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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What are the coordinates for 12z?
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I don't see any reason we won't have TD1 in the next 48hrs as long as sheer continues to relax(anti-cyclone aloft moving in tandom w/93L)as it moves slowly to the wnw imo...
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Quoting Tazmanian:
wow looks like 93L is heading in too vary low wind shear

It's already in very low windshear.
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1093. xcool
15.4N/74.3W 18Z position IMO IMO
Member Since: September 26, 2009 Posts: 2 Comments: 15603
loooks like MX is the one that needs too watch 93L now
Member Since: May 21, 2006 Posts: 5089 Comments: 114050
1091. 900MB
Quoting IKE:


I see the spin there now. This ain't hitting Haiti at those coordinates.


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?
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1090. Chigz
Nice vorticity around 40W - 7N with good convection - looks better than 93L HAHA!
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wow looks like 93L is heading in too vary low wind shear

Member Since: May 21, 2006 Posts: 5089 Comments: 114050
Quoting TankHead93:
So what does that mean?

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.
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1086. Crawls
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my post from earlier:
Quoting stillwaiting:




that is correct,very much near 15.5N,75W....very evident on vis sat loops!!!,what most think is a low level circulation trying to form is a developing MLC which indicates a system that is not yet vertically stacked,I expect new convection to form w/this possble surface feature,as the MLC moves ashore causing fooding in haiti:(
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there is one thing I have learn't never get fooled by a developing storm and you guys might know the reason(s) why
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Quoting IKE:


850mb's.
ok.
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1082. xcool





Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting Hurricanes101:


that is a different vortex that will likely die out soon, I think they have the coordinates right


I just respectfully disagree, which is o.k.
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1079. IKE
Quoting FLWeatherFreak91:
What height is that at?


850mb's.
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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


but look at how disorganized it is. I wouldn't be surprised if a new center formed north closer to Hispaniola where all the convection is.
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1077. hydrus
Quoting Funkadelic:
Looking at the latest frames, it looks like 93L is moving NNW but it's probably just a jog.
The blobs wobble a lot during the formation stage.jmo:)
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Quoting kmanislander:
The 850 vort still does not match up with the new "center" position. Until that happens there is still work for it to do.

yes it seems to...
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Quoting IKE:
What height is that at?
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1074. IKE
Quite an expansion of convection w/93L.
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Quoting IKE:


I see the spin there now. This ain't hitting Haiti at those coordinates.





Been saying,dammm knowbody ever listens,lol(I also had called for a TD before 11am and a TS by tonight,guess I'll have to work on my intensity forecasts,my track has been pretty good via my blog from yesterday
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Quoting Chicklit:
Wow, the gyre just tightened.
ShearMap
And check out the 850 mb vorticity all of a sudden.
So what does that mean?
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Quoting DaytonaBeachWatcher:


I think its way to the northeat of that. More like 16.5 and 71.0


that is a different vortex that will likely die out soon, I think they have the coordinates right
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I wouldnt expect much from 93L until it gets into the WCARB.

Recon tomorrow should be cancelled if nothing major happens until then.
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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



I think its way to the northeat of that. More like 16.5 and 71.0
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Quoting IKE:


looking like it is consolidating, I expect that spin and convection to die off going into Hispaniola; the real action will begin at the 18Z coordinates then
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The 850 vort still does not match up with the new "center" position. Until that happens there is still work for it to do.
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Quoting Chicklit:
Wow, the gyre just tightened.
ShearMap
And check out the 850 mb vorticity all of a sudden.
If the CIMSS maps are accurate on both counts, there should be a show to watch tonight. My day off is tomorrow and I am thinking of trying for DMAX after seeing this.
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Quoting DestinJeff:


I don't know, KMan. I have never once seen you post anything about the significance of the 75W longitude, and its relationship with TC development potential.

