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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Quoting Neapolitan:
It was very hot in parts of the nation's midsection today, primarily Oklahoma, which saw a number of record high temps in the mid 90s. That'll be short-lived, however, as the CPC is now calling for some pretty cold weather for a huge chunk of the U.S. centered around the lower Mississippi Valley in the 6-10 day period. The West Coast and the extreme Northeast will remain toasty, but, still, next week's setup looks very fall-like...

cold

The 8-14 day outlook shifts the cold weather to the east some while the warm temps come further east too. Half the country would still remain in a welcomed fall pattern while others are pretty warm. The eastern 1/3 of the country would remain wet while the other 2/3 are average to below average, besides the Pacific NW.
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I like that model, but it appears that they are in windshield wiper mode...

WxChaer97 - I guess we are entitled to a good weather day every once in a while. Although I really, really like the winters down here. Not a lot of rain, humidity, and usually the temperature is nice. (Never gets too cold for me, but sometimes we still get hot days)
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both gfdl and hwrf shift eastward..
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Quoting GeorgiaStormz:


Take me with you!

My swim meet was fine, just an early season foray back into competition. I didnt do too well or too poorly but I can judge where I'm at.

Nah, I'm good going by myself.
So in short you didn't do good and you are trying to make yourself feel better.

Quoting Dakster:
It is down right pleasant outside right now... Low(er) humidity and feels like it is under 80F.

What happened?

I had perfect weather today where I'm at. There were no clouds in the sky and temps were in the 50s to 60s for the day. Maybe today was good weather day?
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18z HWRF imitates GFS and also shifts east.

Member Since: April 29, 2009 Posts: 75 Comments: 14904
It was very hot in parts of the nation's midsection today, primarily Oklahoma, which saw a number of record high temps in the mid 90s. That'll be short-lived, however, as the CPC is now calling for some pretty cold weather for a huge chunk of the U.S. centered around the lower Mississippi Valley in the 6-10 day period. The West Coast and the extreme Northeast will remain toasty, but, still, next week's setup looks very fall-like...

cold
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It is down right pleasant outside right now... Low(er) humidity and feels like it is under 80F.

What happened?
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Quoting wxchaser97:

How was your swim meet today, sorry but I had to ask?
I volunteer to not send you to the NE. I'll just go myself and bring back video.


Take me with you!

My swim meet was fine, just an early season foray back into competition. I didnt do too well or too poorly but I can judge where I'm at.
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First dry air out of the north here in Key West that we have had so far this year. Before today I was going through 3 shirts a day it was so humid. Maybe this does have enough juice to take 99l NE. We will see.
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512. beell
Quoting TomTaylor:
Good question, I was asking myself this last night.

Looking at the low levels there are no obvious features that would pull this storm out of the Caribbean. However, if we compare the surface level to the mid level it is clear that this system is not only heavily weighted to the NE in terms of convection and precipitation, but also severely vertically tilted -- if you can even call it that. The center of the mid level circulation is a few hundred miles to the NE of the surface low. The displacement of the mid level circulation is a direct result of the shear and strong divergence caused by an upper level trough to the west of the system. As this trough amplifies, it is pushing convection off to the eastern half of the storm by inflicting westerly shear. Furthermore, the amplification of the subtropical jet produces a strong outflow jet to the NE of the storm, providing divergence and allowing convection to flourish in that area. As a result, we get a lopsided storm with the strongest convection in the NE quad. Since the convection is so much stronger to the NE, the surface low is naturally favored under the area, which causes it to follow the convection.

18z 250 mb Winds and Heights @39hrs




Upper level trough feature is traced out in purple. Notice the subtropical jet providing an outflow channel/jet out to the NE.

18z Surface Analysis @39hrs




18z 500mb Vorticity and Heights @39hrs



Notice the center of the mid level circulation is just south of Jamaica here, a few hundred miles to the NE of the surface low. Also notice how the 582mb line of the storm extends very closely to the 582mb line of the mid-Atlantic trough just to the N of the lesser Antilles. In fact, in between these 582mb lines we can make out a weak trough feature in the wind barbs (looking just north of PR). This is likely helping pull the storm out of the Caribbean.

So it is the shear and upper divergence weighting the storm to the NE forcing the surface low to follow the mid level circulation out to the NE. Furthermore, the relatively strong mid level circulation produced as a result of the massive area of convection is feeling a bit of the weakness left behind by a passing trough in the Atlantic. These two features appear to be what is initially drawing the storm out of the Caribbean.


