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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Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

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1047. sunlinepr
8:05 PM GMT on September 28, 2010
Seems like October is going to be full of surprises...

Member Since: August 2, 2010 Posts: 21 Comments: 9882
1046. KimberlyB
8:03 PM GMT on September 28, 2010
Quoting MarathonZiggy:


This trough is really advancing I believe, more than forecasted earlier, thus it'll have a greater impact on TD16, like keeping all those winds & precip to the east of the CoC. Hell, Ft Myers' is only forecasting a high of 81 tomorrow. Fall has arrived early in the sunshine state.


And yet here, in New Port Richey (about an hr north of St.Pete / Tampa) we are expecting a high tomorrow of close to 90. Doesn't seem like fall is anywhere near us, and your south of us.
Member Since: October 21, 2007 Posts: 27 Comments: 329
1045. Waltanater
7:55 PM GMT on September 28, 2010
Quoting tropicfreak:





Thanks for the maps there.
Member Since: May 16, 2010 Posts: 0 Comments: 1472
1044. Gustavike
7:52 PM GMT on September 28, 2010
Continued heavy rain falling on the mountains of central Jamaica and Cuba. Soon we will hear of damage.
Member Since: January 16, 2009 Posts: 1 Comments: 67
1043. futuremet
7:45 PM GMT on September 28, 2010


Member Since: July 19, 2008 Posts: 43 Comments: 4051
1042. OBXNCWEATHER
7:44 PM GMT on September 28, 2010
Looks like we're in for a good blow here on the Outer Banks of NC... especially if the COC of the system goes inland south of us (Wilmington or into SC like some of the models are showing)....
Member Since: June 30, 2010 Posts: 0 Comments: 113
1041. CaptnDan142
7:42 PM GMT on September 28, 2010
Quoting Hurricanes101:


No one jumped the gun, atcf site is the official word of NOAA and the NHC, they upgraded it to a TS

THEY jumped the gun then, not us


You contradict yourself.
Reading into statements can be as bad as jumping the gun, true?
Member Since: August 21, 2007 Posts: 0 Comments: 856
1040. watercayman
7:42 PM GMT on September 28, 2010
Quoting StormChaser81:


NHC said that the TD and TS winds are far to the south east of the system. Hurricane Hunters havnt gone far enough southeast to see those winds.


True, they said that... but we haven't seen anything over about a 15knot gust here in Cayman and we're close to that SE side...
Member Since: September 13, 2007 Posts: 0 Comments: 95
1039. kwgirl
7:39 PM GMT on September 28, 2010
Quoting WhoDat42:


RIDGES might need to apply for a federal grant.
Just come down to Key West and pick up some chickens. But come armed. They are tough birds that don't take any sass.
Member Since: March 28, 2008 Posts: 0 Comments: 1532
1038. NOLALawyer
7:39 PM GMT on September 28, 2010
Quoting MarathonZiggy:
Poor old (new?) TD 16, it's already being rip apart by that super deep (& still diggin) trough.

Adios.

Zig in Marathon, Fla


Pass me some of that good stuff!! Get out a raincoat and a pirogue, because Marathon is gonna get mighty wet.
Member Since: September 3, 2009 Posts: 0 Comments: 520
1037. txngeo
7:37 PM GMT on September 28, 2010
I know that TD16 has all the attention here, but I haven't seen anyone mention this (and my apologies if one has). This was caused by ex-Matthew it seems.


Oaxaca state Gov. Ulises Ruiz told the Televisa television network that the early morning landslide in the town Santa Maria de Tlahuitoltepec buried 100 to 300 houses and speculated that 500 to 1,000 people could be dead.
Member Since: September 19, 2010 Posts: 1 Comments: 12
1036. WandoMarsh
7:37 PM GMT on September 28, 2010
Quoting OctaviaStreet:


Oops, I meant Gaston.


I was about to ask that...

They did upgrade Gaston at the end of the season while doing post-mortems... found a sustained 76mph wind somewhere along the Tail Race if I recall correctly.
Member Since: September 1, 2008 Posts: 0 Comments: 19
1035. TOMSEFLA
7:36 PM GMT on September 28, 2010
20.267N 83.383W center from recon fix
1034. OctaviaStreet
7:35 PM GMT on September 28, 2010
Quoting OctaviaStreet:


Not a Katrina, I grant you, but Gustav was a strong TS/Cat 1 and javelined 5 good-sized sweetgum branches into our roof. (Neighbor's trees, not ours.) Across the street a huge elderly red oak went through the roof of a house causing considerable damage.


