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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You can almost pick the coc on 99l where will it go
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Anybody notice the big model shift at the end? (Remember, I saw it first :):)

Member Since: July 17, 2009 Posts: 71 Comments: 27208
Quoting washingtonian115:
Now watch the models shift out to sea tomorrow..


I was going to say the gulf of Mexico.... But out to sea works too...
Member Since: March 10, 2006 Posts: 0 Comments: 10782
Quoting washingtonian115:
It would be something to have once again 19 named storms again.Looks like this hurricane season wants to go out with a bang.Ida part 2?
Wow, those predictions of an average 2012 hurricane seasons seems so long ago........
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Now watch the models shift out to sea tomorrow..
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99L is Doing good!

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Quoting allancalderini:
I think it might be renumber tomorrow like 99L can`t wait to see which will be Sandy and which one will be Tony.
Is 90L moving SE, before it was at 20.1N now is 19.1N or that is a relocation of the COC?
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Quoting CybrTeddy:


Actually, I guarantee that would be a nor'easter.


An extremely, extremely powerful nor'easter though.
Doooooom.
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2PM

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Quoting TropicalAnalystwx13:
Well isn't that nice. Just your average 70-80 knot hurricane into the Northeast USA.



Actually, I guarantee that would be a nor'easter.


An extremely, extremely powerful nor'easter though.
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Quoting SLU:


It's a very tight and compact system unlike 99L that's a sprawling disturbance so should develop faster .. 90L isn't far away from TD #18.
It would be something to have once again 19 named storms again.Looks like this hurricane season wants to go out with a bang.Ida part 2?
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done CT should be better
Member Since: July 15, 2006 Posts: 178 Comments: 56021
259. SLU
At 1800 UTC, 21 October 2012, DISTURBANCE INVEST (AL90) was located in the North Atlantic basin at 20.2°N and 50.9°W. The current intensity was 25 kt and the center was moving at 8 kt at a bearing of 285 degrees. The minimum central pressure was 1011 mb.
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Member Since: July 2, 2011 Posts: 0 Comments: 1183
257. SLU
At 1800 UTC, 21 October 2012, DISTURBANCE INVEST (AL99) was located in the North Atlantic basin at 14.6°N and 76.9°W. The current intensity was 25 kt and the center was moving at 9 kt at a bearing of 270 degrees. The minimum central pressure was 1006 mb.
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90L fattening up.

99L as well.

WE may have two new TDs by tomorrow morning.
Member Since: July 2, 2011 Posts: 0 Comments: 1183
255. SLU
Quoting washingtonian115:
Well it does look better in satellite presentation.I give it a conservative 50% chance of ever developing.


It's a very tight and compact system unlike 99L that's a sprawling disturbance so should develop faster .. 90L isn't far away from TD #18.
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Well isn't that nice. Just your average 70-80 knot hurricane into the Northeast USA.

Member Since: July 6, 2010 Posts: 113 Comments: 32813
New England Autumn before the soon-to-fall snow...

...but without the 'New'
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You can thank that large low pressure near England for stopping 99L from going out to sea. Just like Highs, Lows can block systems as well.
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Quoting reedzone:
To be honest, the scenarios being shown by the CMC, GFS, GFDL, and now the EURO is not "impossible". Apparently the storm has nowhere to track when there is a big blocking low to the East and a frontal system to the west. The storm would have to end up recurving NW towards the Conus if those elements are in place by that time. It's going to be a very interesting week, possibly historic if all the pieces can come together.


Dr. Masters mention that its seems unlikely that a cutoff trough will be able to completely pick up it and sent it all the way North. As an area of high pressure could build in trapping 99L and send it to the WNW toward the western Bahamas and the East coast right now I think the model best depicting the set up is the NOGAPS and the CMC.
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KOTG, do you mind if you could remove that last picture? It's destroying my bandwith, thanks!
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and now..

192 hours. "Doomsday"


It's fun to watch these runs go crazy, I must admit. We'll have to see if all the elements can come together when the time comes.
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Quoting reedzone:
12Z EURO (still running)

144 hours.


168 hours.


It doesn't appear to me that the GFS is in fantasy land...
Well at least if I'm going to be affected Florida will be affected as well.Then maybe I'll be a little more happy.Lol J/K.

Post 247 almost reminds me of Micheal in earlier stages.I think the NHC isn't so quick because it's October.
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90L is getting close to tropical depression status.

Member Since: July 6, 2010 Posts: 113 Comments: 32813
Quoting washingtonian115:
Well Sandy would be more fitting for that storm as it shouldn't really bring harm to anyone.The male names have been on a role this year and if 90L is named first 99L will perhaps be Tony and keep the tradition.

Post 234:Oh shoot lol lol.I saw BWI so I thought you were somewhere in Maryland.


lol nope British West Indies ;-p. I think I'm in for a rainy week no matter what becomes of 99L or what name it may get.
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12Z EURO (still running)

144 hours.


168 hours.


It doesn't appear to me that the GFS is in fantasy land...
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244 @ 2:44




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Quoting SLU:
Dvorak says 90L is winning the race.