One last image to drive the point home...

18z GFS 500mb Heights and Humidity 12hrs later @51hrs




Looking at the humidity signature, it is clear this storm will be very strongly weighted to the north and east of the surface low. The displaced convection will force the surface low to follow as the convection naturally produces the area of lowest pressures. Furthermore, we can see the weakness in the mid levels is still left behind by the mid-Atlantic trough which is helping pull on the system.


Having a little trouble finding an actual mid-level center a few hundred miles to the NE of any surface center at the present time.

Your explanation is similar to Levi's and is a workable mechanism at some point. I'll take my monsoon depression scenario and go home now, lol.
(j/k)

And thank you for the detailed response.
Member Since: September 11, 2007 Posts: 145 Comments: 16923
Quoting TomTaylor:
Good question, I was asking myself this last night.

Looking at the low levels there are no obvious features that would pull this storm out of the Caribbean. However, if we compare the surface level to the mid level it is clear that this system is not only heavily weighted to the NE in terms of convection and precipitation, but also severely vertically tilted -- if you can even call it that. The center of the mid level circulation is a few hundred miles to the NE of the surface low. The displacement of the mid level circulation is a direct result of the shear and strong divergence caused by an upper level trough to the west of the system. As this trough amplifies, it is pushing convection off to the eastern half of the storm by inflicting westerly shear. Furthermore, the amplification of the subtropical jet produces a strong outflow jet to the NE of the storm, providing divergence and allowing convection to flourish in that area. As a result, we get a lopsided storm with the strongest convection in the NE quad. Since the convection is so much stronger to the NE, the surface low is naturally favored under the area, which causes it to follow the convection.

18z 250 mb Winds and Heights @39hrs




Upper level trough feature is traced out in purple. Notice the subtropical jet providing an outflow channel/jet out to the NE.

18z Surface Analysis @39hrs




18z 500mb Vorticity and Heights @39hrs



Notice the center of the mid level circulation is just south of Jamaica here, a few hundred miles to the NE of the surface low. Also notice how the 582mb line of the storm extends very closely to the 582mb line of the mid-Atlantic trough just to the N of the lesser Antilles. In fact, in between these 582mb lines we can make out a weak trough feature in the wind barbs (looking just north of PR). This is likely helping pull the storm out of the Caribbean.

So it is the shear and upper divergence weighting the storm to the NE forcing the surface low to follow the mid level circulation out to the NE. Furthermore, the relatively strong mid level circulation produced as a result of the massive area of convection is feeling a bit of the weakness left behind by a passing trough in the Atlantic. These two features appear to be what is initially drawing the storm out of the Caribbean.


One last image to drive the point home...

18z GFS 500mb Heights and Humidity 12hrs later @51hrs




Looking at the humidity signature, it is clear this storm will be very strongly weighted to the north and east of the surface low. The displaced convection will force the surface low to follow as the convection naturally produces the area of lowest pressures. Furthermore, we can see the weakness in the mid levels is still left behind by the mid-Atlantic trough which is helping pull on the system.


Good analysis there. But why NHC keeps saying that enviromental conditions will be favorable?
Member Since: April 29, 2009 Posts: 75 Comments: 14904
Quoting KEEPEROFTHEGATE:


we wait and see the next run i reckon
things will kick into high gear
by tomorrow afternoon and build from there


This is a TX storm.
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Very nice Tropical Tidbit Levi...

Levi's Tropical Tidbit
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Well I'm not visiting Delaware..and no family in Maryland..but I DO have a "ghost hunting" tour booked for my granddaughters 14th birthday for the 27th in St.Augustine Fla....lol..my only hope is it is bad enough for them to reschedule the tours as the tickets had to be paid in advance and are non refundable..oh and good eve all..
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Quoting GeorgiaStormz:


Hey who wants to send me on an all expense paid trip to NE and the Mid-Atlantic for Halloween?
I'll send back video :) jk

How was your swim meet today, sorry but I had to ask?
I volunteer to not send you to the NE. I'll just go myself and bring back video.
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Quoting washingtonian115:
I expect to see post like this over the week.

"I'm visiting Deleware.Would I need to take any caution?"

or

"My family lives in New Jersey what should they expect"

I just know it.It's going to be classic.



