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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okay guys, Im out for a while..play nice

oh Wash..the 6z GFS snow map
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T.C.F.A.
99L/INV/XX/XX
MARK
14.89N/75.69W
Member Since: July 15, 2006 Posts: 174 Comments: 54353
Interesting.But this is the nogaps we're talking about...
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Quoting stormwatcherCI:
How can Florida be the first landfall ? Will it jump out of the Caribbean ?


I was speaking in terms of when potential Sandy might develop into a TS..going over Cuba and the islands will probably keep it a depression..
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Quoting stormwatcherCI:
Please remove the S. Link won't work


it works for me but here it is without the "s"

hope that helps
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I hope the NHC increase the chances in 90L is looking very good.
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It did for me
Quoting stormwatcherCI:
Please remove the S. Link won't work
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Quoting ncstorm:


first landfall..florida


then NC
How can Florida be the first landfall ? Will it jump out of the Caribbean ?
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What will 99L be at 8PM
A. 70%
B. 80%
C. 90%
D. 100%
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Quoting ncstorm:
this is the 18z Nogaps..WHOA!
Please remove the S. Link won't work
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Quoting KEEPEROFTHEGATE:
the potenial for a large scale high impacting event is increasing with time and at any rate warrants a eye to the south the next few days and then some


The first impacts from this will be the heavy rains in the Greater Antilles that may cause plenty of flooding and mudslides that may turn tragic if it moves slowly theu that area.
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Quoting washingtonian115:
"Nobody wants to see a 954 millibar storm over Washington next sunday".Yeah tell me about it.Plans and everything just wasted and tossed to the side.

ncstorm I can't open it up on my phone.What does it show?


first landfall..florida


then NC
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I think they go at least to 80% on 99L at 8 O'clock.
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Quoting ncstorm:
this is the 18z Nogaps..WHOA!


Holy moly!
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the potenial for a large scale high impacting event is increasing with time and at any rate warrants a eye to the south the next few days and then some
Member Since: July 15, 2006 Posts: 174 Comments: 54353
Im back, anynews in the past 24hrs on our invest?

I heard about something strange on the Euro and not recurving.
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slight pressure falls in the western Caribbean and a slight pressure rise in the Central Caribbean.
Member Since: July 17, 2009 Posts: 71 Comments: 26477
"Nobody wants to see a 954 millibar storm over Washington next sunday".Yeah tell me about it.Plans and everything just wasted and tossed to the side.

ncstorm I can't open it up on my phone.What does it show?
Member Since: August 14, 2010 Posts: 10 Comments: 17081
this is the 18z Nogaps..WHOA!
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from Frank Strait over at Accuweather

There's still plenty of reason to hope that the front and the developing upper trough supporting it will steer the storm off the East Coast but I'm less confident in saying that will happen at this point ... my gut feeling is that it will stay off the Southeast at least but it's probably going to be close. And try not to laugh too much the European model's very entertaining model solution. While I don't think it will happen that way, with the storm getting completely phased in with the trough and causing a wild blast of high wind and flooding rain across a lot of the Mid-Atlantic, it is plausible.

Basically, the slower that front moves and the longer the upper trough with it takes to dig in over the eastern part of the country, the farther west any Sandy-to-be can get. Often the models, especially the GFS, tend to be too fast with such features. On the other hand, it seems to have done a decent job with timing lately. Either way, there's plenty of reason for worry here. The GFS is one of the models that keeps the potential Sandy offshore (that's what it has for a week from today at left) but if it's too fast with the front/upper trough ... well then we instead have problems along the East Coast. The 0Z Canadian run illustrated the probably worst-case scenario ... nobody wants to see a 954 millibar storm over Washington next Sunday evening that sort of sits and spins slowly northward through Halloween. Well, maybe I can think of a few people who do, but I won't go there.

