Matthew dissipates; new Western Caribbean disturbance organizing

By: Dr. Jeff Masters , 5:28 PM GMT on September 26, 2010

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Tropical Storm Matthew has dissipated over the high mountains of Mexico, in the same region where Hurricane Karl came ashore. Matthew's remains will dump very heavy rains over a region that doesn't need it, and flash flooding and mudslide will be a concern over this region of Mexico for the next two days. Guatemala was fortunate--Matthew did dump some heavy rain of up to six inches over the country, but the storm unexpectedly moved well beyond the country, and heavy rains have avoided both Guatemala and Belize today. Venezuela was not so lucky, and heavy rains from Matthew are being blamed for the deaths of seven people in Caracas.


Figure 1. Afternoon satellite image of the Western Caribbean and Central America, showing the remains of Matthew over Mexico, and a large area of disturbed weather beginning to develop over the entire region.

Lisa
Tropical Depression Lisa is being torn apart by wind shear, and will likely not exist by Monday morning.

A wet week for the Western Caribbean
A large region of disturbed weather is developing over the Western Caribbean and Central America today. These sorts of large low pressure systems are very dangerous for Central America and the Western Caribbean, even if they do not spawn a tropical storm. In October 2007, a large low I dubbed "the sleeping giant" spent a week spinning over the region, dumping very heavy rains over all of Central America and the countries bordering the Western Caribbean. Rains from this system triggered flooding that killed 45 people in Haiti, damaged thousands of homes in Cuba, and caused heavy rains in Guatemala, El Salvador, Belize, Mexico, Jamaica, the Cayman Islands, and the Bahamas. The models predict a similar type of storm may evolve over the region over the next few days, and heavy thunderstorms from this disturbance are already affecting the Pacific coasts of Nicaragua, El Salvador, Coast Rica, and Honduras. Heavy rains will likely spread to Jamaica, Cuba, Southwest Haiti, and the Cayman Islands on Monday. These rains may be as great as 3 - 6 inches per day, and will be capable of causing dangerous flooding and mudslides. The models continue to have a poor consensus on the future evolution of this area of disturbed weather. The ECMWF model predicts that by late in the week, the low will get drawn north-northeastwards over Cuba and into South Florida and the Bahamas, and may not develop into a tropical storm. At the other extreme is the GFS model, which predicts that the low will spawn a series of two or three tropical storms over the next ten days, with each of these storms moving northwards across Cuba, South Florida, and the Bahamas. The first of these storms would organize on Monday, moving over South Florida by Wednesday, and would likely be at strongest a 50-mph tropical storm. The Hurricane Hunters are on call to investigate anything that might develop over the Western Caribbean on Monday afternoon. NHC is giving a 10% chance that something might develop in the Western Caribbean by Wednesday.

I'll have an update Monday morning.

Jeff Masters

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At least Grothar isn’t posting any of his scary 240 hours model forecasts.
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Quoting buckeyes12:
Should DMAX tonight help get this more organized?
there is no dmax but we do get a temp inversion so to speak as the air temperture drops to below water temps then convection will begin to dev if the convection can defeat the daytime heating then it should maintain itself during the day tomorrow and build even more after sunset monday with a system by tuseday
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PGI48L?
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Quoting Hurricanes101:


1. 26 Invests
2. 15 of them became TDs
3. No


Thanks!

:-)
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Quoting GrillinInTheEye:
On the topic of school closing, Be careful of what you wish for. After Francis and Jeanne, St. Lucie County schools were closed for a month and a half. Kids thought it was great going in. Then came "THE LIST". Yes every parent has one. It's the one that comes when you have been off too long. Then you finally go back to school and find out that your half days are gone, Christmas break is cut in half, and spring break is pretty much non-existent.


Even if your school district does not get the storm directly, schools are often shut so that they can be used as shelters for areas under evacuation notices. Also flooding does occur in may areas of FL that you would never suspect. There are areas that have a underlying area of "hardpan" (clay layer that is rock solid) and anywhere that is from 3 to 6 feet below the sand causes flooding with high rainfall amounts. Areas where no one ever recalls flooding can have this problem if isolated rainfall is sustained over a longer period of time.
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Quoting CaptnDan142:
Question for the statisticians among us:

How many Invests has NHC declared this year?
How many of those went on to become TD or above?
Have any storms (TD or above) formed without first being an invest?


1. 26 Invests
2. 15 of them became TDs
3. No
Member Since: March 10, 2010 Posts: 1 Comments: 7376
Wouldn't that just be plain ironic (and my luck) if the trough pattern that saved the United States from the likes of Earl and Igor acts to screw us once storms start developing in the NW Caribbean in October?

