Isaac is strengthening

By: Dr. Jeff Masters , 2:58 PM GMT on August 24, 2012

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Tropical Storm Isaac is strengthening. An Air Force Reserve hurricane hunter aircraft measured surface winds of 60 mph on the east side of the center, about 170 miles south of Santo Domingo in the Dominican Republic, at 8:40 am EDT this morning. Winds at the aircraft's flight level of 5,000 feet were hurricane force, 76 mph. The surface pressure remained fairly high, at 1000 mb. Tropical cyclones have a warm core, and the Hurricane Hunters typically find that a storm's lowest pressure is also where the warmest temperature are. However, this morning's flight found that Isaac was still disorganized, with the storm showing almost no evidence of a warm core. Isaac's warmest temperatures were displaced 75 miles to the west of where the lowest pressure was. There were no signs of an eyewall beginning to build. Infrared and visible satellite loops show that Isaac is somewhat asymmetric, with a large band of intense thunderstorms to the east, separated from the core region. This is interfering with both the storm's low-level inflow and upper-level outflow, but the band appears to be dying out. An analysis of upper level winds from the University of Wisconsin CIMSS shows an upper-level outflow channel well-established to the north, and an intermittent outflow channel to the south.


Figure 1. Evening shot of Tropical Storm Isaac taken on August 23, 2012, by the NOAA Hurricane Hunters.

Isaac's rains
Radar imagery from Puerto Rico shows that Isaac is dumping some very heavy rains to the south and east of the center. Ponce, Puerto Rico had a wind gust of 37 mph this morning as a heavy band of rain moved through, and radar-estimated rainfall amounts are in excess of 7 inches for the region just north of Ponce. Power outages to 2,000 homes have been reported in Puerto Rico this morning. NOAA buoy 42085 offshore from Ponce reported a wind gust of 54 mph near 9 am EDT this morning. Rainfall estimates from microwave satellite instruments suggest that Isaac's heaviest rains are to the south of the center, and that the Dominican Republic and Eastern Haiti will escape the worst of Isaac's rains. Haiti's southwest peninsula and Eastern Cuba should suffer the heaviest rains.


Figure 2. Radar-estimated precipitation from the Puerto Rico radar shows the region near Ponce has received up to 7" of rain as of 10 am EDT August 24, 2012.

Latest model runs for Isaac
The latest set of 00Z and 06Z (8 pm and 2 am EDT) model runs have come into better agreement, thanks to the dropsonde mission by the NOAA jet yesterday afternoon and evening. Isaac should move over Haiti's southwest peninsula and then eastern Cuba, then track along the spine of Cuba before popping off into the Florida Straits on Sunday. A trough of low pressure will then pull Isaac to the northwest, and then north, towards the Central Gulf Coast. Landfall locations range from Mississippi (06Z HWRF model run) to the Florida Panhandle south of Tallahassee (06Z GFDL model run.) It is possible that the trough of low pressure pulling Isaac to the north may not be strong enough to pull Isaac all the way to the northeast and out to sea, and the ECMWF model indicates that Isaac could stall out after landfall over the Tennessee Valley for several days.


Figure 3. Predicted 5-day rainfall total ending at 2 am EDT Wednesday August 29, from Tropical Storm Isaac. Graphics were generated from the 6Z (2 am EDT) August 24, 2012 run of the HWRF model. Image credit: Morris Bender, NOAA/Geophysical Fluid Dynamics Laboratory.

Intensity forecast for Isaac
Isaac has not intensified as much as predicted, and I think that the storm's very large size is partially responsible for that. It's tough to spin up as much atmosphere as Isaac is attempting to do very quickly. Conditions remain favorable for intensification today, with wind shear low, 5 - 10 knots, ocean temperatures warm, 29°C, and dry air mostly mixed out of the storm's core. The large band of intense thunderstorms to the east, separated from the core region, appears to be dying out now, which will help the storm grow more organized. The storm's structure has improved considerably between 9 am - 10 am EDT, with a fairly tight center forming, exposed to view, on the north edge of Isaac's heaviest thunderstorms. A curved band of heavy thunderstorms is now trying to wrap around this center to the northeast, and this band will bring very heavy rains to Haiti and the Dominican Republic this afternoon. I expect that the Hurricane Hunters will observe a partial eyewall in their vortex reports between 2 - 4 pm EDT this afternoon. The storm's large size and disorganized structure suggests that Isaac will be able to intensify only slowly today, and will have top winds of 70 - 75 mph before encountering Southwest Haiti and Eastern Cuba tonight and Saturday. Isaac will likely be a 50 - 60 mph tropical storm on Saturday and Sunday as it moves over Cuba. Once Isaac pops off the coast of Cuba into the Florida Straits, it will be over very warm waters of 31 - 32°C (88 - 90°F), wind shear will be light to moderate. The upper-level wind pattern favorable may be quite favorable for intensification, with low wind shear due to an upper-level anticyclone over the storm--though the models disagree on whether or not this anticyclone will set up directly over Isaac or not. It will probably take at least 24 hours with the storm's center over water for it to become a hurricane. It is possible that Isaac could be approaching Category 3 strength by the time it makes landfall on Tuesday on the Gulf Coast, as suggested by the latest 06Z run of the HWRF model.

