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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I personally don't want to be affected by a storm named...Sandy..I can see the Spongebob jokes now!.But 99L appears to be no laughing matter according to the models.
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Quoting FunnelVortex:
The thing looks like its gaining convection in its center.

I think it will be classed as a TD by later today.



It will be.
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Quoting ncstorm:


Pepto Bismol..$5.95..Ibuprofen..$6.10..CMC killing Halloween..priceless






I don't think I've ever seen a low bomb out that quickly in reality. 995-959mb in one day? (I've seen some rare hurricanes do it, but never a baroclinic low)
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Good morning all!

MET SERVICE OF JAMAICA

NEWS RELEASE

October 22, 2012 at 6 a.m..

*** SEVERE WEATHER ALERT***

***LOW PRESSURE SOUTH OF JAMAICA LIKELY TO BECOME A TROPICAL STORM TOMORROW***


The Meteorological Service has issued a severe weather alert, effective until 5 a.m. tomorrow.

The area of Low Pressure is southeast of Jamaica and drifts slowly toward the west today and tonight. It is expected to develop into a Tropical Storm over the next day or so as it remains southwest of Jamaica. The system passes over the island Tuesday night as it moves toward the north northeast. Showers and thunderstorms are likely to affect the island which may be heavy at times while strong gusty winds are also likely over Jamaica, beginning tomorrow morning.

In view of this projection, it may be necessary to issue an evacuation notice for marine areas later today. All fishers on the cays and banks are, therefore, urged to hasten preparations with a view to evacuate at short notice, if required.

With weather conditions expected to deteriorate due to the passage of the developing system, marine operators are urged not to venture far from the mainland.

All interests are urged to pay special attention to subsequent news releases from the Meteorological Service.

rar
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The thing looks like its gaining convection in its center.

I think it will be classed as a TD by later today.

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Member Since: July 17, 2009 Posts: 71 Comments: 27210
Quoting AztecCe:
Are the models still showing an east coast brush or landfall? or have they changed?
They have moved more east now.Hopefully it keeps moving more east..
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Member Since: July 17, 2009 Posts: 71 Comments: 27210
Are the models still showing an east coast brush or landfall? or have they changed?
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Good morning everyone. Well I see by the satelitte map the two storms the models predicted are showing up! I see that the models are predicting a northern movement, perhaps drawn by that front that has moved through the East coast. I just hope they are correct! We don't need another Wilma!
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AL, 99, 2012102212, , BEST, 0, 137N, 779W, 25, 1003, LO

no renumbering yet???
Member Since: April 23, 2011 Posts: 104 Comments: 14873
Quoting kmanislander:
Good morning

Only time for one post for now. The repositioning of 99L down to 13.7 ( see Oscat pass which confirms this ) raises an interesting question as to how, if at all, this affects the next set of model runs. The farther South 99L gets to the stronger the trough would need to be to pull it up and out to the NE.

This may also affect both the track and intensity forecasts.


That may be, or possibly to hit the E US it needs to get as far north as possible before the trough gets there, so as to be too far up to get turned away, but im not sure.

So either going south puts the US in more or less danger.
Bold statement I made, I know.
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Quoting GeorgiaStormz:


Models typically dont resolve a very fluid situation till very close. Sat should still be 2-3 days.
This could become like Debby, a hair away from going to sea or phasing into a big storm for the NE.


Interesting week indeed..

Okay guys will be back later..have fun
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Quoting ncstorm:


fri or sat? thats cutting it close..


Models typically dont resolve a very fluid situation till very close. Sat should still be 2-3 days.
This could become like Debby, a hair away from going to sea or phasing into a big storm for the NE.
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Quoting aspectre:
733 ncstorm: When South Meets North - The Evolving Scenarios Posted by: [Bryan Norcross]...on October 22, 2012

On the one hand, THANKS for bringing his newest blog to my attention.
On the other hand, couldn't plus ya cuz it's really BAD netiquette to repost someone else's blog in its entirety (and a copyright violation to post more than snippets... but intellectual property law is written mostly by crooks mostly for the benefit of crooks, so the non-compliance with standards of politeness bothers me in a way that piracy doesn't)


