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 Jeff9641:


Hey buddy, 93L looks very good right and LLC is developing right now and it seems to be moving NW.


???

and this pertains to whether the GFS develops it or not how?
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Quoting WinterAnalystwx13:


I tagged you last night ;P
AH shoot...thats right :(
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Lurking at the floater over 97 -- visible loop -- zoom into the area 16.5N and 70W to see spin. Also, I can see venting or outflow.
Link
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Quoting IKE:


You mean debbykat?


you do know what name is next right? think about it

stormkat, stormno, debbykat? so will we see debbyno?
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Quoting RecordSeason:
*ahem*

Today's Potential Intensity Map


Wow, parts of the gulf support a strong Cat 5.
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Unless something major changes, which it doesn't look like it will with 93L organizing slowly, I doubt the Hunters will fly tomorrow.
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389. IKE
Quoting tropicfreak:
speaking of downcasting, wheres stormno.


You mean debbykat?
Member Since: June 9, 2005 Posts: 23 Comments: 37858
shear is going to become a problem if the northern circulation takes over
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well now looking at things, they could cancel recon tomorrow, but we will see

I guess I took scotts' post a bit out of context
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385. IKE
I will say 1 thing.. July-Oct will bring alot of storms.

It does almost every year.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
This place sounds, right now with all the speculation and percentages being thrown around, like some of the betting rooms in Las Vegas; just replace the monitor images of horse races with a few loop frames of 93L....... :)
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speaking of downcasting, wheres stormno.
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As much as I disagree with scottsvb on alot of things, I agree that development if any, won't occur for another few days until the energy comes together.
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Quoting WinterAnalystwx13:
I believe once 93L develops, it has a chace to go through Rapid Intensification. This is due to:

Tropical Cyclone Heat Potential:



Sea Surface Temperatures:



Wind Shear:

Tag! I win!
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hes saying its not gonna develop an llc by tomorrow, and you are saying it will. yet hes downcasting even though hes right and you are wrong so far...
Quoting Hurricanes101:
I give it a 95% chance that scott will keep downcasting 93L lol
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Quoting Hurricanes101:
I give it a 95% chance that scott will keep downcasting 93L lol


Is Dr. Masters a downcaster?
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Latest High Seas Forecast

Excerpt:

.CARIBBEAN TROPICAL WAVE ALONG 72W MOVE W 10 KT. N OF 15N
WITHIN 120 NM W OF WAVE AXIS NE TO E WINDS 20 KT . SEAS TO 8
FT. N OF 15N WITHIN 60 NM OF WAVE AXIS SE WINDS 20 KT. SEAS
LESS THAN 8 FT.
.24 HOUR FORECAST TROPICAL WAVE ALONG 77W DEVELOPING EMBEDDED
LOW PRES 1009 MB...POSSIBLE TROPICAL CYCLONE...NEAR 17N77W. N
OF 15N E OF WAVE TO 66W SE WINDS 20 KT. SEAS TO 9 FT. S OF
17N FROM 61W TO 66W NE WINDS 20 KT. SEAS 8 FT. N OF 15N W OF
WAVE TO 80W NE WINDS 20 TO 25 KT. SEAS TO 9 FT.
.48 HOUR FORECAST TROPICAL WAVE ALONG 81W WITH LOW PRES...
POSSIBLE TROPICAL CYCLONE...NEAR 18N81W. WITHIN 120 NM W OF LOW
PRES CENTER WINDS 20 TO 25 KT. SEAS 8 FT. WITHIN 60 NM E OF
LOW PRES CENTER WIND 20 KT. SEAS TO 8 FT. WIND AND SEAS
HIGHER IN NUMEROUS TSTMS IN SQUALLS NEAR LOW PRES CENTER.
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Quoting cyclonekid:
Agreed. LOL.


LOL its not downcasting.. hey I want a storm just like you all do. I'm just telling you the facts. Nothing within 48hrs.

