ATL: ISAAC - Post-Tropical - Discussion

[CyclonicFury]

No longer a hurricane

[artist]

[HurricaneRyan]

Isaac is reminding me of Joyce from 2000. Started off as a hurricane that the islands needed to watch, and then it just slowly died while getting near the Eastern Caribbean.

[EquusStorm]

If it can somehow escape whatever it is keeping it restrained (slight shear? Drier air? Poor divergence aloft?) it wouldn't take much for such a small storm to ramp back up significantly in the short term, but it could just as easily stay sickly. Not that those in its path would be upset about the latter solution

[floridasun78]

title need change to ts

[AtlanticWind]

Much stronger on GFS South of Hispanola

[AtlanticWind]

Weakens as it hits Haiti

[ConvergenceZone]

This might be the slow demise of Isaac. It didn't suppose to weaken this quickly. May not be much left of it by the time it hits the islands and that's a good thing....

[jlauderdal]

gfs weaknes it but the energy makes it into the straits, will have to see if it can survive but definitely needs to be monitored especially with the slow movement in a typically favorable area

[cycloneye]

BULLETIN
Tropical Storm Isaac Advisory Number 15
NWS National Hurricane Center Miami FL AL092018
500 AM AST Tue Sep 11 2018

...ISAAC REMAINS A STRONG TROPICAL STORM OVER THE CENTRAL TROPICAL
ATLANTIC...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...14.6N 48.1W
ABOUT 880 MI...1420 KM E OF THE LESSER ANTILLES
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...997 MB...29.44 INCHES

Tropical Storm Isaac Discussion Number 15
NWS National Hurricane Center Miami FL AL092018
500 AM AST Tue Sep 11 2018

Isaac has not changed much overnight. Satellite images indicate
that the strong tropical storm still has a central dense overcast
pattern and a limited amount of outer bands. Earlier microwave
data indicated that the center was not located in the middle of the
convection, however, likely due to some westerly shear. Since
the cyclone has changed little during the past several hours, the
initial intensity is held at 60 kt, which is an average of the TAFB
and SAB Dvorak final T- and CI-numbers. A nearby NOAA buoy shows
that the wind field of Isaac is very compact, with tropical-storm-
force winds only extending up to 40 n mi from the center.

Satellite fixes suggest that Isaac continues to move westward at 13
kt. Although there remains a fair amount of spread in the models,
the usually more reliable GFS and ECMWF models continue to show a
westward motion during the next several days as the storm moves on
the south side of a strengthening mid-level ridge. The NHC track
forecast continues to follow that theme, and this forecast lies
near a blend of the GFS and ECMWF aids. This forecast is a little
slower than the previous one, and takes Isaac across the Lesser
Antilles and into the eastern Caribbean in 2 to 3 days.

Predicting Isaac's intensity has been challenging. Isaac appeared
to have been in relatively favorable conditions during the past day
or so, but it did not strengthen. The upper-level pattern should
remain relatively favorable for another day, so modest strengthening
back to a hurricane is possible during that time. Thereafter,
however, an increase in shear first from a trough in the central
Atlantic and then from the outflow of Florence should cause some
weakening when the storm moves into the Caribbean. The models
are in a little better agreement this cycle as the HWRF is no
longer showing Isaac becoming a major hurricane. The NHC intensity
forecast is very similar to the previous one and is fairly close to
the consensus aids.

Key Messages:

1. Isaac is expected to be at or near hurricane intensity when it
approaches the Lesser Antilles. However, confidence in the forecast
is lower than normal.

2. Interests in the Lesser Antilles should continue to monitor
Isaac during the next couple of days. Watches will likely be
required for portions of the Lesser Antilles later today.

