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 WxBlogAddict:
Just watched Levi's tidbit. thank you! I've seen/heard the word bariclynic (spelling challenged) and I'd like to know the correct spelling so I can look it up. thanks


Extratropical Cyclone:
A cyclone of any intensity for which the primary energy source is baroclinic, that is, results from the temperature contrast between warm and cold air masses.
Member Since: September 23, 2005 Posts: 14 Comments: 11027
NEW ATCF 18 Z Tracks


18z Early Cycle NHC model tracks
TD-16
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)






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Quoting VAbeachhurricanes:


special advisory?


Given the proximity to US and other populated areas, probably. I know a lot of the local school boards--Monroe, Miami-Dade, Broward, Palm Beach, Collier--are meeting this afternoon to decide on a course of action for tomorrow, as are a lot of businesses, so that's something they'll want to know, and soon...
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this has what I have been saying all morning... what will this storm do once in the Florida Straits.....

Quoting A4Guy:
Our storm is really starting to wrap moisture around herself. depending on how quickly she can fill in the gaps, she might have her act together once in the FL straits, and be a strong trop storm.
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Broad low pressure will require much time to organize, thus the reason there is little to no chance of Nicole becoming anything other than a weak to moderate TS prior to reaching Florida.. It will then merge with the stalled frontal boundary and become baroclinic. Although, it's likely to strengthen upon becoming baroclinic and the Carolinas are more likely than Florida to receive the worst of any associated winds with Nicole. (Including post-tropical status)
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Quoting WxBlogAddict:
Just watched Levi's tidbit. thank you! I've seen/heard the word bariclynic (spelling challenged) and I'd like to know the correct spelling so I can look it up. thanks
spelling is not my forte but try this "Baroclinic"
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The highest surface winds I have seen from HHs are 29 mph, weak TD at best in terms of wind.I don't know I could be looking at wrong data though
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The feminine of Nicholas, Nicole means "victory of the people."
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Quoting BobinTampa:


actually, if you use the XTRAP intensity forecast, it will be a 300MPH storm by then.


Is that possible? I thought the theoretical limit was 220 mph
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Is it just me or is the center of AL16 consolidating to the southwest of the previous position?
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Nicole is born

So that is 14 named storms, what a boring season

On September 28th:

1995 had Opal in the Gulf; 15 named storms, next storm formed on October 4th
2005 was up to Rita; 17 named storms, TD 19 formed on September 30th
2010 has Nicole now; 14 named storms

Not bad for a boring season lol
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835. HCW
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834. A4Guy
Our storm is really starting to wrap moisture around herself. depending on how quickly she can fill in the gaps, she might have her act together once in the FL straits, and be a strong trop storm.
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833. flsky
Quoting TOMSEFLA:
recon back turning nw back to center

I've been trying to figures out why you don't member info listed.
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Anyway, I am off to the office. Catch you all later.
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Just watched Levi's tidbit. thank you! I've seen/heard the word bariclynic (spelling challenged) and I'd like to know the correct spelling so I can look it up. thanks
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Quoting Fla55Native:


Sarasota native here. Bee Ridge and McIntosh area. TD16 has a rather large gyre. Expecting rain pretty soon.
.....will be going live near the hospital for a bit today,I lbs on siesta and will have a live stream from the old piers tomorro as well
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#811, so we now offically have Nicole?
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Quoting scott39:
What does that mean in regards to TD16?
the track will shift to the west
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Quoting cchsweatherman:
Hurricane Hunters not finding significant winds yet, but definitely finding broad lowering pressures throughout the region. Definitely indicative of some further development occurring.


Yeah, well I am now showing pressure of 1000 mb even in Grand Cayman and falling rapidly. Not sure why the HH is only finding 1000 mb.

And before anyone suggests I calibrate my weather station I did that recently. LOL
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Hi again, quick post trying to stay caught up here, watch my grandson (9 1/2 mos and trying to walk) and get some things done around the house!

anyway I was out running an errand and had to go into a City Hall here in Broward.. they had NO IDEA we even had a storm out there and actually told me "No we are not under any watches or warnings" I had to tell them, Yes we are under a Tropical STorm Warning...

so much for our government officials... even here in Ft Lauderdale area.. one would think...
'just saying.. LOL


anyway, they probably will not make any decisions about schools for tomorrow until 5pm tonight....

