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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If the GFDL pans out Halloween will be a trick alright.
Member Since: March 10, 2006 Posts: 0 Comments: 9661
Quoting 7544:


if and when this becomes a td the cone from the nhc will be interesting to see is the plane canceled for today at 4pm yet

Yup, recon is cancelled today which, I think, isn't a bad call.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
99L doing good now!:)
Quoting Grothar:
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Quoting Stormchaser2007:
Interesting Halloween



trick a treat
Member Since: July 15, 2006 Posts: 163 Comments: 52096
Quoting Stormchaser2007:
Interesting Halloween


I don't think it would be a treat for people. Hopefully, and probably, this solution will be gone on the next run.

Member Since: March 16, 2012 Posts: 123 Comments: 7885
Quoting 7544:


if and when this becomes a td the cone from the nhc will be interesting to see is the plane canceled for today at 4pm yet


Yes, recon cancelled....
Member Since: March 10, 2006 Posts: 0 Comments: 9661
Starting out to be a bad week first a potential hurricane coming my way and I just found out Fidel is making a live appearance in Cuba.... everyone here was hoping he was finally gone. Apparently that man is gonna challenge Grothars longevity.

What's next?
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164. 7544
Quoting Grothar:




if and when this becomes a td the cone from the nhc will be interesting to see is the plane canceled for today at 4pm yet
Member Since: May 6, 2007 Posts: 0 Comments: 6617
Member Since: July 17, 2009 Posts: 63 Comments: 23672
Quoting 7544:
hmm looks like fl could be looking for a hurricane in less than 5 days and the gfdl has it 97 knots keep one eye on this one
Next week is Wilma anniversary. Let's hope Sandy stays away. Weather here in South Florida has just turned to fall; beautiful. We don't need no stinkin TC.
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Member Since: July 17, 2009 Posts: 63 Comments: 23672
Changing GFDL to Grothars FLORIDA Doom Low.
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Interesting Halloween

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Quoting KEEPEROFTHEGATE:
its happen before the last hazel flooded out most of toronto with nearly 300mm of water in 24 hrs as she track up and over the western lake ontario regions


Hazel was so big, that even though it tracked through PA and upstate NY into Canada, NYC and Long Island had winds over 100mph. I'm not sure, but I think Hazel still holds the record for the strongest winds in NYC.
Member Since: July 17, 2009 Posts: 63 Comments: 23672
I do not believe 97 kts are surface winds. It would be lower.




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Quoting Dakster:


We can only hope....

I wouldn't mind the season being over after Sandy and or Tony. Especially is the east coast is battered like it is shown in this run.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
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Quoting wxchaser97:
Holy yeah, it is a good thing this is in fantasy land. Hopefully this solution does not happen as this would be a bad thing for many people. Now that is a nor'easter with an attitude.

yes yes yes!!!
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Quoting Tropicsweatherpr:


It looks on long range that after Sandy and Tony,season will be over.


We can only hope....
Member Since: March 10, 2006 Posts: 0 Comments: 9661
Quoting MAweatherboy1:
It drags a ton of cold air in behind it as it heads north, this could bring snow to Maine:


SSSNNNNNOOOOOOWWWWW??????????????
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Quoting NCHurricane2009:
I think Hazel went more NNW into Ontario...this would come at Ontario while going more west:

Link to 06Z GFS surface anim

By the way...the 12Z GFS doesn't show this...it now shows the storm making a small loop near the mid-Atlantic shore then zooming NE...

I saw that and that would bring some interesting times here if that happened. That low would be dumping rain, snow for some areas, and winds all over the Great Lakes and NE.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Quoting MAweatherboy1:
It drags a ton of cold air in behind it as it heads north, this could bring snow to Maine:



It looks on long range that after Sandy and Tony season will be over.
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Member Since: July 15, 2006 Posts: 163 Comments: 52096
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The worst-affected areas were communities near the Humber River, Holland Marsh, and Etobicoke Creek. Prone to flooding, the Humber River raced downstream from Woodbridge when an earthen dam failed. In the weeks prior to Hazel, Toronto had received copious amounts of rain, and the soil could not hold as much as 200 mm (7.9 in) of rain; consequently, over 90% of it went into Toronto's waterways. The Humber heavily flooded Weston, and killed 35 people in Raymore Drive. Holland Marsh was severely flooded; while no one was killed, the economic losses were severe as the region's crops were harvested but not collected. At the village of Long Branch, the Etobicoke Creek killed seven people and swept numerous dwellings into Lake Ontario. Toronto's infrastructure also took a major hit, with as much as 50 bridges being washed out by the rising waters.

The situation was exacerbated by the lack of preparedness and awareness. Torontonians did not have prior experience with hurricanes, and the storm as whole proved to be extremely unpredictable—even the arrival of Hazel came as a surprise. Also, the low-lying areas near the Humber were mostly residential, which were among the worst-affected during the storm. In fact, following Hazel, residential development in areas along Toronto waterways was prohibited, and they became parks instead.

