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 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.
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Quoting StormChaser81:
The convection ball to the south east of TD 16 is actually moving away from the LLC.


its called anticyclonic outflow..
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Quoting hurricanejunky:
Is there any chance the storm moves slowly enough to miss the approaching trof and meanders south of Cuba? Just wondering if that is even possible?


It's getting caught in the trough flow and the flow is getting stronger.

I think it might leave the convection ball behind at this rate.

But regardless its caught in the trough flow.

The more it organizes the more it can get grabbed by the trough.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
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, else be grouped together with the likes of "The National Enquirer...actually, they broke the John Edwards affair and love child so I guess we can't rag on them anymore...


Any such pronouncement is always in recorded history, with the "recorded" being silent.

This is not some newfangled notion, this is how extreme weather events are covered.
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Quoting hydrus:
This trough is the strongest i have seen for a long time for late September. It looks like a late October or early November system, and even then, I would considerate strong for that time of year....
Almost looks like an ULL forming NW of Cuba.

Notice the retrograding of moisture back over the Tampa area. The front has been thwarted.
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The convection ball to the south east of TD 16 is actually moving away from the LLC.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
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, else be grouped together with the likes of "The National Enquirer...actually, they broke the John Edwards affair and love child so I guess we can't rag on them anymore...
You should tell that to Dr. Masters , he give the scientific facts, he doesn't have the information beyond 133 years, do you have it? And if you don't like the information he provides, in "his" blog, what are you doing here? By the way in which way Mr. Edwards family additions have to do with weather??????
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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....

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.
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Is there any chance the storm moves slowly enough to miss the approaching trof and meanders south of Cuba? Just wondering if that is even possible?
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The HWRF is the most aggresive on intensity, but I think this is an unlikely scenario. I'll stick with the NHC forecast for the time being.

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I think 20-25 knots of shear is significant for this storm,,,, we will see.
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Do we have anything from the CPB models on this storm?
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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.


Whats your point 20-25 knots of shear is still a lot and will keep this system in check its whole life.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting VAbeachhurricanes:


yeah, scary stuff watching it


Yes - weird to think that happened at the PCL. Used to study there during Undergrad, and grad. Local news said everything is still locked down last I checked b/c they received diff descriptions of the gunman and wanted to ensure there wasn't a second person.

On the tropics, our local weather said they were watching the area in the Caribb but it sounds like we are doing ok so far, is that accurate? Haven't been checking in as often last few days.. welcome a quick update!
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Mexico City, Mexico (CNN) -- Up to 1,000 people may have been trapped by a landslide in the southern Mexico state of Oaxaca, Gov. Ulises Ruiz said Tuesday morning.
A hill about 650 feet wide (200 meters) collapsed early Tuesday, sending tons of mud over as many as 300 houses, Ruiz told CNN affiliate Televisa.
The government-run Notimex news agency reported that nearly 50 homes in the Santa Maria Tlahuiltotepec municipality were buried by the landslide, according to the State Civil Protection Institute.
Rescue officials, heavy machinery and police and military authorities were on their way to the scene, Ruiz said.
"We expect to get there in time to rescue these people," he said.
Ruiz said several rivers have overflowed their banks due to heavy rain in the area and many roads are blocked by landslides, making it difficult for rescuers to reach the affected areas.
Some residents were complaining Tuesday morning that help was slow in coming.
"Police and rescue officials still have not arrived at the landslide zone and there are many landslides on the road," one person posted on the Twitter internet blogging site.
The region has been plagued by extremely heavy rainfall over the past two weeks, most recently by the remnants of Tropical Storm Matthew, which are still stalled over the area Tuesday, according to CNN Meteorologist Brandon Miller.
Satellite data indicates that nearly 12 inches (300 mm) of rain has fallen in the area of the landslide in the past three days, Miller said.
Many houses are built on the edge of ridges on the steep terrain in the state, which stands 2,000 feet above sea level, making it conducive to landslides in severe weather.
More rain is forecast in the region in the next day and a half, Miller said.
The severe weather led civil protection authorities to declare a state of emergency Monday for the Oaxaca state municipalities of Oaxaca de Juarez, San Felipe Tejalapam, San Jacinto Amilpas, San Lorenzo Cacaotepec, San Pablo Etla, Santa Lucia del Camino and Tlalixtac de Cabrera. A municipality in Mexico is a geographic division within a state, similar to a county in the United States.
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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.
Member Since: July 1, 2008 Posts: 13 Comments: 7390
Quoting kwgirl:
Especially here on lower Duval!