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We have TS. Nicole see post 811
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Quoting nrtiwlnvragn:
AL 16 2010092818 BEST 0 212N 829W 35 1000 TS


Appears to be official... most likely by 5PM today.
Member Since: August 14, 2008 Posts: 4 Comments: 4960
recon back turning nw back to center
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Quoting Neapolitan:
We have Nicole:

BEGIN
NHC_ATCF
invest_al162010.invest
FSTDA
R
U
040
010
0000
201009281826
NONE
NOTIFY=ATRP
END
SIXTEEN, AL, L, , , , , 16, 2010, TS, O, 2010092718, 9999999999, , , , , , WARNING, 1, AL162010
AL, 16, 2010092712, , BEST, 0, 185N, 855W, 25, 1003, LO, 0, , 0, 0, 0, 0,
AL, 16, 2010092718, , BEST, 0, 190N, 847W, 25, 1003, LO, 0, , 0, 0, 0, 0, 1008, 300, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092800, , BEST, 0, 194N, 841W, 25, 1003, LO, 0, , 0, 0, 0, 0, 1008, 300, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092806, , BEST, 0, 198N, 835W, 30, 1003, LO, 0, , 0, 0, 0, 0, 1008, 240, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092812, , BEST, 0, 204N, 832W, 30, 1001, TD, 0, , 0, 0, 0, 0, 1006, 360, 180, 40, 0, L, 0, , 0, 0, SIXTEEN, D,
AL, 16, 2010092818, , BEST, 0, 212N, 829W, 35, 1000, TS, 34, NEQ, 0, 250, 0, 0, 1005, 375, 180, 0, 0, L, 0, , 0, 0, SIXTEEN, D,


special advisory?
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So far, negligible winds. (mid 20s)
Member Since: January 6, 2009 Posts: 0 Comments: 217
AL 16 2010092818 BEST 0 212N 829W 35 1000 TS
Member Since: September 23, 2005 Posts: 14 Comments: 11027
Quoting Neapolitan:
We have Nicole:

BEGIN
NHC_ATCF
invest_al162010.invest
FSTDA
R
U
040
010
0000
201009281826
NONE
NOTIFY=ATRP
END
SIXTEEN, AL, L, , , , , 16, 2010, TS, O, 2010092718, 9999999999, , , , , , WARNING, 1, AL162010
AL, 16, 2010092712, , BEST, 0, 185N, 855W, 25, 1003, LO, 0, , 0, 0, 0, 0,
AL, 16, 2010092718, , BEST, 0, 190N, 847W, 25, 1003, LO, 0, , 0, 0, 0, 0, 1008, 300, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092800, , BEST, 0, 194N, 841W, 25, 1003, LO, 0, , 0, 0, 0, 0, 1008, 300, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092806, , BEST, 0, 198N, 835W, 30, 1003, LO, 0, , 0, 0, 0, 0, 1008, 240, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092812, , BEST, 0, 204N, 832W, 30, 1001, TD, 0, , 0, 0, 0, 0, 1006, 360, 180, 40, 0, L, 0, , 0, 0, SIXTEEN, D,
AL, 16, 2010092818, , BEST, 0, 212N, 829W, 35, 1000, TS, 34, NEQ, 0, 250, 0, 0, 1005, 375, 180, 0, 0, L, 0, , 0, 0, SIXTEEN, D,


Thanks for the info!
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recon doing 180 back to center
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The Big Picture
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Quoting CallMeCocoa:


my goodness, merritt lsland will sure get flooded, can't imagin what north tropical trail would look like after it stops raining. but that is insane that your getting rain 10 mins ago. feels like it's night time here. hope you don't get to much flooding there.


It definitely does that. Fortunately there is plenty of room in my lake for all this rainfall. It is 3+ feet below where it should be. So bad, in fact, that I haven't been able to use the sprinklers to water, because the water is below the level of the piping.
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Quoting StSimonsIslandGAGuy:


Actually the stronger the trough is, and the closer the trough gets to developing a 'negative tilt' the further west the storm will go.


There is energy dropping into the longwave trough right now causing it to deepen. That is why convection over Fla is moving back to the NNW along the old surface boundry.

