Western Caribbean disturbance 96L growing more organized

By: Dr. Jeff Masters , 5:14 PM GMT on October 21, 2011

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A region of disturbed weather in the Western Caribbean (Invest 96L) is bringing heavy rains to coastal Nicaragua, and has the potential to develop into a tropical depression this weekend. Visible satellite loops show that 96L is beginning to show signs of organization. Some rotation is apparent, and the upper-level cirrus clouds streaming away from the center indicate that 96L is establishing an upper-level outflow channel to the east. The heavy thunderstorm activity is quite limited at present, because a large region of dry air to the east of 96L is interfering with development, as seen on water vapor satellite loops. An ASCAT pass at 11:05 am EDT showed no signs of a surface circulation, with surface winds in the 25 - 30 mph range. Surface pressures are slowly falling at San Andres Island, near the center of 96L. Wind shear is a moderate 10 - 20 knots in the region, and is expected remain in the moderate range through Monday. Water temperatures are very warm, 29 - 30°C, and these warm waters extend to great depth.


Figure 1. Afternoon satellite image of 96L.

Forecast for 96L
The moderate wind shear and warm waters should allow some modest development of 96L over the next few days, though this will be slowed by the dry air to the storm's east. The models are quite enthusiastic about developing 96L into a tropical depression, and our top four reliable models for forecasting genesis--the ECMWF, GFS, UKMET, and NOGAPS--have all been predicting formation of a tropical depression by Monday in one or more of their runs over the past day. 96L is in an area of weak steering currents, and will move little over the next three days. On Tuesday and Wednesday, a strong trough of low pressure will be passing over the Eastern U.S., and this trough has the potential to turn 96L northwards into Cuba. This is more likely to happen if 96L is stronger and deeper, and thus able to "feel" the upper-level winds the trough will bring. The 12Z run of the GFS model and 00Z runs of the ECMWF and UKMET models predict 96L will develop into a tropical storm that hits Western Cuba on Wednesday or Thursday, and potentially affecting the Cayman Islands, South Florida, and the Bahamas as well. If 96L remains a weak and shallow system, it is more likely to stay trapped in the Western Caribbean and make landfall in Nicaragua. This is the solution of the NOGAPS model, which has 96L moving ashore on Tuesday over Nicaragua as a weak system. NHC gave 96L a 30% chance of developing into a tropical depression by Sunday in their 8 am Tropical Weather Outlook. A hurricane hunter mission is scheduled to investigate 96L Saturday afternoon.

I'll have a new post on Saturday, but might wait until the afternoon, when the hurricane hunter data becomes available.

Jeff Masters

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Quoting MiamiHurricanes09:
Time to get back into blogging mode now that 96L poses a threat to both Florida and much of the western Caribbean.

60% at 8p.m seems good to me. Still has some work to do on it's circulation and convective organization before we get too hyped on classifying this.
welcome back we have missed your insights
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Quoting pottery:

I'll check it's shadow tomorrow.
Good idea.
Thanks.

p.s., what do I look for???

pps, Mole Crickets are eating all my grass, too!


Look for anything out of the ordinary.

pps. Spray the mole crickets with an environmentally friendly pesticide.
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Quoting kmanislander:


Compare the 925 mb map ( 2500 feet ) to the 850 mb map ( 5000 feet ). The vort at 925 is displaced to the NE of the 850 so right now it is not stacking up. Work to do.


Both of those products are somewhat sketchy and to compare one to the other is even more sketchy.
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Quoting wunderkidcayman:


yes but you and I know that it can take very little time for that to change hey btw did you check out the 925vort here take a look
Link


Compare the 925 mb map ( 2500 feet ) to the 850 mb map ( 5000 feet ). The vort at 925 is displaced to the NE of the 850 so right now it is not stacking up. Work to do.
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Quoting MiamiHurricanes09:
Time to get back into blogging mode now that 96L poses a threat to both Florida and much of the western Caribbean.

60% at 8p.m seems good to me. Still has some work to do on it's circulation and convective organization before we get too hyped on classifying this.

