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 ryang:
How is this ''new GFS'' any different?


Link
Member Since: Posts: Comments:
1795. ATL
Quoting MiamiHurricanes09:
I'm calling 30% (orange).

I think that's about right. They'll be hesitant to raise it a lot after dropping it down several times. They may even keep it at 20% until the invest consolidates a bit more.
1792. Patrap
Quoting homelesswanderer:


How far out does the dynamic show hour wise?


120 hrs from Initialization
Member Since: July 3, 2005 Posts: 419 Comments: 127371
Quoting Tazmanian:
new poll


the new two

A the same


B 30%-40

C 50-70%

D 80% +
.
E None of the above.
Member Since: Posts: Comments:
Quoting Patrap:
Dynamic Models (More sophisticated models)




Early Model Wind Forecasts




How far out does the dynamic show hour wise?
Member Since: August 15, 2008 Posts: 10 Comments: 3665
30% at 8pm... 60% at 2am, and 80% at 8am
Member Since: Posts: Comments:
1786. ryang
How is this ''new GFS'' any different?
Member Since: Posts: Comments:
Quoting StormW:
Maybe run into Haiti

IR2 LOOP
From that loop sure looks like it's headed more nw than wnw. Poor people in Haite can't catch a break.
Member Since: Posts: Comments:
Quoting Chucktown:
Hand drawn takes 93L entity into the NW Gulf next week - that trough the GFS is showing will not make it through the southeast - not in late June at least. Fropas are very rare down here between Memorial Day and Labor Day.

Link


that's what i'm thinking
Member Since: August 24, 2006 Posts: 0 Comments: 1867
1782. IKE
Quoting MiamiHurricanes09:
I would pick the GFS over the NOGAPS any day.


I think the NOGAPS is too fast.
Member Since: Posts: Comments:
Quoting Tazmanian:
the next two will be back up too %50
I'm calling 30% (orange).
Member Since: Posts: Comments:
1779. Drakoen
Well... this is more like a sequel
Member Since: October 28, 2006 Posts: 57 Comments: 29864
1777. centex
Quoting Drakoen:


Dolly part 2
I've been trying to get this blog to watch the larger spin, they all chasing little swirls. Lets up our game.
Member Since: Posts: Comments:
Quoting weatherwatcher12:
So where I have placed the red L is where the possible area of low pressure is forming? Also is the direction I am showing correct?



Image courtesy of NASA MSFC Earth Science Office

Bingo Thats around where I said the LLC would be or is forming!
Member Since: Posts: Comments:
1775. hydrus
Quoting Tazmanian:




the CMC is the one being the wishcaster it has two land falling storms and one fishstorm
I found it interesting. it is early in the game. The models will be more interesting on Thursday.
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Quoting IKE:
18Z NOGAPS through 120 hours. Much faster on movement then the GFS.
I would pick the GFS over the NOGAPS any day.
Member Since: Posts: Comments:
the next two will be back up too %50
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Quoting StormW:


That looks about right.

Ok, thanks.
Member Since: Posts: Comments:
Quoting Patrap:
Dynamic Models (More sophisticated models)




Early Model Wind Forecasts





the mode runs of DOOM
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
1769. IKE
18Z NOGAPS through 120 hours. Much faster on movement then the GFS.
Member Since: Posts: Comments:
1768. Patrap
Floater - RGB Color Infrared Loop
Member Since: July 3, 2005 Posts: 419 Comments: 127371
1767. hydrus
Quoting Acemmett90:

wow, wow, oh crap and wow
Did you watch the entire loop?
Member Since: Posts: Comments:
1766. Drakoen
Quoting MississippiWx:


Probably will only help the surface circulation strengthen. The mid-level vort should die out over the high terrain of Haiti and stop robbing energy from the developing low to the southwest.


Dolly part 2
Member Since: October 28, 2006 Posts: 57 Comments: 29864
Quoting DestinJeff:
Was this already mentioned from the 12Z CMC:



originates with energy currently in se caribbean


Just noticed that has a storm off the se coast too. be nice if thats all that happened. :(
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Quoting hydrus:
Link You want to see something unsettling....




the CMC is the one being the wishcaster it has two land falling storms and one fishstorm
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Not even Dmax yet and you can see this thing starting to go off.
Member Since: Posts: Comments:
1760. Patrap
Dynamic Models (More sophisticated models)




Early Model Wind Forecasts


Member Since: July 3, 2005 Posts: 419 Comments: 127371
I'm putting my money down on 15.3N, 75.0W.
.
.
Trying to find some low spin in the Central Caribbean is like playing "Where's Waldo" right now. Or betting on a roulette wheel.
.
.
Maybe once it passes the 75th parallel we'll get something, but at the moment this is one sickly looking "L".
Member Since: Posts: Comments:
1757. hydrus
Quoting Tazmanian:



lol
Link.... You want to see something unsettling....
Member Since: Posts: Comments:
1756. IKE
Quoting DestinJeff:
Was this already mentioned from the 12Z CMC:



originates with energy currently in se caribbean


I posted the run.
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Quoting StormW:


I know...that's what I was referring to. I can see the other down there by Jamaica.


Probably will only help the surface circulation strengthen. The mid-level vort should die out over the high terrain of Haiti and stop robbing energy from the developing low to the southwest.
Member Since: July 15, 2006 Posts: 17 Comments: 10159
So where I have placed the red L is where the possible area of low pressure is forming? Also is the direction I am showing correct?



Image courtesy of the NASA MSFC Earth Science Office
Member Since: Posts: Comments:
Quoting Acemmett90:

yup i know that would get a luagh while this blog is turning into an insane assilyume



lol
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Quoting ssmate:
Taz,
It's for a good cause.
POST 2,000 = $200



now if you want too do it the other way a round i would not mine haveing $200 i can get my new X Box 360 with that
Member Since: May 21, 2006 Posts: 5091 Comments: 114649
Quoting Chucktown:
Hand drawn takes 93L entity into the NW Gulf next week - that trough the GFS is showing will not make it through the southeast - not in late June at least. Fropas are very rare down here between Memorial Day and Labor Day.

Link


Yeah saw that earlier. I'm hoping the GFS does pan out and only develop a storm off the east coast and sends it out to sea. Best 4 everyone that way.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
1746. Dakster
Quoting Acemmett90:

hey this is a weather blog not male speed dating


Yeah I know - that is why you two need to go get a room....

Stormw - That IR really puts the developing center into perspective. I can actually see it now.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.