99L a heavy rainfall threat for Jamaica, Haiti, and Eastern Cuba

By: Dr. Jeff Masters , 2:35 PM GMT on October 21, 2012

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A tropical wave embedded in a large trough of low pressure (Invest 99L) covers a large portion of the Central Caribbean between Hispaniola and the northern coast of South America. This storm has the potential to be a dangerous rainfall threat for Haiti, Jamaica, and eastern Cuba. The disturbance is headed west at less than 5 mph, is over very warm waters of 29°C, and is in a moist environment. 99L has a large area of heavy thunderstorms that have a good degree of spin. These thunderstorms are beginning to organize into spiral bands, as seen on visible satellite loops. However, the amount of heavy thunderstorm activity is about the same as yesterday, and there are no signs of a surface circulation. An Air Force hurricane hunter aircraft is scheduled to investigate 99L this afternoon, but I expect this flight will be rescheduled for later.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is a low 5 - 10 knots, and is forecast to be in the low to moderate range, 5 - 20 knots, through Tuesday. This should allow for some steady development of 99L, and there has been a good deal of model support for 99L becoming a tropical depression by Wednesday. Steering currents favor a continued slow westward movement for 99L through Tuesday. On Wednesday, a strong trough of low pressure to the north of 99L is expected to turn the storm to the north or north-northeast, which should put 99L in the vicinity of Jamaica on Wednesday and Eastern Cuba on Thursday. By Friday, 99L should be in the Central or Eastern Bahamas. It is unclear at this point whether or not the trough pulling 99L to the north will be strong enough to pull the storm all the way out to sea to the northeast; a narrow ridge of high pressure has the potential to build in over 99L late this week and force the storm west-northwest, with a potential threat to the western Bahamas and U.S. East Coast by next weekend. In their 8 am EDT tropical weather outlook, NHC gave 99L a 70% chance of developing into a tropical cyclone by Tuesday morning. 99L will be capable of bringing heavy rains of 5 - 10 inches, with isolated amounts of up to 15 inches in mountainous areas, to Jamaica and Haiti, Monday through Wednesday. Heavy rains will begin on Tuesday in Eastern Cuba, and spread northwards into the Central and Eastern Bahamas by Wednesday.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 830 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a small amount of heavy thunderstorms, as seen on visible satellite images, and has gotten tangled up with an upper-level low pressure system. This upper-level low is providing 90L the spin it needs to become a tropical cyclone, but is also pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a moderate 10 - 20 knots, and is forecast to remain in the moderate range until Tuesday. This may allow for some slow development of 90L before it encounters high wind shear of 20 - 30 knots on Tuesday night through Thursday. None of the reliable computer models develop 90L into a tropical cyclone, and it's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 30% chance of developing into a tropical cyclone by Tuesday morning.

The next name on the list of Atlantic tropical storms for 2012 is Sandy.

Jeff Masters

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SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE THAT A TROPICAL
DEPRESSION COULD BE FORMING OVER THE SOUTHWESTERN CARIBBEAN SEA
ABOUT 300 MILES SOUTH OF JAMAICA. THE LOW IS EXPECTED TO BE NEARLY
STATIONARY TODAY AND SHOULD BEGIN TO MOVE NORTHWARD TOWARD JAMAICA
AND EASTERN CUBA ON TUESDAY. THIS SYSTEM HAS A HIGH CHANCE...90
PERCENT
...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
HEAVY RAINS FROM THIS DISTURBANCE ARE LIKELY TO SPREAD OVER
JAMAICA...HISPANIOLA...AND EASTERN CUBA DURING THE NEXT SEVERAL
DAYS. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND
MUD SLIDES...ESPECIALLY IN AREAS OF HIGH TERRAIN. AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THIS
SYSTEM THIS AFTERNOON.

SHOWERS AND THUNDERSTORMS HAVE BECOME A LITTLE BETTER ORGANIZED NEAR
A SMALL AREA OF LOW PRESSURE OVER THE CENTRAL ATLANTIC ABOUT 700
MILES EAST-NORTHEAST OF THE LEEWARD ISLANDS. ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR DEVELOPMENT BEFORE
UPPER-LEVEL WINDS BECOME LESS FAVORABLE ON TUESDAY. THIS SYSTEM
HAS A MEDIUM CHANCE...50 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES NORTHWARD AT ABOUT 10 MPH.
Member Since: July 6, 2010 Posts: 113 Comments: 32870
I'm going to school, be everyone. It will be interesting to see how 99L handled the day when I get back.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
The 4 to 5 day rain on HPC
Member Since: May 23, 2012 Posts: 0 Comments: 4984
Area in the EPAC remains at 20%.