IUt is this energy that should cause the trough to go negative tilt inducing an upper low to form to the north of TD16. This interaction will cause the rapid transition to extratropical.
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Hurricane Hunters not finding significant winds yet, but definitely finding broad lowering pressures throughout the region. Definitely indicative of some further development occurring.
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We have Nicole:

BEGIN
NHC_ATCF
invest_al162010.invest
FSTDA
R
U
040
010
0000
201009281826
NONE
NOTIFY=ATRP
END
SIXTEEN, AL, L, , , , , 16, 2010, TS, O, 2010092718, 9999999999, , , , , , WARNING, 1, AL162010
AL, 16, 2010092712, , BEST, 0, 185N, 855W, 25, 1003, LO, 0, , 0, 0, 0, 0,
AL, 16, 2010092718, , BEST, 0, 190N, 847W, 25, 1003, LO, 0, , 0, 0, 0, 0, 1008, 300, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092800, , BEST, 0, 194N, 841W, 25, 1003, LO, 0, , 0, 0, 0, 0, 1008, 300, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092806, , BEST, 0, 198N, 835W, 30, 1003, LO, 0, , 0, 0, 0, 0, 1008, 240, 90, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 16, 2010092812, , BEST, 0, 204N, 832W, 30, 1001, TD, 0, , 0, 0, 0, 0, 1006, 360, 180, 40, 0, L, 0, , 0, 0, SIXTEEN, D,
AL, 16, 2010092818, , BEST, 0, 212N, 829W, 35, 1000, TS, 34, NEQ, 0, 250, 0, 0, 1005, 375, 180, 0, 0, L, 0, , 0, 0, SIXTEEN, D,
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Quoting stormpetrol:
The COC appears be directly NW of Grand Cayman, between Grand Cayman and the Isle of Youth.


Pretty close. Buoy 42056 near the Yucatan has NNW winds and almost the same pressure as we do. The Little Cayman buoy has SSW winds and pressure around 1001.7 as reported a half hour ago.
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809. Jax82
NEFL can expect some rain this afternoon/evening as the rain appears to be filling in from the south.

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Currently, much of the precipitation those along the Florida Peninsula are experiencing is associated with the cold front which has already stalled along the eastern gulf coast and CFL. The forecast for the effects of TD16 will change, if TD16 takes a more westerly course, due to convection & wind displacement. Those which have experienced the heavy rainfall today would likely have had a slight reprieve with an eastern track, however, if a western track occurs, it is likely that the heaviest axis of rain will be over SEFL, and thus a weaker, but still present, rain event would exist over SW FL and S CFL. If the current trends persist, and TD 16 takes the path along the west coast, It looks as if SEFL would take the brunt of the heavy rainfall and any winds associated with the system. Predicted rainfall totals for SEFL would then increase to around 6-8 inches rather than 4-6 inches. Likewise, whereas an easterly course would result in only an inch or two of rain for SW FL, a westerly course would bring a total of 2-4 inches of rain over that area.

Just a current note: It appears that trough associated with the M-ULL over the North-Central U.S. has ceased southward motion, which might be why the models are trending westward as it doesn't appear the cold front over Florida will stall any further east than its current position.
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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:)


Link
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TD-16 Floater - Rainbow Color Infrared Loop
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0.2" rain in the last 5 mins here in Merritt Island, FL... equates out to 2.8"/hr. Really coming down out there now!
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Uncertainty

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Quoting StSimonsIslandGAGuy:


It would be wild if you were just east of the center and the center was reforming further south. That would change everything!

It won't and it wouldn't ! :)
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Quoting kmanislander:


Odd because I now have 1000.2 mb and falling rapidly. Either the low is very broad or the heavy convection over us is creating a localised pressure drop.


I think it is quite broad, atm.

Definitely appears to be starting to tighten up, though.
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Quoting Seastep:


I like this "at-a-glance" chart. Link


Thank you very much for posting that chart, as I had the same question about mb conversion. Nice, handy chart!
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Quoting ecflweatherfan:


Just across the river from you in Merritt Island near the 528. It just started raining about 10 mins ago, and sun finally disappeared about 20 mins ago. Been hearing lots of thunder though, some very close.


my goodness, merritt lsland will sure get flooded, can't imagin what north tropical trail would look like after it stops raining. but that is insane that your getting rain 10 mins ago. feels like it's night time here. hope you don't get to much flooding there.
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797. flsky
Wind picking up here in DBS. Lots of thunder from the SSW, but haven't seen any lighting yet. Hope we don't have another tornado warning.
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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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