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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Hurricane Sandy,

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Member Since: July 3, 2005 Posts: 423 Comments: 127807
820. Skyepony (Mod)
Quoting afj3:
Greetings! Question for the group: Which model is more reliable in this case with 99L, the GFS or the ECMWF? Or are they both good?


Here's model error for 99L so far. It has all the models just about except the ECMWF. AEMN (gfs), FIM9 (except the last run initialized way off), MRFO & Models starting with the letter T seem to be getting this one so far. You can plot these out on Google map through a link off that page too. They all take it right to Jamaica..
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Quoting SouthDadeFish:
BEGIN
NHC_ATCF
invest_RENUMBER_al992012_al182012.ren
FSTDA
R
U
040
010
0000
201210221416
NONE
NOTIFY=ATRP
END

90L should get the same treatment.
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818. WunderAlertBot (Admin)
JeffMasters has created a new entry.
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Quoting SouthDadeFish:
BEGIN
NHC_ATCF
invest_RENUMBER_al992012_al182012.ren
FSTDA
R
U
040
010
0000
201210221416
NONE
NOTIFY=ATRP
END
Nooo looks like 99L will become Sandy..kinda root'in for it to at least be Tony..
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We now have TD 18 according to the ATCF database (advisories likely to be initiated at 11AM)

BEGIN
NHC_ATCF
invest_RENUMBER_al992012_al182012.ren
FSTDA
R
U
040
010
0000
201210221416
NONE
NOTIFY=ATRP
END
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Quoting TropicalAnalystwx13:

We are NOT going through this again. :|
Don't worry we'll have another storm to track at least so no "N" storm repeat again.She just wouldn't go away and made a strange track I tell ya she did...
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breaks over bb at lunch
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Quoting Chucktown:
Oh the westcasters will be in full force today. This is not going to be a southeast US event. As the trough digs later this week, it will keep the system either moving north or even northeast for a while. It won't be until the trough itself goes negative this weekend and the trough axis becomes NW - SE oriented over the SE US. It is thereafter that if the system is still "within reach" and hasn't already moved too far NE, then there is a chance that it could be pulled back NW towards the Mid - Atlantic and NE US. Way too many variables and most likely if there is some sort of NE US impact, it will be transitioning from tropical to more of a nor'easter type storm.



sometimes things can just happen

its to do what ever it wants

we are to show possible outcomes
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Quoting ncstorm:
LOL!!!!

Has anyone seen this???


We are NOT going through this again. :|
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Quoting afj3:

Thank you! Well I guess we can get used to some high surf here on Florida's East Coast if nothing else. Good for the surfers though hopefully erosion won't be too bad
But those rip currents will be such a pain as well.I suspect we'll see lots and lots of rescues if such an event was going to happen.
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807. afj3

Quoting TropicalAnalystwx13:

They are nearly equal in performance, although, the ECMWF holds the title for most reliable.
Thank you! Well I guess we can get used to some high surf here on Florida's East Coast if nothing else. Good for the surfers though hopefully erosion won't be too bad
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T.C.F.A
99L/INV/D/XX
MARK
13.89N/77.59W
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Oh the westcasters will be in full force today. This is not going to be a southeast US event. As the trough digs later this week, it will keep the system either moving north or even northeast for a while. It won't be until the trough itself goes negative this weekend and the trough axis becomes NW - SE oriented over the SE US. It is thereafter that if the system is still "within reach" and hasn't already moved too far NE, then there is a chance that it could be pulled back NW towards the Mid - Atlantic and NE US. Way too many variables and most likely if there is some sort of NE US impact, it will be transitioning from tropical to more of a nor'easter type storm.
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Quoting ncstorm:
LOL!!!!

Has anyone seen this???

Looks like 90L will make a 9 for us!.
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Quoting afj3:
Greetings! Question for the group: Which model is more reliable in this case with 99L, the GFS or the ECMWF? Or are they both good?
They are two best models and should always be considered. The GFS has performed very well this year though.
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Quoting afj3:
Greetings! Question for the group: Which model is more reliable in this case with 99L, the GFS or the ECMWF? Or are they both good?

They are nearly equal in performance, although, the ECMWF holds the title for most reliable.
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LOL!!!!

Has anyone seen this???

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Quoting CybrTeddy:


I agree, watch for a renumber with 90L. That could very well beat 99L to TD status today.



wont it be funny if 90L gets too sandy 1st and 99L takes tony
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Quoting Tazmanian:
22/1145 UTC 20.5N 51.8W T2.0/2.0 90L -- Atlantic
22/1145 UTC 14.8N 77.7W T1.5/1.5 99L -- Atlantic




90L is up too 2.0 i think we may see TD 19 today has well


I agree, watch for a renumber with 90L. That could very well beat 99L to TD status today.
Member Since: July 8, 2005 Posts: 259 Comments: 23888
Here is what my local forecast by Capital weather Gang calls for next Sunday..