Oops, I meant Gaston.
Member Since: July 16, 2007 Posts: 0 Comments: 41
1032. GoodOleBudSir
7:34 PM GMT on September 28, 2010
NEW BLOG
Member Since: July 30, 2008 Posts: 0 Comments: 261
1031. rmbjoe1954
7:34 PM GMT on September 28, 2010
Quoting reedzone:


Next run may be shifted slightly to the left tonight.. Gonna see if the trend continues and how the pattern is.


Hi Reed,

I would expect the TS warnings to perhaps reach as far north as Sebastian Inlet on the east coast of FL at 5pm.
Member Since: June 16, 2005 Posts: 0 Comments: 1439
1030. WandoMarsh
7:33 PM GMT on September 28, 2010
Quoting jholmestyle:


Work on Kiawah, should be an interesting drive in.


Or float/swim...

The question was raised earlier about Market Street and a foot of rain around high tide... I'm more concerned about the Crosstown and the tidal marshes around Mount Pleasant, James Island, and Johns Island.
Member Since: September 1, 2008 Posts: 0 Comments: 19
1028. chrisdscane
7:33 PM GMT on September 28, 2010
Quoting CyclonicVoyage:


Setting the stage for some modest strengthening overnight as natural pressures fall. Should see the winds catch up then.


i agree tonight 8pm or later it'll begin to strenthen
1027. Neapolitan
7:33 PM GMT on September 28, 2010
FWIW, everyone's favorite model--the CMC*--shows another weak hurricane off the coast of Miami on Sunday morning that then strengthens as it slides up and hugs the east coast, followed by a strong hurricane approaching the Windward Islands by Monday.

* - Continuously Making Cyclones; Constantly Manufacturing Circulations, etc.
Member Since: November 8, 2009 Posts: 4 Comments: 13803
1026. StormChaser81
7:31 PM GMT on September 28, 2010
Quoting TOMSEFLA:
have not seen one wind over 25 mph from recon flight


NHC said that the TD and TS winds are far to the south east of the system. Hurricane Hunters havnt gone far enough southeast to see those winds.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
1025. CyclonicVoyage
7:31 PM GMT on September 28, 2010
Quoting WxLogic:


If it's able to get some convection to build up on its "center" or at least close enough then we should be able to see winds catching up to the pressure drop.


Setting the stage for some modest strengthening overnight as natural pressures fall. Should see the winds catch up then.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
1024. Patrap
7:31 PM GMT on September 28, 2010
Member Since: July 3, 2005 Posts: 428 Comments: 129902
1023. nrtiwlnvragn
7:31 PM GMT on September 28, 2010
NEW BLOG
Member Since: September 23, 2005 Posts: 15 Comments: 11343
1021. StormChaser81
7:30 PM GMT on September 28, 2010
Quoting MarathonZiggy:


This trough is really advancing I believe, more than forecasted earlier, thus it'll have a greater impact on TD16, like keeping all those winds & precip to the east of the CoC. Hell, Ft Myers' is only forecasting a high of 81 tomorrow. Fall has arrived early in the sunshine state.


Not from my view, I see the trough pulling north and allowing TD 16 to get further west than expected.

Link
Member Since: August 11, 2008 Posts: 0 Comments: 2315
1020. WhoDat42
7:30 PM GMT on September 28, 2010
Quoting StormChaser81:


Need more funds for a new super reed computer.


RIDGES might need to apply for a federal grant.
Member Since: July 6, 2010 Posts: 0 Comments: 50
1019. Patrap
7:30 PM GMT on September 28, 2010
NOAA Tropical System Products


Member Since: July 3, 2005 Posts: 428 Comments: 129902
1018. Hurricanes101
7:29 PM GMT on September 28, 2010
Quoting MarathonZiggy:


This trough is really advancing I believe, more than forecasted earlier, thus it'll have a greater impact on TD16, like keeping all those winds & precip to the east of the CoC. Hell, Ft Myers' is only forecasting a high of 81 tomorrow. Fall has arrived early in the sunshine state.


???

Radar clearly shows the trough is now moving back to the north
Member Since: March 10, 2010 Posts: 1 Comments: 7874
1017. ecflweatherfan
7:29 PM GMT on September 28, 2010
Quoting tropicfreak:


I don't know about the extratropical part, remember the front could still stall.


The front has stalled... currently over northern sections of central Florida
Member Since: March 19, 2010 Posts: 0 Comments: 1147
1016. OctaviaStreet
7:29 PM GMT on September 28, 2010
Quoting CyclonicVoyage:
Highly unlikely however, possible. I think it will be a high end TS. No difference from a low end CAT 1 if you ask me.


Not a Katrina, I grant you, but Gustav was a strong TS/Cat 1 and javelined 5 good-sized sweetgum branches into our roof. (Neighbor's trees, not ours.) Across the street a huge elderly red oak went through the roof of a house causing considerable damage.
Member Since: July 16, 2007 Posts: 0 Comments: 41
1015. WxLogic
7:28 PM GMT on September 28, 2010
Quoting kmanislander:
It has the pressure of a TS but does not have the winds to go with it.

