Caribbean disturbance 99L a dangerous rainfall threat for Haiti, Jamaica, and Cuba

By: Dr. Jeff Masters , 4:12 PM GMT on October 20, 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 are beginning to show some organization, as seen on visible satellite loops. 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, which will bring a multi-day period of heavy rains to Haiti, Jamaica, and eastern Cuba beginning on Sunday. The Dominican Republic may also see some heavy rains, though not as great. On Wednesday, a strong trough of low pressure will approaching the Eastern U.S., and the GFS and ECMWF models predict that this trough will turn 99L to the north, bringing the storm into the southeast Bahama Islands on Thursday or Friday. In their 8 am EDT tropical weather outlook, NHC gave 99L a 30% chance of developing into a tropical cyclone by Monday morning. I put these odds higher, at 40%. An Air Force hurricane hunter aircraft is scheduled to investigate 99L on Sunday afternoon.


Figure 1. Morning satellite image of Invest 99L.

Invest 90L in the middle Atlantic
A tropical wave (Invest 90L) about 1000 miles east-northeast of the northernmost Lesser Antilles Islands is headed west-northwest at about 10 mph. The disturbance has a modest 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 pumping cool, dry air into the disturbance, which will keep any development slow over the next few days. Wind shear is a high 20 - 25 knots, but is forecast to drop to the moderate range, 10 - 20 knots, Sunday through Monday. This may allow for some slow development of 90L before it encounters very high wind shear of 20 - 40 knots on Tuesday and Wednesday. None of the reliable computer models develop 90L into a tropical cyclone. It's unlikely that 90L will affect any land areas. In their 8 am EDT tropical weather outlook, NHC gave 90L a 20% chance of developing into a tropical cyclone by Monday morning.

Jeff Masters

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954. beell
3:07 PM GMT on October 21, 2012
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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953. aspectre
2:56 PM GMT on October 21, 2012
.
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952. Hurricanes305
2:43 PM GMT on October 21, 2012

Right now the CMC and the GFDL are the most logical models. This Cutoff trough has to be really strong and potent to pick it up from the SW Caribbean and deflect all the way NNE over the SE Bahamas and out to sea is just ridicules as it would have to be moving more to the north for that to occur. The most logical scenario is for it to continue on its zonal path till it feel the trough and respond by going more Northwesterly, North and then eventually NE which means that would by the NW Bahamas and Florida in to the equation which is climatology favored path. A West then NE turn would favor heavy troughing over the Eastern seaboard acting as a defense mechanism. A pattern more climatology favoring in November.
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951. WunderAlertBot (Admin)
2:35 PM GMT on October 21, 2012
JeffMasters has created a new entry.
950. ProgressivePulse
2:29 PM GMT on October 21, 2012

000
NOUS42 KNHC 201446
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1045 AM EDT SAT 20 OCTOBER 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 21/1100Z TO 22/1100Z OCTOBER 2012
TCPOD NUMBER.....12-154

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (CENTRAL CARIBBEAN SEA)
FLIGHT ONE -- TEAL 71
A. 21/2100Z
B. AFXXX 01EEA INVEST
C. 21/1630Z
D. 16.0N 77.0W
E. 21/2030Z TO 21/2330Z
F. SFC TO 10,000 FT


$$
EC

Take Off @ 4pm
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949. Doppler22
2:28 PM GMT on October 21, 2012
If everything comes together is a Hurricane Hazel track possible with 99L? ( The northern part of it at least... where it goes North of Haiti and Cuba...)
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948. ProgressivePulse
2:25 PM GMT on October 21, 2012
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947. Grothar
2:20 PM GMT on October 21, 2012
The HWRF has 99L further to the East.

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946. stormwatcherCI
2:19 PM GMT on October 21, 2012
Quoting Hurricanes305:
99L is starting to fire up convection again it still has some work to do before it can be classified. The models has shifted west from the SE Bahamas to Now the Central and NW Bahamas. My be the cutoff trough might not be strong enough to dig it up out of the SW Caribbean and immediately send it off to NNE. This seem too sharp of a turn.
That is the same thing I think. For it to impact the SE Bahamas it would need to move north now which it clearly is not doing.Seems to be pulling moisture from the blob in the GOH.
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945. Grothar
2:17 PM GMT on October 21, 2012
Quoting 7544:


well that joins the fl camp how strong is that tia


The GFDL models have been very close. I think they shifted a little to the west since the earlier run. I'm waiting for the new ones to come out shortly. The one thing I see is almost all the models have a quick turn to the North as the trough approaches. Where that would be is still too early to tell.
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944. Grothar
2:14 PM GMT on October 21, 2012
Quoting SunriseSteeda:


Grothar, do you remember when Floyd passed by? Of course he was a Category 5 at the time, but we had some interesting weather, if I have the right storm.

