quoting Patrap:
Yes,,we just saw the GFDL ,,thanx



what did gfdl show
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kemah, tx

102 F

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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.