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Tropical Storm Ian Forecast Discussion


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WTNT44 KNHC 291500
TCDAT4

Tropical Storm Ian Discussion Number  28
NWS National Hurricane Center Miami FL       AL092022
1100 AM EDT Thu Sep 29 2022

The center of Ian has emerged into the western Atlantic Ocean to
the north of Cape Canaveral.  While satellite images show the
system is becoming a hybrid cyclone, with frontal features outside 
of the core of Ian, the winds from multiple sources are notable.  
Velocity data from NWS Doppler radar indicate maximum winds of about 
70-75 kt at 10,000 ft over land, and sustained winds of about 55 kt 
were recorded in the Daytona Beach area earlier this morning.  These 
data support a higher initial intensity, now 60 kt for this 
advisory.

The storm is moving northeastward at about 8 kt.  Ian has stubbornly 
gone east of the track forecast for the past couple of days and has 
moved back over water faster than expected.   A mid-level shortwave 
trough moving southward across the southern United States should 
turn Ian northward overnight and north-northwestward on Saturday. 
The official track forecast is shifted to the east, consistent with 
the latest consensus guidance.

Ian should move over the Gulf Stream tonight and tomorrow for a 
longer period of time than previously anticipated, which should 
maintain Ian's central convection.  Additionally, an increased 
pressure gradient on the northwestern side from a stationary front 
near the southeastern US, should provide a boost to the wind speeds 
on that side of the storm.  We now expect Ian to become a hurricane 
again by this evening.  As the system approaches South Carolina, Ian 
should maintain this intensity, and Hurricane Warnings have been 
issued for the entire coast of South Carolina.  This scenario is 
consistent with the global and regional hurricane model guidance.  
It is worth noting that Ian is forecast to have atypical structure 
when it nears the southeastern United States, and strong winds will 
extend well ahead of the center, even on the northwestern side.


Key Messages:

1. There is a danger of life-threatening storm surge through Friday
along the coasts of northeast Florida, Georgia, and South Carolina.
Residents in these areas should follow any advice given by local
officials.

2. Hurricane-force winds are expected across the South Carolina
coast beginning early Friday, where a Hurricane Warning has been
issued. Hurricane conditions are possible by tonight along the
coasts of northeastern Florida and Georgia, where a Hurricane Watch
is in effect.   Preparations should be rushed to completion since
tropical-storm-force winds will begin well before the center
approaches the coast.

3. Ongoing major-to-record river flooding will continue across
portions of central Florida, with considerable flooding in northern
Florida.  Considerable flash and urban flooding is expected across
coastal portions of northeast Florida through Friday. Local
significant flooding in southeastern Georgia and eastern South
Carolina is expected through the end of the week.


FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 28.7N  80.4W   60 KT  70 MPH
 12H  30/0000Z 30.0N  79.9W   65 KT  75 MPH
 24H  30/1200Z 31.8N  79.8W   65 KT  75 MPH
 36H  01/0000Z 34.0N  80.3W   45 KT  50 MPH...INLAND
 48H  01/1200Z 35.9N  81.1W   30 KT  35 MPH...POST-TROP/EXTRATROP
 60H  02/0000Z 37.0N  82.0W   15 KT  15 MPH...POST-TROP/EXTRATROP
 72H  02/1200Z...DISSIPATED

$$
Forecaster Blake



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