SARCASM FLAG: ON


LMAO. I won't say the name, just post the initials J.H. LOL
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Quoting weatherwatcher12:
Coordinates are out
AL, 93, 2010062218, , BEST, 0, 155N, 744W, 25, 1010, WV, 34, NEQ, 0, 0, 0, 0, 1011, 120, 60, 0, 0, L, 0, , 0, 0, INVEST, S,

It's heading just north of due west



I've been saying the center postion is near 15N,75W for the last 3 hrs!!!,while most have been calling the mlc the COC,guess I'm learning to read sat maps pretty good then????
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Lat and Long from Tropical storm position page from SSD

22/1745 UTC 16.7N 71.0W TOO WEAK 93L
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Quoting RobertM320:


We didn't stop flying airplanes for six months after 9/11, did we? You put the necessary precautions in place and move on. For instance, there's virtually NO RISK at all in drilling through rock and earth. Its not until you tap the oil reservoir that the risk arises. So, you keep the wells drilling until right before they tap in. In the meantime, you define the parameters for going forward. Risk is avoided and the working folk keep their jobs...its a win-win.


I understand the need for people to keep their jobs, truly I do...maybe the oil industry, whose focus has NEVER been on the safety of their people or the environment should be paying unemployment while someone other than the oil industry figures out if it's safe or not to drill at 5000 feet? I'm not even worried about whether it's "safe", per se, but I'd really like to know if another of these deep water wells goes we have some way to stop the damned thing in less than 6 months.

The funny thing here is that BP couldn't possibly have cared less about the fishermen that would be out of work when they made the decisions they did with no fall back position...I think a brief moratorium is the smart thing to do while we figure out if we're going to be looking at this mess all over again but a little further west next time...or east...I don't want anyone out of work, but try thinking about TWICE the oil in the water right now

As for the no fly after 911, it was 3 days for select flight, but 10 days before flight returned to "normal"...
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1058. xcool
DEL
Member Since: September 26, 2009 Posts: 2 Comments: 15603
1057. IKE
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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

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Quoting IKE:


I see the spin there now. This ain't hitting Haiti at those coordinates.


I took my glasses off and crossed both eyes and did detect something like a spin there.
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1053. xcool
THAT BIG HIGH P OMG
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Wow, the gyre just tightened.
ShearMap
And check out the 850 mb vorticity all of a sudden.
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Quoting weatherwatcher12:
Coordinates are out
AL, 93, 2010062218, , BEST, 0, 155N, 744W, 25, 1010, WV, 34, NEQ, 0, 0, 0, 0, 1011, 120, 60, 0, 0, L, 0, , 0, 0, INVEST, S,

It's heading just north of due west


If that is the "best" and the 850 vort is way up there at 17N 72W then 93L has a long way to go to becoming a TD IMO. Anyway, having been a longstanding proponent of the rejuvenative effects of a weak system getting to 75 West I will keep an open mind on this for now.
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1049. IKE
Quoting weatherwatcher12:
Coordinates are out
AL, 93, 2010062218, , BEST, 0, 155N, 744W, 25, 1010, WV, 34, NEQ, 0, 0, 0, 0, 1011, 120, 60, 0, 0, L, 0, , 0, 0, INVEST, S,

It's heading just north of due west


I see the spin there now. This ain't hitting Haiti at those coordinates.
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Quoting weatherwatcher12:
Coordinates are out
AL, 93, 2010062218, , BEST, 0, 155N, 744W, 25, 1010, WV, 34, NEQ, 0, 0, 0, 0, 1011, 120, 60, 0, 0, L, 0, , 0, 0, INVEST, S,

It's heading just north of due west

Then it's finally under the anticyclone.
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Quoting kmanislander:


The models are out to lunch with this and every other system before they are classified. I pay no attention to models when we are dealing with a large amorphous mass with no well defined circulation. One run a Cat 4 the next nothing.

I have been watching that deep convection to the North of where the so called center of 93L is supposed to be. There is no vorticity to speak of further South.

It may well be that the only circulation it has is at the 5000 foot level so for now that stands the best chance IMO of reflecting to the surface and taking over, assuming it doesn't run aground in Haiti first. Those mountains will do a number on it pretty quickly. The Barahona Peninsula has decapitated much stronger systems than this.
Beautiful place with soaring mountains that drop into the ocean. Reminded me of Hawaiia.

Here's a pic of the mountains further north in the Dominican. Some up to 12k feet.
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AL, 93, 2010062218, , BEST, 0, 155N, 744W, 25, 1010, WV,
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About JeffMasters

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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