I was playing in a softball tournament at Mills Pond Park in Fort Lauderdale and it was very hot and very breezy with the winds gusting over 40mph. I remember hitting a pop-up fly ball that should have been an out in short left field, but instead it landed on a trailer beyond the parking lot, about 340 feet away from me for my first tournament home run.


Yes, I do. That was a big one. We were supposed to evacuate for that one. We had bad erosion on the beaches and some parts of A1A were flooded if I remember. Mills Pond Park is just a few miles from our home.
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943. Hurricanes305
2:13 PM GMT on October 21, 2012
99L is starting to fire up convection again it still has some work to do before it can be classified. The models has shifted west from the SE Bahamas to Now the Central and NW Bahamas. My be the cutoff trough might not be strong enough to dig it up out of the SW Caribbean and immediately send it off to NNE. This seem too sharp of a turn.
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942. 7544
2:08 PM GMT on October 21, 2012
Quoting Grothar:
GFDL 126 hours




well that joins the fl camp how strong is that tia
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941. interstatelover7165
2:06 PM GMT on October 21, 2012
Do you think we will get to Tony?
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940. Grothar
2:05 PM GMT on October 21, 2012
GFDL 126 hours


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939. SunriseSteeda
2:04 PM GMT on October 21, 2012
Quoting Grothar:


When systems like this move close to the Florida coast, a strong pressure gradient sometimes forms and the winds can be near TS force, even though the system is quite far away. If it move up off the east coast the same could happen.


Grothar, do you remember when Floyd passed by? Of course he was a Category 5 at the time, but we had some interesting weather, if I have the right storm.

I was playing in a softball tournament at Mills Pond Park in Fort Lauderdale and it was very hot and very breezy with the winds gusting over 40mph. I remember hitting a pop-up fly ball that should have been an out in short left field, but instead it landed on a trailer beyond the parking lot, about 340 feet away from me for my first tournament home run.
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938. stormpetrol
2:01 PM GMT on October 21, 2012
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937. belizeit
2:00 PM GMT on October 21, 2012
Quoting sar2401:

Good morning, everyone. While all eyes seem to be focused on 99L, that area of disturbed weather off the Yucatan and Guatemala looks at least as impressive to me. I think we'll have another invest there soon. I think the combination of these two storms will have a tendency to shift 99L much further west than models are calling for now. That other area of disturbed weather is what may become the biggest threat over time. The models need a real low in one of the two areas before they start to get a handle on things.
Please don,t call Belize Guatemala we are a independent country.
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936. Grothar
1:50 PM GMT on October 21, 2012
Quoting ProgressivePulse:


Morning Gro, it's going to be a close call. Beaches will suffer the greatest damage, again.


Yeah, I was just looking at one of the models. These things can cause a lot of erosion and sometimes coastal flooding, if it does come as close as this


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935. washingtonian115
1:50 PM GMT on October 21, 2012
Quoting Grothar:


When systems like this move close to the Florida coast, a strong pressure gradient sometimes forms and the winds can be near TS force, even though the system is quite far away. If it move up off the east coast the same could happen.
Reminds me of Noel back in 2007.
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934. Grothar
1:47 PM GMT on October 21, 2012
Quoting 7544:
morning all 99l should start to gather all the convection today as it is doing so now also more models have this close to so fl could become a td by 11pm tonight imo fl should keep one eye on this one looks like its goin to be close call . even if goes east of fla they will see some kind of effects imo


When systems like this move close to the Florida coast, a strong pressure gradient sometimes forms and the winds can be near TS force, even though the system is quite far away. If it move up off the east coast the same could happen.
Member Since: July 17, 2009 Posts: 71 Comments: 26117
933. 7544
1:45 PM GMT on October 21, 2012
Quoting TropicalAnalystwx13:
Good morning guys.

The fact that all of the global models, with the exception of the ECMWF, blow this up into at least a Category 1 hurricane as it exits the coast of Cuba shows the favorable upper-air environment 99L will have throughout most of its lifespan. As the trough first sags south and draws 99L northward, there may be some wind shear, but I highly doubt it will be intense enough to cause substantial weakening. After 99L clears Cuba, the consensus seems to be for quick intensification into a hurricane within the Bahamas by 144 hours out (6 days). I doubt 99L, or Sandy by the time, makes a direct impact on the state of Florida, although heavy rainfall and gusty winds are now definitely possible for the eastern portion of the state. A strong trough of low pressure should save the Carolinas from a landfall as well, although again, heavy rainfall and gusty winds are a possibility.