I got that from FACEBOOK..as it was written on facebook..not from WU..he does posts elsewhere besides WU..
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Quoting ncstorm:


Pepto Bismol..$5.95..Ibuprofen..$6.10..CMC killing Halloween..priceless







thats a super negatively tilted trough it phases into, lol at the 540 line.
If only some of that precip could get to GA and it could be january.
We are supposed to get our first frost(and first 30s) possibly following this next cold front in 7-10 days.
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733 ncstorm: When South Meets North - The Evolving Scenarios
Posted by:
[Bryan Norcross]...on October 22, 2012

On the one hand, THANKS for bringing his newest blog to my attention. On the other hand...
...couldn't plus ya cuz it's really BAD netiquette to repost someone else's blog in its entirety (and a copyright violation to post more than snippets*)

* But intellectual property law is written mostly by crooks mostly for the benefit of crooks, so the non-compliance with standards of politeness bothers me in a way that piracy doesn't.
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Quoting GeorgiaStormz:
Still very uncertain at this time frame:

AT THIS TIME RANGE WE MUST EXPECT THE DETERMINISTIC
MODELS TO WAVER BACK AND FORTH BETWEEN PHASED AND UNPHASED SOLUTIONS
FOR THE REMAINDER OF THE UPCOMING WEEK. THE INTERACTION BETWEEN THE
POLAR JET /ITS AMPLITUDE AND TILT/ AND POTENTIAL TROPICAL CYCLONE IS
VERY COMPLEX AND OFFERS LOW PREDICTABILITY AT THIS TIME RANGE. THUS
MODELS WILL UNLIKELY RESOLVE THESE COMPLEX INTERACTIONS UNTIL
SOMETIME FRI OR SAT.


fri or sat? thats cutting it close..
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HPC 5 day precip map
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Quoting kmanislander:
Good morning

Only time for one post for now. The repositioning of 99L down to 13.7 ( see Oscat pass which confirms this )raises an interesting question as to how, if at all, this affects the next set of model runs. The farther South 99L gets to the stronger the trough would need to be to pull it up and out to the NE.

This may also affect both the track and intensity forecasts.
Location is reminding me of Paloma. BTW, good morning.
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Good morning

Only time for one post for now. The repositioning of 99L down to 13.7 ( see Oscat pass which confirms this ) raises an interesting question as to how, if at all, this affects the next set of model runs. The farther South 99L gets to the stronger the trough would need to be to pull it up and out to the NE.

This may also affect both the track and intensity forecasts.
Member Since: Posts: Comments:
Still very uncertain at this time frame:

AT THIS TIME RANGE WE MUST EXPECT THE DETERMINISTIC
MODELS TO WAVER BACK AND FORTH BETWEEN PHASED AND UNPHASED SOLUTIONS
FOR THE REMAINDER OF THE UPCOMING WEEK. THE INTERACTION BETWEEN THE
POLAR JET /ITS AMPLITUDE AND TILT/ AND POTENTIAL TROPICAL CYCLONE IS
VERY COMPLEX AND OFFERS LOW PREDICTABILITY AT THIS TIME RANGE. THUS
MODELS WILL UNLIKELY RESOLVE THESE COMPLEX INTERACTIONS UNTIL
SOMETIME FRI OR SAT.
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Quoting GeorgiaStormz:
The Euro and CMC want to phase a Mega trough( one that was negatively tilted and had a 100+ kt jet streak) with a cat 2 hurricane and plow it into the NE.
Gulp.

I'm tending to lean toward their representation of the trough too because the Euro, while not picking up on everything as soon as the GFS has following its update, still has been far better at forecasting trough timing and amplitude within 200hrs or so.

I also would like to see a super storm but thats another story.



that would get rid of all the leaves and the nice fall colors even the trees themselves...lol
Member Since: April 23, 2011 Posts: 104 Comments: 14873


6Z GFS takes the storm outta sea....curious.
Member Since: April 23, 2011 Posts: 104 Comments: 14873
The Euro and CMC want to phase a Mega trough( one that was negatively tilted and had a 100+ kt jet streak) with a cat 2 hurricane and plow it into the NE.
Gulp.

