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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Quoting JRRP:
90L could be a surprise

It's not a surprise if you're thinking about it.
Member Since: July 6, 2010 Posts: 113 Comments: 32877
620. JRRP
90L could be a surprise
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Quoting JLPR2:
90L is tiny.



Remember Michael?
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618. JLPR2
90L is tiny.

Member Since: September 4, 2007 Posts: 7 Comments: 8747
612 CaicosRetiredSailor Weather Channel's Parent Company Is Renamed -- via nytimes.com
The Weather Channel Companies became the Weather Company, signifying a shift to media outside television.


Should rename it the Weather Canal... to reflect the evergrowing Anthropogenic influence.
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Quoting KoritheMan:


Cody longing to be insulted already, eh? Sad.

Be there after I blog. Done shortly.

Lol, MSWX is in too so Cody is getting it tonight. I finished one blog, Link, and I'm working on another. You will realize why two are coming out in such a short time once you read it.
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Quoting wxchaser97:

Oh but that is where you are wrong. We will see who wins when 99L gets north. Chat?


Cody longing to be insulted already, eh? Sad.

Be there after I blog. Done shortly.
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Quoting KoritheMan:


Well I won't lose, so...

Oh but that is where you are wrong. We will see who wins when 99L gets north. Chat?
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Quoting CaicosRetiredSailor:


The way it's heading East, looks like I may get Kablobered...



I liked this not because you may have a storm, but due to the use of "Kablobered" :)

I do like that word.
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Weather Channel’s Parent Company Is Renamed

via nytimes.com

The Weather Channel Companies became the Weather Company, signifying a shift to media outside television.
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting wxchaser97:

So when you lose this bet then what happens, I never lose.


Well I won't lose, so...
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Quoting KoritheMan:


I never lose.

So when you lose this bet then what happens, I never lose.
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Quoting KoritheMan:


I didn't see it. So it's a done deal then.

I also thought about doing a deal for next year's hurricane season and say that 80% of all named storms avoid the United States mainland once again, but I'm not quite so confident of that.

I wouldn't go that far as we aren't even done with this hurricane season. But I am all in and ready for this bet.
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Quoting TropicalAnalystwx13:

'Cause you know you'd be proven wrong...again.


I never lose.
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Quoting KoritheMan:


I didn't see it. So it's a done deal then.

I also thought about doing a deal for next year's hurricane season and say that 80% of all named storms avoid the United States mainland once again, but I'm not quite so confident of that.

'Cause you know you'd be proven wrong...again.
Member Since: July 6, 2010 Posts: 113 Comments: 32877
Quoting wxchaser97:

I am in for the bet thing you mentioned, just if you didn't see. I'll go to the other side for the sake of the bet, even though I am more in the middle with a slight lean to a recurve for now.


I didn't see it. So it's a done deal then.

I also thought about doing a deal for next year's hurricane season and say that 80% of all named storms avoid the United States mainland once again, but I'm not quite so confident of that.
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Quoting KoritheMan:


I don't have cable in my room, so no. Anything interesting (read: scientifically sound) to report?

I am in for the bet thing you mentioned, just if you didn't see. I'll go to the other side for the sake of the bet, even though I am more in the middle with a slight lean to a recurve for now.
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Derived from NHC_ATCF data for Invest99L @ 22Oct.12am
14.6n76.9w was reevaluated &altered
14.6n76.8w-14.6n77.7w are now the most recent positions

CDD-PuertoLempira :: PUZ-PuertoCabezas :: KIN-Kingston

The longest line is a straightline projection through 99L's 2 most recent positions to its closest approach to an inhabited coastline.
99L's center was headed toward passage over the second largest island in the MiskitoCays
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Quoting KoritheMan:


I don't have cable in my room, so no. Anything interesting (read: scientifically sound) to report?


Very weak science, it's mostly for entertainment, so I don't expect them to go over all the research and journals, lol.
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Quoting Grothar:
Small blob in the Bahamas.



