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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Not exactly what the Gulf Doctor ordered, huh?



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looks like tonight will be intresting 93L is trying to get into shape all it needs is dmin
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Quoting Chicklit:
Why it doesn't develop in 30C waters with an upper cyclone above it is beyond me. Just goes to show you the intricacies of nature!
There still not enough centripetal momentum yet. It will happen.
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Link
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Quoting Hurricanes101:
12Z ECMWF out 48 hours

thats futher south Intresting
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Quoting gator23:
KENT's Law of Global Fluid Dynamics:
The effectiveness of a forcast model is directly and inversly proporational to the location of the user. If a storm is shown to be heading your way the model is "dead on" if said model shift away form your area than that same model is "on crack"



Your post makes about as much sense as this latest GFDL model run Gator23.
That is Scientifically speaking of course. [laughs]

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12Z ECMWF out 48 hours



notice the ECMWF does not develop 93L by Thursday, it never really did
Member Since: March 10, 2010 Posts: 1 Comments: 7872
There is some upper level winds blowing from Southwest to Northeast over Jamaica right now from this satellite:

http://www.wunderground.com/tropical/tracking/at201093_sat.html#a_topad

Also interaction with Hispaniola is impedding development at the moment.
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http://www.ssd.noaa.gov/goes/flt/t1/loop-rgb.html

Circulation Visible
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886. IKE
Quoting DestinJeff:
when does ECMWF release?


Next 15-30 minutes.
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Quoting DestinJeff:
when does ECMWF release?


the Raleigh site will start to release within the next few minutes

the entire run is available by 3pm
Member Since: March 10, 2010 Posts: 1 Comments: 7872
Quoting pottery:
Greetings.
Just in briefly to say --
weather conditions in Trinidad are most 'peculiar' today.
during the morning the sky looked like dense Dust or even smoke down to the surface. Looked 'miasmic' and unhealthy. Like polution..
South winds right now, becoming s/e occasionaly.
Heavy thunderclouds with rumblings going on. Some very heavy showers dropping out of scattered cumulus,

But looking at the sat.maps and images, there is nothing overhead!!??

Photo would be nice. Thx for the report.
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Why it doesn't develop in 30C waters with an upper cyclone above it is beyond me. Just goes to show you the intricacies of nature!
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Quoting reedzone:
I think a center forms south of where you all think.. Just by looking at the latest visible.


I would have to agree. Link I think that a more central position for a defined LLC would be the case.
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Wave to the First Wave to Make it Mid Gulf..

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Pressure here has dropped from 1014 to 1011 (and dropping) between 11:00am and 2:30 pm.
Hot, humid 91%, still, gloomy weather.
Strange area of confused conditions...
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Looking to see maybe some turning around 15.5N 73W ... Just my opinion..
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Quoting centex:
I was just picking up on JM main point "The main negative for 93L continues to be lack of spin."

Wrong! There are 2 areas of vorticies one near hispaniola & one to its Southwest. The whole are continues to be broad. I said earlier the area to the Southwest would win over. So will see what happens.
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Will 93L develop one or the other Circ?

Will 93L become a Depression in 48?

Will 93L become Oil-Zilla ?

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Quoting CaicosRetiredSailor:
...well I see we have some empty space and missing post numbers in the comments earlier.


I wonder who could've been blocked???
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KENT's Law of Global Fluid Dynamics:
The effectiveness of a forcast model is directly and inversly proporational to the location of the user. If a storm is shown to be heading your way the model is "dead on" if said model shift away form your area than that same model is "on crack"
Member Since: August 26, 2008 Posts: 0 Comments: 2182
GOM IR Loop

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Quoting ElConando:


That is not from 93L.


ok so the meager convection to the SW of that spinning area is 93L?
Member Since: March 10, 2010 Posts: 1 Comments: 7872
This is only my opinion. I believe that the NHC has lowered the chances for the following reasons. 1) there is a lot of uncertain on where the center of circulation will develop if it ever does. 2) If there is some development, it may be close to the Southwest coast of Haiti causing the storm to suffer. There is also very little water before it starts interacting with the high mountains of eastern Cuba. Again this is only my opinion most likely I am wrong because I am not an expert.
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I think a center forms south of where you all think.. Just by looking at the latest visible.
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Quoting RecordSeason:
Yah, Patrap...

I can assure you, Springfield is currently getting one of the heaviest downpours in the past 4 or 5 years.


The Tropical Wave Axis in the GOM is Kicking up I think..

Like August out there.




