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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They may have to announce a new computer model today. One that takes into account three or four storms, give or take a couple.
Member Since: Posts: Comments:
Quoting beeleeva:
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!


BEELEEVA be very careful out there. If a lot of these models verify, or even if some do, TX/LA'S waters will be rough. Check weather cast b4 going offshore. With models showing landfall from NOLA to Brownsville could get bad.
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Would not be surprised to see a little stall on the 8 o'clock call.
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I am still struggling with the notion (with no science per se to back me up) about the inverse relationship between e-pac and the atlantic and my comment last week that the atlantic would not get going (in terms of storms) until the e-pac storms died down/dissipated......Don't have a clue if this theory holds water but I don't have the time to research this issue of concurrent storms between the two basins in June/July (not often) and how often do they actually "alternate" between the two which is what I have seen the past few years...It would actually make a good research paper for someone.....
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Quoting StormW:


Where is the upper level anticyclone centered?





With all due respect storm.....I have seen several
storms form not directly under the anticyclonic high. You honestly feel the LLC will form directly under this high? Seems a bit obsessive.

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3240. 7544
Quoting IKE:
The three stooges.....with a big floodlight shining on them....take yer pick...



ha morning looks like 3 ducks in a row who gets shot down first and where will the go .
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oh said 93: can have a baby sister
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3237. IKE
Upper level divergence is...very little where 93L is at.....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
remember yesterday the cmc was showing 2 storms so maybe it was right on target
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Lots of "blob" talk on the blog, lol...
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94L???????
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3233. IKE
Quoting weatherwatcher12:
Which coordinates are correct ssd's:
23/0545 UTC 17.4N 72.3W TOO WEAK 93L

or the ftp site's?


I don't think anyone really knows.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting StormW:


Where is the upper level anticyclone centered?





Normally that would be so but having the anticylone overhead has not done anything for 93L over the past 48 hrs.

I think we could see 94L from this feature today and that to me is the bigger threat now.

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Which coordinates are correct ssd's:
23/0545 UTC 17.4N 72.3W TOO WEAK 93L

or the ftp site's?
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Quoting wunderkidcayman:
Let's get something straight helove2trac 92L died long time ago don't even think its in the Caribbean any more yes we do have 93L but might be relocated south of Haiti and we do not have 94L yet but we might soon.

Ughh something like that. Its all a bit confusing.
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3229. IKE
Quoting leo305:
mhm at full speed I can see a surface broad spin south of jamaic and moving w, But it has barely any convection..

while at the same time I am seeing the blob gaining some feeder like bands..


No LLC with the coordinates from the NHC....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
chill wunder it was just a joke to wake everyone up dont be so serious ROFLMAO
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Thank you Storm.That was really well put.It is a watch and see from this point on.
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3226. leo305
mhm at full speed I can see a surface broad spin south of jamaic and moving w, But it has barely any convection..

while at the same time I am seeing the blob gaining some feeder like bands..
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I wonder whats going to come out of all of this
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Let's get something straight helove2trac 92L died long time ago don't even think its in the Caribbean any more yes we do have 93L but might be relocated south of Haiti and we do not have 94L yet but we might soon.
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Quoting alaina1085:

Oh thanks, I had them done! Oh.. you mean the tropics.. my bad. :p
lmao!
Member Since: August 12, 2009 Posts: 0 Comments: 203
Quoting StormW:


Where is the upper level anticyclone centered?




Jamaica it is. So NHC does have it correct.
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Oh please Alaina before real girl.
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Good morning!

93L is Still 20%. Next "Two" should be coming in momentarily though...
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Good Morning......Now we have "two" blobs to watch in the Caribbean. Couldn't beging to tell you which one may develop on down the road. Only certain thing right now is that most of the local NWS offices around the Gulf Region are starting to forecast the possibility of some type of tropical "moisture" into their regions over the weekend (Tallahassee office made first mention of this this morning). In what form is anyones guess at the moment.
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3217. IKE
Quoting StormW:


Where is the upper level anticyclone centered?





Where there's little to no convection at.

This is nowhere near being designated. At least 36-48 hours more....if then.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Good morning Storm.Boy it looks like the tropics are starting to take shape arent they.I looked at the models everyone has posted. And if it all holds true Tex/La could have their hands full.It will be catastrophic for the oil spill.They said it would take a week for all the vessels to be moved out.Then another 10 days after storm passes to get everything up and going again.My goodness that would be awful.
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hmmm, W24 has been absent for a while.
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I think 94L will be from the system ~42W ~7N
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2 circles in the Caribbean, one in the Atlantic my bet for 8 o'clock.
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Quoting StormW:
There's one way to tell which "center"? is possibly going to win out.


Good morning. And the answer is ??
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I'm putting down $5 for the Blob SSE of PR.
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3207. leo305
Quoting wunderkidcayman:
StormW on the last few frames it look like that COC disipates on ir channel 2 mabe the new COC is near 16.8N 72.3W


I barely see a spin there.. at the same time I see lots of convergence with that blob south of haiti, which formed above the remnant middle level low that was so vigorous throughout the day yesterday, it's certainly possible that a center can reform.. but..
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Well, down to detail and fact sifting.

1. There are two areas of good 850 vorticity. One is over Jamaica and the other is due South of PR.

2. The given location for 93L has very little convection and is not colocated with the vort over Jamaica. If that is really where 93L is then it is no better organized than 12 hours ago.

3. There is good convection colocated with the 850 vort S of PR. To my mind that is the a threat now to develop. It has lots of sea room to work with.

4. The two big blobs are, well, blobs. BUT, one of them could get some surface action going although there is no 850 vort associated with either at this time. One of those blobs will likely win the battle for energy as they are too close together for both to survive IMO.

Summary ?

93L still a watch and wait

We could see 94L from the smallest blob S of PR

The two big blobs are wild cards.
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Quoting tramp96:
Wow thats a nice set of blobs.

Oh thanks, I had them done! Oh.. you mean the tropics.. my bad. :p
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3202. IKE
I think the blob south of Haiti won out over where the NHC has this positioned at.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
WELL NOW WE HAVE 92L 93L 94L
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StormW on the last few frames it look like that COC disipates on ir channel 2 mabe the new COC is near 16.8N 72.3W
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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!
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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.