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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I think it is quite broad, atm.
Definitely appears to be starting to tighten up, though.
It won't and it wouldn't ! :)
Link
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.
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.
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,
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.
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.
Thanks for the info!
special advisory?
Appears to be official... most likely by 5PM today.
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....
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
I've been trying to figures out why you don't member info listed.
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
Is that possible? I thought the theoretical limit was 220 mph
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...
18z Early Cycle NHC model tracks
TD-16
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)
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.
What she does with the pressure falls tonight will be key. She's broad and hopefully that's our best friend. Out of respect to the reliable models shifting west, the NHC should follow suit and split the difference with a track between Lake O and the East Coast. Not a big deal however unless she tightens up the circulation.
Oh that BITES!
Thanks for the info, this is the first year my daughter is in preschool and I was wondering about closures for tomorrow!
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