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I've also been wondering about the recent revelation (this past winter) by NASA that the atmosphere "contracts" during a Solar Minimum. According to a NASA report, which I do not have handy, the planet's atmosphere shrinks from 400 miles down to 280 miles. How does this affect upper level atmospheric cooling? Does the increase in density allow a more rapid release of air temperature at night?

Out here in the CA desert where I live, the temps are falling DRAMATICALLY at night, as soon as the sun drops every evening. I'm not complaining as it makes being outside enjoyable for once!

Hurricane seasons during Solar Minimums have traditionally been below normal. The question is why?
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...well I see we have some empty space and missing post numbers in the comments earlier.
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Quoting Hurricanes101:
Actually now that I am looking at it, it really is disorganized

take a look there is an MLC or something of some sort spinning NW towards Hispaniola, on that path it will not have hardly any time over water

to the SW of that is another area of disorganized showers


I can absolutely see how the NHC feels this is less organized than yesterday


That is not from 93L.
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Quoting stillwaiting:
Me tinks deirs a low pressa formn' at da suwface:

The low level deck is completely exposed where your lower west to east red arc is and not one low level cloud is going that way which is West to East.. put your cursor in one spot and watch. There are two high level arcs of clouds at 11N 73W heading NE but thats it.
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I was just picking up on JM main point "The main negative for 93L continues to be lack of spin."
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Cuba Radar: Link
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Quoting Baltimorebirds:
It wasn't directed to you.


Oh, I know, I was just saying.. Cause normally I get accused of hyping. I look at the pattern and maps, sometimes I can be off, or sometimes, like with Bill last year, I could be dead on ;)
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Actually now that I am looking at it, it really is disorganized

take a look there is an MLC or something of some sort spinning NW towards Hispaniola, on that path it will not have hardly any time over water

to the SW of that is another area of disorganized showers


I can absolutely see how the NHC feels this is less organized than yesterday
Member Since: March 10, 2010 Posts: 1 Comments: 7872
Quoting Drakoen:
Shear is 10-20 knots over the system versus the 5-10 knots we saw yesterday. That could be why although it doesn't appear to be hindering the system.


for now.
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Will be interesting if they still plan on flying tomorrow or waiting?
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I don't know what some of you are talking about lack of spin, there is plenty of spin with 93L, but not one concentrated spin. The circulation of this whole system is broad. And because of its proximity to Haiti, the system is disorganize as many in the past i.e. Fay & Ernesto once were. Once it passes 75W look for development. Which it should do sometime tomorrow based on its forward speed.
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Quoting scottsvb:


Um, 1st off I didnt attack you, I just said midlevel circulation, 2nd your the 1 whos doing the attacking, and its probably cause your upset the NHC is inline with what I'm seeing, Txmet and a few others.

What happens is alot of you dont want to accept a Mets or someone with weather knowledge who isnt a Met if they say something wont develop or isn't ready to develop. You start calling Me/Us downcasters when we tell ya why its not developing.

I have called out a few peeps before,,thats correct but thats after continued challenges to my forecasts that dont include a developing storm. Until something does come up, it is dreamcasting if you dont have evidence to back up something.

When the teacher teaches you something in school.. you should listen. When a Met or someone tells ya whats happening in here. You should listen, not challenge Me/Us.

We all have our opinions, but back up with data.

Also there is no need for your insults. I didnt insult you. End of Discussion about this.


I simply stated you can see rotation and agreed with StormW when he also stated there was rotation and you made it out like I said Low Level Circulation when I never did.
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852. IKE
I don't recall any model that developed 93L into a TD/TS/cane before the end of this week. I don't really understand why 93L was ever put at 50%.

That said...the GFDL...HWRF...new GFS...CMC...ECMWF and maybe even the NOGAPS develop 93L more today then yesterday. If they're all wrong then throw all of them in the garbage. I can't believe all of them are wrong. But I could be wrong.

ALL of them don't develop 93L until a few more days have passed. This may not get designated until Friday or later, if ever.

EDIT...take the ECMWF out of the class I posted above. It was more yesterday then today, but it's still forming a system.
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Quoting alaina1085:
That red is coming straight for me Pat



Boomers around.
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Quoting reedzone:


I never hyped this storm, nor am I RIPing it. Just saying it will take time.

me too this torm hasn't done anything in spite of favorable conditions, I don't think it wants to form.
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it appears to me we have a midlevel spin getting crankes up with 93L to the southeast of the haiti/dominican republic border on the south coast
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StormW, for some reason when I saw your reply to my post, that church hymn "he's got the whole world...in his hands!" popped into my head.

Anyway, I think people often get so wrapped up in whether a particular invest has an LLC that they dont bother to check out what is or isnt rolling out of Africa.
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.