93L slow to develop, but bringing heavy rains to Haiti

By: Dr. Jeff Masters , 1:50 PM GMT on June 22, 2010

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A modest region of intense thunderstorms (Invest 93L) is over the central Caribbean, a few hundred miles south of Hispaniola. This disturbance has the best chance to become Tropical Storm Alex of any system we've seen so far this year. We don't have any buoys near 93L, but pressures at the ground stations surrounding the storm are not falling. A pass of the ASCAT satellite over the Central Caribbean at 9:45 pm EDT last night revealed a modest wind shift associated with 93L, but nothing at all close to a surface circulation. Top surface winds seen by ASCAT were 15 - 20 mph. Water vapor satellite loops show that 93L is embedded in a large region of moist air. The atmosphere over the Caribbean has moistened over the past day, which should aid development of 93L. Wind shear is a low 5 - 10 knots. The high wind shear associated with the strong winds of the subtropical jet stream are over the northern Caribbean, too far north to interfere with development, but close enough to provide good upper-level outflow for the storm. Visible satellite loops show high level cirrus clouds streaming away from 93L to the northeast, evidence of the upper-level outflow channel that is developing to the storm's north. Sea Surface Temperatures are plenty warm, a record 29 - 30°C. The Madden-Julian oscillation (MJO) currently favors upward motion over the Caribbean, which will act to increase the chances of tropical storm formation this week. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The main negative for 93L continues to be lack of spin. The University of Wisconsin 850 mb relative vorticity analysis is showing that spin at 850 mb (roughly 5,000 feet in altitude) has increased over the past day, but 93L needs to acquire additional spin before it can grow more organized. I speculate that it is this lack of spin that contributed to the loss of much of 93L's heavy thunderstorm activity last night. The storm is now going through a cycle where it is building another respectable mass of heavy thunderstorms, and the increased inflow of low-level air that will feed these thunderstorms will likely enhance 93L's spin today. The Hurricane Hunters are on call to investigate 93L on Wednesday afternoon.


Figure 1. Morning visible satellite image of the central Caribbean disturbance 93L.

Forecast for 93L
NHC is giving 93L a 40% chance of developing into a tropical depression by Thursday morning, which is a reasonable forecast. Given the storm's current lack of spin and relatively modest amount of heavy thunderstorms, the earliest I'd expect 93L to become a tropical depression would be Wednesday afternoon, with Thursday more likely. Wind shear is expected to be low, less than 10 knots, over the central and western Caribbean this week. Water temperatures will be warm, dry air absent, and the MJO favorable. I don't see any major impediments to the storm becoming a tropical depression by Thursday, and it is a bit of a surprise to me that the computer models have been reluctant to develop 93L. The GFS, NOGAPS, and UKMET models do not develop 93L, and the ECMWF model doesn't develop 93L until after it crosses the Yucatan Peninsula and enters the Gulf of Mexico in a about a week. The current (2am EDT) run of the GFDL model predicts 93L will be a weak tropical storm in the Gulf of Mexico in five days; its previous run had 93L as a major hurricane in the Gulf. Given all this model reluctance and the current disorganization of 93L, I give the storm a low (less than 20% chance) of becoming a hurricane in the Caribbean. Expect 93L to bring flooding rains of 3 - 6 inches to Jamaica, eastern Cuba, and southwestern Haiti today through Wednesday. These rains will spread to the Cayman Islands and central Cuba by Thursday, and western Cuba and Mexico's Yucatan Peninsula on Friday. The current run of the SHIPS model has 93L slowing down late this week to a forward speed of just 6 knots (7 mph) from its current speed of about 10 mph, in response to a weakening in the steering currents. A trough of low pressure is expected to swing down over the Eastern U.S. early next week. If this trough is strong enough and 93L develops significantly, the storm could get pulled northwards and make landfall along the northern Gulf of Mexico coast in the oil spill region. This is the solution of the Canadian GEM model. If 93L stays weak and/or the trough is not so strong, the storm would get pushed west-northwestwards towards the Texas coast. This is the solution of the ECMWF model. The amount of wind shear in the Gulf of Mexico next week is highly uncertain. There is currently a band of high shear near 30 knots over the Gulf, and some of the models predict this shear will remain over the Gulf over the next 7 - 10 days. However, other models predict that this band of high shear will retreat northwards and leave the Gulf nearly shear-free. The long-term fate of 93L remains very murky. My main concerns at this point are the potential for 3 - 6 inches of rain in Haiti over the next two days, and the possibility 93L could become a hurricane in the Gulf of Mexico next week.