To help with the cleanup, the army was summoned. Due to the destruction in Canada, as well as the United States and Haiti, the name Hazel was retired, and will never again be used for an Atlantic hurricane. Since it was retired before the creation of formal lists, it was not replaced with any particular name.
Member Since: July 15, 2006 Posts: 163 Comments: 52096
Quoting KEEPEROFTHEGATE:
its happen before the last hazel flooded out most of toronto with nearly 300mm of water in 24 hrs as she track up and over the western lake ontario regions
I think Hazel went more NNW into Ontario...this would come at Ontario while going more west:

Link to 06Z GFS surface anim

By the way...the 12Z GFS doesn't show this...it now shows the storm making a small loop near the mid-Atlantic shore then zooming NE...
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It drags a ton of cold air in behind it as it heads north, this could bring snow to Maine:

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Quoting CybrTeddy:


That looks like an extra-tropical nor'easter to me.

Definitely. It doesn't matter though, the effects would be the same.
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Quoting MAweatherboy1:
It just stalls out in the mid Atlantic! This would be very bad...



That looks like an extra-tropical nor'easter to me.
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It weakens as it pulls away and passes the NE:

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Quoting NCHurricane2009:

I think the GFS solution your looking at shows something sorta like Gloria in the '80s for a landfall.

If you keep going I think it then shows it swing westward across New York State...and then into the Great Lakes area as a non-tropical low...that would be really weird and unprecedented if it happened like that. The models are putting on quiet a show today...
its happen before the last hazel flooded out most of toronto with nearly 300mm of water in 24 hrs as she track up and over the western lake ontario regions
Member Since: July 15, 2006 Posts: 163 Comments: 52096
It just stalls out in the mid Atlantic! This would be very bad...

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Holy yeah, it is a good thing this is in fantasy land. Hopefully this solution does not happen as this would be a bad thing for many people. Now that is a nor'easter with an attitude.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Quoting MAweatherboy1:
Geez:




nic nor ester
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Geez:

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Well if 90L does develop first...this crazy storm could end up with the name Tony...that would make this more interesting...

I'm out for now...
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Quoting wxchaser97:
966mb, something you wouldn't want to mess with. Also the trough isn't as strong this run so I don't get much or any snow like previous runs and Sandy is closer to the US.




that could be sandy or tony if 90L gets name 1st
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GFS definitely trying to come more in line with the CMC this run, it's not quite as far west as the 0z CMC was but still a pretty dramatic shift. Time will tell if this is a one run fluke or the start of a bigger trend.
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966mb, something you wouldn't want to mess with. Also the trough isn't as strong this run so I don't get much or any snow like previous runs and Sandy is closer to the US.
Member Since: March 16, 2012 Posts: 123 Comments: 7885
132. 7544
hmm looks like fl could be looking for a hurricane in less than 5 days and the gfdl has it 97 knots keep one eye on this one
Member Since: May 6, 2007 Posts: 0 Comments: 6617
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Quoting MAweatherboy1:
This would cause so much beach erosion...


and a fun few days of tracking it!
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Quoting MAweatherboy1:
Wow:


I think the GFS solution your looking at shows something sorta like Gloria in the '80s for a landfall.

If you keep going I think it then shows it swing westward across New York State...and then into the Great Lakes area as a non-tropical low...that would be really weird and unprecedented if it happened like that. The models are putting on quiet a show today...
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Quoting NCHurricane2009:

Last time was Hazel in '54...and that wreaked more havoc than Fran in '96. But Hazel hit when NC was less populated...so Fran was more damaging...

I think so...a month ago I wasn't so sure...

Big westward shift...GFS yesterday has this thing curve ENE into the open Atlantic after moving over the E Cuba/Haiti area...but it may go back the other way....that's why models can't be trusted this far out...so all this talk is just talk....


Come on now, it is a discussion blog and an excercise in mental masterbation at this point.

Although for all we know this could be a GOM storm by the time the westward shift is done.
Member Since: March 10, 2006 Posts: 0 Comments: 9661
Quoting MAweatherboy1:
I still think 90L will develop. What is it missing?




a close low?


90L may beat 99L
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This would cause so much beach erosion...

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Quoting interstatelover7165:
Does anyone think we will make it to Tony?

I think we can get to at least Tony this year. I feel that 90L could become Tony.

Well this wouldn't be good for the east coast, a 971mb storm sliding up the coast(180hrs).
Member Since: March 16, 2012 Posts: 123 Comments: 7885
Wow:

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Member Since: August 2, 2010 Posts: 21 Comments: 9648
Quoting TropicalAnalystwx13:
An October hurticane hit here in NC would be very rare but cool.

Last time was Hazel in '54...and that wreaked more havoc than Fran in '96. But Hazel hit when NC was less populated...so Fran was more damaging...
Quoting interstatelover7165:
Does anyone think we will make it to Tony?

I think so...a month ago I wasn't so sure...
Quoting MAweatherboy1:
Correct me if I'm wrong but this looks like a westward shift on the GFS, it's brushing the Carolinas:


Big westward shift...GFS yesterday has this thing curve ENE into the open Atlantic after moving over the E Cuba/Haiti area...but it may go back the other way....that's why models can't be trusted this far out...so all this talk is just talk....
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Quoting MAweatherboy1:
Correct me if I'm wrong but this looks like a westward shift on the GFS, it's brushing the Carolinas:


You are correct, the GFS has shifted west toward the US.

Quoting TropicalAnalystwx13:
An October hurticane hit here in NC would be very rare but cool.

It would be pretty cool and a sight to see. I do have one question, what is a hurticane? I know you meant hurricane I'm just playing.
Member Since: March 16, 2012 Posts: 123 Comments: 7885

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.