Current Details from the National Hurricane Center (NHC)

Transcription

1 Current Watches and Warnings A Warning is in effect from South Santee River, South Carolina to Cape Lookout, North Carolina; Pamlico Sound A Surge Warning is in effect from Myrtle Beach, South Carolina to Ocracoke Inlet, North Carolina; Pamlico Sound, including the Neuse and Pamlico Rivers Current Details from the National Hurricane Center (NHC) COORDINATES: 33.6 north, 79.6 west LOCATION: 40 miles (65 kilometers) west of Myrtle Beach, South Carolina MOVEMENT: west at 2 mph (4 kph) WINDS: 45 mph (75 kph) with gusts to 60 mph (95 kph) RADIUS OF TROPICAL STORM-FORCE WINDS: 150 miles (240 kilometers) MINIMUM CENTRAL PRESSURE: 995 millibars SAFFIR-SIMPSON SCALE RANKING*: LANDFALL LOCATION: Wrightsville Beach, North Carolina LANDFALL TIMEFRAME: 7:15 AM local time (11:15 UTC) September 14 LANDFALL INTENSITY: 90 mph (150 kph) Category 1 Latest Satellite Picture Source: NASA/NOAA Risk. Reinsurance. Human Resources.

2 Discussion Florence, located approximately 40 miles (65 kilometers) west of Myrtle Beach, South Carolina, is currently tracking west at 2 mph (4 kph). Florence continues to slowly meander westward and weaken across eastern South Carolina. NOAA Doppler radar data indicate strong winds near 70 mph (110 kph) a few thousand feet above the surface within intense rainbands that remain situated between the Cape Fear/Wilmington area and Bogue Inlet, North Carolina. Although those velocity values would typically correlate to 60 mph (95 kph) surface winds, those winds appear to be associated with small mesoscale circulations and possible supercell thunderstorms, and not the larger tangential wind field. In contrast, surface observations during the past couple of hours have only shown sustained winds of around 45 mph (75 kph), which is what the NHC has set for this advisory. The estimated central pressure of 995 millibars is based on nearby surface observations across eastern South Carolina. Radar data and surface observations indicate that Florence has turned more westward and has slowed down even more. The forecast models remain in very good agreement that a mid-level ridge of high pressure currently centered over the upper Midwest will slide eastward across the lower Great Lakes to the U.S. Northeast during the next 48 hours. This feature is expected to steer Florence and its remnants in a general westward motion for the next 24 hours, followed by a turn toward the northwest on Monday. The ridge will continue to shift eastward and weaken, allowing Florence's circulation to get caught up in the faster mid-latitude westerlies and accelerate toward the northeast on Day 3 and toward the eastnortheast on days 4 and 5 as an extratropical low pressure system. Florence's inner-core convection and wind field will continue to weaken throughout the next 72 hours. However, the outer wind field and an associated band of deep convection in the eastern semicircle will likely produce sustained tropical-storm-force winds for another 12 hours, with some high gusts continuing until the band moves inland by late Sunday. More importantly, continued heavy rains will be produced by this band of convection, which will exacerbate the already catastrophic flooding that is occurring across much of southeastern North Carolina. The official NHC intensity forecast shows that post-tropical Florence on days 4 and 5 may strengthen due to baroclinic processes after moving over the relatively warm waters of the northwestern Atlantic Ocean. It is worth noting that the NHC strongly maintains that although coastal storm surge flooding will gradually subside today, especially after the midday high-tide period ends, extremely heavy rainfall will continue to be a serious hazard associated with slow-moving Florence. More than two feet of rain has already fallen across portions of southeastern North Carolina, and more rain is still to come, which will cause disastrous flooding that will spread inland through the weekend. Key Messages from the National Hurricane Center 1. Life-threatening storm surge will continue along portions of the North Carolina coast through today, and also along the Neuse and Pamlico Rivers in western Pamlico Sound, where rainfall and freshwater flooding will also contribute to high water levels. Dangerous storm surge could also affect portions of the northeast coast of South Carolina coast today. 2. Life-threatening, catastrophic flash floods and prolonged significant river flooding are likely over portions of the Carolinas and the southern to central Appalachians from western North Carolina into westcentral Virginia and far eastern West Virginia through early next week, as Florence moves slowly inland. In addition to the flash flood and flooding threat, landslides are also possible in the higher terrain of the southern and central Appalachians across western North Carolina into southwest Virginia. Cat Alert: Florence 2

