Caribbean disurbance 96L nearly a depression; hottest day ever in Los Angeles

By: Dr. Jeff Masters , 1:54 PM GMT on September 28, 2010

Share this Blog
4
+

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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

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

Viewing: 447 - 397

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21Blog Index

447. JLPR2
Quoting JRRP:


Yeah, looking slightly better today.
Member Since: Posts: Comments:
446. JRRP
Member Since: Posts: Comments:
Quoting Portlight:


affirmative
Quoting Patrap:
Also having a had a converstaion with Presslord about the situ,,this morning .Portlight is in a Preparatory mode to assist in His Region should the Storm bring the additional forecasted rain to saturated area's in some rural regions His way.
We will have another call this evening to address that possibility as well


I am in the same region as Press and would be happy and willing to assist my time.
Member Since: Posts: Comments:
444. HCW
Member Since: Posts: Comments:
Once TD 16 gets going, it will take off like a rocket.... I dont know if it will be in one peticular area long enough to cause flooding.... I think it will be moving to fast!
Member Since: July 17, 2005 Posts: 0 Comments: 1025
The 12 Z Early Cycle Dynamic run was tightly clusterd so I dont expect any deviation from the 18z ones this afternoon.

The flow aloft is set,,and isnt going to change drastically thru the period .

Member Since: Posts: Comments:
Cloudy and breezy in south dade. A little sun off and on. I guess today's forcasted 80% starts tonight
Member Since: Posts: Comments:
Quoting leo305:
it almost looks like it's drifting west..
Looks to moving east to me...
Member Since: Posts: Comments:
Quoting CAAM:


Thanks. lol well, with all this record heat, who knows what can happen...

Either way, I'm not looking forward to the commute tomorrow. :P


The tropics have been spinning up ridiculously wet storms lately, no doubt.
Member Since: Posts: Comments:
Quoting hydrus:
I was wondering if that would happen. And if this becomes sub-tropical or a hybrid like system, the front will back up even further..Look at this image, it has extra-tropical cyclo-genisis written all over it...


I noticed the front hanging up early this morning. It was right on top of me (W to E). Now, it's definitely lifted north of my location. I can see the delineation of the cloud cover on visible sat.
Member Since: Posts: Comments:
Quoting CaptDanny:
Preasure is 1008 in Ruskin Fl. Down from 1010 12 hours ago


A sign of rapid intensification, perhaps?
Member Since: September 22, 2010 Posts: 0 Comments: 88
Quoting Patrap:
Also having a had a converstaion with Presslord about the situ,,this morning .Portlight is in a Preparatory mode to assist in His Region should the Storm bring the additional forecasted rain to saturated area's in some rural regions His way.
We will have another call this evening to address that possibility as well


affirmative
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Organizing now.

Member Since: August 19, 2006 Posts: 0 Comments: 15813
Quoting TampaTom:
Do we have anything from the CPB models on this storm?
lol
Member Since: Posts: Comments:
Funny stuff!

Link
Member Since: Posts: Comments:
Also having a had a converstaion with Presslord about the situ,,this morning .Portlight is in a Preparatory mode to assist in His Region should the Storm bring the additional forecasted rain to saturated area's in some rural regions His way.
We will have another call this evening to address that possibility as well
Member Since: Posts: Comments:
Preasure is 1008 in Ruskin Fl. Down from 1010 12 hours ago
Member Since: September 2, 2008 Posts: 0 Comments: 62
this isn't moving at 10mph.. its almost stalled.. drifting around..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
If I recall correctly, all of the systems this season are intensifing faster and stronger than the "official" forecasts. Not to mention being more resilient. Models are based to some extent on historical data. They might not apply to some degree due to watertemps being near or above historical parameters
Member Since: Posts: Comments:
seafaring music for your listening pleasure while bloggingLink
Member Since: Posts: Comments:
Quoting leo305:
it almost looks like it's drifting west..