The way it's heading East, looks like I may get Kablobered...
Member Since: July 12, 2007 Posts: 0 Comments: 6069
Quoting Slamguitar:
Anyone else watching this weather modification segment on Discovery?


I don't have cable in my room, so no. Anything interesting (read: scientifically sound) to report?
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Anyone else watching this weather modification segment on Discovery?
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599. beell
Quoting Grothar:
Small blob in the Bahamas.



Can you drag that over to 99L?

Member Since: September 11, 2007 Posts: 145 Comments: 16926

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Intensity models down quite a bit.

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Quoting TampaBayStormChaser:
I'm on Grand Cayman Island right now, and it has gotten breezy but nothing too bad. 


Nice breezy night here for sure, I'm enjoying the cool down.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Meh...

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Always keep an eye on the ensembles..

Member Since: August 19, 2006 Posts: 13 Comments: 16225
Small blob in the Bahamas.

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Quoting GeoffreyWPB:


Loser sends the money to Portlight.


Deal.
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Quoting KoritheMan:


I'm serious. If you promise to give me $20 if I win, I will promise in the same vein to give you $20 if you win.

From the sound of things though, you're in the recurvature camp also, which makes any sort of wager between us impossible.

Offer still stands.

You know what, I'll go on the other side just for the sake of a bet. I can seriously make $20 back in a heartbeat if I lose. So I guess I'm in and I promise.
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Quoting KoritheMan:


I'm serious. If you promise to give me $20 if I win, I will promise in the same vein to give you $20 if you win.

From the sound of things though, you're in the recurvature camp also, which makes any sort of wager between us impossible.

Offer still stands.


Loser sends the money to Portlight.
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Quoting KoritheMan:


I wanted to say "I love you" in the voice of Han Solo, but realized it'd be too... disgusting. How about I just call it sexy instead? Will that work?


Kori...You are way too cool.
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Quoting wxchaser97:

Hey I'll take $20, but I am mostly on the recurve bandwagon but keeping an eye on a hurricane to nor'easter scenario.


I'm serious. If you promise to give me $20 if I win, I will promise in the same vein to give you $20 if you win.

From the sound of things though, you're in the recurvature camp also, which makes any sort of wager between us impossible.

Offer still stands.
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Quoting MAweatherboy1:
As complicated as the overall situation is, the models are actually in excellent agreement right now. They could easily shift or lose agreement but right I think it'd be foolish to bet against something like this:


They even show a northward/north-northwestward bend towards the end, which is to be expected given the pattern.

I see this avoiding a landfall for North Carolina, South Carolina, Georgia, and Florida, but it will definitely be hard-pressed to get the storm to miss the Northeast states if it takes the trajectory it should following the pattern. However, as always, timing will be the final determinant.
Member Since: July 6, 2010 Posts: 113 Comments: 32877
if we get S and T storm from 90 and 99L i wounder if the gfs show any storms fourming for nov? i think we olny need two more name storms
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Quoting KoritheMan:


NAO, ENSO, MJO, it doesn't matter. Until I see concrete proof suggesting otherwise, the US is protected by a magical hurricane barrier.

Any takers? Offer still stands. :P

Hey I'll take $20, but I am kinda on the recurve bandwagon but I am definitely keeping an eye on a hurricane to nor'easter scenario.
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AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
843 PM AST SUN OCT 21 2012

