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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93L lacking organization after looking on satellite, but the circulation seems to be better defined as 850 millibar vorticity has tightened some and improved.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting Drakoen:
The NHC is absolutely correct when they lowered the chances within 48 hours. The system is really not what we have been monitoring south of the DR and Haiti. Probably just a mesoscale convective vortex. The area we need to focus on is between 75W-72W.
DRak/ I see what you mean, between 14.5 & 16.5 N
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1144. quante
This board is like slowing down for an accident. I know there is nothing to see, but yet I keep looking.
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Wow.......Dr. M stepping up....Real Cool.
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1142. ssmate
Why is there a break?
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Quoting weathermanwannabe:
1122. shauntanner (Admin) 4:04 PM EDT on June 22, 2010

I have never seen that type of entry before (othern than his Blog entries).....Is he taking requests?


No. There was a post from Admin a week or two ago saying that questions for Dr. M were to be posted elsewhere. I think he is simply rescinding that earlier post now.
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Dr Masters,what do you think the chances are of 93L being hurricane as it approaches the yucatan area and when do you believe the downward mjo we'll be over the caribean basin???
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Quoting CyclonicVoyage:


Exactly what everyone is doing... LOL!
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Quoting Drakoen:
The NHC is absolutely correct when they lowered the chances within 48 hours. The system is really not what we have been monitoring south of the DR and Haiti. Probably just a mesoscale convective vortex. The area we need to focus on is between 75W-72W.


It's getting there. Taking it's sweet time but if you study the low clouds in the region you speak of, it's there.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
After looking at some various loops, 93L looks somewhat better than I thought.

Still shouldnt develop until Thursday.
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1135. shauntanner (Admin)
Listen to Dr. Masters show here

http://www.wunderground.com/wxradio/wubroadcast.html
Dr. M, what do you think the sea temps will be by August/September?
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1122. shauntanner (Admin) 4:04 PM EDT on June 22, 2010

I have never seen that type of entry before (othern than his Blog entries).....Is he taking requests?
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1132. leo305
Three areas of concern, CMC develops all of them.. and the conditions are there for them all to form.
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1131. xcool
Drakoen thanks
Member Since: September 26, 2009 Posts: 2 Comments: 15670
1130. Crawls
Dr. M, Any change in your thoughts from this mornings blog?
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75W?
Member Since: May 21, 2006 Posts: 5091 Comments: 115074
1128. Drakoen
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1127. Crawls
Happy debating bloggers. I'll check back in tomorrow to see what 93L is doing.
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1126. Drakoen
The NHC is absolutely correct when they lowered the chances within 48 hours. The system is really not what we have been monitoring south of the DR and Haiti. Probably just a mesoscale convective vortex. The area we need to focus on is between 75W-72W.
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Quoting Acemmett90:

that looks like a dying animal




not that wave the wave more too the W
Member Since: May 21, 2006 Posts: 5091 Comments: 115074
Quoting kmanislander:


Grenada, 1012 mb

93l's vorticity has been on the increase though, so who knows what will happen.
Member Since: December 1, 2006 Posts: 2 Comments: 3619
1122. shauntanner (Admin)
Post questions for Dr. Masters here now
Quoting Hurricanes101:


yup ECMWF does not develop 93L until Friday -Saturday now

people here will have no hair by then lol


LOL! That is funny! I was just saying earlier that all we can do is "Hurry up and Wait" and that's like pulling your hair out just waiting! LOL!
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Quoting kmanislander:


Grenada, 1012 mb



This is system is experiencing northerly shear caused by the upper level high and the TUTT. It should be watched as it moves westward.
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Out for now. Maybe 93L will decide something soon. Catch you all later.
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un less that comes 94L 1st

Quoting kmanislander:


Grenada, 1012 mb

Member Since: May 21, 2006 Posts: 5091 Comments: 115074
looks like we may see 94L

Member Since: May 21, 2006 Posts: 5091 Comments: 115074
Quoting FLWeatherFreak91:
haha. There's so much that could happen in the next day or two


Grenada, 1012 mb

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okay, here goes...
WVLoop
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1113. nwcarib
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In the loop of the floater focused over the 93L, it is very easy to discern a low level circulation center, despite of its definition.

Please give a faster speed in the animation, and you could see it. Moreover, this possible LLCC is moving well NW, just south of the limit between Rep. Dominicana & Haití.
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1111. xcool

Member Since: September 26, 2009 Posts: 2 Comments: 15670
This debate happens every year on emerging systems.....It's like finding a needle in a hay stack sometimes until a dominant center emerges, and, we can look at some other data, other than satt loops, to try and locate the "real" swirl.....
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Quoting frostynugs:
"We didn't stop flying airplanes for six months after 9/11, did we?"

Planes didn't keep crashing into buildings for 2 months after 9/11, did they? They weren't still crashing into buildings every day when they ban on flight was lifted, were they?


Nice point, that...
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Quoting kmanislander:
Meanwhile, further to the SE convection is building in an area where it is actually colocated with the 850 vort.

haha. There's so much that could happen in the next day or two
Member Since: December 1, 2006 Posts: 2 Comments: 3619
"We didn't stop flying airplanes for six months after 9/11, did we?"

Planes didn't keep crashing into buildings for 2 months after 9/11, did they? They weren't still crashing into buildings every day when they ban on flight was lifted, were they?
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1105. Crawls
CMC @ 138 hrs



gfdl @ 126 hrs

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1103. leo305
there is a weak tropical low in the central atlantic and it's beginning to tap into some moisture and being wrapped with it.. I think that system has the potential to become something..

as for 93L, it's still very disorganized as a strong mid level spin is the the NW of the "center" and is robbing a bit of it's energy, the low to the south east of 93L is beginning to erupt with some convection, if it continues moving WNW/NW it will move into a favorable environment for tropical development
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1102. xcool
NOT MOVE nw
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Quoting 900MB:


So the spin many of us have been seeing at 71.7W/17N is the mid-level circulation?

When the two spins meet up we are in business?



not a chance,any LLC is moving wnw while the MLC will soon die out as it comes ashore along the DR/haiti border!!!
Member Since: October 5, 2007 Posts: 20 Comments: 4970
Meanwhile, further to the SE convection is building in an area where it is actually colocated with the 850 vort.

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Quoting Hurricanes101:
For those playing the home game, this is where the atcf has the center of 93L, it is well south of Hispaniola and is not going over it anytime soon. It is also not moving NW



I agree with the current position


Based upon what I am currently looking at on the vis loops, I have to disagree that the atcf location is presently correct.....I think it's much further north at the moment as some have noted.
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Quoting Chicklit:

If you click on that link and look at those spinny spirals? Well, the center of them is about the same place they've just initialized the center of 93L. That's a good thing for the system because of the ventilation provided. So far, 93L hasn't been able to get the spinny thing going and the anticyclone will help it to do this. Also, the colors at the surface indicate there is low pressure energy there which is also good for 93L; the lower the pressure (ie., yellow to red to white), the stronger the system. You can also click on those other top buttons to see what shear was -3 (3 hrs. ago) +3 (3 hours from now). The other numbers on the lines tell you how high the shear is. High shear (20 and up) is bad for systems; the lower the better.
This is layman's terms. Hope it helps.
Thank you! that definately helped. :)
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What are the coordinates for 12z?
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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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