A DISORGANIZED AREA OF DISTURBED WEATHER ASSOCIATED WITH AN
ELONGATED LOW PRESSURE SYSTEM IS LOCATED ABOUT 400 MILES SOUTH OF
ACAPULCO MEXICO. SOME GRADUAL DEVELOPMENT OF THIS DISTURBANCE IS
POSSIBLE OVER THE NEXT FEW DAYS AS IT MOVES WESTWARD AT ABOUT 10
MPH. THIS SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
Member Since: July 6, 2010 Posts: 113 Comments: 32870
CMC
Member Since: May 23, 2012 Posts: 0 Comments: 4984
Quoting MahFL:


You mean east of Florida ?

I meant east, sorry I'll fix that.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Convection has finally fired over 99L's low-level center. If it can persist and build, we may have a tropical depression later today.

Member Since: July 6, 2010 Posts: 113 Comments: 32870
714. MahFL
Quoting icmoore:
Good morning.
a href="Photobucket" target="_blank">


That image is curently only updating every 3 hours.
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713. MahFL
Quoting wxchaser97:
The GFS, ECMWF, CMC, UKMET, NOGAPS, GFDL, and HWRF all make 99L into a hurricane north of the Caribbean islands. They are generally to the west of Fl and just to the west of the Bahamas. After that they either send it out to sea, take it to the NE or even farther inland, or the run stops.


You mean east of Florida ?
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The GFS, ECMWF, CMC, UKMET, NOGAPS, GFDL, and HWRF all make 99L into a hurricane north of the Caribbean islands. They are generally to the east of Fl and just to the east of the Bahamas. After that they either send it out to sea, take it to the NE or even farther inland, or the run stops.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Quoting Doppler22:
Umm seeing some of the model runs from the last page.... I'd rather not have a strong hurricane at my doorstep in the NE at the moment.......


I want snow! But I do think that this situation is gonna be interesting to follow.
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Everyone have a great Monday! Be interesting to see what the models say this afternoon when I get home.
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Speaking of the GFS, the 06z run develops a hurricane but, yet again, sends it out to sea after a brush with Florida. It also doesn't do as much with 90L as it previously has.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Umm seeing some of the model runs from the last page.... I'd rather not have a strong hurricane at my doorstep in the NE at the moment.......
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Good morning everyone, I see 99L and 90L are looking better. It should still take a day or so for 99L to become a depression but the chance was raised by the NHC to 80%.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Another day of "model roulette"!

This may end up epic! Time will tell.
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Good morning. Looks like 99L is continuing to gradually organize:



Also looks like we could see a classic Euro/GFS showdown with this after the Euro brought it to the US in its 0z run while the GFS continues to shift further east. I'm heavily inclined to believe the GFS at this point as the Euro has been inconsistent and the overall pattern does not favor significant US impacts right now.
Member Since: February 11, 2012 Posts: 84 Comments: 8049
GFS has not moved from this solution/track for 99...................................GFS at 72 hours
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GOOD MORNING FOLKS!.......................
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Good morning/evening, all. If I hadn't been following 99L I would have known something was up due to the number of comments since yesterday.
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Quoting TXCWC:
Where would this SNOWSTORM rank all time??





Is that snow, in extreme Northern Florida? In October...

Welp, models looking good for Florida, Bad for the NE CONUS at the moment. See how they flip-flop today.
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Quoting TXCWC:
Where would this SNOWSTORM rank all time??





Worst ever by a long shot?
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695. TXCWC
Where would this SNOWSTORM rank all time??



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Unless I'm seeing things ...





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693. TXCWC
Quoting sar2401:
OK, here are my guesses as to what will happen with 99L:

1. The push of dry air from the north will keep the system disorganized and push it into Central America as a tropical wave.

2. 99L becomes a tropical depression as it moves over Cuba. It will exit over far eastern Cuba and then develop into a tropical storm as it moves at least 100 miles to the east of the Bahamas

3. It will finally become a hurricane north of 30N, just as all the other major hurricanes have this year.

This is not going to become an east coast storm. All the models are still moving around with each run because we still don't have a closed low and a real COC. I'll start believing anything other than my three scenarios when the models really have something to work with. The major convection is still mostly land based in Venezuala and Columbia, moving into the Caribbean from there. Until 99L can pull away from South America and develop a closed circulation, I'm not buying the East Coast doomcasting.


I agree in so far as we are talking about an undeveloped system and still a week out from any east coast hit...problem is CMC, EURO, AND GFS (at least the 12Z run) SHOW VERY SIMILAR SCENARIO OF SANDY GETTING CAUGHT UNDER A BLOCKING HIGH...so to say that this will not be an east coast storm is just as rash a thing to say RIGHT NOW as saying it will be...RIGHT NOW BOTH scenarios (east coast hit/no east coast hit) are on the board as viable options
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OK, here are my guesses as to what will happen with 99L:

1. The push of dry air from the north will keep the system disorganized and push it into Central America as a tropical wave.

