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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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)
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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:

Member Since: July 6, 2010 Posts: 113 Comments: 32832
GFS
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Just updated...

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Quoting MAweatherboy1:
The 0z CMC brought it very close to S FL:



It later brings it to the Mid Atlantic as an extremely powerful storm system, 954mb:



The UKMET is beginning to show more development:

The CMC knows I was making fun of it.So now it sends me Sandy to show who's boss.lol.
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last night got to 59!! and a High of 84F. Winds from the NNE at 10 to 15 mph.
Quoting FLWeatherFreak91:
Perfect radiational cooling conditions last night! Low of 52 with a forecast high of 86 lol...

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Perfect radiational cooling conditions last night! Low of 52 with a forecast high of 86 lol...

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Morning everyone! We now have very strong model support for 99L developing into a strong tropical storm. The 00z European run took 99L all the way down to 999 mb in the Caribbean, but for some strange reason it still wants to turn it into a trough like system once it leaves the Caribbean. The GFS has dropped that idea, and now shows 99L becoming a 987mb hurricane or TS in the Bahamas. The CMC blew this up to a powerful hurricane, no surprise, but has it getting pretty close to Florida unlike the GFS. Even the UKMET is aggressive with 99L once it leaves Cuba, which is impressive.
Member Since: July 8, 2005 Posts: 259 Comments: 24575
12z Best Track for 90L.

AL, 90, 2012102112, , BEST, 0, 192N, 497W, 25, 1012, DB
Member Since: April 29, 2009 Posts: 75 Comments: 14900
It going to get cold in FL
TALLAHASSEE FL

WPB!!
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12z Best Track for 99L.

AL, 99, 2012102112, , BEST, 0, 147N, 755W, 25, 1006, DB
Member Since: April 29, 2009 Posts: 75 Comments: 14900
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Quoting Tropicsweatherpr:
Good morning.

I think this afternoon's mission will be canceled due to lack of convection.

If it does go ahead, it could be useful data for the models.
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Quoting T3b0w:
how many named storm days does 2012 have so far and what is the average

2012 has had 17 named storms.
You can find more info here.
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890. T3b0w
how many named storm days does 2012 have so far and what is the average
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Quoting Tropicsweatherpr:
Good morning.

I think this afternoon's mission will be canceled due to lack of convection.
Good morning. Should still be a go. Chances have increased to 70%.
Member Since: October 9, 2008 Posts: 0 Comments: 8436
99L up to 70%...

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT SUN OCT 21 2012

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

SHOWERS AND THUNDERSTORMS HAVE BEEN INCREASING OVER THE PAST FEW
HOURS NEAR A TROPICAL WAVE AND BROAD AREA OF LOW PRESSURE OVER THE
CENTRAL CARIBBEAN SEA. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE
FOR A TROPICAL DEPRESSION TO FORM DURING THE NEXT COUPLE OF DAYS...
AND THIS SYSTEM HAS A HIGH CHANCE...70 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY
WESTWARD. HEAVY RAINS FROM THIS DISTURBANCE ARE LIKELY TO SPREAD
OVER JAMAICA...EASTERN CUBA...AND HISPANIOLA OVER THE NEXT SEVERAL
DAYS. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND
MUD SLIDES...ESPECIALLY IN AREAS OF HIGH TERRAIN.

SHOWER ACTIVITY LOCATED ABOUT 850 MILES EAST-NORTHEAST OF THE
LEEWARD ISLANDS IS ASSOCIATED WITH AN UPPER-LEVEL LOW INTERACTING
WITH A TROPICAL WAVE. UPPER-LEVEL WINDS COULD BECOME A LITTLE MORE
CONDUCIVE FOR DEVELOPMENT DURING THE NEXT DAY OR SO...AND THIS
SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT
5 TO 10 MPH.
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Miami NWS Disco

EXTENDED PERIOD...WEDNESDAY THROUGH SATURDAY...HIGH PRESSURE...
CENTERED OVER THE MID ATLC STATES WEDNESDAY...WILL SLOWLY MOVE NE
THROUGH THE WEEK AS A COLD FRONT MOVES FROM THE GREAT PLAINS EAST
-WARD TO THE ATLC COAST BY SATURDAY. AS THIS HIGH PRESSURE CENTER
MOVES NE...A SURFACE LOW OVER THE CENTRAL CARIBBEAN WILL ALSO MOVE
NE ACROSS E CUBA INTO THE ATLC AND OVER THE SOUTHERN BAHAMAS. A
TIGHT PRESSURE GRADIENT WILL REMAIN OVER S FLA WHICH WILL LEAD TO
BREEZY CONDITIONS ACROSS THE AREA THAT MAY BECOME WINDY EASTERN
ZONES IN THE LATTER PART OF THE WEEK. POPS WILL REMAIN MINIMAL
THROUGH THE PERIOD.
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If 90L forms, it will take a track similar to that of Hurricane Otto from 2010.
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Good morning.

