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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18z gfs has a stronger reflection in 36 hours..actually develops a surface low in just 12 hours

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This seems to be what is going on.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting RobertM320:
"I think part of the 6 month timeline was to give enough time to make some relatively informed decisions as to what safety guidelines are to be put in place; it doesn't take much to be disgusted by the fact that the drilling industry has increased the ability to drill while at the same time doing absolutely NOTHING to improve safety and fall back in the event of a blow out like this. BP's reps were saying really confidence inspring things like "we're trying what we know" and "no one has had a blow out at 5000 feet before". That begs the question: Why were you doing it if you had no idea how to stop it if it got out of hand?"

I don't disagree with any of the points you make. So, when all the retail stores and all the restaurants in South Louisiana shut down, and half the State ends up on unemployment, thats ok? I make over $100K a year running my retail business, I have over $18K a year in mortgage and taxes and insurance on my home. Unemployment for an entire year pays a max of $14,404...you do the math. I guess its easy to say shut it down when its just someone elses life.


Do you not understand how BI inusrance works? Living where you do, I would have to think you're as professional from your side of it as I am from mine...you need to apply as soon as you can qualify, to your carrier and to BP...if your carrier pays, they will file for subrogation against BP...do you suppose P&J hasn't applied? The shrimpers, fishermen and the vacation renmtal owners? BP is on the hook for the BI and most of the losses faced by business owners and your business is as directly effected as a shrimper that can't fish, you know?
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1390. xcool
lol
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I was merely asking a question. No need to be insultive.

-Snowlover123
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Quoting StormW:


Kinda.
But with that said, you have explained in detail to me wind sheer (at all levels), steering currents, hot tops, cold tops, models, and the list goes on. Thanks
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Quoting CapeObserver:
NBC just reported that should a hurricane enter the Gulf it would take up to a week to evacuate everyone on the oil spill and another 10 days after to reinstate them. During that time oil will, once again, be spilling freely into the Gulf.


I feel sick after reading that. :(
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Quoting Clearwater1:


Storm, do you have a system as to the number of question marks you give when replying to a post. I mean the more absurd the post, the more question makes? For example, I fully expect no less than five, maybe more ?????? after this post. lol But with that said, you have explain in detail to me, wind sheer, at all levels, steering currents, hot and cold tops and list goes on. thanks


As if I'm not around.
-Snow
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1379. NRAamy
where's STORMTOP?
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1321. thnks StormW! :)
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I have a question:

How real is the ADT technology to measure Hurricane winds?
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Quoting StormW:


???


Storm, do you have a system as to the number of question marks you give when replying to a post. I mean the more absurd the post, the more question makes? For example, I fully expect no less than five, maybe more ?????? after this post. lol But with that said, you have explain in detail to me, wind sheer, at all levels, steering currents, hot and cold tops and list goes on. thanks
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Is this recent?
Member Since: July 8, 2005 Posts: 259 Comments: 24262
Quoting NOLALawyer:


Judge Feldman is beyond reproach. He also is probably the most intelligent judge on the bench in the EDLA. He follows THE LAW and he is usually pro-government. So, do not attempt to taint his ruling with the tinge of self-serving motives.

Mike


Mike, you can't blame folks for the appearance of impropriety; Louisiana in general has a taint of "good natured larceny" about it, and given the connection to the oil industry, you have to wonder.

Now, that having been said, I will defer to your opinion in this matter...
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hmmm... this is different:

OFFNT3
OFFSHORE WATERS FORECAST FOR THE SW AND TROPICAL N ATLANTIC AND
CARIBBEAN SEA
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
530 PM EDT TUE JUN 22 2010
OFFSHORE WATERS FORECAST FOR THE TROPICAL N ATLC FROM 07N TO 22N
BETWEEN 55W AND 65W...THE SW N ATLANTIC S OF 31N W OF 65W
INCLUDING BAHAMAS...

