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 Baltimorebirds:
In any giving season a major in the gulf will not be good.But mother nature is trying to find a way to cool off those ocean temps and what it we won't like....
The Oil!!
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I am thinking still "Yellow" at 8pm... but up the chance to 30%.
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Quoting HadesGodWyvern:


yikes?!



oh boy party time oh has the pizza
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
1593. HadesGodWyvern (Mod)
There are several models doing that too but varying in intensity.
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At 6:23 PM 10 comments were posted, damn.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1590. IKE
New version of the GFS at 144 hours....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Acemmett90:

yah why is it going over the red portion tonight


Nope, developing broad low SE of Jamaica. North of the official point.
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Quoting unf97:


The NW Caribbean is extremely high in TCHP. Any organized low pressure area that reaches that area has the potential to intensify, along with the proper upper air pattern favorable for development for a tropical cyclone.



yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
93L today cat 5 by PM wed
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
1583. unf97
Quoting Tazmanian:



and looks like 93L may go overe the main part of it


The NW Caribbean is extremely high in TCHP. Any organized low pressure area that reaches that area has the potential to really intensify, along with the proper upper air pattern favorable for development for a tropical cyclone.
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1582. hydrus
Quoting Acemmett90:

dont be racist
lmao.
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Anything in GOMEX, not good right now--- or ever for that matter
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1580. centex
Quoting Acemmett90:

dont be racist
Your the racist, I don't think like that.
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1579. NRAamy
Whiskey Tango Foxtrot with that map...


hahahahahahahaha!

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Quoting leo305:
I think its beginning to develop, there is a very area of convection forming were I believe the COC is going to form.




coc has from
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
CONUS sector is in RSO for GOES 13 due to the severe weather in the North.

Get those visible images in while you can.

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Quoting Baltimorebirds:
93l will be traveling over hot water.Let's see what it does.Will it be like Ida from last year.....who knows.


I wish it would be like Ida...Ida was nothing when it hit the coast. Winds were not impressive and over 3 or 4 inches of rain. Surge was not bad at all either. If 93L is like that I will welcome it...drop the temps here and give the grass a nice drink.
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Quoting Stormchaser2007:
Tonight could be interesting.


Yes it should. I think we'll be looking at something very interesting tomorrow.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
93L you play nic now
Member Since: May 21, 2006 Posts: 5091 Comments: 115247
Quoting HadesGodWyvern:


yikes?!


Yeah. Didn't like that one either. :)
Member Since: August 15, 2008 Posts: 10 Comments: 3665
1571. IKE
Quoting TOMSEFLA:

gfs model should of gotten its upgrade today anybody got new model links?


Link
Member Since: June 9, 2005 Posts: 23 Comments: 37858
1569. ssmate
Quoting Stormchaser2007:


They canceled many flights for pre-Dolly in 2008 and that looked 10x better than this ever did.
That is right on. I do think it will be an issue later on though.
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1568. leo305
I think its beginning to develop, there is a very area of convection forming were I believe the COC is going to form.
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Tonight could be interesting.
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1565. hydrus
Quoting HadesGodWyvern:


yikes?!
That is a little unsettling isnt it.
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Yeah, I'll see your post one day. Went to Dauphin Island yesterday and all was oil free. Lots of activity and lots of folks to feed. If you own a simple food stand on the Island you'd be making money!
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Quoting Drakoen:


They have canceled in the past before. I do think it needs some more organization.


With the oil spill disaster, I think they will fly in… on the side of caution. Unless it completly falls apart during the evening and early morning hours.
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1561. Dakster
Quoting ecflweatherfan:
Yeah Dakster... would not be the first time that has happened, unfortunately. Special K did that in '05


Yep. I do remember. a major cane in the GOM would not be a good thing.
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Quoting TOMSEFLA:

gfs model should of gotten its upgrade today anybody got new model links?


Date was changed to July 27, but it is running in parallel with the operational version.

Link
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1557. centex
It's going to Jamacia Mon.
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Quoting TOMSEFLA:

gfs model should of gotten its upgrade today anybody got new model links?


They postponed it a while back.

Not happening until LATE July.
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1554. NRAamy
Hey BB....sorry I missed your shout out...

:)
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1553. Dakster
Quoting HadesGodWyvern:


yikes?!


Whiskey Tango Foxtrot with that map...
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Quoting Drakoen:
StormChaser put on the Ship reports with the vort product. It fits in pretty nicely.


Indeed.


Theres also quite a few cumulonimbus atop the developing low.

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Yeah Dakster... would not be the first time that has happened, unfortunately. Special K did that in '05
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Quoting weatherwatcher12:
Winds very calm here in Jamaica. It's still.

Does this mean anything for 93L.
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1546. Dakster
Quoting StormW:


See post 1519


I know, you beat me to it! :)
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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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