I think this afternoon's mission will be canceled due to lack of convection.
Member Since: April 29, 2009 Posts: 75 Comments: 14900
Quoting MAweatherboy1:
The 0z CMC brought it very close to S FL:



It later brings it to the Mid Atlantic as an extremely powerful storm system, 954mb:



The UKMET is beginning to show more development:


uggh
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Goog morning
I invite you to my blog about the weather in Cuba
http://consultorageomet.blogspot.com/
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Quoting wxchaser97:

I doubt 99L will impact you guys. I have a low threat due to some ensemble members and other non-global models taking 99L near Central America. I don't think that is likely at all but I have done that for the sake of covering everything.


Hello, greetings!
I have lived in Costa Rica my whole life, and I know what these systems down Jamaica do to us when they form in October in terms of rain. Costa Rica has very high mountains ( highest is 3820Mts above sea level), and the moisture that gets pulled from our South,Central, and North Pacific coasts
to the core of the system produces heavy rainfall in the Pacific Region, though amazingly fair weather in caribbean Costa Rica ( unless the system gets too close). I know what you mean by low threat, maybe as to winds.

Tomas killed many people in our country. So I would not say it is not going to impact Central America, at least wet Costa Rica.

I just wanted to point out how broad the idea of "impact" may be.
By the way,we are getting some rain right now.. not sure is from possible future Sandy yet. The good thing this time is that it seems that the models are taking this system of out of the Caribbean rather quickly.



Cerro Chirrpo is Costa Rica's highest point, standing tall at an elevation of 12,526 feet (3,818 m).
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The 0z CMC brought it very close to S FL:



It later brings it to the Mid Atlantic as an extremely powerful storm system, 954mb:



The UKMET is beginning to show more development:

Member Since: February 11, 2012 Posts: 84 Comments: 8040
Good morning. 99L was beaten down hard from a convective standpoint last night, but it retained a very good structure and convection is starting to bounce back, especially on its east side:

Member Since: February 11, 2012 Posts: 84 Comments: 8040
7-day for Tampa Bay area
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Quoting NCHurricane2009:
Right now...99-L is probably listening to this tune...specifically the beat from 0:00 to 1:43

But once DMAX picks up...the beat is going to be more like from 1:43 and onwards...


Oh...it would be rather this:

Link
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Check out this fiery red sky here tonight. It was very beautiful

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Quoting TomTaylor:
edited my post a bit to expand on it. But yeah, that's about it. The door rattle lasted only maybe 5-10 seconds. I'm honestly surprised I felt anything at all. My campus is about 120 miles away from the earthquake's location so it is pretty remarkable that I felt it this far away considering it was only a 5.3 earthquake.


ohh ok.
Member Since: April 23, 2011 Posts: 104 Comments: 14873
Quoting trHUrrIXC5MMX:
scary!!!!

5.3 quake
Date-Time
Sunday, October 21, 2012 at 06:55:09 UTC
Saturday, October 20, 2012 at 11:55:09 PM at epicenter
Location
36.311°N, 120.856°W
Depth
9.4 km (5.8 miles)
Region
CENTRAL CALIFORNIA
Distances

Wake up L.A and San Fran.
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Quoting trHUrrIXC5MMX:


just that!?
edited my post a bit to expand on it. But yeah, that's about it. The door rattle lasted only maybe 5-10 seconds. I'm honestly surprised I felt anything at all. My campus is about 120 miles away from the earthquake's location so it is pretty remarkable that I felt it this far away considering it was only a 5.3 earthquake.
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Quoting TomTaylor:
Just felt some very light shaking here in Santa Barbara. Noticed it with door lightly rattling against the door frame.


just that!?
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Quoting trHUrrIXC5MMX:
scary!!!!

5.3 quake
Date-Time
Sunday, October 21, 2012 at 06:55:09 UTC
Saturday, October 20, 2012 at 11:55:09 PM at epicenter
Location
36.311%uFFFDN, 120.856%uFFFDW
Depth
9.4 km (5.8 miles)
Region
CENTRAL CALIFORNIA
Distances
I felt some very light shaking here in Santa Barbara. I happened to be leaning back in my chair and noticed I rocked a little bit. At first I thought it was just me and I wasn't paying attention because I was tired. But then I noticed the door in my room was lightly rattling against the door frame.
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Member Since: April 23, 2011 Posts: 104 Comments: 14873
scary!!!!

