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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12Z GFS 72HR!!
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hr 66

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Quoting Hurricanes305:


Or it feel the ridge building behind that trough and it forces 99L back to the WNW as mentioned by Dr. Masters.


Thanks for your answer. The modeled "look" or circulation of 99L does not match the signature of a TS or Hurricane. It is far too large. The forecast track does not match the synoptics for a "conventional" system. It does if one considers the larger, broad circulation and 99L as a small feature embedded in the larger circulation. The large scale feature should drift north/northeast as the SE US ridge lifts north in advance of the trough. 99L goes along for the ride.

Anyway, just trying to come up with an explanation for the poleward movement well in advance of the trough over the next 72-96 hrs.

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hr 60

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Quoting Grothar:
I posted these earlier. GFDL at 126 hours



hey Gro.. wow 952 mb. clearly overdone but not all out of the question
Member Since: April 23, 2011 Posts: 104 Comments: 14869
hr 54

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hr 48

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hr 45

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In terms of movement steering flow will be very weak for 99L as a trough early this week misses it. It will have to wait until late in the week to move. Think sfl threat increasing.
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hr 36

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99L WV Loop

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ZCZC MIATWOAT ALL
TTAA00 KNHC DDHHMM

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SUN OCT 21 2012

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

1. SHOWERS AND THUNDERSTORMS HAVE BEEN INCREASING OVER THE PAST FEW
HOURS NEAR A TROPICAL WAVE AND BROAD AREA OF LOW PRESSURE OVER THE
CENTRAL CARIBBEAN SEA. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE
FOR A TROPICAL DEPRESSION TO FORM DURING THE NEXT COUPLE OF DAYS...
AND THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY
WESTWARD. HEAVY RAINS FROM THIS DISTURBANCE ARE LIKELY TO SPREAD
OVER JAMAICA...EASTERN CUBA...AND HISPANIOLA OVER THE NEXT SEVERAL
DAYS. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND
MUD SLIDES...ESPECIALLY IN AREAS OF HIGH TERRAIN.

2. SHOWER ACTIVITY LOCATED ABOUT 850 MILES EAST-NORTHEAST OF THE
LEEWARD ISLANDS IS ASSOCIATED WITH AN UPPER-LEVEL LOW INTERACTING
WITH A TROPICAL WAVE. UPPER-LEVEL WINDS COULD BECOME A LITTLE MORE
CONDUCIVE FOR DEVELOPMENT DURING THE NEXT DAY OR SO...AND THIS
SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT
5 TO 10 MPH.

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

$$
FORECASTER BERG
NNNN
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hr 24

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Quoting MAweatherboy1:
I don't think recon will go today, it'll be a waste of time if they do. 99L is organizing but it's clearly not there yet, not enough convection near the center:



Looks like a well organized structure as there is some spiral banding and a decent spin to it but that feature to its west is probably responsible for stealing some of the system's convection. However new thunderstorms are starting to fire and the convection on the eastern side is wrapping up with the circulation once it gets going with some convection we could have a renumber later on this evening.
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12z gfs run 12 hr to 144 hr

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Quoting NCHurricane2009:

O_o...

Where does it go after that frame? To NC?

That is where the run end so it is a mystery.
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The S.Carolina Jails are much nicer than the N. Carolina ones.

...er, so I've Heard
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Quoting Tropicsweatherpr:
Recon canceled for today.

REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1115 AM EDT SUN 21 OCTOBER 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 22/1100Z TO 23/1100Z OCTOBER 2012
TCPOD NUMBER.....12-155

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (WESTERN CARIBBEAN)
FLIGHT ONE -- TEAL 71 FLIGHT TWO -- TEAL 72
A. 22/1800Z A. 23/1200Z
B. AFXXX 01EEA INVEST B. AFXXX 0218A CYCLONE
C. 22/1330Z C. 23/0730Z
D. 13.8N 78.5W D. 14.2N 78.6W
E. 22/1730Z TO 22/2030Z E. 23/1130Z TO 23/1400Z
F. SFC TO 10,000 FT F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY.....CONTINUE 12-HRLY FIXES
IF SYSTEM DEVELOPS.

3. REMARKS: THE LOW-LEVEL INVEST MISSION FOR 21/2100Z WAS
CANCELED BY NHC AT 21/1230Z. THE 22/1200Z INVEST IN TCPOD
12-154 HAS BEEN RE-TASKED FOR 22/1800Z AS SPECIFIED ABOVE.


I'm not surprised due to the lack of convection right now. Tomorrow should be a better day to fly into 99L. I still think it will be a TD in a day or so.
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Quoting Grothar:
I posted these earlier. GFDL at 126 hours


O_o...

Where does it go after that frame? To NC?
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Quoting Grothar:
I posted these earlier. GFDL at 126 hours



GFDL
Grothar Forecasted Doom Low
: )
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Quoting beell:
I keep hearing about this trough that will pull 99L out of the Caribbean. It's modeled effects are apparent over the Bahamas later in the week but something else must be in play to get it headed that direction in the short term.

There is no trough anywhere near as 99L crosses Cuba-still off to the west. Nothing but ridging over the Gulf. All I see is the possibility for the ridge to begin lifting N and allowing 99L to begin a more northward track.

Comments, corrections?


