Caribbean disurbance 96L nearly a depression; hottest day ever in Los Angeles

By: Dr. Jeff Masters , 1:54 PM GMT on September 28, 2010

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Pressures continue to fall over the Western Caribbean this morning as a strong tropical disturbance (96L) organizes. Surface observations suggest that 96L has a large circulation covering most of the Western Caribbean, as evidenced by winds out of the southwest sustained at 29 - 34 mph observed at Buoy 42057 to the southeast of 96L's center this morning. Rotation of 96L can be seen on radar loops out of Pico San Juan, Cuba, and well as satellite imagery. The heavy thunderstorms are currently quite disorganized, but are bringing torrential rains to the Cayman Islands, Jamaica, Cuba, and Honduras. A Personal Weather Station in George Town on Grand Cayman Island has picked up 3.64" of rain in the twelve hours ending at 8am this morning. 96L is not the typical sort of disturbance one sees in the Atlantic, since it is much larger than normal. What has happened is that the atmospheric flow pattern of the Eastern Pacific has shifted eastwards into the Western Caribbean, bringing in the Eastern Pacific ITCZ (Intertropical Convergence Zone, a region of converging surface winds that creates a band of strong thunderstorms). 96L resembles the "monsoon depressions" common in India's Bay of Bengal or the Western Pacific. A monsoon depression is similar to a regular tropical depression in the winds that it generates--about 30 - 35 mph near the outer edges (and usually stronger on the eastern side of the circulation.) Monsoon depressions have large, calm centers, and can evolve into a regular tropical storms, if given enough time over water to develop a tight, closed circulation. The Hurricane Hunters are scheduled to fly into 96L this afternoon near 2pm EDT to see if it has become a tropical depression.


Figure 1. Morning radar image of 96L. Image credit: Cuban Institute of Meteorology.

Forecast for 96L
Because 96L is so large and lacks a well-defined surface circulation, it will take more time than a typical disturbance for it to spin up into a strong tropical storm. Given that the steering currents are expected to pull 96L north-northeastwards over Cuba and into South Florida and the western Bahamas on Wednesday, the storm lacks sufficient time over water to be any stronger than a 55 mph tropical storm for Florida. I think the top winds in Southeast Florida are likely to be in the 30 - 45 mph range on Wednesday. By the time 96L makes landfall in North Carolina or South Carolina on Thursday morning or afternoon, it could be as strong as a 55 - 65 mph tropical storm, but I think it is only 20% likely that 96L will make it to hurricane strength on Thursday. The primary danger from the storm is heavy rainfall. A potent upper-level low and stationary front over the U.S. East Coast have been bringing moist, tropical air from the Caribbean northwards over the past few days, bringing heavy rains that have saturated the soils. Wilmington, NC received 10.33 inches of rain yesterday, its second greatest one-day rainfall since record keeping began in 1871. Only the 13.38" that fell during Hurricane Floyd on September 15, 1999 beat yesterday's rainfall total. With 96L expected to bring another 6 - 8 inches of rain to the region later this week, serious flooding is likely, and flash flood watches are posted for the North Carolina/ South Carolina border region. South Florida is also under a flood watch, for 3 - 5 inches of rain. Flooding rains of similar magnitude can also be expected in Cuba, the Cayman Islands, and the Western Bahamas through Wednesday night.


Figure 2. Radar-estimated precipitation since Saturday for the North Carolina/South Carolina border region. Widespread rain amounts of 5 - 10 inches have occurred.


Figure 3. Forecast precipitation for the 5-day period from 8am today through 8am EDT Sunday, October 3, 2010. Image credit: NOAA Hydrometeorological Prediction Center.

Elsewhere in the tropics
Once 96L moves out of the Caribbean, the GFS model predicts that the Western Caribbean will "reload" and produce another tropical disturbance capable of developing into a tropical depression late this week or early next week. The other models are not showing this, but do predict a continuation of the disturbed weather pattern over the Western Caribbean. A second disturbance, if it develops, would be subject to similar steering currents, and may also move northwards across Cuba, Florida, and the Bahamas, then up the U.S. East Coast. This second disturbance might be more dangerous, since it would be dumping heavy rains on regions already drenched by 96L.

