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 models zoomed in on the GOM


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Quoting sebastianflorida:
Just spoke to Blog three, it said bye bye; Blob 2 said I am jealous of 1 stealing the show; Blob 1 said see me starting to spin? I replied yes I think I see that.


Oh uh ok. Great! Now I'm dizzy! :)
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"Quoting Jeff9641:


Storm it stayed offshore. It moved back WSW later in the evening this is the reason for code orrange this morning with this blob as it is the mid level circulation. Look at the vis animation.


HOW? Mid level steering flow was from SE to NW all day yesterday.

STEERING"

Because people keep placeing the "storm"s location to where there is the most convection.
But it's an open wave. So the Seed point for models is picked somewhere along that wave. I have yet to find out how and what the criteria are. So the L can move anywhere along the wave.
This is why I keep saying don't go looking for a COC or LCC until it definitely exists... you start throwing the "storm" all over the map with improbable/impossible scenarios.

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IF ONE BLOB FORMS WILL IT PULL THE OTHER 2 INTO IT?
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Jeff, you are correct because I tracked the positions of both areas and the spin yesterday is where we see the development today and the models have shifted toward the north from yesterday toward the spin you forecasted. Very good work. I think you helped some people see the way things can materialize when a circulation is centered nearer the high pressure than the models indicate at first.
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3388. Walshy
Quoting Tazmanian:
am going too start Ignoreing evere time each time they say John Hope rule you do it with evere storm


A its vary annyoing


B it gets evere one off key



i love you
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look at the 500mb theta e-gfs-1st blob much bigger.
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3386. IKE
Quoting medic2luv:
Ok So this would be a bad situation if this were to happen! Talk about pouring salt into an open wound!! See image below: gfdl at 120h



Throw out that run. Based off old coordinates. Wait on 12Z.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting txag91met:

That is just t-storms.


I think it is more than just that. Take a look at the lower right side of this image.

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Quoting homelesswanderer:


Lol. Lotta that going round the gulf. From SE TX
Channel12 Link

At it's current speed, the system will move into the Gulf of Mexico on Monday. Here, rapid strengthening is possible. High pressure aloft will be anchored to our northeast over Georgia to Arkansas. The clockwise flow will push the tropical system to the west and into the Northwest Gulf of Mexico by Friday. Model data continues to support the idea of at least a tropical storm...but again, it is very early.

Much can change and it probably will, but we will continue to monitor and update our forecasts. So keep checking back.

We remind you to have your hurricane supplies stocked with a family hurricane plan established.

Just spoke to Blog three, it said bye bye; Blob 2 said I am jealous of 1 stealing the show; Blob 1 said see me starting to spin? I replied yes I think I see that.
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3382. RTLSNK
I have been reading back for about an hour, as always, some great information and discussion. For those who haven't finished their preparations, do it now. Do not be surprised.

"Did you ever observe to whom the accidents happen? Chance favors only the prepared mind." (Louis Pasteur, 1822-1895)

Headed for work, will check in later.
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Quoting kmanislander:


Normally that would be so but having the anticylone overhead has not done anything for 93L over the past 48 hrs.

I think we could see 94L from this feature today and that to me is the bigger threat now.


That is just t-storms.
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Ok So this would be a bad situation if this were to happen! Talk about pouring salt into an open wound!! See image below: gfdl at 120h

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Quoting Crawls:
The local Baton Rouge LA weather showed spagetti models this morning. They said there is an area worth watching we may get something early next week and we may not. Sounded like a CYA broadcast.


Lol. Lotta that going round the gulf. From SE TX
Channel12 Link

At it's current speed, the system will move into the Gulf of Mexico on Monday. Here, rapid strengthening is possible. High pressure aloft will be anchored to our northeast over Georgia to Arkansas. The clockwise flow will push the tropical system to the west and into the Northwest Gulf of Mexico by Friday. Model data continues to support the idea of at least a tropical storm...but again, it is very early.

Much can change and it probably will, but we will continue to monitor and update our forecasts. So keep checking back.

We remind you to have your hurricane supplies stocked with a family hurricane plan established.

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Quoting DestinJeff:
Is this still accurate?



The Navy site seems to think so but the NHC appears to have finally gone away from that position. From yesterday many of us questioned the feature they were tracking to the area seen in your image.
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Quoting extreme236:


Dude, we all saw that thing go inland yesterday.

Still no well defined circ yet.
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3371. IKE
Quoting DestinJeff:
Is this still accurate?



Nope...throw it out.

*hands Floodman one*
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting aquak9:


when that's the first thing I see on this blog, do I even wanna read back???


LOL
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I hope all Jamaicans get to high ground later today and tonight, enough with the drowning in floods already this year.
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3366. Walshy
Quoting rmbjoe1954:


Hi. I'm curious to learn what exactly is the John Hope rule?


If it hasn't developed by the time it gets in the eastern Caribbean, it won't until it reaches the western Caribbean.
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The mid level circulation has become the center of the blob today. It stayed offshore and mergde with energy over the warm waters as the hurricane center showed on the graphic at 8 last night. That's why the longitude is important to remember when looking at model plots.
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Quoting StormW:


I think you made it mad, kman!


Yes, I shouldn't have been so deprecating last night about blowing out candle flames LOL
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Time to review the
Fujiwhara Effect

http://weather.about.com/od/hurricaneformation/a/Fujiwhara.htm

And article on a few past hurricanes that were close.
http://weather.about.com/od/hurricaneformation/a/two_hurricanes.htm
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repost..

Hola StormW!

What's with Mickey Mouse?
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Looks like the NHC has this right now. This blob is in a fighting mood.

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3357. aquak9
Quoting IKE:


Nope....don't do it.

*pops another one*


pass the bowl this way, Ike...mmm tastes like popcorn if ya add some butter
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Quoting IKE:


Nope....don't do it.

*pops another one*
If we're already popping valiums, and we haven't even had a NAMED storm YET, we're all going to need something stronger.
Maybe we should pass a doobie around.
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Yesterday, the models had the center forming further southwest than the mid level circulation and lower level circulation near Haiti. That "mid level circulation" is and was reaching to the lower levels and is now the shift in focus farther northeast than previously believed. The circulation did stay over warm waters and was closer to the high pressure than the original models indicated. That is why the hurricane center changed the focus to the area farther north last night at 8.
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3352. aquak9
Quoting Becca36:
Good morning everyone! I know I need help when I run to the computer before I even turn the coffee on to "blob" watch. LOL


i toldja, girl...."welcome to the addiction"
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Quoting Walshy:
BElieVe iN th3 John Hope Rule. don't forget it...


Hi. I'm curious to learn what exactly is the John Hope rule?
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Yea 93 is causing more headache than 92 so we dont even need a 94
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what's with Mikey Mouse, StormW?
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Quoting Crawls:
The local Baton Rouge LA weather showed spagetti models this morning. They said there is an area worth watching we may get something early next week and we may not. Sounded like a CYA broadcast.


Yeah, they were talking about it here last night (North Texas)...the met was using the 06Z model runs from yesterday at 10PM
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3347. IKE
Quoting aquak9:


when that's the first thing I see on this blog, do I even wanna read back???


Nope....don't do it.

*pops another one*
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting tropicfreak:


Looks so timy and compact.


Hope it stays that way. Most models bring it Gulfward and that's the last thing we need with that gusher still spewing oil all over the GOM.
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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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