Last thing Florida needs, or anyone for that matter, is what the 18z GFS is showing!
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Its almost here!!! YEA


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Quoting coffeecrusader:
Everybody keeps saying South Florida, if it is it will be Southwest Florida. Miami is too far east for this storm.


You are so correct, it must come thru SW Fla before we get it in SE Fla... but you guys did not slow down Wilma much as it plowed thru our areas..


Member Since: August 29, 2005 Posts: 297 Comments: 40882
Question for the statisticians among us:

How many Invests has NHC declared this year?
How many of those went on to become TD or above?
Have any storms (TD or above) formed without first being an invest?
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Quoting Thaale:
"COMPUTER MODELS
ARE IN SOMEWHAT AGREEMENT SUGGESTING THAT SOME OF THE ENERGY AND
INSTABILITY LEFT FROM MATHEW IN THIS REGION COULD DEVELOP INTO A
RATHER STRONG LOW PRESSURE SYSTEM
OVER THE NW CARIBBEAN BY THE
MIDDLE OF THE WORK WEEK...WITH MODERATE TO STRONG CONVECTION
MOVING NORTHWARD ACROSS CUBA AND EVENTUALLY THE SOUTHERN FLORIDA
PENINSULA
BY THE END OF THE WORK WEEK."

Could somebody with more experience than I please offer some insight into parsing Garcia's meaning in the sections I've highlighted?

TIA


It's going to rain.
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Everybody keeps saying South Florida, if it is it will be Southwest Florida. Miami is too far east for this storm.
Member Since: August 21, 2006 Posts: 0 Comments: 254
888. flsky
Link
Where are the clouds disappearing to??
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Any guesses as to how strong this system gets? I say anywhere from a depression to a Cat 1. Also, I think Bahamas is way too far east for landfall. As Joe Bastardi says: "Florida is goig to take a hit."
Member Since: August 21, 2006 Posts: 0 Comments: 254
If we are going to have a hurricane in South Florida on Wednesday we need a system out there so warning can be issued soon.


if this sneaks up on us like so many in the past have.. not good.


Dolphin Game on now.. will check back later.
Member Since: August 29, 2005 Posts: 297 Comments: 40882
12z CMC



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"COMPUTER MODELS
ARE IN SOMEWHAT AGREEMENT SUGGESTING THAT SOME OF THE ENERGY AND
INSTABILITY LEFT FROM MATHEW IN THIS REGION COULD DEVELOP INTO A
RATHER STRONG LOW PRESSURE SYSTEM
OVER THE NW CARIBBEAN BY THE
MIDDLE OF THE WORK WEEK...WITH MODERATE TO STRONG CONVECTION
MOVING NORTHWARD ACROSS CUBA AND EVENTUALLY THE SOUTHERN FLORIDA
PENINSULA
BY THE END OF THE WORK WEEK."

Could somebody with more experience than I please offer some insight into parsing Garcia's meaning in the sections I've highlighted? Is a rather strong low pressure system a TD, or a CAT 4, or either or both? Similarly, is moderate to strong convection something like pre-Leslie (No-name 2000 storm), or more like Donna? Or again they're leaving the door open for either?

TIA
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Quoting marmark:
umm...we always close schools for tropical storms here in Martin County. One reason is they don't want the buses running in that kind of wind.It's a safety issue. I work for the school district here (past 20 years) and the schools have closed for every tropical storm. Being in the cone is the deciding factor.


You are in Martin County not Broward.

We have begged them to close schools with TS warnings but no way....because the big companies and employers will not close so no one can pick up the kids...
Member Since: August 29, 2005 Posts: 297 Comments: 40882
Should DMAX tonight help get this more organized?
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Quoting breald:


Ahh...don't worry about stupid stuff like that. Nobody is perfect.


I'm sure your words are very comforting to 7544. Of course, he took no offense in the first place. And you're 200 plus comments behind.
Member Since: July 23, 2010 Posts: 1 Comments: 12414
878. xcool
btwntx08 say hey all
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Quoting srada:
Good Evening Everyone! From the local NWS Wilmington, NC

this will not be a good week for NC at ALL..

Disagree; it will be a great week as most of the state is in at least moderate drought. Just need to keep the high winds away.
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Agree with the 10%

No real organization currently.


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7pm news headline was Flash flood watch. Here's the release from the met service...

NEWS RELEASE
September 26, 2010 –5:00 p.m.