Well, its definitely not moving north or northeast yet...
Member Since: Posts: Comments:
Very heavy squall line coming up from the SW of Grand Cayman. I can see the leading egde from my office window on the water front.

Member Since: August 19, 2006 Posts: 0 Comments: 15813
Also Im in FULL agreement with Dr. Jeff Masters on the Carolina's Impact form this one..

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


Member Since: Posts: Comments:
Shear Shear Shear for TD 16!
Member Since: Posts: Comments:
Quoting barotropic:


Thats because front has already began to backup...a bit.
I was wondering if that would happen. And if this becomes sub-tropical or a hybrid like system, the front will back up even further..Look at this image, it has extra-tropical cyclo-genisis written all over it...
Member Since: Posts: Comments:
Quoting flwthrfan:


Call the school...it's not true! NO decisions have been made at this time!


Sigh, its a private school. They can do WHAT they want.
Member Since: Posts: Comments:
Quoting FSUCOOPman:


Any idea which model runs will have their data?


18Z but 00Z should definitely be a better output.
Member Since: Posts: Comments:
Quoting weatherboyfsu:
Patrap,


What do you think about TD 16 crossing Florida?

Just looking at the trough, I dont see how it could move directly north? Do you?



I favor and agree with the Late Cycle OFCI Track..its a good representation of the NHC Thinking and the Given trend and setup thru the period.

Member Since: Posts: Comments:
415. CAAM
Quoting cmahan:


Love the avatar, I wonder what the chances of urban syrup flooding are?


Thanks. lol well, with all this record heat, who knows what can happen...

Either way, I'm not looking forward to the commute tomorrow. :P
Member Since: Posts: Comments:
it almost looks like it's drifting west..
Member Since: April 17, 2010 Posts: 0 Comments: 1753
"official" word from American Heritage is that they are keeping school open today and will most likely make decision for tomorrow around 3pm today... but for now it is status quo there (Plantation, Florida - Broward county).

Now to go and hunt down wife for slightly "incorrect" info... my apologies.
Member Since: Posts: Comments:
Quoting smartinwx:


Yes, the Cowboys won. That was weird.


That, and I didn't cuss the heat when I walked outside. The weather has been nice.

Did I miss something?
Member Since: Posts: Comments:
I'm scared!!!!!!!
Member Since: Posts: Comments:
GOES Water Vapor Loop of Gulf and Caribbean
Member Since: Posts: Comments:
Patrap,


What do you think about TD 16 crossing Florida?

Just looking at the trough, I dont see how it could move directly north? Do you?
Member Since: July 17, 2005 Posts: 0 Comments: 1025
Quoting StormChaser81:


Not with 30 knots of shear keeping it in check.
This system may be more like a sub tropical storm, there for shear may not be as much of an issue as it would be with a true tropical storm.....
Member Since: Posts: Comments:
Cuba Animated Radar
Member Since: Posts: Comments:
Quoting reedzone:
12Z GFS moves TD16 due north into Southwest FL, Dunno if that's gonna happen.


Thats because front has already began to backup...a bit.
Member Since: Posts: Comments:
Quoting Saltydogbwi1:
Hurricane Hunters on the way in now


Any idea which model runs will have their data?
Member Since: Posts: Comments:
Quoting sporteguy03:

Looks like Orlando would get more rain then expected?


If it pans out that way we will.
Member Since: Posts: Comments:
12z GFS brings it right through Charleston heading up the coast.

We'll see how dry the western edge of this system is.
Member Since: Posts: Comments:
TD 16 def doesnt look to impressive....actually looked better yesterday than today IMO.... Even with the models saying the shift to the West... the water vapor loop looks even more vigorous.......still dont tampa and orlando get much more than 30 mph gust.....
Member Since: July 17, 2005 Posts: 0 Comments: 1025
Quoting WxLogic:
30HR 12Z GFS:



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

Looks like Orlando would get more rain then expected?
Member Since: Posts: Comments:
Member Since: Posts: Comments:

Viewing: 447 - 397

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Overcast
67 °F
Overcast