There is no drainage. I dont recall seeing sewer opens for rain water.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting stormwatcherCI:
No surprise with that one,eh ?


Maybe our national hurricane committee is in a huddle as we type LOL
Member Since: August 19, 2006 Posts: 0 Comments: 15826
Quoting will40:


it has to do with the temperature differences in a system.
a baroclinic low is a low that has temperature advection associated with it

A baroclinic low is one that is driven by temperature differences across the surface (aka a "cold core" low). A tropical low is not driven by temperature differences at the surface, but rather by thunderstorms that release energy as evaporated water cools as it rises.
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Quoting KeysieLife:
And you would too! Seems like anytime it rains in KW the streets flood...gotta be one of the worst drainage areas of all time!
Especially here on lower Duval!
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Quoting FLHurricaneHunter:
I would be more interested in seeing what this system does once it is in the straits of Florida and approaching southern Florida.

Historical issue with systems intensifying rapidly as they approach coast of Florida...


Not enough time or perfect conditions for RI
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326. afj3
Quoting barotropic:


Less effect, maybe, florida wont be affected, I don't believe that.

Sorry. I meant seriously affected....
Member Since: June 10, 2008 Posts: 0 Comments: 347
Tropical Depression sixteen is rotating in the south Cuba. The island can receive large rainfall totals without many problems due to the severe drought that has suffered since 2009. The danger is that the rains of this system
can fill the reservoirs and a new storm would cause major flooding and landslides.
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when do the 12z models come out Eastern time.
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Quoting FLHurricaneHunter:
I would be more interested in seeing what this system does once it is in the straits of Florida and approaching southern Florida.

Historical issue with systems intensifying rapidly as they approach coast of Florida...


Not with 30 knots of shear keeping it in check.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Key West Long Range Radar you can see the north part of the circulation East of the Isle of Youth

http://radar.weather.gov/radar.php?rid=BYX&product=N0Z&overlay=11101111&loop=yes
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Quoting DaytonaBeachWatcher:


I see your government is like our government. LOL


Well, Governments seem to be the same the world over !. Actually, with the system already North of us and conditions very tame here now I personally do not see why a TS warning would make any sense for us. The heavy convection is to the east on the way to Jamaica and the TD will almost certainly remain a lopsisded structure as I was posting this morning.

There could be some heavy weather coming up from the SW later today on the tail end of TD 16 but unlikely to TS force except the odd gust here or there. Schools are open and business as usual here today .
Member Since: August 19, 2006 Posts: 0 Comments: 15826
Quoting FSUCOOPman:


shined? shunned?


Does it really matter, lol.
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wheels up on HH
Member Since: September 19, 2005 Posts: 2 Comments: 4229
I would be more interested in seeing what this system does once it is in the straits of Florida and approaching southern Florida.

Historical issue with systems intensifying rapidly as they approach coast of Florida...
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Quoting largeeyes:
Can someone explain this?

DYNAMICAL GUIDANCE SHOWS THE CYCLONE MERGING WITH A FRONTAL
ZONE. DISSIPATION SHOULD OCCUR IN 72 HOURS OR SOONER AS THE MODELS
DEPICT A NEW BAROCLINIC DEVELOPMENT NEAR THE CAROLINAS.
This trough is the strongest i have seen for a long time for late September. It looks like a late October or early November system, and even then, I would considerate strong for that time of year....
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Quoting TOMSEFLA:
waiting on levi update.

stormw has shined this blog


shined? shunned?

