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Hurricane Florence Forecast Discussion Number 59
2018-09-14 04:58:21| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Thu Sep 13 2018 486 WTNT41 KNHC 140258 TCDAT1 Hurricane Florence Discussion Number 59 NWS National Hurricane Center Miami FL AL062018 1100 PM EDT Thu Sep 13 2018 Radar imagery and data from an Air Force Reserve Hurricane Hunter flight indicate that Florence has an inner eye that is open on the east side, and a secondary wind maximum that has already begun to spread inland across southeastern North Carolina. The highest flight-level wind (102 kt) was actually measured within the outer band that is moving onshore in the Wilmington area. However, the highest SFMR-measured wind was 73 kt, and the highest land observation so far was a sustained wind of 72 kt at Cape Lookout, North Carolina. On top of that, NOAA Doppler radar velocities have been running around 100 kt at about 5,000 feet. All of these data support reducing the initial intensity to 80 kt, but based on the higher flight-level winds, the gust factor is being set a little higher than is typical for an 80-kt hurricane. Florence has been wobbling a little since the previous advisory, but the 12-hour motion is northwestward, or 305/5 kt. Nearly all of the track models agree that Florence will turn westward or west-southwestward during the next 36 hours, bringing the hurricane's center inland over extreme southern North Carolina and extreme eastern South Carolina Friday and Friday night. After 48 hours, Florence is expected to recurve across the western Carolinas and the central Appalachian Mountains around a western Atlantic ridge. No major changes were required to the NHC official track forecast, and it is generally close to the multi-model consensus aids. It should be noted that the ECMWF, HCCA, and Florida State Superensemble still take Florence on a more southern track, straddling the coast of South Carolina before turning inland. While that is not shown by the official forecast, it cannot yet be ruled out as a possibility. Florence's intensity is not likely to change much in the 12 hours or so it has left over water. Once the center moves inland, the intensity is forecast to decrease. However, since a good portion of Florence's circulation will remain over water for the next 36-48 hours, the NHC intensity forecast is a blend of the regular SHIPS model (which assumes a storm staying over water) and the Decay-SHIPS model (which assumes the storm has moved inland). Based on that, Florence should weaken to a tropical storm just after 24 hours and then below tropical storm strength after 48 hours. Florence remains a large hurricane. Life-threatening storm surge, heavy rainfall, and damaging wind will cover a large area regardless of exactly where the center of Florence moves. Key Messages: 1. A life-threatening storm surge is already occurring along portions of the North Carolina coast and will continue through Friday. This surge is also likely along portions of the South Carolina coast. The greatest storm surge inundation is expected between Cape Fear and Cape Hatteras, including the Neuse and Pamlico Rivers and western Pamlico Sound. 2. Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians through early next week, as Florence is expected to slow down as it approaches the coast and moves inland. 3. Damaging hurricane-force winds are occurring along portions of the North Carolina coast and are expected to spread to portions of the South Carolina coast on Friday. Strong winds could also spread inland into portions of the Carolinas over the next couple of days. 4. Large swells affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas will continue this week, resulting in life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 34.0N 76.8W 80 KT 90 MPH 12H 14/1200Z 34.2N 77.6W 75 KT 85 MPH 24H 15/0000Z 34.0N 78.5W 65 KT 75 MPH...INLAND 36H 15/1200Z 33.8N 79.2W 50 KT 60 MPH...INLAND 48H 16/0000Z 33.8N 80.2W 40 KT 45 MPH...INLAND 72H 17/0000Z 35.5N 82.9W 25 KT 30 MPH...INLAND 96H 18/0000Z 39.5N 82.0W 20 KT 25 MPH...POST-TROP/INLAND 120H 19/0000Z 44.0N 72.5W 25 KT 30 MPH...POST-TROP/INLAND $$ Forecaster Berg
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