Hottest day in Los Angeles history
The mercury hit a blistering 113°F (45.0°C) at 12:15 pm PDT yesterday in downtown Los Angeles, making it the hottest day in Los Angeles history. It may have gotten hotter, but the thermometer broke shortly after the record high was set. The previous record in Los Angeles was 112°F set on June 26, 1990; records go back to 1877. Nearby Long Beach tied its hottest all-time temperature yesterday, with a scorching 111°F. And Christopher C. Burt, our new featured blogger on weather records, pointed out to me that Beverly Hills hit 119°F yesterday--the hottest temperature ever measured in the Los Angeles area, tying the 119°F reading from Woodland Hills on July 22, 2006. Yesterday's record heat was caused by an unusually large and intense upper-level high pressure system centered over Nevada that generated winds blowing from the land to the ocean, keeping the ocean from exerting its usual cooling influence. Remarkably, Los Angeles had its second coldest summer on record this year, and temperatures just five days ago were some the coldest September temperatures in the region for the past 50 years.

The remarkable summer of 2010
Wunderground is pleased to welcome a new featured blogger--weather historian Christopher C. Burt. Chris is a leading expert in the U.S. on weather records, and is author of the world's most popular weather records book published to date, Extreme Weather: A Guide and Record Book. He's spent a lifetime collaborating with like-minded individuals from around the world, and no one--including official sources such as the National Climatic Data Center and the National Extremes Committee--has done as thorough a job correlating the various weather records available and determining the most accurate extreme values of such. Each month he'll be reporting on the notable records for heat, cold, and precipitation set world-wide, and his first post takes a look at the remarkable summer of 2010. It's great to have someone like Chris who stays on top of weather extremes, and I hope you'll pay a visit to his blog and welcome him to the wunderground site!

"Hurricane Haven" airing this afternoon
My live Internet radio show, "Hurricane Haven", will be airing again today at 4pm EDT. The call in number is 415-983-2634, or you can post a question to broadcast@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line.

Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

I'll have updates as the situation with 96L requires.

Jeff Masters

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Quoting NRAamy:
Ecflweatherfan.....where is your avatar from? Cause I wanna be in that water! It's beautiful.


LOL! Me too... don't know where it is from... but it is a place I would love to be right now :-)
Member Since: March 19, 2010 Posts: 0 Comments: 1147
nash stop it
Member Since: June 8, 2008 Posts: 0 Comments: 30
Ecflweatherfan.....where is your avatar from? Cause I wanna be in that water! It's beautiful.
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Map data ©2010 Google, INEGI - Terms of UseMapSatelliteHybrid50 mi100 km Last observation noted. Map currently centered at: 22.833N 84.617W
Quoting cat5hurricane:

That's what I'm keeping a close eye on. Would really hate to see a track taking it directly overhead of Charleston to Myrtle Beach. Granted, someone's gonna get soaked...but much less I think if this thing can stay far East of Savanah, Charleston, & points northward.


My thinking as of now is just west of the NHC forecast track which puts Charleston much closer to the center.
Member Since: July 11, 2005 Posts: 190 Comments: 16972
nash....Market Street is just an old creekbed which has been filled in....it floods worse than any other part of town...it would be a terrible shame if we got stuck at Henry's...I suppose the only responsible course of action in that case would be to continue drinking...
Member Since: August 13, 2007 Posts: 0 Comments: 10490
Quoting MandyFSU:
It's funny that they have TROPICAL STORM SIXTEEN in our forecast this week... right under the clear skies notation.

(I'm in Tallahassee... haven't posted in awhile)



Hello Mandy, long time no see....
Member Since: July 17, 2005 Posts: 0 Comments: 1025
Quoting TOMSEFLA:
recon got the ok to fly over cuba.


They always do. It is an open invitation. Really only Venezuela that is an issue.
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This was named just because its threatening the US. It's not nearly well organized enough to be a TD. Exposed not well defined LLC being the main thing.
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recon had to fly around western cuba. they were not allowed to cross.
Quoting presslord:
'sposed to do sea trial on a new boat Thursday...Think maybe we oughta reschedule?!
Not if you want to check the bilge pumps efficiency LOL
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BY PPL BE VBACK LATER
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Quoting CyclonicVoyage:
Afternoon All.

Models seem to be trending left a tad. @11am NHC said they were on the western edge of the guidance. now they are east.








Stop it!
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581. 7544
here comes nicole conv now forming near the coc n and e might see a new red ball develope .
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looks like the center is north of the track..

drifting towards the N/NNE
Member Since: April 17, 2010 Posts: 0 Comments: 1753
However, right on the TCVN & GFDL.
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Quoting WhoDat42:
when is the trough suppose to start lifting out?


The troughiness and the pattern blocking the majority of the Gulf from receiving a storm should remain at least another week. By that time the Gulf should be in its regular strong front cool down pattern that typically closes the season from the Panhandle and points West. Safe so far unless something unusual happens.
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Afternoon All.

Models seem to be trending left a tad. @11am NHC said they were on the western edge of the guidance. now they are east.






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recon got the ok to fly over cuba.
Back for a few...

