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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Breaking News
Judge blocks drilling moratorium

Judge blocks offshore drilling moratorium imposed by Obama administration after Gulf spill.
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Dr. Masters gives it less than 20%.
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Quoting JFVfromFlorida:
if gfdls shift east i say we are doomed in florida a major cane damn it gfdl please no.

Come on JFV don't start with that. It is too early to start predicting major hurricane for Florida.
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Hey StormW, check out the area at 40W

nice vorticity, convergence, divergence, shear looks pretty good too
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One must remember that the discussions are based on observations and data that are several hours old. If one thinks that the NHC looks at "up to the minute data" in preparation for discussions, then one does not know as much as one thinks!
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Quoting StormW:


You got that right!


INCLUDING ME! LOL!!! UGH! I am in SWLA...lordy, we don't need a tropical system! This is more like a "Hurry up and WAIT" sort of thing eh? LOL!!
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While 93L is taking its own sweet time deciding what to do here is another interesting area to keep an eye on and follow.

Strong vorticity is showing up here both at 850 mb level and on visible loop imagery. There are tell tale inflow streamers from the SE towards convection that is just starting to show up.

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733. xcool
lmao NHC IMO
Member Since: September 26, 2009 Posts: 2 Comments: 15603
The area it is in, is not conducive for quicker development till we hit late July. As soon as 93l reaches the NW Caribbean is when it will develop much faster.
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Quoting StormW:
Maybe dey waitin for a eyewall and an eye.


Dey waten for de puters to make sense so they not eat crow.
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729. IKE
East-Pac firing up another one....

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1100 AM PDT TUE JUN 22 2010

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
CELIA LOCATED ABOUT 515 MILES SOUTH OF MANZANILLO MEXICO.

SHOWERS AND THUNDERSTORMS ASSOCIATED WITH AN AREA OF LOW PRESSURE
LOCATED A FEW HUNDRED MILES SOUTH-SOUTHWEST OF GUATEMALA HAVE
BECOME BETTER ORGANIZED THIS MORNING. ENVIRONMENTAL CONDITIONS
APPEAR FAVORABLE FOR A TROPICAL DEPRESSION TO FORM DURING THE NEXT
DAY OR SO. THERE IS A HIGH CHANCE...80 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
WEST-NORTHWESTWARD AT ABOUT 10 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN

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Quoting IKE:
NHC=Experts.

Me=Amateur.

Looks better this afternoon then it did this morning at the earlier TWO. Maybe I am going blind.


LOL. I'm not sure why they lowered the chance. It looks better now than this morning...
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Quoting Jeff9641:
We will see a TD by tomorrow morning. 93L is about to wrap convection on the NW side. Should pass just north of Jamaica (the center).


NHC dropped their chances of development in the next 48 hours to 20%
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725. myway
Mother nature seems to be yanking the blog worlds chain. Couuld be a long season...i think she has a bizzare sense of humor this year.
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724. Chigz
No one here seems to mention anything about the Wave near 40W-7N - looks good on satellite!!!
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Hello everyone! I'm a newbie but been lurking since 08 during Gustav.I love this blog and and visit everyday for weather updates! You guys rock!I don't have any weather knowl so won't be commenting too much. Howdy, neighbor Pat. HOw you be on ur side of the boot? :)
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Quoting StormW:


I like that prog.
LOL!!! I Don't!!!!! Points it straight at me!!! LOL
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Area in the Central Atlantic looks pretty good
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718. IKE
NHC=Experts.

Me=Amateur.

Looks better this afternoon then it did this morning at the earlier TWO. Maybe I am going blind.
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Eh, that's assuming we have and will have equitable influencing weather conditions to Gustav, which we dont and probably wont.

I'm not much of a fan of doomcasting, though. A lot can happen in a week, and the models are not advanced enough to posess any reliability a week out.
Quoting Hurricanes101:


Looks like Gustavs' track just further west

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Quoting StormW:
Well...there's a center somewhere...may not be low level, but dem clouds is wrapping up and spinnin into it!


Hi StormW, how are you? 93L is gonna drive everyone COO COO!! LOL!
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On that note, I'm going to leave before the infamous 'RIP' calls happen.. on to long.
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Quoting Hurricanes101:


How many people on this blog just started to cry?


Pat could be crying joyful tears but I think he knows better.
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Quoting 69Viking:


Well said StormW, anybody looking at a good visible satellite should be able to see it South of the Islands!


Midlevel circulation.. he didnt say LLvs :)
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Quoting IKE:
...20 PERCENT...LOL!



Im guessing the key phrase in there was the 48hour part. It has been developing kind of slow the past day or so.
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Off topic but fox news is reporting a fed judge has ruled against the off shore drilling ban
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Quoting IKE:


And last night they raised it to 50%.


yea some of us felt that was a bit premature
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Quoting StormW:
Well...there's a center somewhere...may not be low level, but dem clouds is wrapping up and spinnin into it!


Well said StormW, anybody looking at a good visible satellite should be able to see it South of the Islands!
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Quoting Drakoen:
This GFDL 18z run last night was actually more or less accurate...



agree,but with more eastward track(landfall on yucatan not cuba)
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Quoting IKE:
...20 PERCENT...LOL!


How many people on this blog just started to cry?
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700. IKE
Quoting Hurricanes101:
I find it kind of humurous that many thought it was getting better organized today (me included) and boom NHC comes out and says its less organized lol

Guess that is why they are the professionals lol


And last night they raised it to 50%.
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I'm happy they brought it down it looks meek right now. Now later is a different story.
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698. Skyepony (Mod)
After the 1st day the race for who has the least Average Position Error (nm) out of the core models on 93L..We find LBAR in the lead with an error of only 7.5nm. Impressive lead over the rest of the pack BAMD 66.9, MM5B 67.4, HWRF 84.3, MM5E 102.6, GFDL 325.4nm.

GFDL does lead the intensity bit with 7kts error, followed by MM5B 20 & MM5E 25kts.
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Quoting StadiumEffect:
We have a few different opinions on where a developing COC is located, but only time will tell. I'm more inclined to think that the rotation visible within the convective mass near/over Hispaniola is mid/upper levels only. The best lower level would be further to the south and west.




that is correct,very much near 15.5N,75W....very evident on vis sat loops!!!,what most think is a low level circulation trying to form is a developing MLC which indicates a system that is not yet vertically stacked,I expect new convection to form w/this possble surface feature,as the MLC moves ashore causing fooding in haiti:(
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I find it kind of humorous that many thought it was getting better organized today (me included) and boom NHC comes out and says its less organized lol

Guess that is why they are the professionals lol
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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.