Impact on Tampa, Florida
The Republican National Convention begins on Monday in Tampa, Florida. The latest 11 am EDT wind probability forecast from NHC gives Tampa a 17% chance of receiving tropical storm-force winds and a 1% chance of receiving hurricane-force winds on Monday. Tampa is in the NHC cone of uncertainty, though near the edge of it. At a minimum, Tampa will receive very heavy rains and wind gusts in excess of 40 mph. Isaac is going to be hard-pressed to bring hurricane-force winds to the city, though, since any path that takes it close to Tampa would keep the storm too close to land for significant intensification to occur. I put the odds of a mass evacuation being ordered for Tampa during the convention at 1%. I have detailed information on Tampa's storm surge vulnerability in a post from last week.

Invest 97L off the coast of Africa
A tropical wave that moved off the coast of Africa on Thursday has been designated Invest 97L by NHC this morning. The storm has a modest amount of spin and heavy thunderstorms, and is under moderate wind shear of 10 - 20 knots. In their 8 am EDT Tropical Weather Outlook, NHC gave 97L a 30% chance of developing by Sunday morning. The 8 am EDT SHIPS model forecast predicts that 97L will track west-northwest over the next few days, and encounter a region of high wind shear associated with an upper-level low on Monday and Tuesday. This low may be capable of tearing the storm apart, as happened to Tropical Storm Joyce. None of the models currently foresee that 97L will affect the Lesser Antilles Islands, but 97L may pass near Bermuda 7 - 8 days from now.



20th anniversary of Hurricane Andrew
Today, August 24, is the 20th anniversary of Hurricane Andrew, which hit South Florida as a Category 5 hurricane with 175 mph winds--one of only three Category 5 hurricanes ever to hit the U.S. With Isaac churning through the Caribbean this week, I didn't have time to prepare a special post on Andrew, but our Hurricane Andrew archive page has links to satellite and radar images, newspaper headlines, and 49 YouTube videos. Here's an additional link for an Andrew damage video shot by wunderblogger/storm chaser Mike Theiss, when he was 14 years old.

Jeff Masters

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Quoting cchssweatherman:


Okay, after reviewing the data from the Gulfstream-IV along with my own personal instrumentation, I'm able to report my observations and my forecast for this system.  There are a few anomalies that the models don't seem to be picking up on, but which should seem rather obvious to the trained eye.  

First, there is a rather potent riptide traversing the coastline from Maine to just west of Florida, where a substantial area of cooler water is now present.  As my graphic indicates this will serve to weaken Isaac from a category 4 to 3 briefly; however, Isaac will quickly gain category 5 status due in part to the sudden change from cold to extremely warm temperatures as well as a large area of cumulus clouds south of Cuba.  These clouds act to “supercharge” storms due to their shape, which creates the perfect amount of turbulence needed to reach category 5.

The blocking low, along with an area of concern in the Eastern Pacific (though expected to enter the Gulf of Mexico as early as Sunday), will serve to turn Isaac sharply north in a “V” motion.  Shortly thereafter, the Saharan Air Layer over the Eastern Gulf/Texas will cause a slight weaking, albeit only to Category 4.  The Wind, along with the encroaching High over Texas, will cause Isaac to make several right angles, after which the blocking high over Florida will allow Isaac to move north towards the Louisiana coast.  Because this motion will occur rather slowly, the waters off the northern Gulf coast will have churned for quite some time, cooling them substantially.  As a result, combined with the perfect amount of Saharan Air Layer over Florida, shortly after landfall in Louisiana on September 13, when Isaac re-enters the Gulf after a brief eastward trajectory, Isaac will transition to a Noreaster (depicted by blue dots on my graphic).

