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 cat5hurricane:
Without a doubt. I would not be a bit surprised if certain locales pick that up.

If this plays out as currently forecasted, local totals may get really nasty.....really fast.


I simply cannot imagine Market street downtown with over a foot of rain in 24hours.
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For anyone interested i'll be livestreaming on ustream.com in about 20 minutes(handle name is wxjunky)as a nasty squal. Line will be moving in from the se(I live in sarasota,fl) associated w/td16
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Quoting kmanislander:


I just got in and out of Prep before the rush but the line of cars was building quickly and the busses were also getting ready. It won't be fun in about 20 minutes.


The University is also closing and I now need to go and pick up my wife. When I dropped her off this morning the car park was then under 1ft of water, so God Knows what it is going to be like now.
We have been having some real heavy rain for the past 30mins in Georgetown so I am not even going to venture out at the moment. Anyone got a Kayak???
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http://www.neoc.gov.ky/CIFS/index.html

1000mb here in grand cayman
ignore the 81mph gust from this station its subject to jetwash at the airport
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742. afj3
Quoting chrisdscane:


omg guys its 2pm wait until about 5 or later to find out theres no statements yet find out this evening case closed

I know. That was the statement I was looking for--someone on the news saying officials would make an announcement later today.
Member Since: June 10, 2008 Posts: 0 Comments: 347
Quoting smartinwx:


Should be dissipated by then however.


actually, if you use the XTRAP intensity forecast, it will be a 300MPH storm by then.
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not sure where in brevard you are located, but here in Cocoa, it's been raining since 11:00 a.m. hasn't stop much. i can't tell you how much inches of rain i got, but it's enough to flood some of the road outside my house. lots of lightening, and heavy downpours for 10 mins straight.
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739. eddye
broward schools are closed im still in school
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Quoting Hurricanes101:
lowest pressure 1000mb found by recon

they estimated it right



Pressure here now is 1000.4 and falling. TD 16 probably a 995 mb TS
Member Since: August 19, 2006 Posts: 0 Comments: 15842
717/723:

If you let the model run out further, it winds up in the Mediterranean!
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More models trending west. GFDL jumps in with the HWRF and others.


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Quoting BobinTampa:


and eventually Ireland.


Should be dissipated by then however.
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Quoting BLee2333:
RECON is S of Cuba and sending data from their first run.

So far:

21.217N 82.867W recorded a 1000.3mb

This should definately be sub 1k mb storm.


ty for that info were did u get it from?
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Quoting BobinTampa:
how did all that rain completely whiff on Tampa?? amazing.


Happens all of the time for Tampa. Having lived there for eight years I can't tell you how frustrated I got when systems would just flippin disappear on us!
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Quoting smartinwx:
XTRP model shows a Bahamas hit.


and eventually Ireland.
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Quoting nash28:


It also is overdoing it IMO on the intensity. The HWRF backed off on the 12z but the GFDL is now on the upper scale.


I agree in regards intensity as these tend to overdo it a bit.
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Quoting kmanislander:


I just got in and out of Prep before the rush but the line of cars was building quickly and the busses were also getting ready. It won't be fun in about 20 minutes.


Cayman International School is advising all parents to collect children as soon as possible. The school will close at 3:15.
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lowest pressure 1000mb found by recon

they estimated it right

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Quoting BDADUDE:
Its not exactly suffering. They will be in their cars. They could not shut schools because it might rain. That is a huge inconvenience for parents who need to work.


I assume from your handle that you are in Bermuda. I don't know if you ever lived here but there are several schools within a stone's throw of each other on the same road and vehicular access to pick up children during heavy rain is limited at best. Most people here have a helper or parents who can watch children during the day.

Member Since: August 19, 2006 Posts: 0 Comments: 15842
725. Jax82
Quoting StormChaser81:


The front is lifting north


Indeed it is, you can definately see it on the radar. Interesting!
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RECON is S of Cuba and sending data from their first run.

So far:

21.217N 82.867W recorded a 1000.3mb

This should definately be sub 1k mb storm.
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Quoting smartinwx:
XTRP model shows a Bahamas hit.


LOL
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Quoting hurricanelover236:
i hate to say ut but "Nicole" is all much ado about nothing. Does any one else here agree?