I'm tending to lean toward their representation of the trough too because the Euro, while not picking up on everything as soon as the GFS has following its update, still has been far better at forecasting trough timing and amplitude within 200hrs or so.

I also would like to see a super storm but thats another story.

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You are right of course, Tropicalanalystwx13, but would it make more sense to start with # 1 and proceed from there? It would allow easily for one to see out of all the invests, how many got named. That would be interesting.--What percentage got named.
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AL, 99, 2012102212, , BEST, 0, 137N, 779W, 25, 1003, LO

AL, 90, 2012102212, , BEST, 0, 213N, 515W, 30, 1009, DB,
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Quoting TropicalAnalystwx13:

Starts with the number 90, goes to 99, and then repeats. The "L at the end is for Atlantic, the "E" is for East Pacific, and "C" is for Central Pacific.


why L is for the Atlantic..?.shouldn't be A. E for Epac and C for Cpac and W for Wpac
Member Since: April 23, 2011 Posts: 104 Comments: 14873


This is 7+ hours old, but shows where circulation was last night.
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting Eng1n3rd:
Probably a really dumb question, but how are invests numbered?

Starts with the number 90, goes to 99, and then repeats. The "L at the end is for Atlantic, the "E" is for East Pacific, and "C" is for Central Pacific.
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Quoting Eng1n3rd:
Probably a really dumb question, but how are invests numbered?
From 90L to 99L. It repeats every season.
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Probably a really dumb question, but how are invests numbered?
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Let me know when fall starts, lows in mid 70s and highs in low 90s here with very high humidity, havent turned my ac off since March. October has also been very dry here in Texas.
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When South Meets North - The Evolving Scenarios
Posted by: bnorcross, 12:13 PM GMT on October 22, 2012

The tropical disturbance in the Caribbean is getting better organized... and is close to tropical depression status. The upper-air pattern is conducive for it to develop into a tropical storm and perhaps even a Cat 1 hurricane this week. It will likely be "Sandy", though there is a disturbance some 700 miles northeast of the Leewards that has a slight chance of beating it out. The next name would be "Tony".

The best computer forecast models - the American (GFS) and the European (ECMWF) - tell the same story for the next few days... the tropical storm brings extremely heavy rainfall to the northern Caribbean islands midweek. The strengthening storm - either a strong tropical storm or a hurricane - then moves through the Bahamas Wednesday through Friday.

The main effect in the U.S. in this scenario is an extended stretch of windy weather along the Florida east coast causing high surf, beach erosion, and some high-tide flooding.

Beyond that, the models are telling a different story. The GFS takes the tropical system out to sea, like tropical systems are supposed to do in October, and a strong kink in the northern jet stream spins up an separate nor'easter-like system off Long Island a week from now.

The European mixes the tropical system with the northern jet-stream energy and creates a mega winter storm across parts of the northeast back to the Great Lakes.

It's a crazy pattern, but these very sharp kinks in the jet stream caused when a big blocking high develops in the Atlantic are how oddball scenarios develop. For now we stay tuned. No doubt it will change again a number of times. Our main immediate focus is on the Caribbean and the potential for life-threatening rainfall across the northern islands.
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Close shave for Florida in this image from the Euro, right off our coast.
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99L - Perhaps it would confuse modelers more, if I split in half and sent one side to the SW and the other to the NE! Yeah, lets do that!
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Just because the 06z GFS operational is out to the NE, the ensembles arent..expect a shift back west with them







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Models are showing quite the major coldfront moving through Florida by 216 hours.


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Pepto Bismol..$5.95..Ibuprofen..$6.10..CMC killing Halloween..priceless





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ECMWF 00z run is insane, it's showing 99L becoming a nor'easter with a pressure of 954 mb. To give an example, though it wasn't a nor'easter, the 1993 Storm of the Century only had a pressure of 960mb.
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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 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.


Yeah, latest GFS has 99L staying way off shore the U.S.
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Florida needs to brace for this one! History vs the models. Its on!
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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.
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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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