0z GFS 144 hours:



0z UKMET 120 hours:



0z CMC 144 hours:



agree and its only 5 days away and could be at least a cat one .
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932. ProgressivePulse
1:44 PM GMT on October 21, 2012
Quoting Grothar:
Some models have shifted west since the earlier run.





Morning Gro, it's going to be a close call. Beaches will suffer the greatest damage, again.
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931. washingtonian115
1:44 PM GMT on October 21, 2012
Quoting Grothar:
Some models have shifted west since the earlier run.



99L/future Sandy better find it's way out to sea on a one way ticket to Greenland.
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930. icmoore
1:43 PM GMT on October 21, 2012
<
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929. Grothar
1:41 PM GMT on October 21, 2012
Some models have shifted west since the earlier run.



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928. Sfloridacat5
1:41 PM GMT on October 21, 2012
The GFS predictions (model runs) from about 1 week ago at 10 days out are starting to materialize (despite the naysayers).
It quite amazing to see these models predict tropical development that far out in the future.

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927. sar2401
1:39 PM GMT on October 21, 2012
Quoting Ftmyersstorm1:
Is this guy a crack puppy or what?

Actually, that's a pretty neat homemade radiation shield for a thermometer. I like it!
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926. 7544
1:38 PM GMT on October 21, 2012
morning all 99l should start to gather all the convection today as it is doing so now also more models have this close to so fl could become a td by 11pm tonight imo fl should keep one eye on this one looks like its goin to be close call . even if goes east of fla they will see some kind of effects imo
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925. sar2401
1:36 PM GMT on October 21, 2012
Quoting Ftmyersstorm1:
I agree I think this puppy is going to FL in the long run because that it where history this time of year always points to. Also the increase of motion that just exploded of the Yucatan may pull the circulation more west. What does everyone think?

Good morning, everyone. While all eyes seem to be focused on 99L, that area of disturbed weather off the Yucatan and Guatemala looks at least as impressive to me. I think we'll have another invest there soon. I think the combination of these two storms will have a tendency to shift 99L much further west than models are calling for now. That other area of disturbed weather is what may become the biggest threat over time. The models need a real low in one of the two areas before they start to get a handle on things.
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924. stormwatcherCI
1:35 PM GMT on October 21, 2012
Quoting Ftmyersstorm1:
I agree I think this puppy is going to FL in the long run because that it where history this time of year always points to. Also the increase of motion that just exploded of the Yucatan may pull the circulation more west. What does everyone think?
I agree with you. I think since it is still moving west with all that convection in the western Caribbean the chances for a more Central or Western Cuba and a Florida impact increases greatly.
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923. Ftmyersstorm1
1:34 PM GMT on October 21, 2012
Quoting FLWeatherFreak91:
I just completed this homemade radiation shield.... Ooohh la la
Is this guy a crack puppy or what?
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922. AussieStorm
1:34 PM GMT on October 21, 2012
Quoting CaicosRetiredSailor:
Follow up on Icelandic earthquake swarm...

There is no risk of volcano activity in this area following this earthquake swarm. Since there are no volcanoes in this area of Iceland. This earthquakes are strike-fault earthquakes.

That's a fairly big swarm.
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921. Ftmyersstorm1
1:32 PM GMT on October 21, 2012
We need to watch this one! I think that with all the moisture of the Yucatan that this may developed more west. Climatilogically speaking FL is where most of these end up. Also this early I see those tracks just need to move a couple hundred miles west and bingo! Rick Scott is on Tv in FL warningpeople to prepare. Any comments?
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920. FLWeatherFreak91
1:29 PM GMT on October 21, 2012
I just completed this homemade radiation shield.... Ooohh la la
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919. Ftmyersstorm1
1:25 PM GMT on October 21, 2012
Quoting Autistic2:
I have 0 faith in model tracks untill they at least have a closed circ to lock onto or a TD would be better. Untill its closed there are just to many varibles.
I agree I think this puppy is going to FL in the long run because that it where history this time of year always points to. Also the increase of motion that just exploded of the Yucatan may pull the circulation more west. What does everyone think?
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918. washingtonian115
1:24 PM GMT on October 21, 2012
Quoting clwstmchasr:
Crown Weather not ruling out a South Florida threat.

So, here are my thoughts:
As I have really mentioned, I do think that 99L will be named Sandy by Tuesday at the very latest and a track north-northeastward right across Jamaica as a moderately strong tropical storm seems likely right now. The timeframe for this would be Wednesday evening. From there, Sandy may turn more northward and it “feels” the trough of low pressure to its west and starts to get captured by that trough. This means a track across the central/northwestern Bahamas is possible from near the southern end of Andros Island to right across Great Abaco Island on Thursday night or Friday morning. Now, a caveat here: A track further west very near southeastern Florida on Friday morning is certainly possible and this is something that will need to be watched for very closely.

