Atlantic Basin Tropical Cyclones

Hurricane Ian Forecast Discussion


025 
WTNT44 KNHC 300847
TCDAT4

Hurricane Ian Discussion Number  31
NWS National Hurricane Center Miami FL       AL092022
500 AM EDT Fri Sep 30 2022

Ian continues to display hybrid tropical/extratropical 
characteristics, and the satellite appearance is increasingly 
taking on the pattern of an occluded low.  Some deep convection has 
still been developing just northwest of the center, however.  Based 
on SFMR measurements from an earlier Air Force Reserve Hurricane 
Hunter aircraft, the initial intensity is 75 kt, and as of right 
now, all sustained hurricane-force winds are located within the 
western semicircle.

The motion of Ian's center has been somewhat discontinuous during 
the past 6 to 12 hours, with multiple swirls apparently rotating 
around a common center.  The smooth motion is toward the 
north-northeast, or 015/9 kt, although Ian should turn northward 
very soon.  A turn toward the north-northwest is expected by tonight 
as Ian moves around and merges with a shortwave trough over the 
southeastern United States.  Track models appear to have stabilized, 
and all show Ian's center crossing the coast of South Carolina this 
afternoon, and then moving across eastern South Carolina and central 
North Carolina tonight and on Saturday.  Since there has been no 
noticeable shift in the guidance on this cycle, the new NHC forecast 
essentially lies right on top of the previous prediction.

Although very strong southwesterly shear is affecting Ian, the 
hurricane is likely deriving its energy from a mixture of the warm 
waters of the Gulf Stream and favorable interaction with the 
southeastern U.S. shortwave trough.  Those two influences should 
continue today, and no significant changes to the intensity are 
expected up until Ian's anticipated landfall this afternoon, which 
is generally in line with the SHIPS and LGEM guidance.  It should be 
noted that hurricane-force winds are expected to develop within the 
eastern semicircle soon, particularly as Ian begins to move faster 
toward the north.  After landfall, fast weakening is expected, and 
Ian is also forecast to become fully extratropical by 36 hours, if 
not a little sooner.  The extratropical low is then forecast to 
dissipate near the North Carolina/Virginia border by Saturday night.

One additional note: a frontal boundary that extends to the 
northeast of Ian is expected to shift inland later today, and the 
extensive area of tropical-storm-force winds shown in the 
northeastern quadrant is forecast to contract considerably later 
today and tonight.


Key Messages:

1. There is a danger of life-threatening storm surge today along the 
coasts of northeast Florida, Georgia, and the Carolinas within the 
Storm Surge Warning areas.  Residents in these areas should follow 
any advice given by local officials.

2. Hurricane-force winds are expected along the coasts of South
Carolina and southeastern North Carolina within the Hurricane 
Warning area by this afternoon.  Hurricane conditions are possible 
in North Carolina within the Hurricane Watch area by this afternoon. 
Preparations should be rushed to completion.

3. Ongoing major to record river flooding will continue through next 
week across portions of central Florida. Considerable flooding is 
expected through today across portions of coastal and northeast 
South Carolina. Locally considerable flooding is possible across 
portions of North Carolina and southern Virginia through today.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 30.8N  79.1W   75 KT  85 MPH
 12H  30/1800Z 32.5N  79.3W   75 KT  85 MPH
 24H  01/0600Z 34.6N  79.9W   45 KT  50 MPH...INLAND
 36H  01/1800Z 36.3N  80.3W   30 KT  35 MPH...POST-TROP/EXTRATROP
 48H  02/0600Z...DISSIPATED

$$
Forecaster Berg




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