Hey who wants to send me on an all expense paid trip to NE and the Mid-Atlantic for Halloween?
I'll send back video :) jk
But this could be a fun experience for those living there, depending on how this pans out.
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Quoting beell:
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?
Good question, I was asking myself this last night.

Looking at the low levels there are no obvious features that would pull this storm out of the Caribbean. However, if we compare the surface level to the mid level it is clear that this system is not only heavily weighted to the NE in terms of convection and precipitation, but also severely vertically tilted -- if you can even call it that. The center of the mid level circulation is a few hundred miles to the NE of the surface low. The displacement of the mid level circulation is a direct result of the shear and strong divergence caused by an upper level trough to the west of the system. As this trough amplifies, it is pushing convection off to the eastern half of the storm by inflicting westerly shear. Furthermore, the amplification of the subtropical jet produces a strong outflow jet to the NE of the storm, providing divergence and allowing convection to flourish in that area. As a result, we get a lopsided storm with the strongest convection in the NE quad. Since the convection is so much stronger to the NE, the surface low is naturally favored under the area, which causes it to follow the convection.

18z 250 mb Winds and Heights @39hrs




Upper level trough feature is traced out in purple. Notice the subtropical jet providing an outflow channel/jet out to the NE.

18z Surface Analysis @39hrs




18z 500mb Vorticity and Heights @39hrs



Notice the center of the mid level circulation is just south of Jamaica here, a few hundred miles to the NE of the surface low. Also notice how the 582mb line of the storm extends very closely to the 582mb line of the mid-Atlantic trough just to the N of the lesser Antilles. In fact, in between these 582mb lines we can make out a weak trough feature in the wind barbs (looking just north of PR). This is likely helping pull the storm out of the Caribbean.

So it is the shear and upper divergence weighting the storm to the NE forcing the surface low to follow the mid level circulation out to the NE. Furthermore, the relatively strong mid level circulation produced as a result of the massive area of convection is feeling a bit of the weakness left behind by a passing trough in the Atlantic. These two features appear to be what is initially drawing the storm out of the Caribbean.


One last image to drive the point home...

18z GFS 500mb Heights and Humidity 12hrs later @51hrs




Looking at the humidity signature, it is clear this storm will be very strongly weighted to the north and east of the surface low. The displaced convection will force the surface low to follow as the convection naturally produces the area of lowest pressures. Furthermore, we can see the weakness in the mid levels is still left behind by the mid-Atlantic trough which is helping pull on the system.
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Quoting washingtonian115:
I expect to see post like this over the week.

"I'm visiting Deleware.Would I need to take any caution?"

or

"My family lives in New Jersey what should they expect"

I just know it.It's going to be classic.


Also there could be "I got family in Maryland so will they be ok?"
I seriously though do have family in Maryland but I know they should be fine.
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I expect to see post like this over the week.

"I'm visiting Deleware.Would I need to take any caution?"

or

"My family lives in New Jersey what should they expect"

I just know it.It's going to be classic.

Member Since: August 14, 2010 Posts: 10 Comments: 17823
Quoting wxchaser97:

I wouldn't be afraid of 99L, at least not right now. There are too many variables so we don't know where it will go and how strong when/if it gets that far north. Just monitor the progress of 99L and continue on with your daily life.


Thats what I also do :)
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Quoting Speeky:
I live in New York. Should I be afraid of 99L?

be afraid....very afraid...............not

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Quoting Speeky:
I live in New York. Should I be afraid of 99L?

I wouldn't be afraid of 99L, at least not right now. There are too many variables so we don't know where it will go and how strong when/if it gets that far north. Just monitor the progress of 99L and continue on with your daily life.
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I live in New York. Should I be afraid of 99L?
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Quoting beell:
Amazing structure...

All I see is abstract art from the blobist school.
Member Since: August 30, 2010 Posts: 0 Comments: 339
496. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Disturbance Summary
3:00 AM JST October 22 2012
====================================

At 18:00 PM UTC, Tropical Depression (1004 hPa) located at 6.0N 134.0E has 10 minute sustained winds of 25 knots with gusts of 40 knots. The depression is reported as moving west northwest slowly.
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May be time to trim the coconut trees.

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Quoting Levi32:


Pressure gradient increasing to the north.




