ATL: ISAAC - Post-Tropical - Discussion

[meriland23]

NHC says wnw now, 16.3 N and 70.8W

[Hurricane Andrew]

That empty spot is not the COC.
http://www.ssd.noaa.gov/PS/TROP/floater ... imated.gif

[nativefloridian]

BULLETIN
TROPICAL STORM ISAAC ADVISORY NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1100 AM EDT FRI AUG 24 2012

...ISSAC STRENGTHENS A LITTLE MORE AS IT MOVES WEST-NORTHWESTWARD
TOWARD THE SOUTHERN COAST OF HISPANIOLA...

[Aric Dunn]

"
RECONNAISSANCE AIRCRAFT DATA AND SATELLITE IMAGERY INDICATE THAT
ISAAC HAS BECOME BETTER ORGANIZED DURING THE PAST SEVERAL HOURS. "

[meriland23]

Bit from 11 am discussion on NHC

THE 12Z POSITION USED A MEAN CENTER...WHICH RESULTED IN A SOUTHWARD
ADJUSTMENT. SINCE THEN...ISAAC APPEARS TO HAVE ACQUIRED A STRONGER
NORTHWARD COMPONENT OF MOTION...AND THE INITIAL MOTION IS A
SOMEWHAT UNCERTAIN 295/12.

[BoudreauxWPB]

Why are they taking so long to post the new forecast map? Is it because they are adjusting watches and warnings?

Nevermind, it's up now.

[Aric Dunn]

NHC says wnw now, 16.3 N and 70.8W

yeah thats a 6 hour overall motion recon found nw but the difference is not that far off.

[Blown Away]

Bit from 11 am discussion on NHC

THE 12Z POSITION USED A MEAN CENTER...WHICH RESULTED IN A SOUTHWARD
ADJUSTMENT. SINCE THEN...ISAAC APPEARS TO HAVE ACQUIRED A STRONGER
NORTHWARD COMPONENT OF MOTION...AND THE INITIAL MOTION IS A
SOMEWHAT UNCERTAIN 295/12.

Critical uncertainty for future effects on CONUS. IMO only if more NW then SFL if more W then NGOM.

[ObsessedMiami]

Surprised no watch for the Keys at this time

[Blown Away]

NHC says wnw now, 16.3 N and 70.8W

yeah thats a 6 hour overall motion recon found nw but the difference is not that far off.

NHC says 295 heading, hard to get much closer to NW than that!

[meriland23]

when does recon pass again?

[nativefloridian]

Surprised no watch for the Keys at this time

Excerpt from NHC 11am advisory:
"...INTERESTS THE REMAINDER OF CUBA...THE REMAINDER OF THE BAHAMAS...
SOUTH FLORIDA...AND THE FLORIDA KEYS SHOULD MONITOR THE PROGRESS OF
ISAAC. WATCHES WILL LIKELY BE REQUIRED FOR PORTIONS OF THE FLORIDA
KEYS LATER TODAY AND ARE ALSO POSSIBLE FOR PORTIONS OF THE SOUTHERN
FLORIDA PENINSULA."

[cpdaman]

NHC says wnw now, 16.3 N and 70.8W

yeah thats a 6 hour overall motion recon found nw but the difference is not that far off.

NHC says 295 heading, hard to get much closer to NW than that!

u do realize true NW is 315?

[MGC]

11am advisory shifted landfall to the Destin area...I imagine that will shift around a good bit the next several days. Isaac looks much better on the satellite loop this morning...MGC

[cycloneye]

The 11 AM EDT discussion by Dr Jeff Masters.

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.

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.

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.

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.

[cpdaman]

11am advisory shifted landfall to the Destin area...I imagine that will shift around a good bit the next several days. Isaac looks much better on the satellite loop this morning...MGC

i enjoy your posts, if i could ask u to speculate a bit, where do you think this will cross the islands (dr, cuba) and emerge , or is it not even comfortable guessing since it's a crap shoot in your mind

thank u

[SouthFLTropics]

Back on topic...The next 12-24 hours are crucial. The interaction with the islands and what kind of frictional forces may affect the track of the storm. Each model run coming out is critical for South Florida. Interaction with the islands, where the center ends up, and how long the weakness holds...All very important right now.

SFT

[bucman1]

SouthFLTropics & ARIC ,

What type of conditions do you think we might expect of the West Coast near Tampa?

[Aric Dunn]

SouthFLTropics & ARIC ,

What type of conditions do you think we might expect of the West Coast near Tampa?

this kind of conditions. check back to this link every day and you will know

http://forecast.weather.gov/MapClick.ph ... L%2C%20USA

[Weatherboy1]

Yes, these next 12-24 hours are indeed critical when it comes to determining what impact we will have in SE FL from Isaac. Can't wait to see the midday models to see if any shift further east or not.