If you were experiencing the heavy rain and occasional squalls along with the flooding for people living in low lying areas you might be singing a different tune
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Quoting NHCaddict:
Sorry for the newbie question, but how to you change barometric pressure from inches to mb? It's currently 29.68" at my house west of Orlando, but I'd like to know what it is in mb and be able to calculate that myself. TIA:)


I like this "at-a-glance" chart. Link
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Quoting smartinwx:
XTRP model shows a Bahamas hit.


That's not a model.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
how did all that rain completely whiff on Tampa?? amazing.
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Quoting WxLogic:
12Z GFDL also shifted W.


It also is overdoing it IMO on the intensity. The HWRF backed off on the 12z but the GFDL is now on the upper scale.
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XTRP model shows a Bahamas hit.
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Quoting Chapelhill:


More people die from inland flooding associated with tropical systems than from surge or hurricane winds. Look at what just happened in Mexico.


yep Floyd is a good example
Member Since: September 19, 2005 Posts: 2 Comments: 4251
Quoting Jax82:
2PM, look at the GFS, hmmmmm



http://icons.wunderground.com/data/images/at201016_model_zoom.gif


The front is lifting north
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12Z GFDL also shifted W.
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Quoting hurricanelover236:
I mean much ado about nothing for florida. Do you agree with that?

NO!
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Convection starting to consolidate around the center, this IS organizing at a slow pace.

Member Since: July 1, 2008 Posts: 13 Comments: 7396
is td 16 shifing to a more n course.....
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Quoting afj3:
Hello All
Had to run errands. Just got back. Any word on Dade County Schools? I didn't see anything on news web sites....


omg guys its 2pm wait until about 5 or later to find out theres no statements yet find out this evening case closed
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NOT looking to see it track any further west. Been raining for two hours here in Fort Myers already... we need our football practice tonight!
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708. Jax82
2PM, look at the GFS, hmmmmm



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Quoting cat5hurricane:
Nope, not good at all. I didn't think I'd make anyone's day by posting that. In fact I cringed doing so.

We're in the middle of the zone as of now...don't even want to envision my yard!

The thing about those QPF graphics is that they tend to be averages. Some areas will get a little less than indicated by the graphic but others will get much more than shown, and with that much shown already, I could see there being some 15 inch+ totals before it is all said and done.
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Seems the front is backing up a little bit.

Check out the moisture plume starting to form over the state.
Link
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting StormChaser81:


If it doesnt start building a east side to the storm, do see Florida getting very much of anything.

But that all depends if the track shifts west. Even with a track shifting west the convection is very displaced on the southeast of the LLC.


Correct. It needs to tighten up and wrap that convection around. The west side as of now is very dry.
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Quoting kmanislander:


I have seen schools closed before due to locally heavy flooding such as was easily anticipated today. But, too late now, parents and children will have to suffer through torrential rain which is now falling.
Its not exactly suffering. They will be in their cars. They could not shut schools because it might rain. That is a huge inconvenience for parents who need to work.
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Quoting Cayman2010:


All public schools are closing at 1pm. Trying to find out about CIS.


I just got in and out of Prep before the rush but the line of cars was building quickly and the busses were also getting ready. It won't be fun in about 20 minutes.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting nash28:


Not exactly. Even though this will not be a major hurricane rolling through, there will still be the potential for some very hairy weather as it passes. Torrential rain is actually worse than heavy winds.. Not to mention the threat of isolated tornadoes.


More people die from inland flooding associated with tropical systems than from surge or hurricane winds. Look at what just happened in Mexico.
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Quoting palmbaywhoo:

Still no rain here either. Kinda hoping it would start and get going so I can go ahead cancel certain plans for tonight....
I am expecting 2 inches or so from this system... much needed!


The storms up here are moving very slowly... could get two inches in a real hurry. Agreed, much needed!!!
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700. afj3
Hello All
Had to run errands. Just got back. Any word on Dade County Schools? I didn't see anything on news web sites....
Member Since: June 10, 2008 Posts: 0 Comments: 347
Quoting KmanGal:
Yes, all Govt. schools will close at 1pm. And most likely all private schools will follow.

Naturally they couldn't close this morning as no Watches/Warnings were issued until 10am local time.


I have seen schools closed before due to locally heavy flooding such as was easily anticipated today. But, too late now, parents and children will have to suffer through torrential rain which is now falling.
Member Since: August 19, 2006 Posts: 0 Comments: 15842
Quoting TOMSEFLA:
recon got the ok to fly over cuba.
Link?
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Hey. Whats up folks? I'll be on here throughout the day here in South Florida tracking Tropical Depression 16. Working on updates right now.
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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.