*** FLASH FLOOD WATCH NOW IN EFEFCT FOR ALL PARISHES***

The Meteorological Service has extended the Flash Flood Watch to low-lying and flood prone areas of all parishes until 5:00 p.m. tomorrow.

A FLASH FLOOD WATCH means flooding is possible and citizens are advised to take precautionary measures, keep informed by listening to further News Releases from the Meteorological Service and be ready for quick action if flooding is observed or if a warning is issued.

A broad area of Low Pressure has been producing widespread showers and thunderstorms over the northwestern Caribbean, including Jamaica.

Radar indicates that widespread showers and thunderstorms affected the island especially sections of southern parishes today.
The forecast is for showers and thunderstorms to continue through the night and Monday. Deteriorating conditions are expected to persist over the island into Wednesday as the Trough drifts northward away from Jamaica. As a result a Flash Flood Watch is now in effect for all parishes.

Fishers and other marine interests are being advised to exercise caution as strong, gusty winds are likely in areas of showers and thunderstorms mainly over inshore and offshore areas of the south coast.


The Meteorological Service will continue to monitor the progress of this system.


cdj
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873. xcool
i was rigth keep at 10%
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Quoting GrillinInTheEye:
On the topic of school closing, Be careful of what you wish for. After Francis and Jeanne, St. Lucie County schools were closed for a month and a half. Kids thought it was great going in. Then came "THE LIST". Yes every parent has one. It's the one that comes when you have been off too long. Then you finally go back to school and find out that your half days are gone, Christmas break is cut in half, and spring break is pretty much non-existent.
After Ivan down here a lot of the schools were damaged and others being used for shelters. The week after Ivan kids went back to "school" outside on the grass and sidewalks.
Member Since: October 9, 2008 Posts: 0 Comments: 8268
871. IKE
I can see why the NHC kept it at 10%....

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On the topic of school closing, Be careful of what you wish for. After Francis and Jeanne, St. Lucie County schools were closed for a month and a half. Kids thought it was great going in. Then came "THE LIST". Yes every parent has one. It's the one that comes when you have been off too long. Then you finally go back to school and find out that your half days are gone, Christmas break is cut in half, and spring break is pretty much non-existent.
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I also agree with the NHC 10% for the next 48. Ppple seem to be ignoring the entire season's experience, which highlights the fact that these "monsoonal" areas of low pressure don't quickly move from the broad disorganized area to a defined low worthy of a name or even invest status. I'd say if anything develops we're more likely to see something in the range of Thursday or Friday.

Of course once it DOES start to organize, all bets are off as to what happens . . .. [thinking about Mitch and Wilma]
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Quoting MiamiHurricanes09:
If the GFS were to verify I would miss a couple of weeks of classes with all the tropical storm warnings that would have to be issued. Lol.
IF the GFS were to verify it would also mean billions in property lost, billions more in costs past onto everyone in the country, and likely a few hurt and even some dead.
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Member Since: August 2, 2010 Posts: 21 Comments: 9706
Sorry Sammy...no 96L and still at 10%.
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Everyone talking bout Florida but east coast up to NC to be in trouble also with possible strengthening storms as the ride up the coast. CMC has a strong cane hitting NC.
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Evening all.

Just noticing that with the demise of Lisa we are storm-less for virtually the first time in 5 weeks... I'm wondering how long this lull will last.

Does anyone else think we have a chance of at least one more CV storm before the season is done? I do agree w/ kman that the CAR is full of potential, IMO for up to 5 additional systems before November is over. I can't help remembering that Michelle 2001 was a November storm...
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Repost earlier from Max Mayfield:

NHC's determination of the low, medium or high chance of development is done subjectively. they make use of everything available, including all model forecasts and the current observations which routinely includes satellite imagery but can at times include aircraft and radar data if available. And they have verified their chance of development forecasts in house from 2007 through 2009 and there is some skill in their subjective forecast. In fact, there was skill in giving the chance of development to the nearest 10%. See page 19 of http://www.nhc.noaa.gov/verification/pdfs/Verification_2009.pdf as well as Table 13 and Figure 15.

Regards,
Max
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860. bwi
Good evening. I've been watching the S winds at the buoy due south of the Cayman Islands and the pressure steadily falling at the buoy in the far NW Caribbean.

Regardless of whether some tropical storms form, it just seems like that's eventually going to set up a stream of tropical moisture up the East Coast of the U.S. I can remember a couple times in recent years when similar setups caused surprise flooding in our area.
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Quoting kmanislander:
I'm out for dinner. Will check in a little later.
Wind has been basically from the e to ese all day up here today but see now it is from the wsw.
Member Since: October 9, 2008 Posts: 0 Comments: 8268

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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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