Hey.
Member Since: July 6, 2010 Posts: 113 Comments: 32254
Quoting pottery:

Hmmm,
It's confused by this Season.
Like me!
Dropped a bunch of leaves and put them back on, over the last 2 weeks.
Never did that before.

It's a Very Serious Portent.
I just dont know what it MEANS !



Speaking of Portents...

some of my wild orchids here are blooming in the first week of October...
These are the ones which we call "Christmas Orchids"
...is it Christmas already?

However, I have been enjoying fresh picked mushrooms
in my morning omelets lately... which says we had plenty rain mon...
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Quoting MiamiHurricanes09:
Time to get back into blogging mode now that 96L poses a threat to both Florida and much of the western Caribbean.

60% at 8p.m seems good to me. Still has some work to do on it's circulation and convective organization before we get too hyped on classifying this.

Oh, there you are. Been a while.
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Quoting kmanislander:


Only the shadow knows LOL

I'll check it's shadow tomorrow.
Good idea.
Thanks.

p.s., what do I look for???

pps, Mole Crickets are eating all my grass, too!
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Quoting kmanislander:
The 850 mb vorticity is elongated which indicates that it still has some distance to go to consolidate.



yes but you and I know that it can take very little time for that to change hey btw did you check out the 925vort here take a look
Link
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Time to get back into blogging mode now that 96L poses a threat to both Florida and much of the western Caribbean.

60% at 8p.m seems good to me. Still has some work to do on it's circulation and convective organization before we get too hyped on classifying this.
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Quoting pottery:

Hmmm,
It's confused by this Season.
Like me!
Dropped a bunch of leaves and put them back on, over the last 2 weeks.
Never did that before.

It's a Very Serious Portent.
I just dont know what it MEANS !


Only the shadow knows LOL
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Quoting Seflhurricane:
i really think this may be our last system of the season IMO.


Maybe one more in November :-)
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Quoting CaicosRetiredSailor:


u r welcome...
how is "The Tree" doing, any Portents or Signs...

Hmmm,
It's confused by this Season.
Like me!
Dropped a bunch of leaves and put them back on, over the last 2 weeks.
Never did that before.

It's a Very Serious Portent.
I just dont know what it MEANS !
Member Since: Posts: Comments:
from the NWS Key West

HIGHER UNCERTAINTY ENTERS THE FORECAST REASONING FOR THE MIDDLE AND
LATER PORTIONS OF NEXT WEEK. AN EARLIER RUN OF THE ECMWF HAD AN AREA
OF LOW PRESSURE LIFTING OUT OF THE WESTERN CARIBBEAN AND ACROSS THE
KEYS THROUGH THE MIDDLE OF NEXT WEEK...WHILE AT THE SAME TIME THE GFS
WAS MUCH QUICKER AND DEEPER REINFORCING THE UPPER TROUGH WHICH KEPT
ANY CIRCULATION WELL OFF TO OUR SOUTHEAST. HOWEVER...THE LATEST RUNS
HAVE SHIFTED MORE NORTH AND NORTHWEST WITH A STRONGER LOW THANKS TO A
MUCH WEAKER UPPER PATTERN ACROSS THE EASTERN UNITED STATES. THE GFS
HAS COME MORE IN LINE WITH THE PREVIOUS ECMWF...WHILE THE ECMWF
ITSELF HAS SHIFTED WESTWARD AND IS SLOWER WHEN COMPARED TO ITS
PREVIOUS SOLUTION. IT IS STILL TOO FAR OUT TO MAKE SIGNIFICANT
ADJUSTMENTS TO THE LATER PERIODS OF THE FORECAST. HOWEVER...DID
INCREASE OUR MID PERIOD RAIN CHANCES DUE TO THE WESTWARD AND MORE
NORTHWARD TREND IN THE MODEL SOLUTIONS. BUT I REMAINED WELL BELOW THE
GFS MOS POPS THROUGH THE MIDDLE OF THE WEEK. OUR NUMBERS WILL BE
MIDDLE-OF-THE-ROAD CHANCE ON THIS ISSUANCE. OF COURSE WE WILL SEE
MANY MORE MODEL RUNS UNTIL NEXT WEEK...BUT WE WILL NEED TO KEEP CLOSE
ATTENTION ON THE EVOLUTION OF THE SYSTEM IN THE WESTERN CARIBBEAN.

