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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1546. Dakster
Quoting StormW:


See post 1519


I know, you beat me to it! :)
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Quoting Dakster:


That is what I am afraid of. Go to bed and it is a CAT 1 and wakeup to a CAT 4.



or cat 5 with 882mb
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Anything higher than 80 allows for the possibility of rapid intensification.
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Quoting Stormchaser2007:


High enough? We have August levels of TCHP in the NW Caribbean.





and looks like 93L may go overe the main part of it
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1541. Dakster
Quoting ecflweatherfan:
Dakster... think that RI is completely possible, over the western Caribbean since shear values are expected to be virtually non-existant, water temps of 29-30C (84-86F) and very high TCHP


That is what I am afraid of. Go to bed and it is a CAT 1 and wakeup to a CAT 4.
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Quoting Drakoen:
StormChaser put on the Ship reports with the vort product. It fits in pretty nicely.

gfs model should of gotten its upgrade today anybody got new model links?
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1538. HadesGodWyvern (Mod)


yikes?!
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Quoting Drakoen:


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


They canceled many flights for pre-Dolly in 2008 and that looked 10x better than this ever did.
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Quoting Drakoen:


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

Yes, yes they have however not happening tomorrow. Just sit by your computer with Google Earth up, grab some popcorn and enjoy the show.
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1534. Drakoen
StormChaser put on the Ship reports with the vort product. It fits in pretty nicely.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
I see the spin at 15N 75W ok so look back at about 5 or 6 pages back and see my comments

quoting myself
I say we get our COC by tonight (check)we get our convection by early morn and we get our TD1 by mid day tomorrow at the most tomorrow afternoon when the Hurricane Hunters fly in

everything is set in motion
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Uh oh... just began to thunder here... :o
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New GFS has a low out in the Atlantic also.


Member Since: September 23, 2005 Posts: 15 Comments: 11343
Quoting Dakster:
Assuming 93L organizes and becomes Alex. What are the chances for RI (rapid intensification). Are the THCP values high enough to support it?


High enough? We have August levels of TCHP in the NW Caribbean.


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1527. Drakoen
Quoting HaboobsRsweet:

Not going to happen...just watch. They will fly tomorrow.


They have canceled in the past before. I do think it needs some more organization.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Dakster... think that RI is completely possible, over the western Caribbean since shear values are expected to be virtually non-existant, water temps of 29-30C (84-86F) and very high TCHP
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1524. Dakster
Quoting Snowlover123:


That's okay... I'll google search "MJO map"



I know that Stormw keeps alot info on MJO. He is a featured blogger. Also, W456 (Where is he btw?) usually keeps up to date info as well.
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Interaction with land may actually help to tighten the circulation, that is provided it doesn't spend too much time in the mountains. The MLC has become pretty vigorous today, would be nice to see some local ship reports.
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93L will be going overe vary high tropical cyclone heat potential
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1521. unf97
Quoting IKE:


They could cancel it.


Yes they could cancel, but that appears unlikely at this point. The system is definitely exhibiting signs of slow organization, and the hunters need to get in there to retrieve data.
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Quoting Baltimorebirds:
It's tchp or in other words tropical cyclone heat potential.



all most right
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Winds very calm here in Jamaica. It's still.
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting CybrTeddy:


92L and 93L have been bad signs for the season. 92L almost become a tropical depression.. that far east so early in the season has almost never happened. 93L looks like a disturbance one would see in late July not mid to late June.


92L - "almost" counts in horseshoes and hand grenades. This is neither. Besides, 'accurate' weather tracking is maybe 30-40 years old. So, we don't really have a lot of history to go by, do we?
93L - looks like a bunch of clouds looking for direction. It would hardly be much of a disturbance in July, August or September, either.

I keep forgetting how much of "the sky is falling" attitude permeates this board.

IF 93L becomes anything greater than a TD (assuming it gets that far), I will be stunned.
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Quoting Drakoen:


Indeed, 93L will have to organize some convection over the broad low or they very well could cancel it.

Not going to happen...just watch. They will fly tomorrow.
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1514. Dakster
Assuming 93L organizes and becomes Alex. What are the chances for RI (rapid intensification). Are the THCP values high enough to support it?
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Quoting Tazmanian:



sorry i do not have any


That's okay... I'll google search "MJO map"

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1512. Drakoen
Quoting Stormchaser2007:
Interesting ship reports....


That is interesting. The low could be a little further north than they though based on that.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
D max is not really a time period it is the instant before sunrise.
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1509. ACEhigh
I agree with jeff on this one. If this system develops at all in the short term it will be from the mid level vortex near 17n 71.5w. If you look at the RBG loop it seems as if it is making some effort to manifest itself near the surface. A lot of low level clouds flowing north towards that point. I really see nothing much where the models are initiating the system. The big problem with the northern mid level circulation is that it is rapidly running out of sea room. Still, it could maintain a vigorous mid level circulation with minimal disruption even with a glancing blow to sw hispasnola.
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Quoting Snowlover123:


Do you have any maps for the MJO? Would greatly appreciate it.

-Snowy



sorry i do not have any
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1506. Drakoen
Quoting IKE:


They could cancel it.


Indeed, 93L will have to organize some convection over the broad low or they very well could cancel it.
Member Since: October 28, 2006 Posts: 57 Comments: 30825
Interesting ship reports....
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Quoting MiamiHurricanes09:
You seem to forget that D-Max isn't until 2:00 AM EDT - 8:00 AM EDT. What 93L is about to go into is D-MIN.




and 93L is relly starting too pop
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Quoting Tazmanian:




how about right now lol


Do you have any maps for the MJO? Would greatly appreciate it.

-Snowy
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1501. Drakoen
Again the spin you guys are seeing on the tip of the DR is a mesoscale convective vortex associated with 93L's bands. Here's a satellite loop centered with the NHC coordinates.

Link
Member Since: October 28, 2006 Posts: 57 Comments: 30825
1500. centex
rock this loop.

Link
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I put the coc (so to speak) at 73 17n. Anyone agree, disagree or have another oppinion?
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1498. IKE
Quoting HaboobsRsweet:
Like I said earlier this debate will be so much better tomorrow after the two missions fly in the storm. They are a go for tomorrow so we will get much better data.


They could cancel it.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting Drakoen:
93L will probably wait until it gets into the central Caribbean to really organize.


Isn't in the central Caribbean now?
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Quoting msuwxman:
Good timing for 93L. Get a LLC just in time for DMax.
You seem to forget that D-Max isn't until 2:00 AM EDT - 8:00 AM EDT. What 93L is about to go into is D-MIN.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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