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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00Z final GFS hr 144 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Quoting Grothar:
Doesn't look like it wants to move much KEEP.
i hope this is not another 2012 zombie storm
Member Since: July 15, 2006 Posts: 178 Comments: 55978
not as strong this run
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Doesn't look like it wants to move much KEEP.
Member Since: July 17, 2009 Posts: 71 Comments: 27208
Quoting sunlinepr:

Looking at your loop, 99L looks to be breaking up. Could it happen?
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00Z GFS hr 132 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
114 hours

Member Since: July 17, 2009 Posts: 71 Comments: 27208
00Z GFS hr 120 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00Z GFS hr 111 hr 144
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00Z GFS hr 102 hr 144
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00Z GFS hr 093 hr 144
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00Z GFS hr 084 hr 144
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Good night blog, 99L reminds me of Ernesto, who kept taking FOREVER to decide whether or not he wanted to be a hurricane.
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00Z GFS hr 075 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Quoting Slamguitar:
99L is on the up again.



Big flareup of convection in the SW.

Member Since: July 17, 2009 Posts: 71 Comments: 27208
00Z GFS hr 066 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00Z GFS hr 057 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
99L is on the up again.

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00Z GFS hr 048 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Blog update.
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00Z GFS hr 036 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Quoting NCHurricane2009:


What makes you believe so?
its to stop moving and sit a bit then drift backbuilding off the heat of the water
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00Z GFS hr 024 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
646. JRRP
JA
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00Z GFS hr 012 hr 144
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Quoting KEEPEROFTHEGATE:
true enough but we should begin to see some significant convective feedback by tomorrow in the mid to late afternoon maybe in by late am

i like the new avatar by the way


What makes you believe so?
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00Z GFS hr 000 hr 144
Member Since: July 15, 2006 Posts: 178 Comments: 55978
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.

I bet 20 bucks that next year we get an above average chance of a major hurricane strike on the United States (if not this, then at least a threat or two of this happening). And i will bet one million bucks that if nothing happens next year, that with a certainty of 100%, 2014 will see a major hurricane on the US coast. I say this because in history's past, the midpoints in every decade going back a century have seen major hits on the United States.
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Quoting KoritheMan:


It's possible it doesn't significantly develop until reaching the western Atlantic in a few days.
true enough but we should begin to see some significant convective feedback by tomorrow in the mid to late afternoon maybe in by late am

i like the new avatar by the way
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Quoting JLPR2:
90L is tiny.


Just did my daily & very detailed Atlantic tropical update. I think it is extremely likely that 90-L becomes Sandy in the next 24 hrs...and I also explain how 99-L became less organized today....
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Quoting KoritheMan:
Doesn't look like a decoupling to me:




That's a side by side comparison of the lower troposphere (top image) and the upper troposphere (bottom image). It's very obvious where the circulation center is, and there is no apparent displacement. I don't see anything akin on satellite pictures either.

Now I'm not trying to downplay your analysis or anything. You are an excellent poster. I'm just not seeing your point this time.
My post was referring to the GFS model at 39hrs, it had absolutely nothing to do with current analysis lol

beell had asked what was it that the models were seeing that dragged the storm out of the Caribbean. So that post was explaining the model evolution and what allowed the storm to be pulled out of the Caribbean. I thought it was pretty clear what I was responding to, but maybe I lost you with the length of my post lol
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638. JLPR2
Quoting LostTomorrows:


Remember Michael?


Yep. Little ones under the right conditions could explode.

Didn't mean "little" as a bad thing.
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00z gfs is up next
Member Since: July 15, 2006 Posts: 178 Comments: 55978
Quoting KoritheMan:


Well I won't lose, so...

Hey Kori, what's up with the new icon you have? It's cool, but who is it supposed to be?
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Quoting KEEPEROFTHEGATE:


just got to wait till tomorrow afternoon
if its not a go by then

well

i would become apprehensive


It's possible it doesn't significantly develop until reaching the western Atlantic in a few days.
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Quoting gordydunnot:
One thing is clear you'll need a WU secret decoder ring to figure out where and what 99L is up to tonight. That being said, I wish all a goodnight. Tomorrow is a another day.


just got to wait till tomorrow afternoon
if its not a go by then

well

i would become apprehensive
Member Since: July 15, 2006 Posts: 178 Comments: 55978
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One thing is clear you'll need a WU secret decoder ring to figure out where and what 99L is up to tonight. That being said, I wish all a goodnight. Tomorrow is a another day.
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Interesting Precipitation plot over the next 84hrs.

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00Z NAM (non-tropical model) hr 084 hr 084 final
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00Z NAM (non-tropical model) hr 072 hr 084
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00Z NAM (non-tropical model) hr 060 hr 084
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00z Surface Analysis.

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00Z NAM (non-tropical model) hr 048 hr 084
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00Z NAM (non-tropical model) hr 036 hr 084
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00Z NAM (non-tropical model) hr 024 hr 084
Member Since: July 15, 2006 Posts: 178 Comments: 55978
00Z NAM (non-tropical model) hr 012 hr 084
Member Since: July 15, 2006 Posts: 178 Comments: 55978
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: 32804

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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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