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The 850 mb vorticity is elongated which indicates that it still has some distance to go to consolidate.

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Quoting pottery:

Gee! Thanks, man!


u r welcome...
how is "The Tree" doing, any Portents or Signs...
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Quoting kmanislander:


Late season is always our biggest worry IMO. Not easy to put up shutters when it is blowing 15 to 25 mph.

yep I know I tries to push and pull my accordian shutters to tes today and it was really darn tough
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i really think this may be our last system of the season IMO.
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Quoting Seflhurricane:
Kman looking at the computer models they kind of want a wilma type track or a track like hurricane Irene in 1999 from western/ central cuba and into the florida keys and then bend sharply NE.


I agree. I looked at the steering through 96 hours and beyond for both the GFS and CMC and at the shallow and deep levels thay have that same solution which looks reasonable to me at this time.
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I have to also mention that the cayman islands and cuba could be dealing with a significant system especially if it moves as slow as anticipated we could have a cat3 hurricane nearing cuba and southern florida
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Quoting TropicalAnalystwx13:

When do you think this will become a TD (96L)? Tomorrow?
well if it gets a good DMAX and the dry air vanishes then tomorrow afternoon sounds good. the latest i see is sunday afternoon monday morning so i think in about 24 hours possibly 48 though
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Quoting CaicosRetiredSailor:


Pottery gets the XTRP...

...and the CLP5

it's two for one Friday.

Gee! Thanks, man!
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Quoting kmanislander:


I doubt that whatever 96L may becomne would ever get as far N as Tampa. I would think a track across South Florida over or just N of the keys from Western Cuba.
Kman looking at the computer models they kind of want a wilma type track or a track like hurricane Irene in 1999 from western/ central cuba and into the florida keys and then bend sharply NE.
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Quoting stormpetrol:


I'm very concerned about the already rainy and windy conditions here, it could hamper preparations for some which i think we need to start doing from now. I'm very concerned about this one!

yep I am also worried as well I hope my friends from the Royal Navy are keeping an eye on this but look here stormpetrol I just hope if thing go down hill that the Gov. doesn't do anything stupid like they did in Ivan do u remember that
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Quoting TropicalAnalystwx13:

When do you think this will become a TD (96L)? Tomorrow?


24 to 36 hours, closer to 36 IMO. Still very disorganized.
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Quoting kwad:


2010 TOMAS Hit St Lucia on October 31st. Started developing in the same location. We cannot afford another. Hope it stays in a westerly direction. Please not NW.

West is not good, either....
Best we can hope for is NorthEast!

:):))
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Hi guys looking at 96L i agree with kman i would stick to a 60% but system looks much better organized all we need is the center to become more defined and we should have a TD by tomorrow afternoon IMO
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Quoting BullShoalsAR:

Yeah sure, at the present, it's a non-factor. But what until she gets up near Tampa's latitudes like Teddy is suggesting. Those troughs did deep down, you are aware of that, correct? Furthermore, mid-level shear is more adverse to a strong tropical storm or hurricane, because of the massive influx of dry air entrained into it's core.


I doubt that whatever 96L may becomne would ever get as far N as Tampa. I would think a track across South Florida over or just N of the keys from Western Cuba.
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Quoting kmanislander:


Late season is always our biggest worry IMO. Not easy to put up shutters when it is blowing 15 to 25 mph.

When do you think this will become a TD (96L)? Tomorrow?
Member Since: July 6, 2010 Posts: 113 Comments: 32254
Quoting whepton3:


Shear is becoming less and less of an issue, on the decline in the area of 96L.

even if the subtropical jet was there in the gulf and we had a cat 3 going towards SW florida but the hurricane had an anticyclone no shear would affect it. its like a barrier. once it losses it a cat 4 could weaken all the way to a ts. its all about timing
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Quoting stormpetrol:


I'm very concerned about the already rainy and windy conditions here, it could hamper preparations for some which i think we need to start doing from now. I'm very concerned about this one!