This Noreaster status could potentially cause more problems for the northern Gulf coast than even Isaac’s landfall as a Category 4 hurricane.  Nor’Isaac is expected to produce substantial hail and snow, with Louisiana and Mississippi possibly experiencing blizzard-like conditions for upwards of a week.  Residents should prepare accordingly.  

In addition to Isaac, forecasters should note the additional two areas of concern I have highlighted.  I will update my forecast as additional information rolls into the instruments in my parents’ basement.  

CCHS signing off for now!


You sure put alot of thought into that anaylsis.....
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Quoting Hurricanes101:


12Z Euro isn't out , comes out at 230pm


apologies - that must have been yesterday's....my bad :p
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Quoting cchsweatherman:


Lovely. I got another imposter on the blogs here. Not how he uses 2 s in the handle while mine is the original. Must be doing something right for people to want and impersonate me.
i was very surprised but i know its not you check that out
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708. FOREX
Quoting Seflhurricane:
what the hell is this ???


lmao
Member Since: August 17, 2011 Posts: 0 Comments: 2335
Quoting cchssweatherman:


Okay, after reviewing the data from the Gulfstream-IV along with my own personal instrumentation, I'm able to report my observations and my forecast for this system.  There are a few anomalies that the models don't seem to be picking up on, but which should seem rather obvious to the trained eye.  

First, there is a rather potent riptide traversing the coastline from Maine to just west of Florida, where a substantial area of cooler water is now present.  As my graphic indicates this will serve to weaken Isaac from a category 4 to 3 briefly; however, Isaac will quickly gain category 5 status due in part to the sudden change from cold to extremely warm temperatures as well as a large area of cumulus clouds south of Cuba.  These clouds act to “supercharge” storms due to their shape, which creates the perfect amount of turbulence needed to reach category 5.

The blocking low, along with an area of concern in the Eastern Pacific (though expected to enter the Gulf of Mexico as early as Sunday), will serve to turn Isaac sharply north in a “V” motion.  Shortly thereafter, the Saharan Air Layer over the Eastern Gulf/Texas will cause a slight weaking, albeit only to Category 4.  The Wind, along with the encroaching High over Texas, will cause Isaac to make several right angles, after which the blocking high over Florida will allow Isaac to move north towards the Louisiana coast.  Because this motion will occur rather slowly, the waters off the northern Gulf coast will have churned for quite some time, cooling them substantially.  As a result, combined with the perfect amount of Saharan Air Layer over Florida, shortly after landfall in Louisiana on September 13, when Isaac re-enters the Gulf after a brief eastward trajectory, Isaac will transition to a Noreaster (depicted by blue dots on my graphic).

This Noreaster status could potentially cause more problems for the northern Gulf coast than even Isaac’s landfall as a Category 4 hurricane.  Nor’Isaac is expected to produce substantial hail and snow, with Louisiana and Mississippi possibly experiencing blizzard-like conditions for upwards of a week.  Residents should prepare accordingly.  

In addition to Isaac, forecasters should note the additional two areas of concern I have highlighted.  I will update my forecast as additional information rolls into the instruments in my parents’ basement.  

CCHS signing off for now!


LOL! Great work. That's the most comprehensive personal forecast I've seen in the last week. :)
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Quoting oceanblues32:

Wait that shows it going right in my back yard is this run consistent with any others?


Consistent within its own boundaries. You don't see it making drastic jumps to the E or W like some others on the last couple runs.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
no.answer.for.haiti.
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Quoting SSideBrac:


Was in Hazard Management Site - Press Releases.

An Exercise relating to a fictitious Hurricane Stuart - advising all people in GCM to seek shelter immediately - as I said the message has now gone

I'd say thats bad timing
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Quoting WPBHurricane05:


Holy crap. Hate to get political, but I wonder how much of that actually gets to the people and not the politicians.


It gets to the people trust me, I participated in the recovery in Indonesia after the Tsunami and the Navy and the US gave more than anyone will ever know, we always do!
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Quoting Seflhurricane:
what the hell is this ???


Lovely. I got another imposter on the blogs here. Not how he uses 2 s in the handle while mine is the original. Must be doing something right for people to want and impersonate me.
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Quoting harleydchick:
12Z ECMWF - favoring central LA coastline.........hmmmmmm.