So, while we expect mostly quiet weather for the next few days, those near the East Coast need to carefully watch the way this situation plays out over the next several days and prepare accordingly. One more thing today, no matter the timing and whether or not some huge storm hits, behind whatever does come to pass next weekend will come some rather chilly air, probably sending temperatures for most of the South as far below normal as they will be above normal over the next 3-5 days.
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after 99L leaves the Caribbean could another storm form in the Caribbean or it would be the last one?
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extended forecast large errors do apply

HOUR 240 OCT 31 18Z





gonna try this format next run at 00z gfs
Member Since: July 15, 2006 Posts: 174 Comments: 54353
Quoting ncstorm:
got this from henry margusity fan page-snow map from the 12z Euro
I'm excited that we could see flakes here in D.C but then again we saw that last October and saw how the winter ended up as...
Quoting avthunder:
What do you think the timing would be? Flying out of Fort Lauderdale to NYC on Thursday, coming back Sunday; seems like both locations could be impacted. Jeez, I was really hoping the season was over.
I was hoping this damn season was over to.
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Quoting TropicalAnalystwx13:
The 18z GFS has some snow across New York, Pennsylvania, Ohio, West Virginia, Virginia, and Kentucky. Nothing significant, however.

Is there snow in the Baltimore area?
Member Since: February 13, 2012 Posts: 11 Comments: 3772
Quoting GeoffreyWPB:


Taking the current forecasted track, portions of south Florida could be under at least a Tropical Storm Watch/Warning, depending on its size and wind radii.

Gro, have the models been trending differently during the afternoon?
What do you think the timing would be? Flying out of Fort Lauderdale to NYC on Thursday, coming back Sunday; seems like both locations could be impacted. Jeez, I was really hoping the season was over.
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got this from henry margusity fan page-snow map from the 12z Euro
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Quoting ncstorm:
18z GFS 10m Wind map..





Bad hair day!.lol.
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Quoting TomTaylor:
On satellite imagery broad cyclonic turning is evident at the surface. The cyclonic turning is a result of the broad low developing along the tropical wave and being enhanced by the monsoon trough. 18z surface analysis reveals this mess. Last night I thought it would reach TD status faster, but given the broad nature and scattered, as opposed to consolidated, convection this system will take it's time. Shear over the western half isn't helping either.



I thought that things were favorable but there is shear. Will that go down with time?
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443. JRRP
99L is moving WSW
Link
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Quoting Astrometeor:


I am cursed at seeing a meteor shower. I have gone out as much as I can every time clear weather + a meteor shower has come along, in the hopes of seeing one. That means standing outside in short-sleeve shirt, and shorts (pajamas) at 13 degrees with 3 inches of snow on the ground.

The best night of watching meteors was outside of a shower when I saw 7 meteors and 13 satellites in 3 hours of staring up at Bluewater State Park, New Mexico. That sucked too since there were 30-40 mph gusts blowing that night. Had a coat and still felt the wind.

I have never seen a good meteor shower, while others report 100 per hour counts, while all I saw was 1 or 2 per hour.


I saw one in 1966 that had thousand per hour. I never saw anything like it again. I think it was November though.
Member Since: July 17, 2009 Posts: 71 Comments: 26477
18z GFS 10m Wind map..





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Quoting TropicalAnalystwx13:
The 18z GFS has some snow across New York, Pennsylvania, Ohio, West Virginia, Virginia, and Kentucky. Nothing significant, however.
But it's still snow!.
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Quoting Astrometeor:


I am cursed at seeing a meteor shower. I have gone out as much as I can every time clear weather + a meteor shower has come along, in the hopes of seeing one. That means standing outside in short-sleeve shirt, and shorts (pajamas) at 13 degrees with 3 inches of snow on the ground.

The best night of watching meteors was outside of a shower when I saw 7 meteors and 13 satellites in 3 hours of staring up at Bluewater State Park, New Mexico. That sucked too since there were 30-40 mph gusts blowing that night. Had a coat and still felt the wind.

I have never seen a good meteor shower, while others report 100 per hour counts, while all I saw was 1 or 2 per hour.


I wish you luck tonight then! Sounds like you get the determination award for this.
Member Since: March 10, 2006 Posts: 0 Comments: 10435
On satellite imagery broad cyclonic turning is evident at the surface. The cyclonic turning is a result of the broad low developing along the tropical wave and being enhanced by the monsoon trough. 18z surface analysis reveals this mess. Last night I thought it would reach TD status faster, but given the broad nature and scattered, as opposed to consolidated, convection this system will take it's time. Shear over the western half isn't helping either.

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Quoting Dakster:
I remember someone sayin this earlier, but bears repeating.

