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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lt looks like some banding features developing on both blobs

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Latest model runs for 93L

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Visible should be up in the next hour or so..
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Quoting JFLORIDA:
It looks more like 3 separate storms.



Not saying they will all do something. But its very busy.


Didn't one or two of the model runs foreshadow multiple storms in the Gulf in the last day or so?


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the area se of the islands looks to be getting organise faster than the one in the central caribbean. this is the area to watch down the road
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Was going to say something about the three stooges but see someone already got that one. So I'll leave it at its not nice to play with mother nature. I ain't touching this one but who ever can figure this out could pocket the nomination for forecaster of the year award.
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The way this season is starting - numerous tropical disturbances/blobs occurring where they don't usually occur this early in the hurricane season - seems to indicate that the "weathermasters" at the NHC will be busy for the remainder of the hurricane season.
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What is wrong with this? Compare these two images.

Link

Link



The mid-level circulation seem to be hogging all of the convection for itself--making it harder for the more organized surface low to the west to develop.

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the area about1200 miles ESE of the southern windward islands could be classified as 94L today
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futuremet with your comment# 3125 are you going left to right or right to left
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morning
very stormy day in the caribbean today.apart from the area in the central caribbean which is still very slow to organise, there is another large area of disturbed weather at 8N 4OW. the system is moving west at 10-15 mph.
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Quoting futuremet:
New 850mb vorticity is out.


Wow! This should be interesting. :)
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The circulation near Jamaica seems to be winning.
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3129. guygee
Quoting JFLORIDA:
It looks more like 3 separate storms.



Not saying they will all do something. But its very busy.
JFL - They look to be fighting it out under the same broad upper high. Outflow will not be the problem, but hard to get decent low-level convergence spinning up with the convection so disorganized.

Think I'll check back later this morning, I hate it when I wake up at 3 AM to check the weather ;~)
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New 850mb vorticity is out.
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you are right jeff I am just waiting for the nhc to see this unless if this blob at 16.8N 72.1W can move over where the offi. center is but anyway hopefully the Hurricane Hunters fly so we can get a good view and they might give the COC relocation
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Quoting JFLORIDA:
It looks more like 3 separate storms.



Not saying they will all do something. But its very busy.


This is in fact what it is. The one in the middle is just a blob. The first one barely generating any surface convergence.The second has a well-defined mild level circulation, but it is not proliferating to the surface.
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Morning everyone...

Photobucket

Larry, Moe, and Curly?

All kidding aside, TAFB has the Low south of Jamaica

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Also the other blob at 16.0N 68.5W is moving west toward the blob that could be the COC

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3118. guygee
Are the models still initializing near 15N,75W?
I am just not seeing that as making sense. Waiting for the next run...
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Quoting wunderkidcayman:
Hey guys I see a possible center relocation to 16.8N 72.1W



This mid level circulation had strengthened substantially overnight, but has failed to drop down to the surface.

500m vorticity

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Quoting Jeff9641:


It was great and I needed it. Good to be back though.

glad you had a good time. gots to move on see ya later.
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Quoting Jeff9641:


Hey my friend!! I am doing great about to get ready for work. How are you doing.

I,m doing well and at work already. how was your vacation?
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Quoting JLPR2:
this is an interesting view, we have three blobs, one is related to 93L, the second is a piece that seems to have broken off 93L and the third is a TW


we have a battle of the blobs! LOL!
Well, goodnight to anyone out there or good morning, choose the most appropriate XD


Thats what I'm seeing 3 blobs. Glad you explained em cuz I was lost. :)
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Hey guys I see a possible center relocation to 16.8N 72.1W

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Pretty much nothing left of 93L convective wise. Im starting to doubt if it develops at all. It remains very poorly organized. Recon should get scrubbed later today. Not much help flying into a few clouds...
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Quoting Jeff9641:
A major rain event is on the way to Florida this weekend as a result.

Morning, Hey how are you? Things look really interesting for next week.
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3105. Walshy
93L still slowly developing.
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3102. HadesGodWyvern (Mod)
93L is just "waiting" for developing.
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3101. tea3781
Quoting all4hurricanes:
93L is not dead it's in ideal conditions it's just not doing anything with it


93L is not dead however I dont think that you can put a lot into the models right now until something develops.
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Quoting SykKid:
93L RIP
93L is not dead it's in ideal conditions it's just not doing anything with it
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3099. guygee
3-Day Genesis Potential Forecast, Vort 850 mb - Vort 200 mb, 2010-06-23-00Z.

Interesting product, but based on what global model?
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3097. guygee
I hereby nominate the convection near 17N, 72W as the official "blob of the hour".
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3096. HadesGodWyvern (Mod)
National Hurricane Center
Tropical Cyclone Advisory #17
SEVERE TROPICAL CYCLONE CELIA (EP042010)
9:00 AM UTC June 23 2010
==================================

At 9:00 AM UTC, Hurricane Celia (980 hPa) located at 11.9N 108.0W or 675 NM south of the Southern tip of Baja California, Mexico has sustained winds of 75 knots with gusts of 90 knots. The cyclone is reported as moving west at 9 knots.

Forecast and Intensity
======================
24 HRS: 12.3N 112.2W - 85 knots (SVR Cyclone SSHS-2)
48 HRS: 13.6N 116.8W - 90 knots (SVR Cyclone SSHS-2)
72 HRS: 14.9N 120.8W - 70 knots (SVR Cyclone SSHS-1)
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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.