That area centered around 12N 42W is showing good rotation in both the High and Mid level winds.
A large area, with lots of potential there...
Member Since: October 24, 2005 Posts: 0 Comments: 24307
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when is the trough suppose to start lifting out?
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Quoting weatherwart:


Otto's been postponed to the 2011 season. Check back next year.


LOL, you would have to postpone Otto until 2016. Unless you expect him to come back as Ophelia.
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loks to me on the visible td16 appears to be TRYING to get better organized shear could be dropping, however its gota way to go before looking like a ts showers/ts are trying to wrap around the center i do believe (im in kendal fl btw) that Sfl we'll fell moderate TS conditions what do u guys think?
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Quoting Waltanater:
Why do you mention these storm names when they don't even exist yet!?


GFS has been showing those storms developing over the next 1-2 weeks, and at least one of them has usually been a Florida impact of some type. It's a forecast, not a nowcast...
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Quoting barotropic:


Well, its definitely not moving north or northeast yet...
More time to develop then...
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Quoting kshipre1:
thanks for the info. the weather pattern seems to be almost the same with potential Otto except like you said making landfall on the west coast. who knows?? could even go as far north as the tampa bay area but probably not likely.

do you have any info on possible intensity levels?


Exactly, that trough pattern setting up seems to favor the Carolinas, SW and SE Florida. The Gulf shield is holding strong. I don't see these storms getting any more North than a Charlie or Wilma situation. I'm just shocked to see such a powerful cold front this far South cooling things of in the Northern Gulf coast-Western Panhandle region so quickly. Mother nature must not want another Katrina, which is good for us up here on the Emerald Coast, not for the people South of Tampa to over on the East Coast.
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Quoting ecflweatherfan:
IMHO... Props to the GFS model, as it has been showing tropical cyclone development in the NW Carib for about two weeks now. I think that more attention needs to be given to this model for the next possible development. Perhaps not as far as the landfall, but the potential for development at least.


That's what I have been discussing in my blog the past week or more.
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I'm outta here. Be back after the HH reports.
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Quoting KanKunKid:


Thanks Levi. Excellent synopsis and explanation. Very good presentation. Sounds like you finally got some sleep.


Agreed.
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Quoting kshipre1:
if potential Otto does follow a charlie track, then why would it go northeast towards the east coast of florida? if anything, the high building in would force Otto further west. am I not understanding correctly?


Most likely another trough influences the Northern movement.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting kshipre1:
if potential Otto does follow a charlie track, then why would it go northeast towards the east coast of florida? if anything, the high building in would force Otto further west. am I not understanding correctly?


That high will be a surface High. Mid level and upper level trough expected to persist over the eastern CONUS for the next several days. In other words, the same steering level winds are supposed to persist over the region for several days.
Member Since: March 19, 2010 Posts: 0 Comments: 1147
IMHO... Props to the GFS model, as it has been showing tropical cyclone development in the NW Carib for about two weeks now. I think that more attention needs to be given to this model for the next possible development. Perhaps not as far as the landfall, but the potential for development at least.
Member Since: March 19, 2010 Posts: 0 Comments: 1147
Quoting Levi32:
Good morning all.

Tropical Tidbit for Tuesday, September 28th, with Video


Thank you Levi..great updats as always I learn so much from you I cannot find that same knowledge anywhere else :)
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if potential Otto does follow a charlie track, then why would it go northeast towards the east coast of florida? if anything, the high building in would force Otto further west. am I not understanding correctly?
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Quoting weatherboyfsu:
I dont believe that Central Florida will see much from TD 16 (Nicole) but a windy rainstorm mostly on the east coast. Maybe Otto or Paula might come closer to the west coast of Florida.
Why do you mention these storm names when they don't even exist yet!?
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Quoting Levi32:
Good morning all.

Tropical Tidbit for Tuesday, September 28th, with Video

Thanks Levi. Did you notice the retrograding of moisture on the water vapor loop to the west of Tampa. Looks like the trough is inverting slightly or developing a light ULL NW of Cuba.

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Quoting pottery:

and if it does, you could be in for another soaking...


The 12Z GFS seems to relax the second storm notion...thats at least for this run. But being October, anything can happen in the nW Carib
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Can someone post the latest GFS run please?
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wtf is wrong with the nhc their Satellites are messed up
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thanks for the info. the weather pattern seems to be almost the same with potential Otto except like you said making landfall on the west coast. who knows?? could even go as far north as the tampa bay area but probably not likely.

do you have any info on possible intensity levels?
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I'm out again till this evening.
Hot and Dry here today. Very nice.

That mess East of here that Orca has been threatening me with, is looking a little Ominous right now....
Member Since: October 24, 2005 Posts: 0 Comments: 24307

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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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