It's going to get windy here. I send up a video.
Member Since: July 17, 2009 Posts: 71 Comments: 27210
Quoting beell:
Amazing structure...



just got to fill in


Member Since: July 15, 2006 Posts: 178 Comments: 56140
I think the NHC isn't jumping on 90L so quick is because it doesn't have as much model support as 99L does and conditions are expected be hostile in the next 36 hours.That's my speculation.
Member Since: August 14, 2010 Posts: 10 Comments: 17823
Quoting Grothar:
slight pressure falls in the western Caribbean and a slight pressure rise in the Central Caribbean.


Pressure gradient increasing to the north.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
The epac AOI is up to 20%.

SHOWERS AND THUNDERSTORMS CONTINUE IN ASSOCIATION WITH AN ELONGATED
LOW PRESSURE SYSTEM LOCATED ABOUT 425 MILES SOUTH-SOUTHEAST OF
ACAPULCO MEXICO. SOME GRADUAL DEVELOPMENT OF THIS LARGE
DISTURBANCE IS POSSIBLE OVER THE NEXT FEW DAYS AS IT MOVES SLOWLY
WESTWARD. THIS SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
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Quoting ncstorm:


it works for me but here it is without the "s"

hope that helps
It still won't work but thanks anyhow.
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TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
500 PM PDT SUN OCT 21 2012

FOR THE EASTERN NORTH PACIFIC...EAST OF 140 DEGREES WEST LONGITUDE..

1. SHOWERS AND THUNDERSTORMS CONTINUE IN ASSOCIATION WITH AN ELONGATED
LOW PRESSURE SYSTEM LOCATED ABOUT 425 MILES SOUTH-SOUTHEAST OF
ACAPULCO MEXICO. SOME GRADUAL DEVELOPMENT OF THIS LARGE
DISTURBANCE IS POSSIBLE OVER THE NEXT FEW DAYS AS IT MOVES SLOWLY
WESTWARD. THIS SYSTEM HAS A LOW CHANCE...20 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER STEWART
NNNN
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Quoting beell:
Amazing structure...


I know right, that is the best looking invest I have ever seen. Still has work to do and 99L should be a depression in the next 48hrs.

Quoting washingtonian115:
Well they raised it to 40% should be higher..

Quoting Slamguitar:


40%?? Come on NHC!! This looks better than a 40%.

At least they raised it, but it should probably be a little higher(50-60%) Of course this could end up not developing so they won't raise it too high just yet.
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484. beell
Amazing structure...

Member Since: September 11, 2007 Posts: 145 Comments: 16923
Hey I did get it right, 99L stayed the same and 90L went up. I think 90L should be higher but at least the percentage went up.

A BROAD AREA OF LOW PRESSURE LOCATED A COUPLE OF HUNDRED MILES
SOUTH-SOUTHEAST OF JAMAICA IS PRODUCING A LARGE AREA OF SHOWERS AND
THUNDERSTORMS OVER THE CENTRAL CARIBBEAN SEA. ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR THE FORMATION OF A
TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS AS THE LOW MOVES
SLOWLY WESTWARD AND BECOMES NEARLY STATIONARY WELL TO THE SOUTH OF
JAMAICA. THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HEAVY RAINS FROM THIS
DISTURBANCE ARE LIKELY TO SPREAD OVER JAMAICA...HISPANIOLA...AND
EASTERN CUBA OVER THE NEXT SEVERAL DAYS. THESE RAINS COULD PRODUCE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS
OF HIGH TERRAIN.

A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
SMALL AREA OF SHOWERS AND A FEW THUNDERSTORMS OVER THE CENTRAL
ATLANTIC ABOUT 750 MILES EAST-NORTHEAST OF THE LEEWARD ISLANDS.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR SOME
DEVELOPMENT BEFORE UPPER-LEVEL WINDS BECOME LESS FAVORABLE ON
TUESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
NORTHWESTWARD TO NORTH-NORTHWESTWARD AT ABOUT 10 MPH.
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Well they raised it to 40% should be higher..
Member Since: August 14, 2010 Posts: 10 Comments: 17823
Quoting TropicalAnalystwx13:
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN OCT 21 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE LOCATED A COUPLE OF HUNDRED MILES
SOUTH-SOUTHEAST OF JAMAICA IS PRODUCING A LARGE AREA OF SHOWERS AND
THUNDERSTORMS OVER THE CENTRAL CARIBBEAN SEA. ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR THE FORMATION OF A
TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS AS THE LOW MOVES
SLOWLY WESTWARD AND BECOMES NEARLY STATIONARY WELL TO THE SOUTH OF
JAMAICA. THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HEAVY RAINS FROM THIS
DISTURBANCE ARE LIKELY TO SPREAD OVER JAMAICA...HISPANIOLA...AND
EASTERN CUBA OVER THE NEXT SEVERAL DAYS. THESE RAINS COULD PRODUCE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS
OF HIGH TERRAIN.