12Z Euro isn't out , comes out at 230pm
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btw I just volunteer that info about my preps to possibly help others wondering what they should do. If you don't have the basics yet, you should get them especially if you are in the cone or 100 miles from the outer edges of the cone ;)
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The Space Station is going to have a bird's eye view of Isaac at 3:30 EST, and it will be on NasaTV: http://t.co/m7wHG834
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Quoting Levi32:
Good afternoon.

Blog update:

Tropical Tidbit for Friday, August 24th, with Video



very nice Levi you da man. young man but still da man lol
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Quoting JasonRE:
So this thing is now shifting enough to pull LA out of the cone? Just wondering if any of you think this could possibly stay West enough to affect any of LA? In SE Louisiana here......Lafayette area. Thanks


Until Isaac is off the islands and model run off those coordinates and strength, I would say everyone from FL to TX/LA border needs to watch.
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HH just departed... great.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
Quoting mojofearless:


Haiti fought for and gained independence in 1804. If France is still responsible for Haiti, then Britain is still responsible for the United States of America.


They've been a country 28 years less than us, and they are about 100 years behind. Who's fault is that.
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If only the aid given to Haitians had actually gotten there. If you research how much was given and how much they've actually received it makes you really wonder how many crooks got rich off of the US and the world's good will. It makes me sick.
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Quoting cchssweatherman:


Okay, after reviewing the data from the Gulfstream-IV along with my own personal instrumentation, I'm able to report my observations and my forecast for this system.  There are a few anomalies that the models don't seem to be picking up on, but which should seem rather obvious to the trained eye.  

First, there is a rather potent riptide traversing the coastline from Maine to just west of Florida, where a substantial area of cooler water is now present.  As my graphic indicates this will serve to weaken Isaac from a category 4 to 3 briefly; however, Isaac will quickly gain category 5 status due in part to the sudden change from cold to extremely warm temperatures as well as a large area of cumulus clouds south of Cuba.  These clouds act to “supercharge” storms due to their shape, which creates the perfect amount of turbulence needed to reach category 5.

The blocking low, along with an area of concern in the Eastern Pacific (though expected to enter the Gulf of Mexico as early as Sunday), will serve to turn Isaac sharply north in a “V” motion.  Shortly thereafter, the Saharan Air Layer over the Eastern Gulf/Texas will cause a slight weaking, albeit only to Category 4.  The Wind, along with the encroaching High over Texas, will cause Isaac to make several right angles, after which the blocking high over Florida will allow Isaac to move north towards the Louisiana coast.  Because this motion will occur rather slowly, the waters off the northern Gulf coast will have churned for quite some time, cooling them substantially.  As a result, combined with the perfect amount of Saharan Air Layer over Florida, shortly after landfall in Louisiana on September 13, when Isaac re-enters the Gulf after a brief eastward trajectory, Isaac will transition to a Noreaster (depicted by blue dots on my graphic).

This Noreaster status could potentially cause more problems for the northern Gulf coast than even Isaac’s landfall as a Category 4 hurricane.  Nor’Isaac is expected to produce substantial hail and snow, with Louisiana and Mississippi possibly experiencing blizzard-like conditions for upwards of a week.  Residents should prepare accordingly.  

In addition to Isaac, forecasters should note the additional two areas of concern I have highlighted.  I will update my forecast as additional information rolls into the instruments in my parents’ basement.  

CCHS signing off for now!
what the hell is this ???
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Quoting HrDelta:


I don't think so. I think we are the biggest givers of aid.

Even though are French Creole, we take more care of them than France.


Nothing to do to do with France for many many years! Haitians essentially kicked them out in a revolt!

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ty levi u know ur stuff
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Quoting WxLogic:
12Z CMC

Hmm... at least is consistent now.

Wait that shows it going right in my back yard is this run consistent with any others?
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HH are up!!!!!!!!:)
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Quoting BahaHurican:
Haiti has been an independent country since 1804
BTW, the only country that beat them to it was the US.
Member Since: October 25, 2005 Posts: 19 Comments: 22736
Quoting RTSplayer:


Publicly, no...

Privately maybe.

Most of the money our government does give to foreign nations is related to "nation building" and bribes (for lack of a better term,) to use air space, water ways, etc...