2. 99L becomes a tropical depression as it moves over Cuba. It will exit over far eastern Cuba and then develop into a tropical storm as it moves at least 100 miles to the east of the Bahamas

3. It will finally become a hurricane north of 30N, just as all the other major hurricanes have this year.

This is not going to become an east coast storm. All the models are still moving around with each run because we still don't have a closed low and a real COC. I'll start believing anything other than my three scenarios when the models really have something to work with. The major convection is still mostly land based in Venezuala and Columbia, moving into the Caribbean from there. Until 99L can pull away from South America and develop a closed circulation, I'm not buying the East Coast doomcasting.
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691. TXCWC
needless to say 0z EURO would be a tri-city disaster...THANKFULLY THIS IS ONLY 1 RUN AND STILL ABOUT A WEEK OUT...however is a little bit concerning as GFS was showing a similar scenario earlier
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690. TXCWC
and NOT OUT TO SEA...again very similar to GFS 12Z:



and once again the 12Z GFS


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689. TXCWC
ummmm...0Z EURO looks alot like GFS DID EARLIER IN IT'S 12Z RUN



here was the 12Z GFS

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688. 7544
now 99 is starting to get lots more convection
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687. TXCWC
EURO a lot further west than 0z GFS tonight:



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Atlantic Tropical Weather Outlook


000
ABNT20 KNHC 220555
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT MON OCT 22 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A LARGE LOW PRESSURE SYSTEM LOCATED A COUPLE OF HUNDRED MILES SOUTH
OF JAMAICA IS PRODUCING WIDESPREAD CLOUDINESS AND SCATTERED
THUNDERSTORMS OVER THE CENTRAL AND SOUTHWESTERN CARIBBEAN SEA.
ENVIRONMENTAL CONDITIONS ARE GRADUALLY BECOMING MORE CONDUCIVE FOR
A TROPICAL DEPRESSION TO FORM DURING THE NEXT DAY OR SO. THIS
SYSTEM HAS A HIGH CHANCE...80 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY TO THE
WEST-SOUTHWEST AND BECOMES NEARLY STATIONARY WELL TO THE SOUTH OF
JAMAICA. HEAVY RAINS FROM THIS DISTURBANCE ARE LIKELY TO SPREAD
OVER JAMAICA...HISPANIOLA...AND EASTERN CUBA DURING THE NEXT
SEVERAL DAYS. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH
FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS OF HIGH TERRAIN. AN AIR
FORCE RESERVE RECONNAISSANCE AIRCRAFT IS SCHEDULED TO INVESTIGATE
THE LOW PRESSURE SYSTEM THIS AFTERNOON...IF NECESSARY.

A SURFACE TROUGH INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
SMALL AREA OF SHOWERS AND A FEW THUNDERSTORMS OVER THE CENTRAL
ATLANTIC ABOUT 750 MILES EAST-NORTHEAST OF THE LEEWARD ISLANDS.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR SOME
DEVELOPMENT BEFORE UPPER-LEVEL WINDS BECOME LESS FAVORABLE ON
TUESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
NORTHWESTWARD TO NORTH-NORTHWESTWARD AT ABOUT 10 MPH.

ELSEWHERE...TROPICAL STORM FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER STEWART
99L up to 80%
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685. Skyepony (Mod)
Fresh OSCAT maybe a little south of where 90L is marked on surface map..

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684. HadesGodWyvern (Mod)
India Meteorological Department
Tropical Cyclone Outlook
5:30 AM IST October 22 2012
=====================================

A low pressure area has developed over southeast Arabian Sea. It may concentrate into a depression
during next 48 hours.
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could be a east coaster
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iam gone see ya after 8 am
Member Since: July 15, 2006 Posts: 178 Comments: 56141
00Z GFS hr 204 extended


and then its gone
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00Z GFS hr 192 extended
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Latest coordinates

14.6N 77.7W OZ
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looks like all i have is cold air thats fine by me

as it moves out to sea
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Quoting AussieStorm:

Looking at your loop, 99L looks to be breaking up. Could it happen?


It went to sleep, will keep on going tomorrow,
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00Z GFS hr 180 extended
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00Z GFS hr 171 extended
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Quoting KEEPEROFTHEGATE:
i hope this is not another 2012 zombie storm


Well I posted the 114 hours, look at the 144



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I finished my Berkley Blog, here it is. It is a forecast for my local area based on models and official forecasts, this is my 50th blog.
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Looks to me to be heading for Bermuda based on 0-150hrs
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00Z final GFS hr 144 hr 144
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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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