"We may start to feel the squeeze between a tropical system near or just of the east coast and a cold front approching from the west.I'll call for increasing clouds,a small chance of showers and highs near 70.But this outlook is highly subjective to change confidence--Low.

Post 799:CyberTed I would rather have a storm named Tony impacting me than Sandy.
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797. afj3
Greetings! Question for the group: Which model is more reliable in this case with 99L, the GFS or the ECMWF? Or are they both good?
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22/1145 UTC 20.5N 51.8W T2.0/2.0 90L -- Atlantic
22/1145 UTC 14.8N 77.7W T1.5/1.5 99L -- Atlantic




90L is up too 2.0 i think we may see TD 19 today has well
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from my local NWS in Wilmington, NC

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 300 AM MONDAY...WHILE THU/FRI WILL CONTINUE TO BE WARM AND
DRY...ALL EYES DURING THE EXTENDED WILL BE ON A DEVELOPING TROPICAL
SYSTEM IN THE CARIBBEAN AND HOW IT EVOLVES UP THE EAST COAST. NHC
HAS PUT A 80% CHANCE OF DEVELOPMENT ON A TROPICAL WAVE SOUTH OF
CUBA...AND THE MAJOR GUIDANCE IS IN REMARKABLY GOOD AGREEMENT FOR
THIS FAR OUT THAT DEVELOPMENT WILL BEGIN NEAR CUBA BY THURSDAY.
THEREAFTER...THE ECMWF/GFS/CMC SHOW SLOW NORTHWARD MOVEMENT AS WEAK
STEERING FLOW BENEATH THE UPPER RIDGE PERSISTS. AT THE SAME
TIME...LARGE AND DEEP UPPER TROUGH BEGINS TO TAKE SHAPE ACROSS THE
GREAT PLAINS AND DROP ACROSS THE MIDWEST. HOW THESE TWO FEATURES
INTERACT WILL PLAY A KEY ROLE IN THE TRACK OF THE TROPICAL
CYCLONE...AND HENCE WHAT IMPACTS WILL BE FELT IN THE CAROLINAS. IT
IS TOO EARLY TO GET INTO ANY SPECIFICS...BUT THE HIGHLY AMPLIFIED
TROUGH (OF WHICH WE HAVE SEEN SEVERAL ALREADY THIS SEASON) WOULD
SUPPORT A MORE WESTWARD TRACK.
..IF FEATURES DEVELOP QUICKLY
ENOUGH...AND HENCE THE INHERITED SLIGHTLY HIGHER WINDS/POP FOR THE
WKND SEEM PLAUSIBLE. TEMPS FOR THE WKND WILL BE HIGHLY DEPENDENT ON
CLOUDS/PRECIP AS WELL...BUT SLIGHTLY COOLER HIGHS WITH WARMER MINS
ARE SHOWN AT PRESENT...AND SEE NO REASON TO CHANGE THESE ATTM.

AT THE SAME TIME...CANNOT NEGATE THE MENTION OF A STRONG COLD FRONT
BENEATH THE AMPLIFIED TROUGH WHICH WILL TRY TO WORK TOWARDS THE
CAROLINAS AT THE TAIL END OF THE PERIOD. AS NOTED BY PREVIOUS
FORECASTER...THE TROPICAL SYSTEM MAY TURN OUT TO BE MORE RELEVANT
THAN THE FRONT...BUT IF IT STAYS WELL OUT TO SEA THEN THE COLD FRONT
WOULD BRING A CHANCE FOR THUNDERSTORMS LATE SUNDAY...POSSIBLY LATER
IF IT BECOMES HUNG UP DUE TO THE PRESENCE OF THE LOW PRESSURE
OFFSHORE.
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Quoting Seflhurricane:
I think the NHC is going to wait till recon goes in before its classified but its currently at TD status , to me looks like the models are going to shift to the left some
Don't say left please...I have never liked the left..
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The FIM9 moves 99L over Jamaica and is a little more to the west than the other models. Looks like a slow mover too.

Member Since: July 17, 2009 Posts: 71 Comments: 26009
Quoting watercayman:


Ugh. Let's hope not.


Winds gusty here today, started to pick up last night from the east.Will be interesting to see what the recon' flights reveal for an upgrade to TD status.
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"Aye Aye Captin"
I can't hear you "AYE,AYE Captin"
Ohhhh
Who lives in a Pineapple under the sea
"SpongeBob,Squarepants"
Absorbant and yellow and porous is he
"SpongeBob Squarepants"
If nautical nonsense be something you wish
"SpongeBob Squarepants"
The drop on the deck and flop like a fish
"SpongeBob Squarepants"
READY!
SpongeBob Squarepants
SpongeBob Squarepants
Spongebob Squarepants

Spongebob Sqaurepants

Ah Ahhh Ahahahahahah

(Flute noise).
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Quoting CybrTeddy:
Looks like a TD.