.UPDATE...SHOWERS CONTINUE OFFSHORE IN BOTH THE ATLANTIC AND THE
CARIBBEAN. A FEW WILL MOVE ONSHORE IN THE U.S. VIRGIN ISLANDS AND
THE EAST COAST OF PUERTO RICO...BUT MOST OF THE RAIN HAS ENDED FOR
THE NIGHT DEEPER INTO PUERTO RICO. SOUNDING REVEALED DRIER AIR
ABOVE 500 MB BUT STILL MOIST WITH A PRECIPITABLE WATER OF 2.13
INCHES. EAST TO EAST SOUTHEAST FLOW AT THE SURFACE TO CONTINUE
THROUGH TUESDAY. DISCUSSION BELOW STANDS. NO CHANGES TO THE
GRIDS...GFS HOLDS STEADY ON DEVELOPMENT BUT CONTINUES TO FLIP
FLOP ON MOVEMENT OF WAVE TO TROPICAL CYCLONE IN THE
CARIBBEAN...NEVERTHELESS ALL SOLUTIONS BRING INCREASED SHOWERS LATER
THIS WEEK. WILL NOT RE-ISSUE ZONES.
Member Since: April 29, 2009 Posts: 75 Comments: 14921
Quoting GeoffreyWPB:
I hope it doesn't rain Halloween weekend. My other dog worked so hard on her costume. I'm afraid it might rust...



I wanted to say "I love you" in the voice of Han Solo, but realized it'd be too... disgusting. How about I just call it sexy instead? Will that work?
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Quoting Gorty:


The NAO begs to differ :p


NAO, ENSO, MJO, it doesn't matter. Until I see concrete proof suggesting otherwise, the US is protected by a magical hurricane barrier.

Any takers? Offer still stands. :P
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.
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I hope it doesn't rain Halloween weekend. My other dog worked so hard on her costume. I'm afraid it might rust...

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579. Gorty
Quoting KoritheMan:


I'm serious. I'll make a wager with whoever wants to. Winner gets 20 bucks. I'm that confident this thing will recurve.


The NAO begs to differ :p
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Quoting Gorty:


Let's wait for the 00z and the 12z runs of the GFS.


I'm serious. I'll make a wager with whoever wants to. Winner gets 20 bucks. I'm that confident this thing will recurve.
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577. Gorty
Quoting KoritheMan:


Without even looking at anything, I'm going to bet $20 on a tendency toward recurvature. This pattern has been extremely persistent to the point where I can almost track these things with a blindfold.


Let's wait for the 00z and the 12z runs of the GFS.
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As complicated as the overall situation is, the models are actually in excellent agreement right now. They could easily shift or lose agreement but right I think it'd be foolish to bet against something like this:

Member Since: February 11, 2012 Posts: 84 Comments: 8049
Quoting MAweatherboy1:
Honestly I'm not that impressed with 99L right now. It's struggling for convection (probably at least in part due to DMIN though) and the overall structure looks the same as or worse than last night, much more like a t-wave than an organizing cyclone.



I also see the 18z GFS shifted east some. That seems like a pretty reasonable track to me, I think a grazing hit on S FL is possible but I'm not buying the idea of it coming up the East Coast yet, I say it gets pushed out to sea.
I think (hope?) you are right and the tropical season is over for the conus. Please.
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A beautiful CME left the Sun just a little while ago in association with a moderate solar flare... early indications are it won't be a big deal for Earth, a grazing blow if anything. That could change as 1598 rotates closer in the days ahead.



Link
Member Since: February 11, 2012 Posts: 84 Comments: 8049
Last year on halloween if you can will remember it snowed in the Mid-atlantic all the way down to the jersey coast..Had some light snow for a time in Atlantic city later in the night last halloween. Now a storm may possible hit again during the same time.
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Quoting MAweatherboy1:
Honestly I'm not that impressed with 99L right now. It's struggling for convection (probably at least in part due to DMIN though) and the overall structure looks the same as or worse than last night, much more like a t-wave than an organizing cyclone.



I also see the 18z GFS shifted east some. That seems like a pretty reasonable track to me, I think a grazing hit on S FL is possible but I'm not buying the idea of it coming up the East Coast yet, I say it gets pushed out to sea.


Without even looking at anything, I'm going to bet $20 on a tendency toward recurvature. This pattern has been extremely persistent to the point where I can almost track these things with a blindfold.
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I'm betting the graphic design team is busy over at the Weather Channel with the possible NE set up..Im sure brown and orange with be the color schemes in the DOOM captions to keep with Fall..
Member Since: August 19, 2006 Posts: 13 Comments: 16225

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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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