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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1696. unf97
Quoting IKE:
New GFS at 192 hours...what a trough...



Ike, if that trough is as deep as this model run depicts, then the tropical entity would accelerate N/NE out of the GOM up the Atlantic seaboard. That is quite a run showed by GFS.
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"New" GFS
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Quoting Acemmett90:

taz im also starting to type like u with all the spelling mistakes




i love you tooo
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
1693. xcool
Link


go here taz
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Long-time lurker, first time poster, with a question for LA residents.
I'm due to be in Covington for the first time for a week starting on Sunday.
I know L93's future is highly uncertain, but IF it was to develop, and IF it was to head toward LA, is Covington far enough inland to avoid evacuation?
Any responses appreciated.
Thanks
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1691. hydrus
This model has a storm off the S.E Florida coast in 144 hours.Link
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Interesting new resolution increase on the GFS.
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ssmate... I agree. Does that mean we are all in hot water? LOL
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1686. Drakoen
The 850mb center is slowly becoming better aligned with the upper level anticyclone just to its west.
Member Since: October 28, 2006 Posts: 57 Comments: 30563
Quoting ssmate:
This Blog has gone through RI.



yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
1683. amd
hmmm, didn't expect winds to be this strong with 93L yet.

From sailwx.com

Ever Diamond

Last reported at 2010-Jun-22 20:00 UTC. Time now 2010-Jun-22 22:36 UTC.
Position N 17°30', W 075°24'.

Wind from 090 at 28 knots

Waves 1.0 meters (3 feet), 4 second period

Barometer 1011.0 mb
Air temperature 26.6 ° C
Visibility: greater than 5.4 NM
Dewpoint 23.0 ° C

Recent Wind Information from Ever Diamond, Just North of the supposed center of 93L
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Quoting Baltimorebirds:
Can you post the dievergence please.Thank you.

Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Dakster:
Back to weather...

Dr. M said 93L would be slow to develop and it apparently is doing just that.

I'd still say a 70% chance 93L at one point makes it to TD... Agree or disagree? I'll cite warm ssts, low shear, anticyclone above it as reasons. The reason is won't do it sooner is the hope affect and it will take time to organize itself.


Intensity models (LGEM, SHIPS) have 93L at Cat 1 on Friday.
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Quoting Acemmett90:

whoa when did that happen sothing fishy is going on taz im starting to belive u



re post


Quoting xcool:
2010-Jun-22 20:00 N 17°30' W 075°24' 21 21.3 090 28k 1011.0 5.4 1.0 26.6 23.0
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
1679. marmark
Quoting Tazmanian:



you mean 456
yup-sorry
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1677. IKE
New GFS at 192 hours...what a trough...

Member Since: June 9, 2005 Posts: 23 Comments: 37858
1675. Dakster
I was wondering the same thing about W456... Hope he is ok.
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Quoting Stormchaser2007:
Convergence has increased across our possible broad low. Makes sense:


The three vort maxes seems to be interacting.
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Quoting marmark:
Anyone heard from 486? I know he was sick a couple of weeks ago...



you mean 456
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1671. ssmate
This Blog has gone through RI.
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Agree. I have been seeing that trough across the East Coast since early yesterday (several model runs now).
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1668. Dakster
GeoffreyWPB gets the prize...

And if this storm were to be a Major it looks like we would be in for one heck of a season. Check out the seasons in the list... Notice 2005 has a couple of spots.
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Convergence has increased across our possible broad low. Makes sense:
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1665. IKE
Quoting nrtiwlnvragn:


You can see that in the 12Z GFS Ensembles:




You're correct.
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1663. marmark
Anyone heard from 486? I know he was sick a couple of weeks ago...
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1662. xcool
Link

go here
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1661. Drakoen
Quoting txag91met:

850 vort means nothing until u get surface pressures to fall and u get a closed low. That is when we get a storm.


The cimss 850mb vorticity product is very useful to discern whether we have spin in the lower to mid levels. That product is at the top of the lower levels of the atmosphere roughly 5,000ft. We see vorticity there, which is suggestive of something coming down to the surface.
Member Since: October 28, 2006 Posts: 57 Comments: 30563
Quoting Drakoen:


Definately supports what we are seeing on satellite imagery and the ship reports. Also it appears the vorticity has increase.
I would expect the 00z surface analysis to have a big "L" to the SE of Jamaica, be back in a bit.
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so 93L looks too be heading too the gulf
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
Yes..I Cheated :)

Rank: Name: Date: Winds (mph): Location:
1. Emily July 17, 2005 160 South of Jamaica
2. Dennis July 10, 2005 145 Gulf of Mexico
3. Audrey June 27, 1957 145 Gulf of Mexico
4. Unnnamed Hurricane July 26, 1926 140 Bahamas
5. Alma June 8, 1966 125 Florida Keys
6. Bertha July 8, 2008 120 Southeast of Bermuda
7. Unnamed Hurricane July 5, 1916 120 Gulf of Mexico
8. Unnamed Hurricane July 14, 1916 115 South Carolina
9. Unnamed Hurricane June 23, 1945 115 Gulf of Mexico
10. Anna July 21, 1961 115 Southern Caribbean
11. Bertha July 9, 1996 115 North of the Domincan Republic
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Quoting IKE:
New version of the GFS at 144 hours....



Can you give me a link to the new GFS version?

Thank you
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1656. IKE
Quoting HaboobsRsweet:
Not liking the latest CMC. I know it is the CMC but holy cow that is one heck of a low in the central Gulf. That is bad news if that verifies haha.


CMC is similar to the latest GFS only a little faster and further west.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Anyone else seeing the almost due west track of the mid-level circulation on the last few images of the RGB?
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Quoting xcool:
2010-Jun-22 20:00 N 17°30' W 075°24' 21 21.3 090 28k 1011.0 5.4 1.0 26.6 23.0



93L has all most 30kt of winds?
Member Since: May 21, 2006 Posts: 5091 Comments: 115241
1652. Drakoen
Quoting Stormchaser2007:
2100 UTC 850 Vort



Definately supports what we are seeing on satellite imagery and the ship reports. Also it appears the vorticity has increase.
Member Since: October 28, 2006 Posts: 57 Comments: 30563
Quoting IKE:
Strong trough on the 18Z GFS.


You can see that in the 12Z GFS Ensembles:


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Quoting IKE:


You asked what if the trough is slower or weaker. I said that would change the outcome of where 93L goes.
Oh sorry, lol.
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Quoting Stormchaser2007:
2100 UTC 850 Vort


850 vort means nothing until u get surface pressures to fall and u get a closed low. That is when we get a storm.
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1647. Dakster
Dudua was arrested on the Mandela Highway on the border between Kingston and St Catherine. He and a church Minister, AL Miller, were heading to the US Embassy where he was going to surrender but the car was stopped by traffic cops for a spot check and he was arrested.
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the blog pick up
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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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