Caribbean disurbance 96L nearly a depression; hottest day ever in Los Angeles
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
Reader Comments
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Met Service of Jamaica
NEWS RELEASE
September 27, 2010 –5:00 p.m.
*** FLASH FLOOD WATCH UPGRADED TO FLASH FLOOD WARNING FOR ALL PARISHES***
The Meteorological Service has upgraded the Flash Flood Watch to a Flash Flood Warning for low-lying and flood prone areas of all parishes until 5:00 p.m. tomorrow.
A FLASH FLOOD WARNING means flooding has been reported or will occur shortly.Motorist and pedestrians should not attempt to cross flooded roadways or other low-lying areas as strong currents are likely. Residents in low-lying areas should be on the alert for rising waters and be ready to move quickly to higher ground.
A broad area of Low Pressure continues to produce widespread showers and thunderstorms over the northwestern Caribbean, including Jamaica.
Radar indicates that widespread showers and thunderstorms affected
the island especially sections of southern and northeastern parishes last night into this morning.
The forecast is for showers and thunderstorms to continue through today, tonight and Tuesday. Deteriorating conditions are expected
to persist over the island into Wednesday as this disorganized area
of Low Pressure drifts northward away from Jamaica. There is a chance of this system becoming a Tropical cyclone during the next 48 hours
as conditions become favorable for gradual development. As a result
a Flash Flood Watch is now in effect for all parishes.
Fishers and other marine interests are being advised to exercise caution as strong, gusty winds are likely in areas of showers and thunderstorms mainly over inshore and offshore areas of the south
coast.
The Meteorological Service will continue to monitor the progress
of this system.
pef
You could drive along the interstate highways and see all the deer trying to stay on the higher grounds along the highways...and m any got killed by cars that did not see them.
Same thing for other "dry land" critters like the panthers and bears, etc.
You are absolutely right. Business will be open and school in session. The only ones that will make benefit from this will be body shops and repair shops.
This will keep on moving though. Agnes stalled.
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 North Carolina/ South Carolina border region
Glad to hear it was not so bad you can't make fun of it! Look like he got caught by the wind switch..
AL 16 2010092812 BEST 0 202N 828W 30 1001 TD
It would have been STD if it was Subtropical. Plus I can't go back enough to find a Subtropical Storm in the Caribbean, too much heat and warm waters to see something so hybrid in my opinion.
Dr. Masters calls this a Monsoonal Depression, far from Subtropical.
Is there any other place it can go besides east west or on top of Miami?
That's horrible... Getting way too clear of a visual thinking about that. Poor animals... :-(
Can it transition, once it interacts with the cold front?
Mid level TS's are like being in a bad thunderstorm, take the wind away and your left with a lots of rain.
Caught off guard from a mid level TS is like getting caught off guard by a strong thunderstorm, I think the people of South FL will do just fine with this storm.
Link
BREAKING NEWS
OAXACA, Mexico--Up to 1,000 people were feared dead after a rain-soaked mountainside gave way and buried hundreds of homes in southwestern Mexico, a local newspaper reported on Tuesday.
At least 300 homes were buried in Santa Mar%uFFFDTlahuitoltepec Mixe, local civil protection officials Carlos Ramos Arag%uFFFDold the Excelsior newspaper.
Heavy rain in the mountains of Oaxaca state loosened the soil around the town, about four hours' drive from the capital of Oaxaca, famous for its colonial buildings and nearby archeological sites.
Authorities said the wet weather had affected roads in the area and would delay rescue teams. A civil protection source declined to comment on the estimated number of victims but Excelsior said 1,000 people were feared dead.
A storm system in the western Caribbean has generated widespread rain in the area over the past week.
There is some confusion as the position page has it mis-tagged as Sub-Tropical. However it is purely tropical at this point.
I agree with Dr Jeff, a lot of rain and some wind but nothing serious....and most of the models keep it off shore so we may not even get that much rain.
but I am talking about this system, and I could be wrong b ut nothing is really panning out as predicted last weekend for mid week.
Yep, could deff. do that.
Riding along the FL coast right into SC/NC.
In PBC, school busses don't go if sustained winds are 30 or 35 I can't remember. But wether there is a Watch or Warning posted, has no effect on the closing of schools.
School has been in sesion under a TS watch before, and even a TS warning, when it was posted later in the day.
But things like sports and clubs after school get canceled.
I think this happened with FAY in 2008.
I'm just speaking for Palm Beach Co.
Thats horrible.
That's going to keep development SLOW.
Where are you quoting that from? I want to see the pic but I cannot find any posts by a utilaeastwind.
This is very sad news. The entire countryside around there is beautiful but the roads are very very narrow up and down those mountains. Alot of the buildings are also not built for these types of storms
The HH don't fly over foregin country's land as far as I know.
they will post a td before nhc advisory
" 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."
I think there were just a few who were thinking a sub trop storm so not really to much an issue. But, convection is no where close to wrapping round the center (eluded to in your prev post) at this point. Also, bouys and cayman observations in the area suggest pressure has leveled off for the time being ranging from 1001 to 1003 mb's now for past 6 hours.
They can get permission to go into there airpsace if needed.
A "Superhurricane", as in Pacific style?!
I didn't think the Atlantic was capable of a monsoonal depression of that magnitude, so never considered one.
I'm NOT saying that this scenario will play out, however it's one that I may not rule out down the road as a possibility if the conditions suggest a lengthy stall over favorable conditions... You have to remember, the currents in that area would replenish any lowered SSTs due to the storm. As long as you have the fuel and it stays over water long enough... Highly unlikely, but could rewrite the books for a "perfect storm".
Anyhow, I'm done rambling. Any thoughts?
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