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:
Where all the thcp is and hot water......
Warm SSTs aren't the only factor.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1845. Patrap
Quoting stormpetrol:
I don't know but on the RGB loop the spin around 16.8N/72.2W looks to become the dominant one.


Looks to be it consolidating
Member Since: July 3, 2005 Posts: 419 Comments: 127358
I don't know but on the RGB loop the spin around 16.8N/72.2W looks to become the dominant one.
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Quoting GeoffreyWPB:
I think still yellow. Needs a lot more organization.
At least now it has a broad area of low pressure which it recently acquired, now it needs to consolidate it more and work on presentation.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Met Service of Jamaica website

June 22, 2010 at 12:00 p.m.

*** STRONG TROPICAL WAVE TO INFLUENCE WEATHER OVER JAMAICA* * *

*** STRONG TROPICAL WAVE TO INFLUENCE WEATHER OVER JAMAICA* * *

Comment
A strong Tropical Wave, currently near Hispaniola, is expected to continue westwards and be just east of Jamaica tonight and early Wednesday. Satellite imagery indicates large areas of showers and thunderstorms associated with this system with the capacity to produce flash floods.

The regional Hurricane Centre in Miami has indicated a 40 percent chance of tropical cyclone development over the next 24 to 48 hours.

Widespread showers and thunderstorm, which may be heavy at times, along with gusty winds, are also expected as the Tropical Wave moves across Jamaica on Wednesday.

Fishers and other marine interests are advised to exercise caution as strong, gusty winds are likely in showers and thunderstorms over inshore and offshore areas.

The Meteorological Service will continue to monitor this system.

cdj/lpb
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The latest satellite seems to be much more conducive to the theory of a bigger storm.
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1838. centex
trolls craping the blog. You need to read past the crap and only take notice to bloggers who post some reason behind there statements. Be back later to see if increased spin works it way down.
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Quoting Stormchaser2007:


No development until the WCARRB.

I'm thinking central Caribbean, after it passes west of Jamaica.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
I think still yellow. Needs a lot more organization.
Member Since: September 10, 2007 Posts: 0 Comments: 10928
I'll go with:
30% for 93L.
Potentially a mention of 9N 39W (not likely, though)

And, a tropical depression appears to be forming for 95E.
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1833. Drakoen
TPC 72 hour forecast:

Member Since: October 28, 2006 Posts: 57 Comments: 29864
1831. Patrap
AL932010 - INVEST
Member Since: July 3, 2005 Posts: 419 Comments: 127358
Quoting alaina1085:
Evening all!

Gotta go back and catch up on the posts. Ready for some more 93L madness!
LOL\
Thats why I like you :o)
You Love the Madness....

Taco :o)
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Quoting Acemmett90:

press +1 button


Oh my! while one is on SE LA the other hits central america then it heads backs into GOM

thanks for telling me Plus1.
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Quoting Patrap:


120 hrs from Initialization


Ok Pat. Thanks. :)seems to me a lot of models are moving in faster than the EURO. The HPC seems to agree with the faster call. Looks as if the NOGAPS agrees too but farther east. Does anyone know a reason they would speed things up? I thought a trough would speed things up. But the faster ones not showing that.

FINAL...

THE 12Z/22 GFS AND GEFS MEAN ARE CLOSER TO THE LARGE SCALE PATTERN
DEPICTED BY THE 00Z/22 ECENS MEAN OVER EASTERN NORTH AMERICA DAY 6
THAN THE GEM GLOBAL AND UKMET...WHICH SHOW A MORE AMPLIFIED
POSITIVE PNA PATTERN. SEE NO GOOD REASON TO DEVIATE FROM THE
RELIABLE ECENS THERE...WITH THE TROUGH COMING INTO THE NORTHWEST
NOT A MAJOR POINT OF CONTENTION. COORDINATION WITH TPC ON THE LOW
IN THE GULF THIS PERIOD RESULTED IN A SLIGHTLY FASTER
FORECAST...WITH THE CIRCULATION APPROACHING THE UPPER TEXAS COAST
DAY 7.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Quoting Acemmett90:

um what ur take on this


No development until the WCARRB.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
1823. Patrap



