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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Quoting Abacosurf:


Acceptance is a virtue ......
I understand that, but there is nothing to support what he is saying.
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3295. Dakster
What are the chances of three hurricanes simulataneously hitting CONUS? I couldn't imagine if all three blobs became hurricanes and hit different areas of the US on the same day.

Gotta be about the same as winning powerball...
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The most amazing thing! Three areas of organized convection, two of which were/are forecast at some point to become TD/TS/TH
All lined up across a few hundred miles of ocean.
Can the models handle this?
I'm thinking of getting in my boat a running to a hurricane hole NOW!!
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3293. IKE
Quoting wunderkidcayman:
ORANGE ALERT OMG HOLY #$&$% THIS IS KINDA EXPECTED AS I SAID IN MY COMMENTS BEFORE THIS POSSIBLE RELOCATION


Try decaf.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Jeff9641:
Very tight spin in the mid levels. This could allow for IR down the road once the surface reflection gets going. Models from last night will shift landfall from Panhandle to FLA's west coast. Very strong trough coming early next week.
Please explain to me where you see this "tight mid-level spin"?
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Calm down wunderkid.. jeez.
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Quoting MiamiHurricanes09:
Looks like they are watching the area of circular convection just south of Haiti. Not much of anything at the surface there.


Acceptance is a virtue ......
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Abacosurf: That is true about storm formation.
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ORANGE ALERT OMG HOLY #$&$% THIS IS KINDA EXPECTED AS I SAID IN MY COMMENTS BEFORE THIS POSSIBLE RELOCATION
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Quoting IKE:


The fact that 93L is centered south of Haiti....throw out the models like the GFDL and HWRF.

Yea, they will have to re-initialize. I wonder how long that will take. Recon definately needs to go in there today and see whats up.
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Quoting IKE:


No...for 93L. There is no 94L.

I see the NHC has the circle centered south of Haiti.
Looks like they are watching the area of circular convection just south of Haiti. Not much of anything at the surface there.
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3282. bassis
Hey chief,
Do we have a new system forming or is this a reforming of the same system
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Met Service Of Jamaica

NEWS RELEASE
June 23, 2010 at 6:00 a.m.

***FLASH FLOOD WATCH REMAINS IN EFFECT FOR ALL PARISHES***


The Meteorological Service has continued the Flash Flood Watch for low-lying and flood-prone areas of all parishes until 5:00 p.m. today.

A FLASH FLOOD WATCH means that flash flooding is possible and residents are advised to take precautionary measures, keep informed by listening to further releases from the Meteorological Service and be ready for quick action if flooding is observed or if a Warning is issued.

A strong Tropical Wave is expected to move across the island later today. Satellite imagery indicates large areas of showers and thunderstorms associated with this system and these have the capacity to produce flash floods. Widespread showers and thunderstorms, which may be heavy at times, along with gusty winds, are therefore expected as the Wave moves across Jamaica.

The Tropical Wave has the potential to develop into a tropical cyclone west of Jamaica within 48 hours. As such, marine interests, particularly fishers on the cays and banks south of the island should take precautionary measures as weather conditions are expected to deteriorate today and tomorrow. Strong, gusty winds are also likely in showers and thunderstorms over inshore and offshore areas of the north and south coasts.

All interests should also pay special attention to subsequent Releases issued by the Meteorological Service.
nch/kjb
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NHC upped 93L to 30%, no other circles
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We'll get a recon in today by 2 pm.
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Quoting StormW:
Morning Jeff; weathermanwannabe.


Morning Storm....Mother Nature is really teasing the Blog this morning...... :)
Member Since: August 8, 2006 Posts: 0 Comments: 9134
3276. IKE
Quoting alaina1085:

Ok. Im getting confused. Thanks.


The fact that 93L is centered south of Haiti....throw out the earlier model runs like the GFDL and HWRF.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Jeff9641:


Hey buddy 93L will be relocated to 72W as there is a mid level circulation working down to the surface and we may see this today. Winds under that blob are in the 20 to 30 knt range this morning.
RGB satellite imagery and 700mb vorticity product does not support that.
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Quoting IKE:


No...for 93L. There is no 94L.

I see the NHC has the circle centered south of Haiti.

Ok. Im getting confused. Thanks.
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Quoting StormW:


Obsessive? Ok...analyze it further...what is the wind flow and speed around that...compare the center of the anticyclone, to where the convection is. is something to have more of a chnace where there is a DIVERGENT flow of 5-10 knots, as opposed to an area of convection having winds straight out of the NW at 20-30 kts?