Remember tonight to watch for the Meteor shower. Supposed to be the best night to watch.



I am cursed at seeing a meteor shower. I have gone out as much as I can every time clear weather + a meteor shower has come along, in the hopes of seeing one. That means standing outside in short-sleeve shirt, and shorts (pajamas) at 13 degrees with 3 inches of snow on the ground.

The best night of watching meteors was outside of a shower when I saw 7 meteors and 13 satellites in 3 hours of staring up at Bluewater State Park, New Mexico. That sucked too since there were 30-40 mph gusts blowing that night. Had a coat and still felt the wind.

I have never seen a good meteor shower, while others report 100 per hour counts, while all I saw was 1 or 2 per hour.
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Quoting Grothar:
Looks like a slow mover too.

like forever another nadine
Member Since: July 15, 2006 Posts: 174 Comments: 54353
Speaking of snow, I was supposed to possibly get some a week from tomorrow, but the change of percip completely disappeared today. What a tease!
Member Since: July 2, 2011 Posts: 0 Comments: 1183
The 18z GFS has some snow across New York, Pennsylvania, Ohio, West Virginia, Virginia, and Kentucky. Nothing significant, however.
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Member Since: July 17, 2009 Posts: 71 Comments: 26477
Looks like a slow mover too.

Member Since: July 17, 2009 Posts: 71 Comments: 26477
Quoting ncstorm:


so the states in blue are getting snow or is that just cold air?

I'm looking at the snow map that shows snow...


Quoting washingtonian115:
Did you say.....snow :).

Yes, yes I did.

I have to go for 10-20 minutes.
Member Since: March 16, 2012 Posts: 127 Comments: 7948
Quoting wxchaser97:

Oh ok, first you literally need to chill to get snow. It is possible that you get snow but not 100%.

is what i changed it too better?
Member Since: February 13, 2012 Posts: 11 Comments: 3772
Quoting ncstorm:


so the states in blue are getting snow or is that just cold air?


Politicol affiliation...
Member Since: March 10, 2006 Posts: 0 Comments: 10435
Quoting Doppler22:

I WANT SNOW!!!!!!!!!!!!!! BRING ON THAT LOW

Oh ok, first you literally need to chill to get snow. It is possible that you get snow but not 100%.
Member Since: March 16, 2012 Posts: 127 Comments: 7948
Quoting GeoffreyWPB:


Taking the current forecasted track, portions of south Florida could be under at least a Tropical Storm Watch/Warning, depending on its size and wind radii.

Gro, have the models been trending differently during the afternoon?


Yes. Expect a lot of rain and a lot of wind at the end of the week.
Member Since: July 17, 2009 Posts: 71 Comments: 26477
Quoting wxchaser97:
Like I said, the NE still isn't safe this run. They get there own storm of their own, of course it is extra-tropical. Coastal areas are getting rain and inland areas would get some snow, happy Halloween.
252hrs:



so the states in blue are getting snow or is that just cold air?
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Quoting wxchaser97:
Like I said, the NE still isn't safe this run. They get there own storm of their own, of course it is extra-tropical. Coastal areas are getting rain and inland areas would get some snow, happy Halloween.
252hrs:

Did you say.....snow :).
Member Since: August 14, 2010 Posts: 10 Comments: 17081
Quoting hurricane23:


Its 2012.. might not even develope at all.

Really? I had no idea it was 2012.

Previous storms in the Caribbean have struggled because of trade winds and wind shear. Neither are a major issue for 99L.
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Quoting wxchaser97:
Like I said, the NE still isn't safe this run. They get there own storm of their own, of course it is extra-tropical. Coastal areas are getting rain and inland areas would get some snow, happy Halloween.
252hrs:


I want snow..... hopefully i get it from that low...
Member Since: February 13, 2012 Posts: 11 Comments: 3772
Quoting TropicalAnalystwx13:
The 18z GFS has the same synoptic pattern as the 12z GFS but shows a completely different track. Doesn't make much sense to me.

A lot of things don't make sense to you...
It was looking similar for a while until it decided to go NE.
Member Since: March 16, 2012 Posts: 127 Comments: 7948
the GFS was showing the splitting of the system in two lows before Cuba and now its showing it around Bermuda..models-smodels..wait and see is all we can do..

GOM, you might be next in the run..
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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.