Elsewhere in the tropics
None of the reliable computer models is calling for tropical cyclone formation elsewhere in the Atlantic over the next seven days.

Floods in China and Burma kill over 250
The deadliest and most destructive weather-related disaster on the planet so far this year is occurring in southern China and northern Burma, where a week of heavy rains has caused flooding that has claimed over 250 lives. The heavy rains and floods ravaging 10 southern Chinese provinces had killed 199 and left 123 missing as of 11:00 a.m. Tuesday, a Ministry of Civil Affairs statement said. Damage is estimated at $6.2 billion. Floods and landslides in neighboring areas of Myanmar (Burma) have claimed at least 63 lives in the past week.


Figure 2. Paramilitary policemen help evacuate residents from Wanjia village of Fuzhou City, East China's Jiangxi province, June 22, 2010. Days of heavy rain burst the Changkai Dike of Fu River on June 21, threatening the lives of 145,000 local people. Local authorities have ordered immediate evacuation, and the army and paramilitary police have begun conducting rescue operations. Image credit: Xinhua.

Wind and ocean current forecast for the BP oil disaster
Southeast to east winds less than 10 knots will blow in the northern Gulf of Mexico today through Saturday, according to the latest marine forecast from NOAA. The resulting weak ocean currents should cause little motion of the oil slick, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range outlook is uncertain, and will depend upon what 93L does.

Resources for the BP oil disaster
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool allows one to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) The latest on 93L
2) Which model is the most reliable?

Today's show will be 30 - 40 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

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1746. Dakster
Quoting Acemmett90:

hey this is a weather blog not male speed dating


Yeah I know - that is why you two need to go get a room....

Stormw - That IR really puts the developing center into perspective. I can actually see it now.
Member Since: Posts: Comments:
Quoting AonaibhRiCheile:
Long-time lurker, first time poster, with a question for LA residents.
I'm due to be in Covington for the first time for a week starting on Sunday.
I know L93's future is highly uncertain, but IF it was to develop, and IF it was to head toward LA, is Covington far enough inland to avoid evacuation?
Any responses appreciated.
Thanks


Mandatory evacs stop at the I-12, which lies literally between covington and mandeville. While you might not be in mandatory zones, covington isn't a place you want to stay in a serious storm. As K taught us, all those 100 foot pines can get pretty hairy in a major wind storm.
Member Since: Posts: Comments:
Quoting Acemmett90:

hey this is a weather blog not male speed dating




lol lol lol AHAHAHAHAHAHHAHAHAH



that was funny
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
1741. ssmate
Taz,
It's for a good cause.
POST 2,000 = $200
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1740. Drakoen
Quoting StormW:
Maybe run into Haiti

IR2 LOOP


The broad area of low pressure is SE of Jamaica. What we were tracking today was a mesoscale convective vortex.
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Quoting centex:
It was crazy Mon. We learned Jamaica has no problems only situations. I think they have a situation coming.


From the Jamaica Observer The fugitive was handed over to police by Reverend Al Miller and is prepared to commit himself to due process and waive his right to an extradition hearing.
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A
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1737. IKE
Quoting unf97:


That would be extremely unusual to have such a deep upper level trough for late June should that evolve.


Yes it would be. Interesting to see what the 00Z ECMWF shows.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1736. Patrap
Floater - Visible Loop
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any one think the new GFS is being a wishcaster tonight be for it was not doing any thing with 93L
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
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Hand drawn takes 93L entity into the NW Gulf next week - that trough the GFS is showing will not make it through the southeast - not in late June at least. Fropas are very rare down here between Memorial Day and Labor Day.