Late season is always our biggest worry IMO. Not easy to put up shutters when it is blowing 15 to 25 mph.
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Quoting kmanislander:


That's aggressive IMO. It doesn't look any better now than when the last update was given. I would stick with 60% :-)


After looking at the satellite loop again, I think you're right, 60% it will probably remain, 70% at most! I think the center is more defined this evening though!
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I also want to let you guys know if the track is over western cuba and florida and shear is low and the dry air dissipates, the GFDL and HWRF solutions wont look crazy or unrealistic. with the very deep hot water and low shear a td could bomb into a cat 4 in 24 hours. everyone from central america to florida bahamas and cuba should looks out even mexcio. i dont think 96L will go any further west than the florida panhandle or further east than cuba. look at wilma. low shear boiling water things happen in the tropics fast.
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Quoting BullShoalsAR:

Yes. The GOM as well. CybrTeddy was mentioning so much energy for 96L to really use up there yet...even despite high southwesterly vertical wind shear.


Shear is becoming less and less of an issue, on the decline in the area of 96L.

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Quoting BullShoalsAR:

Yes. The GOM as well. CybrTeddy was mentioning so much energy for 96L to really use up there yet...even despite high southwesterly vertical wind shear.


I just looked at the shear tendency map and at the upper levels shear is almost non-existent now. In the mid levels it is high to the immediate SW of 96L and it is the mid shear that may be interfering with it at the moment
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Quoting kmanislander:


1.1 inches in South Sound and more to come. My breadfruit and other trees love it LOL


I'm very concerned about the already rainy and windy conditions here, it could hamper preparations for some which i think we need to start doing from now. I'm very concerned about this one!
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I say either 70% or 80% at 8 pm
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Quoting stormpetrol:
I'D go with 80% on 96L at 8 pm est


That's aggressive IMO. It doesn't look any better now than when the last update was given. I would stick with 60% :-)
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Quoting wunderweatherman123:
DMIN and dry air taking a toll on 96L shear is at about 10 to 15 knots so shear isnt the problem. once it goes through dmax it should look better. 60% at the 8pm imo

I agree, although they may go slightly higher at 70%.
Member Since: July 6, 2010 Posts: 113 Comments: 32254
A center trying to get under these cold cloud tops?

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DMIN and dry air taking a toll on 96L shear is at about 10 to 15 knots so shear isnt the problem. once it goes through dmax it should look better. 60% at the 8pm imo
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I'D go with 80% on 96L at 8 pm est
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Quoting kmanislander:


I do not believe that 97L is going to do much. It is very late in the year for something to develop and come up from where it is all the way through the Caribbean. 96L on the other hand could be anywhere from a strong TS to a Cat 3/4 system before reaching Cuba depending on track.

Models typically underestimate the intensity forecasts for late season systems in the NW Caribbean which tend towards RI. Paloma is a recent example of this and the TCHP in this area remains untapped. If it avoids the coast of Nicaragua it could become a very dangerous system as the motion will be slow through 96 hours.

Wow, ok.
Member Since: July 6, 2010 Posts: 113 Comments: 32254
Lots of energy available for 96L to tap into

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hmmmm there appears to be a disturbance in the force....
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Quoting whepton3:


I wonder what people with the mindset that compels them to now troll blogs did before there was the internet?

96L? Wait and see where we get a real center.

97L? Wondering if it gets pulled into this as one of the models suggested earlier today.

They probably picked their noses alot.
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Quoting superpete:
Evening Kman. That was a ton of rain we've had the past 24 hours,soaked up here in Sav'.Expect more through the weekend.


1.1 inches in South Sound and more to come. My breadfruit and other trees love it LOL
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Quoting CaicosRetiredSailor:
Evening Kman,
watch and wait,
Thanks for letting us know you are keeping an eye on these "invests".


I don't like it when they sit to our South, especially the slow movers. If it stays offshore it could be a real problem come Tuesday/Wednesday next week.
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About

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