Uh... both privately and publicly we give the most in the whole world.
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Guys, the 12Z EURO is NOT out yet. You are looking at yesterday's run.
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well im so anxious now my stomach is churning..going to take a break and go down to the beach for awhile..see you all later
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Quoting LargoFl:
arent the french responsible for haiti? ask them what they are doing


Haiti fought for and gained independence in 1804. If France is still responsible for Haiti, then Britain is still responsible for the United States of America.
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Quoting VAbeachhurricanes:
No you guys are right... we are the bad guys

Aid given to Haiti
United States US 466,879,506
Canada CA 130,733,775
World Bank (emergency grant) 82,107,356


Holy crap. Hate to get political, but I wonder how much of that actually gets to the people and not the politicians.
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Most Retired Hurricane Names(By Letter).
I: 9 Storms - If Isaac Is Retired... 10. Which would give I' names the Lead.
C: 9 Storms
F: 8 Storms
A: 7 Storms
D: 7 Storms
H: 5 Storms
G: 4 Storms
J: 4 Storms


1954-2011.
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12Z NOGAPS... tries to pull a GFS and then goes on the current track as NHC currently has outlined.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
Quoting wunderkidcayman:


where did you get this about hurricane exercise meassage


Was in Hazard Management Site - Press Releases.

An Exercise relating to a fictitious Hurricane Stuart - advising all people in GCM to seek shelter immediately - as I said the message has now gone
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Quoting Stormchaser121:

ERUO model still saying western gulf?? I still think its correct.


Hold on there. We don't want what that was selling. Hopefully wherever this storm goes it won't be as bad a storm as that was showing. But we still have to watch though.
Member Since: August 24, 2010 Posts: 0 Comments: 254
Quoting FOREX:


Really?? America is the most giving country in the World. Where are all of the Muslim countries when Indonesia, a Muslim country has a tsunami? Nowhere to be found or heard of.


Publicly, no...

Privately maybe.

Most of the money our government does give to foreign nations is related to "nation building" and bribes (for lack of a better term,) to use air space, water ways, etc...
Member Since: January 25, 2012 Posts: 33 Comments: 1520
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Quoting LargoFl:
this could be very serious..never been to miami..if a storm approaches from the south..is there going to be massive flooding from surge?
I think so, and I also once saw a "it could happen tomorrow" episodes where a cat 2 or 3 comes up from the south and hits miami.
Member Since: August 18, 2011 Posts: 0 Comments: 994
All bets are off track wise and strength wise until it comes off the coast of Cuba.
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Along with most of the poverty in Latin America..it is likely Spain's fault. What it is, the new world colonies stopped getting support from Europe after Spain's bankruptcy and never really got developed in the same sense as the British and French colonies. You can see the same thing in Africa, where only South Africa (and arguably Nigeria) is decently developed south of the Sahara. South Africa being a long term Dutch/British colony where as most Sub-Saharan colonies were only European for less than a century during the race for Africa. If Africa was still under control of Europe still, I'm guessing it would be in a better situation, especially with the social changes in the last century.
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Haiti, for all intents and purposes, is a failed state. This country has had no reliable infrastructure or government for the better part of 10 years. Add the earthquakes and storms, and there is even less to which the people of Haiti may avail themselves if/when Isaac comes to visit.
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Quoting SFLWeatherman:
Q will it go to S FL
A. yes
B. no
I say yes
A
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I'm definitely noticing a shift east in the models, more towards south FL or the west coast of FL. The new HWRF has shifted that way:



I think this intensity is overdone though. If the storm were to go towards S FL I don't think it would be more than a moderate TS since Cuba would weaken it and it would have little time over water to strengthen.
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I think this is a good example of what this might be able to do after moving over Cuba.
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!!!!!!!!!!!!!!!!!!!!!!!!:)
Quoting Levi32:
Good afternoon.

Blog update:

Tropical Tidbit for Friday, August 24th, with Video
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I'm in Western Broward, currently expecting that we will experience Tropical Storm conditions starting sometime Sunday afternoon. I've already bought the usual supplies (batteries, water, canned foods)I do it in June and just refresh everytime I go shopping till hurricane season is over. Today I picked up bread and fresh fruit, since I won't be making the decision regarding shutters and really cleaning up the yard (birdbaths, lawn chairs) till tomorrow. Don't want to deal with long lines if I have yard and house prepping to do. Btw shutters don't go up unless it's Cat 1 or higher.

I honestly don't think we will experience the worst, my concern is the possible tornados and flooding. I think Monday and even Tuesday will just be very nasty days in South Florida.
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12Z ECMWF - favoring central LA coastline.........hmmmmmm.

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Q will it go to S FL
A. yes
B. no
I say yes
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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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