I agree. The NHC likes to wait for recon to confirm, but I don't see why this shouldn't be named at 11 other than that. Recon may find TS winds in the squalls. Who knows?
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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.


Thank you for posting this.

This is why it is important to realize that the computer models are very susceptible to change when there is a lack of a well defined surface circulation. The Euro may be onto something since it has a little slower movement out of the Caribbean vs the GFS. As a result the Euro allows the ridge to the NE of 99L to build in a little more and scoot 99L a little closer to Florida.

People need to remember that the computer models can and will change. Unfortunately, it looks like Jamaica, Cuba, and the Bahamas have a very good chance of experiencing at least tropical storm conditions over the next few days. Residents in those areas need to keep a close eye on 99L.
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i think 94L may be a unname storm that will be added too the list at post season i think it was vary close
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I think the NHC is going to wait till recon goes in before its classified but its currently at TD status , to me looks like the models are going to shift to the left some
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Looks like a TD.
Member Since: July 8, 2005 Posts: 259 Comments: 23888
Quoting ncstorm:


Are you ready kids..

Im sorry I couldnt resist..LOL
Ah man!.Lol.I don't think the kids are ready to have their holloween taken away from them.
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Quoting stormwatcherCI:
Location is reminding me of Paloma. BTW, good morning.


Ugh. Let's hope not.
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Quoting washingtonian115:
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.


Are you ready kids..

Im sorry I couldnt resist..LOL
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Quoting TropicalAnalystwx13:

It's definitely possible this system hits the United States, it's not as impossible as you think. If the storm makes it off the SE coastline while the trough is entering the Great Lakes, it will cause the storm to track northward and then bend to the northwest as it is absorbed into the circulation. It has happened before, don't think it can't now.

I'm not saying it will, but it definitely CAN happen.


Hazel..

oops..I meant this one
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Quoting TropicalAnalystwx13:
Both systems are close to tropical depression status.



I would like to see us make the run of 19 named storms again.So that would be 57 named storms in total over a three year run.Epic!.
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Quoting TomballTXPride:
Timing Timing Timing

This system 99L would have been a threat to either Florida or anywhere along the Eastern Seaboard if this was A WEEK EARLIER.

This system 99L would have been a threat to either Florida or anywhere along the Eastern Seaboard if this was A WEEK LATER.

Timing Timing Timing

Some deep digging trough action going on here, as the CPC takes excerpts from all seven major models and suggests strong trough action going on here. How in the world can this system (if it even develops; but most likely will) affect Florida or anywhere along the Eastern Seaboard? Answer: It can't.



This system will only be a threat to Jamaica, Cayman, Cuba, and the Bahamas where is could be destructive with winds and heavy rain, and even possibly hurricane conditions. CONUS--I think you are out of the woods with this one.

Timing Timing Timing

Disclaimer: This is from an amatuer bloggers opinion. Please heed NWS and NHC warnings and outlooks.


Actually for late season storms such as this one to cause an impact on the eastern united states the trough is normally to blame. Th same mechanisims that cause a nor' easter to retrograte back into the coast are what causes the storm to be pulled north and west. Which is quite simple, storms go up ahead of the trough axis and if the axis is tilted from north west to southeast (negative tilt) the storm will go up and in. Not saying it will happen with this one just saying it can happen. Hugo(to some extent), Hazel, etc.
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Both systems are close to tropical depression status.



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Member Since: July 17, 2009 Posts: 71 Comments: 26009
Future Sandy is giving me the shady eye over here...
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Quoting TomballTXPride:
Timing Timing Timing

This system 99L would have been a threat to either Florida or anywhere along the Eastern Seaboard if this was A WEEK EARLIER.

This system 99L would have been a threat to either Florida or anywhere along the Eastern Seaboard if this was A WEEK LATER.

Timing Timing Timing

Some deep digging trough action going on here, as the CPC takes excerpts from all seven major models and suggests strong trough action going on here. How in the world can this system (if it even develops; but most likely will) affect Florida or anywhere along the Eastern Seaboard? Answer: It can't.



This system will only be a threat to Jamaica, Cayman, Cuba, and the Bahamas where is could be destructive with winds and heavy rain, and even possibly hurricane conditions. CONUS--I think you are out of the woods with this one.

Timing Timing Timing

Disclaimer: This is from an amatuer bloggers opinion. Please heed NWS and NHC warnings and outlooks.

It's definitely possible this system hits the United States, it's not as impossible as you think. If the storm makes it off the SE coastline while the trough is entering the Great Lakes, it will cause the storm to track northward and then bend to the northwest as it is absorbed into the circulation. It has happened before, don't think it can't now.

I'm not saying it will, but it definitely CAN happen.
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Member Since: July 17, 2009 Posts: 71 Comments: 26009
Does 99L going more south or north currently, and therefore turning to go north sooner or later respectivley, increase or decrease the chance that this hits the US?
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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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