Member Since: July 3, 2005 Posts: 419 Comments: 127358
1817. hydrus
Quoting truecajun:


what am i looking at? i don't see anything in gulf in this map. y'all always make me feel so stupid, yet i still keep lurking
You have to go to the bottom of the page and click the (forward) box.
Member Since: September 27, 2007 Posts: 1 Comments: 20328
1816. Patrap
Storm Relative 16km Microwave-Based Total Precipitable Water Imagery

1943 UTC



Storm Relative 16km Microwave-Based Total Precipitable Water Imagery

The relative lack of environmental moisture around a tropical cyclone can adversely affect the deep convection and negatively impact the storm and result in weakening. Luckily there is several low earth orbiting satellites that provide estimates of the amount of water vapor in the atmospheric column, commonly referred to a total precipitable water (TPW). TPW estimates from a single satellite platform, however, often suffer from inadequate temporal coverage and poor refresh rates. To partially rectify this issue, the information from three Advanced Microwave Sounding Units (AMSU) on NOAA satellites and five Special Sensor Microwave Imagers (SSMI) on DOD satellites are combined via a blending algorithm described in Kidder and Jones (2007). Such a product has a refresh rate of approximately 6 hours and a spatial resolution of approximately 16km. This product shows the TPW around the tropical cyclone and to further enhance its utility the images are centered on the current storm location and when looped show TPW features moving to and from the storm center.
Member Since: July 3, 2005 Posts: 419 Comments: 127358
9N39W .... future 94L ?

http://www.ssd.noaa.gov/goes/east/catl/flash-ir2.html
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Quoting Acemmett90:

wow, wow, oh crap and wow


what am i looking at? i don't see anything in gulf in this map. y'all always make me feel so stupid, yet i still keep lurking
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The NHC will probably hold at 20%.

If this doesnt develop any new convection later tonight, 93L is going to have a tough time consolidating that new low and recon would probably be scrubbed.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
257 PM EDT TUE JUN 22 2010

VALID 12Z FRI JUN 25 2010 - 12Z TUE JUN 29 2010



FINAL...

THE 12Z/22 GFS AND GEFS MEAN ARE CLOSER TO THE LARGE SCALE PATTERN
DEPICTED BY THE 00Z/22 ECENS MEAN OVER EASTERN NORTH AMERICA DAY 6
THAN THE GEM GLOBAL AND UKMET...WHICH SHOW A MORE AMPLIFIED
POSITIVE PNA PATTERN. SEE NO GOOD REASON TO DEVIATE FROM THE
RELIABLE ECENS THERE...WITH THE TROUGH COMING INTO THE NORTHWEST
NOT A MAJOR POINT OF CONTENTION. COORDINATION WITH TPC ON THE LOW
IN THE GULF THIS PERIOD RESULTED IN A SLIGHTLY FASTER
FORECAST...WITH THE CIRCULATION APPROACHING THE UPPER TEXAS COAST DAY 7.

CISCO
Member Since: Posts: Comments:
Evening all!

Gotta go back and catch up on the posts. Ready for some more 93L madness!
Member Since: August 2, 2006 Posts: 0 Comments: 1240
1806. ssmate
I call time out. No posting for 2 minutes.
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1805. Dakster
Quoting Patrap:
Floater - RGB Color Infrared Loop


Is that a LLC trying to form? Looks like some hot towers too. If I only had a video about hot towers.
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I really think they are going to keep it relatively low for now, until Dmax sets in to see how it transpires and then really ramp up the chances
Member Since: March 19, 2010 Posts: 0 Comments: 1147
Quoting Tazmanian:
new poll


the new two

A the same


B 30%-40

C 50-70%

D 80% +


40%
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Rhodolady and errantlythought.
Many thanks for the information
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1798. hydrus
Quoting centex:
I've been trying to get this blog to watch the larger spin, they all chasing little swirls. Lets up our game.
Are you swirl profiling? jk:)
Member Since: September 27, 2007 Posts: 1 Comments: 20328
Quoting ecflweatherfan:
30% at 8pm... 60% at 2am, and 80% at 8am


LOL

Patience is a very hard thing to find on here.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting ryang:
How is this ''new GFS'' any different?


Link
Member Since: September 23, 2005 Posts: 14 Comments: 10836

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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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