Link
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Quoting Dakster:


I think you two need a room... :)



yup this me and him


lol this kinding
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
1728. IKE
Quoting nrtiwlnvragn:



Wonder if that fish storm (if it verifies) gets named before 93L?


LOL..it could.

Thanks for the link on the new GFS.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1727. Dakster
Quoting Acemmett90:

ok this just got uncomfortable


I think you two need a room... :)
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1726. marmark
Quoting Tazmanian:
new poll


the new two

A the same


B 30%-40

C 50-70%

D 80% +
B just 4 fun
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Quoting marmark:
456-where are you?


Sick
Member Since: Posts: Comments:
Quoting Tazmanian:
new poll


the new two

A the same


B 30%-40

C 50-70%

D 80% +
B
Member Since: Posts: Comments:
Quoting ssmate:
Post number 2,000 has to give $200 to Portlight. Agreed?



LOL


how about no
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
Quoting hydrus:
This model has a storm off the S.E Florida coast in 144 hours.Link


The other GFS shows it too.
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1720. ssmate
Post number 2,000 has to give $200 to Portlight. Agreed?
Member Since: Posts: Comments:
new poll


the new two

A the same


B 30%-40

C 50-70%

D 80% +
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
Quoting centex:
It was crazy Mon. We learned Jamaica has no problems only situations. I think they have a situation coming.
Serious one with Dudus in custody now. Not gonna be nice down there right now.
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1716. unf97
Quoting IKE:


You may right about track. Maybe it's just a shearing out system.


That would be extremely unusual to have such a deep upper level trough for late June should that evolve.
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1715. marmark
456-where are you?
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1714. centex
Quoting Acemmett90:

ok i just wanted to know good reason though how was that trip
It was crazy Mon. We learned Jamaica has no problems only situations. I think they have a situation coming.
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Most of Covington is north of I-12 so officially out of mandatory evacuation zone. But there are a lot of pine trees to watch out for.
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Quoting Acemmett90:

ok this just got uncomfortable




heh heh this geting lol
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
Quoting Baltimorebirds:
If things continue this way with 93L we could expect a t.d by tomarrow night or thursday.



or may be a TS if the winds keep going up
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
Heading out the door to my grand-daughter's HS graduation. In 50 words or less can someone please give me a quick analysis and is it forecasted at this point to come very near Cayman ? TIA
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1707. marmark
Quoting Jeff9641:
GFS is indicating up to 10" of rain in Florida next week for most of the state.
gosh.we need it. grass is crispy
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1706. IKE
Quoting unf97:


Ike, if that trough is as deep as this model run depicts, then the tropical entity would accelerate N/NE out of the GOM up the Atlantic seaboard. That is quite a run showed by GFS.


You may right about track. Maybe it's just a shearing out system.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:
New GFS at 192 hours...what a trough...




Wonder if that fish storm (if it verifies) gets named before 93L?
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1703. xcool
amd yep
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Quoting Stormchaser2007:
"New" GFS


Thank you very much!
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Quoting xcool:
Link


go here taz



thanks
Member Since: May 21, 2006 Posts: 5089 Comments: 114054
Quoting Baltimorebirds:
Can you post the dievergence please.Thank you.


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1698. IKE
Here's the cold-front plowing through Missouri....

"IN THE SUN NIGHT-MONDAY TIME FRAME THERE IS A
GENERAL MODEL CONSENSUS OF ANOTHER COLD FROPA AND THUS HAVE SOME
CHANCE POPS. ANOTHER NICE SHOT OF COOLER AIR WILL COME INTO THE
AREA BEHIND THIS NEXT FRONT WITH POTENTIALLY AN EXTENDED PERIOD OF
COOLER TEMPS (LM 80S) AND LOW HUMIDITY LASTING WELL INTO THE END
OF NEXT WEEK."
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting smmcdavid:
Can we take a time-out on the political aspect of the oil issue.... thanks. Or take it somewhere else.



yea we got bigger problems ahead
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1696. unf97
Quoting IKE:
New GFS at 192 hours...what a trough...



Ike, if that trough is as deep as this model run depicts, then the tropical entity would accelerate N/NE out of the GOM up the Atlantic seaboard. That is quite a run showed by GFS.
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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.