21/1745 UTC 20.4N 50.9W T1.5/1.5 90L -- Atlantic
21/1745 UTC 14.6N 77.1W T1.0/1.0 99L -- Atlantic
Well it does look better in satellite presentation.I give it a conservative 50% chance of ever developing.
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To be honest, the scenarios being shown by the CMC, GFS, GFDL, and now the EURO is not "impossible". Apparently the storm has nowhere to track when there is a big blocking low to the East and a frontal system to the west. The storm would have to end up recurving NW towards the Conus if those elements are in place by that time. It's going to be a very interesting week, possibly historic if all the pieces can come together.
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Convection has increased significantly since early this morning and spiral banding has starting in response. All 99L needs now is to continue to fire and organize those thunderstorms and we have a TC.
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<
Member Since: July 15, 2006 Posts: 178 Comments: 56021
*yawn*

Quoting reedzone:
12 GFS = Perfect Storm
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238. SLU
Dvorak says 90L is winning the race.

21/1745 UTC 20.4N 50.9W T1.5/1.5 90L -- Atlantic
21/1745 UTC 14.6N 77.1W T1.0/1.0 99L -- Atlantic
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Quoting gordydunnot:
Wow that CMC run is not a pretty picture for S. Fl. and much of the east coast, although it looks further inland for the rest of it's run.


If the Euro and CMC pan out, Florida is gonna be well below average next week!!!
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okay..not liking the GFS or CMC run at ALL..
Member Since: August 19, 2006 Posts: 13 Comments: 16223
Quoting TropicalAnalystwx13:
T-numbers up to T1.5/25 knots with 90L. 30% is way too low.

21/1745 UTC 20.4N 50.9W T1.5/1.5 90L -- Atlantic
Well Sandy would be more fitting for that storm as it shouldn't really bring harm to anyone.The male names have been on a role this year and if 90L is named first 99L will perhaps be Tony and keep the tradition.

Post 234:Oh shoot lol lol.I saw BWI so I thought you were somewhere in Maryland.
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Quoting washingtonian115:
Are you from somehwere in the DMV area?.99L still has a loooooong way to go.
I agree 99L has a ways to go. I'm in the caymans
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Quoting Saltydogbwi1:
img src="">

Hey guys been offline a while....Heres what i see happening with 99L right now.
Are you from somehwere in the DMV area?.99L still has a loooooong way to go.
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T-numbers up to T1.5/25 knots with 90L. 30% is way too low.

21/1745 UTC 20.4N 50.9W T1.5/1.5 90L -- Atlantic
Member Since: July 6, 2010 Posts: 113 Comments: 32813
.
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img src="">

Hey guys been offline a while....Heres what i see happening with 99L right now.
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Seems to be many posts that make no sense in the latter of the season..... I try to keep my intelligence in late October, But late October is not a good time for south Florida... (Wilma comes to mind)
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.
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Quoting Tropicsweatherpr:


Do you have the link as I dont see it at NRL site?



here ya go

Fleet Weather Center Norfolk Virginia


Link
Member Since: July 15, 2006 Posts: 178 Comments: 56021
Wow that CMC run is not a pretty picture for S. Fl. and much of the east coast, although it looks further inland for the rest of it's run.
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Quoting KEEPEROFTHEGATE:
ALERT ATCF MIL 99X XXX 121021120000
2012102112
14.8 284.0
14.8 281.1
100
14.7 284.5
211530
1210211530
1
WTNT21 KNGU 211530
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE
WITHIN 100 NM EITHER SIDE OF A LINE FROM 14.8N 76.0W TO 14.8N 78.9W
WITHIN THE NEXT 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT
IMAGERY AT 211200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 14.7N 75.5W. THE SYSTEM IS MOVING WESTWARD AT 07 KNOTS.
2. REMARKS: CURRENT MODEL GUIDANCE IS DEPICTING INTENSIFICATION OF
A TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN SEA. AT 211200Z,
SATELLITE IMAGERY INDICATED AN AREA OF INCREASED THUNDERSTORM ACTIVITY
THAT HAS PERSISTED OVER THE LAST 24 HOURS. WARM SEA SURFACE TEMPERATURES
OF 83 TO 85 DEGREES FAHRENHEIT IN CONJUNCTION WITH A FAVORABLE UPPER AIR
ENVIRONMENT MAY ENHANCE DEVELOPMENT OF THIS SYSTEM INTO A TROPICAL CYCLONE.
3. THIS ALERT WILL BE UPGRADED TO WARNING OR REISSUED AS REQUIRED
BY 221530Z.//
9912101912 140N 690W 20
9912101918 140N 697W 20
9912102000 141N 705W 20
9912102006 143N 716W 20
9912102012 145N 725W 25
9912102018 146N 732W 25
9912102100 147N 740W 25
9912102106 147N 748W 25
9912102112 147N 755W


Do you have the link as I dont see it at NRL site?
Member Since: April 29, 2009 Posts: 75 Comments: 14890
Quoting beell:


I see something closer to 77W, KEEP.
its going to bounce around awhile yet 24 hrs by afternoon tomorrow we will get a fix with the planes
Member Since: July 15, 2006 Posts: 178 Comments: 56021


Convection impressive now with 99L.
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Quoting KEEPEROFTHEGATE:
POSS T.C.F.A.
99L/INV/XX/XX
MARK
14.89N/73.69W
caribbeans going into labor. ready to give birth
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221. beell
Quoting KEEPEROFTHEGATE:
POSS T.C.F.A.
99L/INV/XX/XX
MARK
14.89N/73.69W


I see something closer to 77W, KEEP.
Member Since: September 11, 2007 Posts: 145 Comments: 16920

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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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