5.3 quake
Date-Time
Sunday, October 21, 2012 at 06:55:09 UTC
Saturday, October 20, 2012 at 11:55:09 PM at epicenter
Location
36.311°N, 120.856°W
Depth
9.4 km (5.8 miles)
Region
CENTRAL CALIFORNIA
Distances
Member Since: April 23, 2011 Posts: 104 Comments: 14873
For anyone who is awake, I finally finished my blog update on 99L and 90L. This is my most detailed and longest blog entry I have wrote yet. Good night/morning everyone!
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Thunderstorm activity increases to the northeast of 99L's center.

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Quoting allancalderini:
low threat to Nicaragua and Honduras is that thing could really affect us ? I doubt. but you are more expert than me.

I doubt 99L will impact you guys. I have a low threat due to some ensemble members and other non-global models taking 99L near Central America. I don't think that is likely at all but I have done that for the sake of covering everything.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Quoting Grothar:


Yes, being German I should. :) Even though I was born in the US, English is really my third language. We were raised mostly in Europe.


That's weird, I thought I remember you saying you were Norwegian, I don't know where I got that idea from then, lol.
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Quoting wxchaser97:
I have finished my forecast graphic that will go into my blog. It now includes a threat level category to go along with the rating scale. The track shown for 99L is not certain. My probability chances for 99L are 80% and 90L is at 40%, I will have the blog out soon.
low threat to Nicaragua and Honduras is that thing could really affect us ? I doubt. but you are more expert than me.
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Quoting TomTaylor:
00z GFS waits until 99L is clear of the Caribbean before bombing it out. I mentioned earlier it was unlikely that we'd see 99L significantly intensify in the Caribbean as a result of the unfavorable upper level environment.

It also takes it closer to the US than it has been. There are still many uncertainties with 99L that have to be worked out. Right now I am thinking we should see a cat1 from 99L.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
862. Skyepony (Mod)
Windsat & ASCAT completely missed 99L, OSCAT pretty much too.
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99L remains at 60% and 90L remains at 30%, phew that makes things easy for me.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
No change in 99L or 90L in percentage. 60% and 30% respectively.

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00z GFS waits until 99L is clear of the Caribbean before bombing it out. I mentioned earlier it was unlikely that we'd see 99L significantly intensify in the Caribbean as a result of the unfavorable upper level environment.
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Quoting HurricaneDean07:
99L has a closed circulation now, all that is needed is convection, which will happen during DMAX...

My Proof
Disable the first 7 frames of the Loop, by clicking on them, and then speed up the loop to full speed. Obvious closed circulation.
Surface circulation doesn't appear closed yet. The RGB loop switches back to IR in the night, so you're seeing mid level cloud features. Based off shortwave infrared it appears like the circulation is still open, though we will have to wait for visible images or an ASCAT pass to confirm this.
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Quoting Slamguitar:


They give me a little wet and fluffy mix as well.

Oct 29 Rain/Snow Showers 46°/31° 60% Rain

It is good to know someone is still up. Me and Kori have switched positions tonight as he got his entry out early while mine is coming out really late. I am working as hard and fast as I can to finish it and my brain will likely be fried afterward.
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Quoting wxchaser97:
Weather.com says rain/snow showers on the 29th for me. That would be a treat for Halloween for me.
Mon
Oct 29 Rain / Snow Showers 48°/36° 60 %


They give me a little wet and fluffy mix as well.

Oct 29 Rain/Snow Showers 46°/31° 60% Rain
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Weather.com says rain/snow showers on the 29th for me. That would be a treat for Halloween for me.
Mon
Oct 29 Rain / Snow Showers 48°/36° 60 %
Member Since: March 16, 2012 Posts: 127 Comments: 7972
Quoting GTcooliebai:
Well I'm going to call it a night. I have to be up early in the morning as I will be volunteering at the Bucs game. Have a good night everyone.

Good night GT, hopefully the weather is good where you are.
Quoting Slamguitar:


Not going to get my hopes up, but some nice huge LES flakes floating down with no wind and temps just below freezing would REALLY hit the spot for me. I'm definitely ready for winter now.

I'm ready for winter and I'm not getting my hopes up either. However there was a run, a day or so ago I think, that had 5-6" over me.
Member Since: March 16, 2012 Posts: 127 Comments: 7972

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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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