AMZ088-230330-
SYNOPSIS FOR THE SW N ATLC INCLUDING THE BAHAMAS
530 PM EDT TUE JUN 22 2010
.SYNOPSIS...A RIDGE WILL REMAIN NEARLY STATIONARY ALONG 31N
TONIGHT THROUGH SUN. A TROPICAL WAVE IN THE CENTRAL CARIBBEAN
EXTENDING N TO NEAR 22N73W WILL MOVE TO THE W-NW THROUGH THE
STRAITS OF FLORIDA THU AND THU NIGHT.
EXPECT VERY HEAVY RAINFALL
ASSOCIATED WITH THE WAVE. A TIGHT PRES GRADIENT BETWEEN THE
RIDGE AND WAVE WILL BE IN PLACE S OF 26N UNTIL FRI.
$$
FORECASTER LEWITSKY

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Quoting marknmelb:


Right. All judges and lawyers are never tainted by $$


And the general populace isn't?
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NBC just reported that should a hurricane enter the Gulf it would take up to a week to evacuate everyone on the oil spill and another 10 days after to reinstate them. During that time oil will, once again, be spilling freely into the Gulf.
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1365. ackee
93L is under performing low shear 29c water still no TD dont think we see Alex until it reach the NW carrb looks like just a wet day for us here in jamaica
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IMO... it looks as IF the low-level circulation forms under where the current mid-level low is located and continues its trajectory, it may move very close (if not over Cuba). If this happens, then land interaction may play a big part over the next few days.
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Quoting Chicklit:


Here is the center according to the last NHC coordinates. 15.5N 74.4W


and lets keep it that way.
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1360. stormy3
perturbation?
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Quoting NOLALawyer:


Judge Feldman is beyond reproach. He also is probably the most intelligent judge on the bench in the EDLA. He follows THE LAW and he is usually pro-government. So, do not attempt to taint his ruling with the tinge of self-serving motives.

Mike


Right. All judges and lawyers are never tainted by $$
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The storm that is producing the 1.5" hail is to the south. It's name is "AO."

-Snowlover123
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Quoting StSimonsIslandGAGuy:


That actually is a good idea. I wonder how much it costs to make and deploy a buoy.


Make the Chinese believe its some kind of cool electronic device and they'll have an inexpensive version out in no time!
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Quoting Jeff9641:
Visible is showing impressive spin just S of DR/Haiti.
Once again, that spin is in the mid levels and will be interacting with land in a couple of hours.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting srada:
Why do you think that will happen?
If this blows up to be a monster, then the trough will pick up it earlier..its about timing of the trough and the strength of the storm


right, if it blows up, that def could happen, then follow the ridge around. Or if if mod. builds, it could get pulled less east towards, well you know
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Quoting Snowlover123:
Why is everyone getting hyped over 93L right now, when the NHC has a 20% chance for it to develop?

-Snowlover123


20% chance to develop over the next 48 hours. Not ever.
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Quoting Jeff9641:
In the upper & mid levels there is a dominate swirl near the Haiti/DR border which is working down to the surface. This feature is moving WNW and will pass north of Jamaica. Watch for intense convection to fire over this tonight and strengthen it further. Disregard all the computer models right now is there will be no low there. If you don't believe it just wait 8 to 12 hours as a dominate low is developing in that area.
850 millibar vorticity doesn't support what you're saying. And I'm pretty sure that there will be no low there as it is moving towards the WNW straight to mountainous land.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting StormW:


???


Perhaps I said the wrong thing.... :o

-Snowlover123
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Quoting Snowlover123:
Why is everyone getting hyped over 93L right now, when the NHC has a 20% chance for it to develop?

-Snowlover123


The 20% chance was given over three hours ago. It has become better organized with a circulation since then.
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Here is the center according to the last NHC coordinates. 15.5N 74.4W...That is, if you have a magnifying glass.
Member Since: July 11, 2006 Posts: 14 Comments: 11358
1347. 900MB
Quoting Snowlover123:


Lighter rains are up further north, and heavier rains are further south. There is actually a storm that is confirmed to produce 1.5" hail!


Yikes! I will try again tomorrow night and watch from the comfort of my couch!
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Quoting Jeff9641:
In the upper & mid levels there is a dominate swirl near the Haiti/DR border which is working down to the surface. This feature is moving WNW and will pass north of Jamaica. Watch for intense convection to fire over this tonight and strengthen it further. Disregard all the computer models right now is there will be no low there. If you don't believe it just wait 8 to 12 hours as a dominate low is developing in that area.

I just noticed the same thing
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About

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