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 OracleDeAtlantis:
Sweet [Nexsat animation] of the action. Thanks again to Watchingnva:


you don't have to thank me:P...but thanks for the thank you....i just love the nexsat....its usually pretty up to date...and the images and options are really nice...im watching that area south of Haiti close...bc...looking at the nexsat loop you see the mlc come up toward Haiti from the southeast then turn west just south of Haiti...and convection just happened to starting popping in the area where it was heading...lol...if 93 has a good dmax over the next 6 hours...we might have a llc around Jamaica...we will have to wait and see...
Member Since: Posts: Comments:
3044. xcool
LOOK AT MY POSTING
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3042. xcool

Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting xcool:
StormGoddess BYE

Bye. :)
Member Since: Posts: Comments:
3040. xcool
HAHA
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3038. xcool
StormGoddess BYE
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Night all.
Member Since: Posts: Comments:
3036. xcool
144HR
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3034. xcool
LOL
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3031. xcool
wow 93L
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3030. xcool
http://raleighwx.easternuswx.com/models/ecmwf.html update damm slow
Member Since: September 26, 2009 Posts: 2 Comments: 15603
there are actually 2 upper level circlations showing up in that area near 93l.

maybe they will cancel each other out.
or worse TWO storms could develop.

i am not buying any of the models at this point.
after seeing this graphic i dont think 93L will
even develop at all.

Member Since: Posts: Comments:
3027. xcool
thank for rember
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3026. xcool
hmm
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Sweet [Nexsat animation] of the action. Thanks again to Watchingnva:
Member Since: Posts: Comments:
3023. xcool
wowow
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting TropicalNonsense:

Alex would be atleast Cat1-2 strength over or near the Deep Water Horizon if the models are correct.

This Scenario could be worse than Katrina, considering the Oil spill.

This could be an EPIC size Disaster in the making if Alex develops and follows a track anywhere even close to what the long range models are predicting.






Member Since: Posts: Comments:
3021. JLPR2
Quoting OracleDeAtlantis:


You're right about the Nexsat, it's beautiful and gives a better dimensional perspective. This crazy storm has divided and a piece of energy has moved westward.


actually its the other way around, a piece of Energy moved to the east and is now sitting south of PR and the DR
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3020. xcool
opps errorsss
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting watchingnva:


test...

can really see the mlc moving nw earlier this evening...i love the nexsat for some reason...

and that oil rain video is pretty sickening...


You're right about the Nexsat, it's beautiful and gives a better dimensional perspective. This crazy storm has divided and a piece of energy has moved westward.
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HWRF/GFDL Model Intensity will only go up once Alex develops.
scary stuff right here....

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3016. xcool
ecwm next
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3015. xcool
Center fm ON 93l
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3014. xcool
CMC NOT DO GOOD.
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3012. JLPR2
Quoting xcool:
Link

here cmc


WTH! CMC has lost it LOL!
It develops the wave behind 93L and shoots it fast to the WNW, once in teh GOM, 93L and the Wave merge into one system
O_o?
What is the CMC thinking? LOL!
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3011. xcool
oh yea 93L fireing convection NOW
Member Since: September 26, 2009 Posts: 2 Comments: 15603
i posted this before... but for whatever reason it was removed.

the very latest 0Z 93l track as Alex....

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3009. xcool
l
Member Since: September 26, 2009 Posts: 2 Comments: 15603
What is the cmc doing? I see it heading for what looks like tx/la border and then it does something...and I dont knw what. Still learning the models ...can anyone explain.
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3007. xcool
Center fm
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3006. xcool
Link

here cmc
Member Since: September 26, 2009 Posts: 2 Comments: 15603
with 5-10 kts of shear and bath water in the Gulf
Alex will most likely be even stronger than the models anticipate.
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Are any new models out at this time?
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3002. xcool
h
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Alex would be atleast Cat1-2 strength over or near the Deep Water Horizon if the models are correct.

This Scenario could be worse than Katrina, considering the Oil spill.

This could be an EPIC size Disaster in the making if Alex develops and follows a track anywhere
even close to what the long range models are predicting.




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2999. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15603
and another one bites the dust
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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.