|#1150418 (Received by flhurricane at: 5:00 PM 30.Aug.2023)|
Tropical Storm Idalia Discussion Number 17
NWS National Hurricane Center Miami FL AL102023
500 PM EDT Wed Aug 30 2023
Idalia`s radar and satellite presentation has become increasingly
asymmetric. A coastal front appears to have developed just inland
of the coasts of Georgia and South Carolina, with heavy rainfall
being enhanced along and to the northwest of this boundary. The
highest WSR-88D velocities observed are about 60-65 kt at an
elevation of 5000 feet, indicating that Idalia is no longer a
hurricane. The advisory intensity is set at 60 kt, which is
probably a bit generous.
The initial motion is now northeastward, or 035/18 kt, with Idalia
moving between the northwestern periphery of a mid-level ridge
located over the Greater Antilles and a deep-layer trough moving
across the northeastern U.S. The storm is expected to turn toward
the east and east-southeast during the next 48 hours, but then slow
down considerably as the trough lifts out and leaves Idalia behind.
There is fairly high confidence that Idalia will move slowly
eastward over the western Atlantic, in the vicinity of Bermuda,
during the latter part of the forecast period, although there is
less confidence in the details of that motion due to large model
Additional weakening is expected while Idalia`s center continues
moving over land through tonight. However, once the center moves
back offshore on Thursday, model fields suggest that Idalia could
interact with the aforementioned coastal front, with an area of
stronger winds developing along the boundary near eastern North
Carolina during the day. Based on this scenario, the NHC intensity
forecast closely follows the GFS solution at 24 and 36 hours.
After 36 hours, there is more uncertainty on Idalia`s intensity and
structure. Some guidance suggests that Idalia will continue
interacting with the front and possibly become post-tropical,
particularly if it struggles to maintain organized deep convection.
For now, the NHC forecast keeps Idalia as a tropical storm for the
entire forecast period.
1. Storm surge is expected along the southeastern U.S. coast within
the Storm Surge Warning area through tonight. Coastal flooding is
also expected within the Storm Surge Watch area in North Carolina on
Thursday. Residents in these areas should follow any advice given
by local officials.
2. Tropical-storm-force winds will affect portions of the
southeastern U.S. coast through Thursday.
3. Areas of flash, urban, and moderate river flooding, with
considerable impacts, are expected from east central Georgia,
through eastern South Carolina and eastern North Carolina into
FORECAST POSITIONS AND MAX WINDS
INIT 30/2100Z 32.2N 81.7W 60 KT 70 MPH...INLAND
12H 31/0600Z 33.4N 79.3W 50 KT 60 MPH...INLAND
24H 31/1800Z 34.1N 75.7W 50 KT 60 MPH...OVER WATER
36H 01/0600Z 33.7N 72.2W 45 KT 50 MPH
48H 01/1800Z 32.8N 69.7W 45 KT 50 MPH
60H 02/0600Z 32.1N 68.2W 45 KT 50 MPH
72H 02/1800Z 31.7N 67.3W 45 KT 50 MPH
96H 03/1800Z 32.3N 65.1W 45 KT 50 MPH
120H 04/1800Z 34.4N 61.3W 45 KT 50 MPH