WTNT44 KNHC 300847

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.


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