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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Thats a LOTTA Junk to Move N to NE next 48,
Someones gonna get the Bizz big time.

Member Since: Posts: Comments:
Quoting VAbeachhurricanes:
999.2mb at 21.2 83.1


is that from recon
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Quoting reedzone:
The REED run is a bit too far east.. hmm, interesting isn't it?

Photobucket
Dude! What are you feeding those chickens to get that color out of them? =)
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Quoting reedzone:
The REED run is a bit too far east.. hmm, interesting isn't it?

Photobucket
Reed,
this is the one time when you should probably go west. LOL
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Quoting presslord:


Stop it!!


i dont get it...
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Quoting smartinwx:
I can't believe with all the tropical activity we haven't had a hurricane landfall in the U.S.

I suspect this is by far the most active (recorded) season without a hurricane landfall in the U.S.

Fortunately, the shear should prevent TD 16 from Hurricane strength.
Great news indeed...


We did have tropical [thunder]storm bonnie hitting fl but that was a bust.
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Quoting KeysieLife:
Most local Mets go by what the NHC puts out, especially in FL...so, unless there is an intermediate advisory, it wouldn't be updated until 5pm. Watch the local news then...bet they say different =)


I see. Will do, thanks!
Member Since: August 18, 2008 Posts: 0 Comments: 474
were you on the island for ivan?
939. flsky
FEMA just issued a news release re TD 16

Link
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Member Since: October 1, 2007 Posts: 81 Comments: 26516
12Z ECMWF has also shifted some W.
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Quoting Patrap:


Big shift west but, still in the cone.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
What this shift west also means is that it gives less land(from cuba) to travel over, so less land, more water, and more strengthening.
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I can't believe with all the tropical activity we haven't had a hurricane landfall in the U.S.

I suspect this is by far the most active (recorded) season without a hurricane landfall in the U.S.

Fortunately, the shear should prevent TD 16 from Hurricane strength.
Great news indeed...
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Quoting Saltydogbwi1:
Link

pressure now 999mb at owen roberts grand cayman


That ties in with what I was seeing before I left home. At least I know my station is accurate. Reading was 999.8 at home.
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.
Quoting P451:


If all things came together just right you couldn't rule out even a Cat 2 affecting SC/NC regions.

At this time at most it would appear a weak Cat 1 is the best "nicole" could achieve with a strong TS more likely.

However given the continued poor organization of TD16? Who knows... could just be a breezy rainmaker in the end.

Intensity forecasts at this time are to be considered as very low confidence.


Thanks P451, I'll keep watching and waiting then. Gotta decide whether to close the office or not, but I can make that decision tomorrow
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Quoting TreasureCoastFl:


But the local weather just came on and showed the same old track of just on the eastern edge of miami? So do they not update track until 5? is that why?
Most local Mets go by what the NHC puts out, especially in FL...so, unless there is an intermediate advisory, it wouldn't be updated until 5pm. Watch the local news then...bet they say different =)
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Quoting HCW:


With that shift I have now loaded my chase gear and might intercept this one. Watches and warnings will change slightly at 5pm for parts of FL. I will try to listen in the the conf call and tell you what they say


Thanks.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Wait now the tracks have magically appeared!

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999.2mb at 21.2 83.1
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Quoting ILwthrfan:


You have a link? Thx!


Link

There you go!
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is goes 15 doing high res rapid scan of 96l
The REED run is a bit too far east.. hmm, interesting isn't it?

Photobucket
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Quoting BobinTampa:
how did all that rain completely whiff on Tampa?? amazing.


watch the loop, it's actually moving north. I think there is no doubt we will see the rain. Probably around the time I have to drive home (7pm).
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OW! Cold front is over my head--I work near Winter Park FL--and my head is the best barometer I have, lol. PWS near here says 29.56/1001. Woo.
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Link

pressure now 999mb at owen roberts grand cayman
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915. A4Guy
If the new model track verifies....more time over the W Carib....less time over Cuba (passing over the narrowest, flattest parts), and more time over the water in the FL straits/extreme SE GOM....plus, SoFla more in the worst weather (assuming the heaviest rain and strongest winds stay East of the center).
Member Since: June 23, 2006 Posts: 0 Comments: 668
From local weatherman : "ATFC indicates that Tropical Depression Sixteen has been upgraded to Tropical Storm Nicole. No official confirmation yet from NHC."
Member Since: August 18, 2008 Posts: 0 Comments: 474
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Quoting Hurricanes101:
I have yet to see a true west wind, are we sure this thing is closed?


WSW. It is definitely closed, imo. Broad, though.

They'll find it before they leave.

~21N/82.6W
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oh my god! This reminds me of hurricane Irene (1999)
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909. HCW
Quoting CyclonicVoyage:


Man, that's a significant shift. I wonder if the NHC will pull the track that far west? That would put the east coast in the heaviest action.


With that shift I have now loaded my chase gear and might intercept this one. Watches and warnings will change slightly at 5pm for parts of FL. I will try to listen in the the conf call and tell you what they say
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Quoting Patrap:


Try the Link here then.

ATCF Tropical Models


No model tracks showed up for 18z, but is this the shift west you all were talking about? This is 00Z.

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Quoting chrisdscane:


thats wut recon is giveing back


It was, but they corrected it.
Sorry to disappoint - no Nicole yet.
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Press....you missed "the Carolinas" comment last night....i was waiting for the doodie to start flying.....

;)
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Quoting sporteguy03:

That puts more of Central FL into play and the Orlando metro area as well.


But the local weather just came on and showed the same old track of just on the eastern edge of miami? So do they not update track until 5? is that why?
Member Since: August 18, 2008 Posts: 0 Comments: 474
Quoting ecflweatherfan:


Wow... not liking those model runs. 1) More time over water. 2) More impact on SE and Central Florida


You have a link? Thx!
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Quoting Hurricanes101:
I have yet to see a true west wind, are we sure this thing is closed?


wat is that web site instead of linking it just tell me its name ty!!!
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So, it looks as though Charleston SC will get a little blow and a lot of water but nothing too major to worry about. Am I right?
Thanks.
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Quoting HCW:


Man, that's a significant shift. I wonder if the NHC will pull the track that far west? That would put the east coast in the heaviest action.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
Quoting HCW:


Wow... not liking those model runs. 1) More time over water. 2) More impact on SE and Central Florida
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Quoting presslord:


+1 for differentiating


Just one press? I should think it is worth like 100 maybe.
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Quoting sunlinepr:
Baroclinity
Density lines and isobars cross in a baroclinic fluid (top). As density is related to temperature, on a surface map, isobars and isotherms cross too Density lines and isobars cross in a baroclinic fluid (top). As density is related to temperature, on a surface map, isobars and isotherms cross too

In fluid dynamics, the baroclinity (sometimes called baroclinicity) is a measure of the stratification in a fluid. A baroclinic atmosphere is one for which the density depends on both the temperature and the pressure; contrast this with barotropic atmosphere, for which the density depends only on the pressure. In atmospheric terms, the barotropic zones of the Earth are generally found in the central latitudes, or tropics, whereas the baroclinic areas are generally found in the mid-latitude/polar regions.


Thank you for that *haven't got that far in my textbook!*
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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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