Beyond that, I have concerns that the forecast guidance are trending towards the idea of Sandy phasing into the eastern trough of low pressure and potentially becoming an intense coastal storm for the Mid-Atlantic states and New England. At this point, it is a possibility and we have more than enough time to watch for this potential.

One final thought: Late season tropical storms and hurricanes in the Caribbean can be extremely fickle and difficult to forecast. If we take a look at climatology for Caribbean storms in late October, they tend to take a north-northwesterly track towards south Florida. Additionally, late season storms are notorious slow moving systems and do not escape out the Caribbean very quickly; so, it is plausible that the global models may be overdoing the track out of the Caribbean with this system. So, nothing is written in stone when it comes to 99L/Sandy and this is a system that bears very close scrutiny.
Well with how whack our weather has been this year nothing will surprise me anymore that's for sure.I just hope this leads to more nor'easters this winter.
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917. Autistic2
1:20 PM GMT on October 21, 2012
Quoting wjdow:
Does having zero faith mean that you think that their pre-closed circulation predictions are no better than chance? That's pretty harsh on your part.


That is correct. We have yet to understand all the varibles, therefore we cannot write the programs to account for them. Therefore, they are nothing more than a educated guess trhat we know cannot be correct.

After they have a TD to lock opnto there are still varibles that we dont uderstand but the numer of them drops drastically.

Remember, I am only speaking about tack here, not formation.
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916. CaicosRetiredSailor
1:17 PM GMT on October 21, 2012
http://www.jonfr.com/volcano/?p=3115
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915. CaicosRetiredSailor
1:16 PM GMT on October 21, 2012
Follow up on Icelandic earthquake swarm...

There is no risk of volcano activity in this area following this earthquake swarm. Since there are no volcanoes in this area of Iceland. This earthquakes are strike-fault earthquakes.
Member Since: July 12, 2007 Posts: 0 Comments: 6032
914. wjdow
1:11 PM GMT on October 21, 2012
Quoting Autistic2:
I have 0 faith in model tracks untill they at least have a closed circ to lock onto or a TD would be better. Untill its closed there are just to many varibles.
Does having zero faith mean that you think that their pre-closed circulation predictions are no better than chance? That's pretty harsh on your part.
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913. Autistic2
1:10 PM GMT on October 21, 2012
I have been coming here for 5 years now. Been a paid member for 4. Well here it is.

Next year I will attempt to make my own forecasts! I saw how some people wailed on Levi for one busted forecast, so I hope you all understand, I have no formal edu. in weather but took this up as a hobby on the advice of my doctor and have become obsessed maybe….

For those that under stand AUTISM… I do tend to be rather OCD.
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911. washingtonian115
1:01 PM GMT on October 21, 2012
Well on the bright side I've done my holloween candy shopping.Got enough bags to last until christmas(Well I use the bags that I don't open and save them until chritmas comes around so I can use it to put in stockings and such).So in case cmc is right(which I v ery highly doubt) me and the fam can feast!.
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910. Autistic2
12:59 PM GMT on October 21, 2012
I have 0 faith in model tracks untill they at least have a closed circ to lock onto or a TD would be better. Untill its closed there are just to many varibles.
Member Since: August 29, 2008 Posts: 0 Comments: 461
909. unknowncomic
12:54 PM GMT on October 21, 2012
I don't know why they even bother with the clp or lbar plot. They always seem to be wrong.
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908. AussieStorm
12:53 PM GMT on October 21, 2012
Quoting unknowncomic:
can anyone explain the time of each point location on the graph line of this model plot? (ie each 12hr= new point)

Correct
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907. CybrTeddy
12:53 PM GMT on October 21, 2012
Quoting T3b0w:
how many named storm days does 2012 have so far and what is the average


17, the average is 10 (1950 - 2000)
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906. TropicalAnalystwx13
12:50 PM GMT on October 21, 2012
By the way, here is my newly-completed Tropical Cyclone Report for Tropical Storm Aletta if anybody missed it and/or is interested.

Tropical Cyclone Report: Tropical Storm Aletta (EP012012)

I'll be back later.
Member Since: July 6, 2010 Posts: 113 Comments: 32001
905. washingtonian115
12:49 PM GMT on October 21, 2012
No hurricane Hazel part two please.Party plans would have to be thrown out the window.
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904. unknowncomic
12:48 PM GMT on October 21, 2012
Quoting GeoffreyWPB:
Just updated...

can anyone explain the time of each point location on the graph line of this model plot? (ie each 12hr= new point)
Member Since: August 2, 2011 Posts: 0 Comments: 1912

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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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