Very odd system.


If it's able to get some convection to build up on its "center" or at least close enough then we should be able to see winds catching up to the pressure drop.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
1014. reedzone
7:28 PM GMT on September 28, 2010
Quoting sammywammybamy:


Next run may be shifted slightly to the left tonight.. Gonna see if the trend continues and how the pattern is.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
1013. Bordonaro
7:28 PM GMT on September 28, 2010
Quoting Neapolitan:

We may have Otto before 9-30-2010, maybe.
Member Since: August 25, 2009 Posts: 20 Comments: 6785
1012. MarathonZiggy
7:28 PM GMT on September 28, 2010
Quoting kmanislander:
It has the pressure of a TS but does not have the winds to go with it.

Very odd system.


This trough is really advancing I believe, more than forecasted earlier, thus it'll have a greater impact on TD16, like keeping all those winds & precip to the east of the CoC. Hell, Ft Myers' is only forecasting a high of 81 tomorrow. Fall has arrived early in the sunshine state.
Member Since: September 6, 2008 Posts: 0 Comments: 26
1011. Patrap
7:28 PM GMT on September 28, 2010
Caribbean - Rainbow Loop


TFP's are available
Member Since: July 3, 2005 Posts: 428 Comments: 129902
1010. Hurricanes101
7:27 PM GMT on September 28, 2010
Quoting TOMSEFLA:
have not seen one wind over 25 mph from recon flight


again for the 5th time, they have yet to go into any of that convection on the east side of the ciruclation

that is where you will find the higher winds
Member Since: March 10, 2010 Posts: 1 Comments: 7874
1009. chrisdscane
7:27 PM GMT on September 28, 2010
Quoting Canealum03:
I know this isn't a typical Atlantic depression and more like a Pacific storm, but doesn't 999mb pressure typically translate into a moderate tropical storm?


based on visible sat image i beleive it is a TS but again its all up to what recon finds
1008. Neapolitan
7:27 PM GMT on September 28, 2010
Quoting Bordonaro:
New record 8 TC's in the month of September, we are now at:

14 TC's, 7 hurricanes and 5 majors so far and the party is not over yet!


Well, not a named storm yet, but almost certainly will be soon. havign saidf that, though, eight named storms in September ties the record, but doesn't set one (both 2002 and 2007 saw eight storms in September).
Member Since: November 8, 2009 Posts: 4 Comments: 13803
1007. GTcooliebai
7:27 PM GMT on September 28, 2010
Quoting Hurricanes101:


It is not a TS yet, atcf jumped the gun

they changed it back to a TD a few minutes later

Well I think it's inevitable so you might as well put it up there ;)
Member Since: August 31, 2009 Posts: 0 Comments: 5628
1006. Patrap
7:27 PM GMT on September 28, 2010
Member Since: July 3, 2005 Posts: 428 Comments: 129902
1005. TOMSEFLA
7:27 PM GMT on September 28, 2010
have not seen one wind over 25 mph from recon flight
1004. Patrap
7:26 PM GMT on September 28, 2010
Member Since: July 3, 2005 Posts: 428 Comments: 129902
1003. islander101010
7:26 PM GMT on September 28, 2010
probally see tropical storm watches go up at 5 hurricane?
Member Since: September 11, 2010 Posts: 1 Comments: 5006
1002. tropicfreak
7:26 PM GMT on September 28, 2010
Quoting sammywammybamy:


I don't know about the extratropical part, remember the front could still stall.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
1001. ElConando
7:26 PM GMT on September 28, 2010
The South and North Carolina are fixing to have a wet weekend. The I'm sure South Carolina would like that I am splitting their identities.
Member Since: September 6, 2009 Posts: 2 Comments: 3784
1000. Bordonaro
7:25 PM GMT on September 28, 2010
Quoting Hurricanes101:


It is not a TS yet, atcf jumped the gun

they changed it back to a TD a few minutes later

Oops, gotta love it!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
999. ecflweatherfan
7:25 PM GMT on September 28, 2010
Quoting hurricanejunky:
Interesting westerly shift in latest models...wonder if NHC will follow suit at 5pm?
Thoughts?


I think they will a little bit... also thinking perhaps adjusting the Trop Storm Watches and Warnings up the coast a little bit.
Member Since: March 19, 2010 Posts: 0 Comments: 1147
997. Patrap
7:25 PM GMT on September 28, 2010
Multiplatform Tropical Cyclone Surface Winds Analysis (MTCSWA)

AL162010 SIXTEEN for Run: 2010-09-28 18Z


Member Since: July 3, 2005 Posts: 428 Comments: 129902

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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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