FORECAST POSITIONS AND MAX WINDS

INIT 11/0900Z 14.6N 48.1W 60 KT 70 MPH
12H 11/1800Z 14.6N 50.1W 60 KT 70 MPH
24H 12/0600Z 14.6N 52.6W 65 KT 75 MPH
36H 12/1800Z 14.8N 55.0W 65 KT 75 MPH
48H 13/0600Z 15.1N 57.6W 60 KT 70 MPH
72H 14/0600Z 15.5N 62.8W 55 KT 65 MPH
96H 15/0600Z 15.6N 67.4W 55 KT 65 MPH
120H 16/0600Z 15.8N 72.0W 50 KT 60 MPH

$$
Forecaster Cangialosi

[Nimbus]

Looks like a hot tower near 14.66N that could be predecessor to an eye on infrared.
Enough moisture now so shear forecast must be holding Isaac back?
I'm still concerned the islands may see a hurricane and if a hurricane reaches the Caribbean the models initialize very differently due to climo experience.

[stormchazer]

Isaac looking improved.

[NDG]

[txag2005]

I really hope this thing doesn't end up in Gulf. Both this and 95L are giving me some bad flashbacks to Harvey.

[AutoPenalti]

Wow, Issac has remarkably improved overnight.

[Michele B]

Just read on another forum that if Flo hangs around near the Carolina coast the way they are projecting, it will create a weakness that Isaac can then steer more northerly. Any credence to that idea?

[NDG]

It looks better on satellite this morning than yesterday morning but the LLC is still outrunning the MLC.

[NDG]

A better microwave image shows the LLC better, confirms that it is on the western edge of most of the convection. But the structure looks better than yesterday.

[artist]

Thanks to Barb, news from St. Maarten-
https://www.thedailyherald.sx/islands/8 ... -requested
Three shelters to open Wed., military assistance requested
10 September 2018
POND ISLAND--Prime Minister Leona Romeo-Marlin has requested the assistance of the Royal Dutch Marines ahead of Hurricane Isaac’s approach to the Lesser Antilles later this week.
The Emergency Operations Center (EOC) was activated by the prime minister. She chaired the EOC meeting in which decisions about precautionary measures for public safety and security were taken.
A decision to close schools will be made during an EOC meeting on Wednesday. This decision will be based on the Wednesday forecast track of Hurricane Isaac.
A curfew is expected to be issued on Thursday, September 13, based on Isaac’s track at that time.
Water and electricity company GEBE will interrupt water service to Point Blanche and Pelican residential areas five hours before Isaac’s passing.
ESF-2 Telecommunications and Post – all telecommunication companies have implemented their disaster preparedness plans which include making sure all generators at mobile phone sites throughout the country are full of fuel.
Ministry of Environment and Infrastructure VROMI advises residents that final pick-up for all garbage will be 12:00pm on Wednesday, September 12.
Three shelters will be opened in connection with the passing storm: Dutch Quarter Community Center, the Cole Bay Christian Fellowship Church, and Milton Peters College. Shelters can accommodate 175 to 200 people. Shelters will open on Wednesday at 5:00PM. Shelters will be open for 72 hours after Isaac’s passing

......
The Meteorological Department said in its Isaac Bulletin, issued Monday evening, that sea conditions will begin to deteriorate by Wednesday with waves peaking near eight feet and will further deteriorate Thursday through Friday up to 10 feet or more.
Winds are expected to increase on Wednesday up to 20 knots (25mph) and from Thursday 30 knots (35 mph) with higher gusts.
Models are not indicating excessive rainfall over St. Maarten (about two inches are expected). Occasional showers will move in on Wednesday and as moisture increases through Thursday rainfall activity will increase further.
Due to Isaac being such a small system there are a lot of uncertainties with the forecast. It is likely that as the system draws closer to the islands the track and intensity may change. Therefore, it is important to keep updated and alert, said the Met Office.
Most models are in agreement that the centre of Isaac will move somewhere between Guadeloupe and Martinique. The models vary with the time and place of landfall at this time. The time will depend on whether the forward speed increases or decreases before the arrival. At this time, it is likely to be sometime between Thursday and Friday

[artist]

Anyone with info, please post here as well, so those in the areas can quickly find updated info. Thanks..