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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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