I will say 1 thing.. July-Oct will bring alot of storms.
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SQUAWK!!!!
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Quoting DestinJeff:
12Z GFS out to +84:



93L stuck in the Yucatan, a very possible solution as much as the GOM monster potential.
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Quoting Hurricanes101:
I give it a 95% chance that scott will keep downcasting 93L lol


I give it 100% chance that a whole bunch of folks are going to end up on my ignore list if things really get cracking. And I am going into lurk mode to stay out of the way of folks that really know something.
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Quoting Hurricanes101:
I give it a 95% chance that scott will keep downcasting 93L lol


We should respect him, he is a MET LOL. METS are always right ;)
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Quoting Hurricanes101:
I give it a 95% chance that scott will keep downcasting 93L lol
Agreed. LOL.
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Quoting weatherwatcher12:

I really doubt that they will cancel with the favorable conditions this thing has in front of it.


They will cancel to save $$$ on waiting 1 more day till something is close to being worth finding a Circulation. They only fly out if they think there might be a circulation.
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Quoting Hurricanes101:
reed, 12Z GFS is not on board


It has a broad low (93L) hitting the Yucatan in 72 hours. The last few runs just had moisture.
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Quoting Patrap:


Thats funny coming from a Guy peeking out a UFO..LOL
no i am the UFO
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Quoting tropicfreak:
Same goes for visible.

Link


nothing close to a LLC from 93L maybe by Thurs.
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reed, 12Z GFS is not on board
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I give it a 95% chance that scott will keep downcasting 93L lol
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Quoting scottsvb:


I give it a 75% chance they will cancel for tomorrow

I really doubt that they will cancel with the favorable conditions this thing has in front of it.
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Quoting KEEPEROFTHEGATE:
first flight on 23 invest flight on 24 cyclone so they expect a cyclone this ain't rocket science


Thats funny coming from a Guy peeking out a UFO..LOL
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Same goes for visible.

Link
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this I think was posted earler

For Today (text issued yesterday)

000
NOUS42 KNHC 211400
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1000 AM EDT MON 21 JUNE 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 22/1100Z TO 23/1100Z JUNE 2010
TCPOD NUMBER.....10-021

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK: POSSIBLE LOW LEVEL
INVEST NEAR 16.ON 77.0W AT 23/1800Z.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
JWP


For Tomorrow (text issued today)

000
NOUS42 KNHC 221500
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1100 AM EDT TUE 22 JUNE 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 23/1100Z TO 24/1100Z JUNE 2010
TCPOD NUMBER.....10-022

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (SOUTH OF JAMAICA)
FLIGHT ONE - TEAL 70
A. 23/1800Z
B. AFXXX 01AAA INVEST
C. 23/1330Z
D. 17.0N 77.5W
E. 23/1700Z TO 23/2100Z
F. SFC TO 10,000 FT

FLIGHT TWO - TEAL 71
A. 24/0600Z
B. AFXXX 0201A CYCLONE
C. 24/0100Z
D. 17.5N 79.5W
E. 24/0400Z TO 24/0830Z
F. SFC TO 10,000 FT

2. SUCCEEDING DAY OUTLOOK: CONTINUE 12 HRLY
FIXES IF SYSTEM REMAINS A THREAT.

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Quoting IKE:
Hispaniola is fixing to get drenched from 93L.
Yes it is. If it moves slowly, it could be another disaster for them. Horrible to say the least.
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Quoting tropicfreak:
Circulation is becoming more visible on Infared.


Link


Infared only shows the mid-upper levels. We need a LLC... and visibles are the best along with ship,bouy reports.. of course Recon gives us the most data.
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Quoting Patrap:


.."I gotta tell ya folks, them wunderbloggers are on top of things"..

Back to you guys in the Studio..


LMAO
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Quoting Patrap:


.."I gotta tell ya folks,them wunderbloggers are on top of things"..

Back to you guys in the Studio..
first flight on 23 invest flight on 24 cyclone so they expect a cyclone this ain't rocket science
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Quoting BWDavis:
I work for the Louisiana Department of Public Safety in IT and watch these storms to know if I will have to man our Emergency Operations Center. Please forgive my ignorance, but I have been wondering about how a low pressure system is named. I notice that it is usually 92L, 93L, etc. What determines the numeric part of the name?

Thank you for any assistance, Brian


i want to thank you on behalf of the people of louisiana for looking after our safety by coming to the right place.
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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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