3 3. storm conditions will continue along the coast within the tropical storm warning area and also well inland across portions of South Carolina and North Carolina today. 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. Additional Information STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water has the potential to reach the following heights above ground: The Neuse, Pamlico, Pungo, and Bay Rivers: 3-5 feet Cape Lookout, NC to Cape Fear, NC: 3-5 feet Ocracoke Inlet, NC to Cape Lookout, NC: 2-4 feet Cape Fear, NC to Myrtle Beach, SC: 2-4 feet The deepest water will occur along the immediate coast in areas of onshore winds, where the surge will be accompanied by large and destructive waves. Surge-related flooding can vary greatly over short distances. RAINFALL: Florence is expected to produce heavy and excessive rainfall in the following areas: Southern and central portions of North Carolina into far northeast South Carolina: an additional 15 to 20 inches, with storm totals between 30 and 40 inches along the North Carolina coastal areas south of Cape Hatteras. This rainfall will continue to produce catastrophic flash flooding and prolonged significant river flooding. Remainder of northern South Carolina into western North Carolina and southwest Virginia: 5 to 10 inches, isolated 15 inches West-central Virginia into far eastern West Virginia, north of Roanoke and west of Charlottesville: 3 to 6 inches, isolated 8 inches. These rainfall amounts will result in life-threatening flash flooding and river flooding, along with an elevated risk for landslides. A preliminary report from a cooperative observer near Swansboro, North Carolina, indicates that more than 30 inches of rain has fallen so far. In Newport, North Carolina, more than 24 inches of rainfall has been measured. WIND: storm conditions will continue today in portions of the warning area along the coast and also over large portions of eastern North Carolina and extreme eastern South Carolina, with tropicalstorm-force wind gusts spreading well inland. TORNADOES: A few tornadoes are possible in southeastern North Carolina northeastern South Carolina today through tonight. SURF: Swells generated by Florence are affecting Bermuda, portions of the U.S. East Coast, and the northwestern and central Bahamas. These swells are likely to cause life-threatening surf and rip current conditions. Cat Alert: Florence 3

4 Hurricane Center (NHC) Forecast Cat Alert: Florence 4

5 National Hurricane Center: Wind Speed Probabilities -Force Wind Probabilities ( 40 mph (65 kph)) Cat Alert: Florence 5

6 NHC: Surge Inundation Cat Alert: Florence 6

7 NHC: Surge Watches/Warnings Cat Alert: Florence 7

8 Weather Prediction Center: Rainfall Potential Cat Alert: Florence 8

9 Weather Prediction Center: Flash Flood Potential Cat Alert: Florence 9

10 Additional Information and Update Schedule Wind intensity forecasts and forecast track information can be found via the National Hurricane Center at NEXT CAT ALERT: Sunday morning after 10:00 AM Central Time (15:00 UTC), unless Florence degrades into a post-tropical cyclone prior to that time. Cat Alert: Florence 10

11 * Intensity Classifications for Global Basins WIND SPEED KTS 1 MPH 1 KPH NE Pacific, Atlantic National Hurricane Center (NHC) Depressio n NW Pacific Joint Typhoon Warning Center (JTWC) Depressio n BASINS AND MONITORING BUREAU NW Pacific Japan Meteorological Agency (JMA) Depression SW Pacific Fiji Meteorologica l Service (FMS) Depression Australi a Bureau Of Meteorology (BOM) Low SW Indian Meteo-France (MF) Depressio n North Indian India Meteorologica l Department (IMD) Deep Depression Cat. 1 Cat. 2 Cat. 1 Cat. 2 Moderate Cyclonic Cyclonic Cat. 1 Hurricane Cat. 3 Cat Cat. 2 Hurricane Cat. 3 Major Hurricane Typhoon Typhoon Cat. 4 Cat. 4 Intense Very Cyclonic Cat. 4 Major Hurricane Cat. 5 Major >140 >160 >260 Hurricane Super Typhoon Cat. 5 Cat. 5 Very Intense Super Cyclonic Cat Alert: Florence 11

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