Or it feel the ridge building behind that trough and it forces 99L back to the WNW as mentioned by Dr. Masters.
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SHORT TERM FORECAST
NATIONAL WEATHER SERVICE SAN JUAN PR
1109 AM AST SUN OCT 21 2012

PRZ001>004-012-013-211900-
SAN JUAN AND VICINITY-NORTHEAST-SOUTHEAST-EASTERN INTERIOR-
CULEBRA-VIEQUES-
1109 AM AST SUN OCT 21 2012

.NOW...
PASSING SHOWERS WITH ISOLATED THUNDERSTORMS WILL CONTINUE TO AFFECT
THESE SECTIONS OF PUERTO RICO AS WELL CULEBRA...AND VIEQUES
THROUGH AT LEAST 3 PM AST. AS A RESULT...CONTINUE TO EXPECT
PERIODS OF MODERATE TO LOCALLY HEAVY RAIN...BRIEF GUSTY WINDS...
REDUCED VISIBILITIES...PONDING OF WATER ON ROADWAYS AND IN POOR
DRAINAGE AREAS.


$$

CASTRO

ADDITIONAL INFORMATION CAN BE FOUND AT /USE LOWER CASE
LETTERS/: HTTP://WWW.WEATHER.GOV/SANJUAN
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Recon canceled for today.

REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1115 AM EDT SUN 21 OCTOBER 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 22/1100Z TO 23/1100Z OCTOBER 2012
TCPOD NUMBER.....12-155

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (WESTERN CARIBBEAN)
FLIGHT ONE -- TEAL 71 FLIGHT TWO -- TEAL 72
A. 22/1800Z A. 23/1200Z
B. AFXXX 01EEA INVEST B. AFXXX 0218A CYCLONE
C. 22/1330Z C. 23/0730Z
D. 13.8N 78.5W D. 14.2N 78.6W
E. 22/1730Z TO 22/2030Z E. 23/1130Z TO 23/1400Z
F. SFC TO 10,000 FT F. SFC TO 10,000 FT

2. OUTLOOK FOR SUCCEEDING DAY.....CONTINUE 12-HRLY FIXES
IF SYSTEM DEVELOPS.

3. REMARKS: THE LOW-LEVEL INVEST MISSION FOR 21/2100Z WAS
CANCELED BY NHC AT 21/1230Z. THE 22/1200Z INVEST IN TCPOD
12-154 HAS BEEN RE-TASKED FOR 22/1800Z AS SPECIFIED ABOVE.
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I posted these earlier. GFDL at 126 hours

Member Since: July 17, 2009 Posts: 63 Comments: 23710
...........whew 99 is sitting in 85 degree waters...
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I don't think recon will go today, it'll be a waste of time if they do. 99L is organizing but it's clearly not there yet, not enough convection near the center:

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Member Since: July 17, 2009 Posts: 63 Comments: 23710
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Quoting presslord:


You won't find me in North Carolina!!! ;-)
Somewhere in the "Carolinas" though. Heeheehee ;)
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Quoting wxchaser97:

It is working for me so I don't think so.


For a moment it went blank for me but I have it back.
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Quoting NCHurricane2009:

Yes they would...


I don't think we are going to make it... but seeing how things are this year we could certainly get to Alpha in November
Member Since: April 23, 2011 Posts: 104 Comments: 14869
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Quoting Patrap:
There are now 60 days until the 2012 Winter Solstice.
what do you think pat..is it going to come true? or it will be just another day?
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Quoting SunriseSteeda:
It will be interesting to see if we exhaust the storm name list in November. Would they then go to the Greek alphabet again?

Yes they would...
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There are now 60 days until the 2012 Winter Solstice.
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Quoting Tropicsweatherpr:
Is the NHC site not working?

It is working for me so I don't think so.
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Hi everyone...

Can any one put up a long-way out model for 99L..just to see what the new changes are, if any
Member Since: April 23, 2011 Posts: 104 Comments: 14869
felt great here this morning..................
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I keep hearing about this trough that will pull 99L out of the Caribbean. It's modeled effects are apparent over the Bahamas later in the week but something else must be in play to get it headed that direction in the short term.

There is no trough anywhere near as 99L crosses Cuba-still off to the west. Nothing but ridging over the Gulf. All I see is the possibility for the ridge to begin lifting N and allowing 99L to begin a more northward track.

Comments, corrections?
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GFS from 144 to 156 hours,midlantic states I'd want to keep an eye on this storm if this verifies...............
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Quoting pcola57:


I've heard of a Big Butted Momma but not a Big Butted High Pat..LOL.
Is that a true met ID or we doin' slang this beautiful AM?.. :)


Los Slang..,least fer me seems.

: )
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www.nhc.noaa.gov
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12z Early Cycle NHC model tracks
Invest99
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)




Early Model Wind Forecasts

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Is the NHC site not working?
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wow GFS at 120 hours..............
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Thanks Dr. Masters!

Good morning everyone, I see 99L has a good environment for developing and should become a depression in the next day or so. Models have shifted a little to the west and stronger. Anyway for those that didn't see I wrote a blog earlier in the morning. Also the weather here is perfect. It is a nice 53F and there are no clouds to be found.
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GFS at 96 hours.....................
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Quoting Patrap:



It indicates a "dissipating" Low.


Note the acronym to the Left of it, and that Huge 1022mb Big Butted High.


I've heard of a Big Butted Momma but not a Big Butted High Pat..LOL.
Is that a true met ID or we doin' slang this beautiful AM?.. :)
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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.