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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As a boater,,what should we make of the chances of a GOM storm heading for E. Texas,,,Louisiana area next week? The Carib. is a real mess this morning!
Member Since: Posts: Comments:
Quoting BenBIogger:
They should cancel recon for today.

No, they need Recon to go in to give them important data that they need.
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Quoting StormW:


No, I don't. I have a subscription to Weathertap and satellite updates like every 6-10 minutes on loops.


K thanks.. they say they update every 30 mins, it's more like every hour..
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting charlottefl:


Morning storm, do you have a link to any visible sat's that update more frequently than what's on the NHC?

Try here and here

Also more great links for anything related to the tropics here.
Member Since: Posts: Comments:
Makes one think, somethings gotta give.
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I spend a lot of time on here during the season but rarely comment but wow this is confusing. Just looked a WunderMap with models and satellite turned on. If any one of these blobs were alone it would be impressive, but three blobs and little "L" sitting away from them??????
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3189. IKE
MEMO to SSD: Need a floater for blob 2....and blob 3.

TIA!

95E in the east-PAC is really firing up.

Correction...storm #4 in the east-PAC...Darby.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
3187. tramp96
Wow thats a nice set of blobs.
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The HH's are going to have a fun afternoon, if they are still going in.
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They should cancel recon for today.
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Quoting IKE:


And it should stay a yellow circle here in a few minutes.


I was more interested in the 3 blobs. I figured one of them must be 93L lol.
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Quoting kmanislander:
Good Morning

Holy triple blob Batman, what have we here ??


LOL
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Morning guys!
Umm so the three stooges it is huh? Interesting.
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3177. IKE
Quoting CyclonicVoyage:


Hence the yellow circle this AM.


And it should stay a yellow circle here in a few minutes.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Good Morning

Holy triple blob Batman, what have we here ??
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Quoting StormW:


15.0N;76.0W...you can see the cyclonic turn where they have posted the center is near.


Morning storm, do you have a link to any visible sat's that update more frequently than what's on the NHC?
Member Since: December 18, 2006 Posts: 7 Comments: 2686
Quoting IKE:


I see it now, but it's completely void of any convection.


Hence the yellow circle this AM.
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I'll make one forecast everybody keep your weather radios handy.
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3170. IKE
Quoting StormW:


15.0N;76.0W...you can see the cyclonic turn where they have posted the center is near.


I see it now, but it's completely void of any convection.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
3169. srada
Quoting wunderkidcayman:
lt looks like some banding features developing on both blobs



Good Morning..wow was the CMC actually right?
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Quoting StormW:


I ain't even started analysis yet this morning, and just looking at the satellite loops, I already got a headache. Time for my first cup o jo.


Got something for ya Storm, Morning BTW.


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3165. IKE
Quoting StormW:


Got it on IR2 Ike:

93L IR2 LOOP


You're an expert....I'm not...but...I don't see much there.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting GainesvilleGator:
Ok, I wake up & there are three blobs in the Carribean. Three blind blobs, three blind blobs, look how they roll, like how they run...

How can we expect any computer models to accurately predict where nothing is going?



Normally I would agree but, the funny thing is that there is quite an agreement among the models. The GFDL was shifting east & west with intensity yesterday, now it's not. It had a 103kt major going to NOLA last night, now, it has a tropical storm going to the same place. That means steering, no matter the strength, should be in the general vicinity.

Nice lil ditty BTW, lol,

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Quoting StormW:
Just when you thought it couldn't get any worse:



175?? Can you say typhoon tip?
Member Since: December 18, 2006 Posts: 7 Comments: 2686
StormW don't break to many pencil points today but you probably won't have an eraser left either.
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Quoting IKE:
...INITIAL CONDITIONS...

LATCUR = 15.6N LONCUR = 76.0W


I don't see anything there.

Sorry...lol...try again.


This is the same problem I had yesterday: convection is dismal over there.
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3156. IKE
If the 2010 version of the GFS is correct, a strong trough will end any chance of a GOM system in about 7-8 days.

How any of the 3 stooges is suppose to make it to Texas(what some models show), is beyond me.

Member Since: June 9, 2005 Posts: 23 Comments: 37858
3154. 606
Things are starting to look interesting.
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3153. IKE
...INITIAL CONDITIONS...

LATCUR = 15.6N LONCUR = 76.0W


I don't see anything there.

Sorry...lol...try again.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
3150. IKE
Quoting GainesvilleGator:
Ok, I wake up & there are three blobs in the Carribean. Three blind blobs, three blind blobs, look how they roll, like how they run...

How can we expect any computer models to accurately predict where nothing is going?



They can't. Like throwing darts at a dart board. Bad enough when there's one blob all of us can analyze...now we get to analyze 3 of em.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Boom, boom, boom....out go the lights. OMG, just checking the blog this mo'nin, and it seems like deja vu. Remember the year in 04 or 05 when we had 3-4 systems bumper-2-bumper in the Atlantic? This is very interesting for me to see in the Carib.

Member Since: Posts: Comments:
Ok, I wake up & there are three blobs in the Carribean. Three blind blobs, three blind blobs, look how they roll, like how they run...

How can we expect any computer models to accurately predict where nothing is going?

Member Since: Posts: Comments:
3147. IKE
The three stooges.....with a big floodlight shining on them....take yer pick...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
lt looks like some banding features developing on both blobs

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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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