A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
SMALL AREA OF SHOWERS AND A FEW THUNDERSTORMS OVER THE CENTRAL
ATLANTIC ABOUT 750 MILES EAST-NORTHEAST OF THE LEEWARD ISLANDS.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR SOME
DEVELOPMENT BEFORE UPPER-LEVEL WINDS BECOME LESS FAVORABLE ON
TUESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
NORTHWESTWARD TO NORTH-NORTHWESTWARD AT ABOUT 10 MPH.

ELSEWHERE...TROPICAL STORM FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH


40%?? Come on NHC!! This looks better than a 40%.
Member Since: July 2, 2011 Posts: 0 Comments: 1183
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN OCT 21 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE LOCATED A COUPLE OF HUNDRED MILES
SOUTH-SOUTHEAST OF JAMAICA IS PRODUCING A LARGE AREA OF SHOWERS AND
THUNDERSTORMS OVER THE CENTRAL CARIBBEAN SEA. ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR THE FORMATION OF A
TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS AS THE LOW MOVES
SLOWLY WESTWARD AND BECOMES NEARLY STATIONARY WELL TO THE SOUTH OF
JAMAICA. THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF BECOMING
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. HEAVY RAINS FROM THIS
DISTURBANCE ARE LIKELY TO SPREAD OVER JAMAICA...HISPANIOLA...AND
EASTERN CUBA OVER THE NEXT SEVERAL DAYS. THESE RAINS COULD PRODUCE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES...ESPECIALLY IN AREAS
OF HIGH TERRAIN.

A TROPICAL WAVE INTERACTING WITH AN UPPER-LEVEL LOW IS PRODUCING A
SMALL AREA OF SHOWERS AND A FEW THUNDERSTORMS OVER THE CENTRAL
ATLANTIC ABOUT 750 MILES EAST-NORTHEAST OF THE LEEWARD ISLANDS.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE CONDUCIVE FOR SOME
DEVELOPMENT BEFORE UPPER-LEVEL WINDS BECOME LESS FAVORABLE ON
TUESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
NORTHWESTWARD TO NORTH-NORTHWESTWARD AT ABOUT 10 MPH.

ELSEWHERE...TROPICAL STORM FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH
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Quoting GeorgiaStormz:
so is this going to transition from hurricane to noreaster?

It could or it could go out to sea not affecting the NE. It is too far out to know.
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Quoting ncstorm:
okay guys, Im out for a while..play nice

oh Wash..the 6z GFS snow map
Epic!.Not likely to happen though but would be lovely if it did all the same.GFS has been trying to send my are some snow since October first.I might be a happy women this winter.
Member Since: August 14, 2010 Posts: 10 Comments: 17823
so is this going to transition from hurricane to noreaster?
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It took me longer but I'm back. I don't think there will be any change for 99L and 90L should go up.
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Quoting Tropicsweatherpr:


The first impacts from this will be the heavy rains in the Greater Antilles that may cause plenty of flooding and mudslides that may turn tragic if it moves slowly theu that area.


we wait and see the next run i reckon
things will kick into high gear
by tomorrow afternoon and build from there

Member Since: July 15, 2006 Posts: 178 Comments: 56140
Quoting ncstorm:


first landfall..florida


then NC
i would be more concerned if it was the gfs.
Member Since: August 2, 2011 Posts: 0 Comments: 2109
I would put 99L at 80% and 90L at 80%, but the NHC would probably put 90L significantly lower, like 50% or 60%.

OFFICIAL SLAMGUITAR TROPICAL WEATHER OUTLOOK "OUTLOOK"
For 8pm October 21st, 2012

99L: 80%
90L: 60%
Member Since: July 2, 2011 Posts: 0 Comments: 1183
Member Since: Posts: Comments:
okay guys, Im out for a while..play nice

oh Wash..the 6z GFS snow map
Member Since: August 19, 2006 Posts: 13 Comments: 16225

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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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JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron