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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Member Since: July 3, 2005 Posts: 426 Comments: 129089
just looking ahead here but anyone have any info on potential Otto?
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NEXRAD Radar
Key West, Base Reflectivity 0.50 Degree Elevation Range 248 NMI

Member Since: July 3, 2005 Posts: 426 Comments: 129089
12Z GFS moves TD16 due north into Southwest FL, Dunno if that's gonna happen.
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Quoting Abacosurf:

Interesting! Check out the erosion of dry air to the west of Fl. The front is being overthrown by TD16


FROPA was expected to be a bit more stronger but didn't pan out that way so there's a potential of a more NNE track for a bit longer than expected. 12Z NAM shifted also W but not by much... but is trend nonetheless.
Member Since: August 14, 2008 Posts: 4 Comments: 5016
Hurricane Hunters on the way in now
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Quoting RickWPB:
For anyone interested, here's a link to Max Mayfield's blog (former NHC director).

Link


is he on wordpress too?
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Not that she'll make it all the way, but ex-Lisa's pressure is down to 1009mb (from a high earlier this morning of 1015), and winds are up to 30 knots. Fun to watch her try, anyway:

AL, 14, 2010092812, , BEST, 0, 294N, 318W, 30, 1009, LO, 0, , 0, 0, 0, 0,
Member Since: Posts: Comments:
Quoting StormChaser81:


There is no drainage. I dont recall seeing sewer opens for rain water.
There is but they empty into the sea. And with our tropical downpours, once the trash blocks the grates, everything rises. We even get street flooding on dry days in especially high tides. The ocean is coming up into the storm drains and the street.
Member Since: March 28, 2008 Posts: 0 Comments: 1532
Quoting CAAM:
Hopefully urban flooding will not be too much of an issue as this storm moves through.


Love the avatar, I wonder what the chances of urban syrup flooding are?
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Being that the heavier rains are not supposed to start effecting the lower keys until later this evening into tonight I think the decision for school closing will not be made until 6 am tomorrow morning.

Currently the wind graph shows a 20 to 30 percent chance of the lower keys receiving TS Force winds. The Upper keys are near 50 percent chance.

IF things stay as they are, I would expect the upper keys schools to close tomorrow Lower keys schools to be open.

Time will tell
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Quoting jitterboy:


according to my local news in Louisiana, our mets said the same thing about Los Angeles,CA.
why all the hating? He merely made a statment of which was true as far as the records go.
good grief!!!
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Updated blog:
Link
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I tried saying that American Heritage was going into "schoolcaster" mode and beginning to work on closing and preparing school for possible storm now that TS warnings went up... took a short lashing for posting that, but that is what wife reported into me... what can I say......

Quoting koneofdeath:
FYI

Looks like the schoolcaster's might get they day off tomorrow. We have gone into backup mode and Payroll is being run a day early. ........Broward County
Member Since: Posts: Comments:
For anyone interested, here's a link to Max Mayfield's blog (former NHC director).

Link
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If the 12 z shift some to the west verifies this could bring more of the significant weather over the SE florida coast.
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Quoting koneofdeath:
FYI

Looks like the schoolcaster's might get they day off tomorrow. We have gone into backup mode and Payroll is being run a day early. ........Broward County

And... I won't be on this blog tomorrow, if that happens... it will be like the daily late-afternoon trollfest all. freakin. day.
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Congratulations Neapolitan, very good answer you for vinotinto.
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you might be right about Otto and Paula. It really depends on how strong and the positioning of the trough and High Pressure at that time

of course things change over time but I was hearing again that Otto could go towards South Florida as well. who knows...
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Quoting WxLogic:
30HR 12Z GFS:



Shifted a more to the W... now going through KFMY. Similar to 06Z HWRF.

Interesting! Check out the erosion of dry air to the west of Fl. The front is being overthrown by TD16
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Quoting WxLogic:
30HR 12Z GFS:



Shifted a more to the W... now going through KFMY. Similar to 06Z HWRF.
nice post. you got up to date info.very good
Gotta hand it to WU. I come onto the docs blog, but first check out where the TS warnings/watches are for TD 16 as I often do, and what do I notice? Tornado watch in effect for my county way up in central NYS. This is the first I had heard of it. WTG WU. Just too odd. OK Thanks E1..HAGD
Bob
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Looks like the bahamas will get some nasty weather but the winds wont go over 60 mph.... the way it looks now....
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374. CAAM
Hopefully urban flooding will not be too much of an issue as this storm moves through.
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Hottest day in history, history is recorded . That is the difference
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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.
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30HR 12Z GFS:



Shifted a more to the W... now going through KFMY. Similar to 06Z HWRF.
Member Since: August 14, 2008 Posts: 4 Comments: 5016
FYI

Looks like the schoolcaster's might get they day off tomorrow. We have gone into backup mode and Payroll is being run a day early. ........Broward County
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Quoting kwgirl:
Maybe the chickens aren't cooperating.
That's because they all got relocated to KW and supplies are running low...great, the models are shot! lol
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Quoting FLHurricaneHunter:
They are beginning with lower classes I understand and should work way to upper school for today.

this is news from wife.. blame her haha



They should let the kids finish the day as normal and focus on tomorrows closures if any are needed.

It's blowing a SOLID 7 MPH now.

The confusion of trying to close schools early today will cause more headaches and is simply uncalled for.
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Quoting StormChaser81:
The convection ball to the south east of TD 16 is actually moving away from the LLC.


As I noted at 5am this morning bouys under that area recorded 27 knt sustained winds alnight long with gusts to 33knts. Pressure though was always higher in this area relative to those up north in and around the are of circulation. All the wind is down to the south east. Had the center developed just a little more south...we would have a much more formidable system with less shear. The only thing I can see I question wth the NHC discussion is that I don't see any northward movement with the circulation at this time, certainly not near 10mph. Seems stationary to me via visible sat.
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Quoting houston144:
for me this is the perfect example of whats wrong with the way systems are tracked, 96L is the remains of Matthew we all watched him pull a 180 and head back out south of cuba...so why the 96L?

Any one notice anything weird the last two days around Dallas Texas?


Yes, the Cowboys won. That was weird.
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These kinds of storms are always a challenge for emergency managers. They must always be prepared for the worst case scenario, and help the public be prepared, as well. So, they have to go through all the work to have everything in place, but when nothing happens the public get upset because they didn't get clobbered.

Oh well...being in EM it's not for the faint of heart. :-)
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They are beginning with lower classes I understand and should work way to upper school for today.

this is news from wife.. blame her haha

Quoting flwthrfan:


Call the school...it's not true! NO decisions have been made at this time!
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Quoting TOMSEFLA:
if the weather stays to east of the center as forecast then sfla may get next to nothing.
Quoting FLHurricaneHunter:
Just FYI... Just received call and my son attends American Heritage (private school) here in Broward county (Plantation) and they are beginning to cancel classes for remainder of today and appears will be closed tomorrow.

Seems they are reacting to TS warnings going up.


Call the school...it's not true! NO decisions have been made at this time!
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I had read this would be expected as storm approaches from south.....

Quoting Buhdog:
Front looks to be retro grading here in SWFL...clouds moving NW when the were E all day yesterday. Looks to me like it is lifting out from personal obs..
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Quoting FLHurricaneHunter:
Like I said, will be interesting to see what this storm does after Cuba.... true short time for any rapid intensification, but still interesting what may be in store for southern Florida....



Only?? That is high as it relates to effect on a Tropical Cyclone
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hey all goodmorning i am in southeast florida just north of miami on the beach and no rain yet this morning but awfully cloudy and breezy i stand corrected had a drizzle this morning!!!!
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Front looks to be retro grading here in SWFL...clouds moving NW when the were E all day yesterday. Looks to me like it is lifting out from personal obs..
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Quoting vinotinto:
With all due respect, how does one say it was the hottest day in LA history when the records only go back 133 years?! Come on guys, stop with the sensational headlines/titles...


Are you serious? Look again at your question: "How does one say it was the hottest day in LA history when the records only go back 133 years?!" You answered it yourself; history goes back to when record-keeping started 133 years ago, and yesterday was the hottest day since then. So, okay, it probably wasn't the hottest day ever there...just the hottest day of the last 48,550 or so.

Funny thing: I've not heard you--or anyone else, for that matter--talk about sensationalism when headlines have mentioned that how coastal California had one of its coldest summers ever, even though there were undoubtably far colder ones during the most recent ice age. That and the John Edwards crack tell me you're one of the multitude of non-science AGW contrarians. Funny how that works, no? ;-)
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Quoting reedzone:
Actually shear will only be 20-25 knots, maybe clinching 30 knots on the way to Florida. The shear map shows a small decrease in shear over in that area the last few days.
Thats a hell of a lot of shear for a developing system.
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Quoting kwgirl:
Especially here on lower Duval!
One of the worst instances I saw was during FF two years ago. Started pouring at 2am. By 3am the streets had 5" of standing water and floating garbage everywhere...100s of drunk people falling in the water too! <- that was kind of amusing though =)
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Quoting leo305:


its called anticyclonic outflow..


Thanx, I forget what that is all the time.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Just FYI... Just received call and my son attends American Heritage (private school) here in Broward county (Plantation) and they are beginning to cancel classes for remainder of today and appears will be closed tomorrow.

Seems they are reacting to TS warnings going up.
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if the weather stays to east of the center as forecast then sfla may get next to nothing.
Quoting kmanislander:


Maybe our national hurricane committee is in a huddle as we type LOL
Most likely. When it is just about out of our area they will close schools etc. down. I knew I kept my grandson home this morning for a reason.
Member Since: October 9, 2008 Posts: 0 Comments: 8423

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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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