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Quoting kmanislander:


LOL.
No surprise with that one,eh ?
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Quoting katadman:
My son is texting me from one of those dorms. It is unclear right now if there even was a second gunman.


its taken them 3 hours to determine if there is a second gunman, they must have a reason to suspect it... some reliable source
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Quoting kmanislander:


LOL.


I see your government is like our government. LOL
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Quoting hurricanejunky:


The NHC are a bunch of Noreaster casters!
Seriously, that is interesting they're calling for a transition to subtropical. Is it because, like Wilma, it is expected to interact with a cold front and become cold core?


It actually makes sense, could be a strong Subtropical Storm though.
Member Since: July 1, 2008 Posts: 13 Comments: 7390
Quoting caneswatch:


Too quick of a mover to be affected by the mountains.

Also to broad. This is not an intense very organized symetric surface circulation like a hurricane or TS but rather a very large area of storms and winds. Mountains won't affect it except to keep it from organizing
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308. 7544
looks like another fay for rain bonnie for winds lol
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Quoting stormwatcherCI:
I see the NHC said the Govt of the CI has issued TS Warnings for the CI but the govet. has not told us anything yet.


LOL.
Member Since: August 19, 2006 Posts: 0 Comments: 15826
Quoting largeeyes:
Can someone explain this?

DYNAMICAL GUIDANCE SHOWS THE CYCLONE MERGING WITH A FRONTAL
ZONE. DISSIPATION SHOULD OCCUR IN 72 HOURS OR SOONER AS THE MODELS
DEPICT A NEW BAROCLINIC DEVELOPMENT NEAR THE CAROLINAS.


it has to do with the temperature differences in a system.
a baroclinic low is a low that has temperature advection associated with it
Member Since: September 19, 2005 Posts: 2 Comments: 4229
My son is texting me from one of those dorms. It is unclear right now if there even was a second gunman.
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OAXACA, Mexico — A landslide buried some 300 homes in a poor, remote area of southwestern Mexico on Tuesday, possibly killing hundreds of people while they slept, local authorities and media said.

Heavy rains in mountainous Oaxaca state are believed to have triggered the landslide near Santa Maria Tlahuitoltepec, a town of about 9,000 people who largely speak an indigenous language.

Oaxaca Governor Ulises Ruiz told Televisa television that 500 to 600 people may have been killed, injured or buried in the landslide.

"It is raining a lot and we are told that an area about 200 meters wide (collapsed)," he said.
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Quoting hurricanejunky:


Downcaster!! :)


He's right. Anyone on the west side of this system will likely recieve significantly less precep than those on the east side as a result of shear.
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Quoting reedzone:
NHC calls for Extratropical transition before hitting the Carolinas.. A Noreaster.


The NHC are a bunch of Noreaster casters!
Seriously, that is interesting they're calling for a transition to subtropical. Is it because, like Wilma, it is expected to interact with a cold front and become cold core?
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TD 16 will pull some nice dry air over FL eventually!!
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I see the NHC said the Govt of the CI has issued TS Warnings for the CI but the govet. has not told us anything yet.
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Quoting VAbeachhurricanes:


yeah, scary stuff watching it


CNN says suspected shooter is dead.
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Quoting katadman:
Don't know if anyone has reported this or not here. There have been shootings on the UT Austin campus.

UT gunsman dead. Killed himself. No one injured other than him. Police looking for possible second gunman. Dorms in lock down.
Member Since: August 14, 2009 Posts: 0 Comments: 460
Quoting afj3:
All the convection is east of the storm's center. Looks like South Florida won't be affected...


Less effect, maybe, florida wont be affected, I don't believe that.
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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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