Storms form NOT directly under anticyclones all the time and then transition themselves under the anticyclone as the storm becomes stronger and needs to vent. The shear to the south of Haiti is in the 10 kt range. The tops are hardly drifting.
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3270. IKE
Quoting alaina1085:
I cant wait to see what happens when these blobs get into the western Carib..

So Ike that 30% is for future 94L blob?


No...for 93L. There is no 94L.

I see the NHC has the circle centered south of Haiti.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
3251. IKE 7:52 AM EDT on June 23, 2010

Makes sense; although we are looking at a few apparently distinct areas of convection right now, NHC is still lumping them together within the same tropical wave; don't know that they would assign a seperate designation to each area at this point....
Member Since: August 8, 2006 Posts: 0 Comments: 9134
3266. IKE
Quoting cirrocumulus:
If one takes a look at the latest infrared this early morning and hurricane season, one can see why there are so many storms forecasted this season. They may have to up it to about 40.


40?

We haven't had one yet....0-0-0.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting MiamiHurricanes09:
Lots of "blob" talk on the blog, lol...

Morning all, lmao at that M09!
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Orange
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I cant wait to see what happens when these blobs get into the western Carib..

So Ike that 30% is for future 94L blob?
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Quoting GeoffreyWPB:
Hmmm...Back up to Code Orange.
Lol, love how you say "code".
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A TROPICAL WAVE LOCATED FROM HAITI SOUTHWARD OVER THE CENTRAL
CARIBBEAN SEA IS PRODUCING SHOWERS AND THUNDERSTORMS OVER MUCH OF
EASTERN CUBA...JAMAICA...HAITI...THE DOMINICAN REPUBLIC...PUERTO
RICO...AND THE ADJACENT WATERS. UPPER-LEVEL WINDS APPEAR CONDUCIVE
FOR SOME SLOW DEVELOPMENT AS THE DISTURBANCE MOVES WESTWARD OR
WEST-NORTHWESTWARD AROUND 10 MPH INTO THE WESTERN CARIBBEAN SEA
OVER THE NEXT DAY OR TWO.
HEAVY RAINFALL COULD AFFECT PORTIONS OF
JAMAICA...CUBA...AND HAITI OVER THE NEXT COUPLE OF DAYS. THERE IS
A MEDIUM CHANCE...30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

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3260. bassis
It may be that I need more coffee but the visible sat it looks like there are three distinct blobs right now
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3259. IKE
Looks like the NHC has gone away from the coordinates of 15.6N and 76W based on their wording above...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
yea of which one?
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If one takes a look at the latest infrared this early morning and hurricane season, one can see why there are so many storms forecasted this season. They may have to up it to about 40.
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As I said before maybe a COC relocation of 93L to 16.8N 72.4W
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MEDIUM CHANCE now!
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Hmmm...Back up to Code Orange.
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3251. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT WED JUN 23 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE LOCATED FROM HAITI SOUTHWARD OVER THE CENTRAL
CARIBBEAN SEA IS PRODUCING SHOWERS AND THUNDERSTORMS OVER MUCH OF
EASTERN CUBA...JAMAICA...HAITI...THE DOMINICAN REPUBLIC...PUERTO
RICO...AND THE ADJACENT WATERS.
UPPER-LEVEL WINDS APPEAR CONDUCIVE
FOR SOME SLOW DEVELOPMENT AS THE DISTURBANCE MOVES WESTWARD OR
WEST-NORTHWESTWARD AROUND 10 MPH INTO THE WESTERN CARIBBEAN SEA
OVER THE NEXT DAY OR TWO. HEAVY RAINFALL COULD AFFECT PORTIONS OF
JAMAICA...CUBA...AND HAITI OVER THE NEXT COUPLE OF DAYS. THERE IS
A MEDIUM CHANCE...30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

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

$$
FORECASTER STEWART/CANGIALOSI


Looks like the NHC has gone away from the coordinates of 15.6N and 76W based on their wording above...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
3250. IKE
...30 PERCENT...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
I've looked over at some graphs and maps and looks like 93L isn't doing so good. The area further south just east of Trinidad and Tobago seems to be more impressive.

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3248. IKE
Quoting weathermanwannabe:
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 actually theory holds water but I don't have the time to research this issue ofconcurrent 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.....


That's usually correct from my experience following the tropics.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
will someone please call drakeon and levi and tell to get on here quickly we have 3 possible storms in the making LOL
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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.
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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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