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Hurricane Nate Forecast Discussion Number 15
2017-10-08 04:52:38| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Sat Oct 07 2017 000 WTNT41 KNHC 080252 TCDAT1 Hurricane Nate Discussion Number 15 NWS National Hurricane Center Miami FL AL162017 1000 PM CDT Sat Oct 07 2017 A ragged central dense overcast persists over Nate's center, but radar trends have shown all of the deep convection migrating to the north and northeast of the center, likely due to increasing south-southwesterly shear. Still, the northern eyewall, which will be moving onshore the Mississippi coast soon, remains quite vigorous. An Air Force Hurricane Hunter aircraft recently measured a maximum 850-mb flight-level wind of 89 kt and some SFMR values around 70 kt. Although the SFMR could be affected by wave shoaling in this case, the data as a whole appear to support an initial intensity of 75 kt. Nate's central pressure has been rising slowly, with the latest report from the plane being 984 mb. Nate has turned northward and slowed down a bit with an initial motion of 360/17 kt. On this course, the hurricane is expected to make a second landfall along the Mississippi coast within the next hour or two. After landfall, Nate should turn gradually toward the northeast and accelerate again during the next day or two while it moves between a large mid-level high off the southeastern U.S. coast and a large trough digging into the central U.S. This steering pattern will take Nate across the Deep South, Tennessee Valley, and central Appalachian Mountains during the next couple of days. The new NHC track forecast is unchanged from the previous one. With landfall imminent, no changes in intensity are expected before that time. After landfall, land and increasing shear should contribute to fast weakening, and Nate is expected to become a tropical storm in 6-12 hours and then weaken to a tropical depression by 36 hours. Nate is likely to become a remnant low by 48 hours, and the global models suggest that the cyclone will be absorbed by another low or cold front by 72 hours. That scenario is now reflected in the NHC forecast. KEY MESSAGES: 1. Nate is expected to bring life-threatening storm surge flooding near and well east of where the center makes landfall, and a storm surge warning is in effect from the mouth of the Mississippi River to the Okaloosa/Walton county line in Florida. Maximum flooding of 7 to 11 feet above ground level is expected along the Mississippi coast within the next several hours. 2. Hurricane conditions are spreading onshore along the coasts of Mississippi and Alabama, where a hurricane warning is in effect. The strongest winds are expected to occur primarily to the east of the track of the center. 3. Nate's fast forward speed after landfall will bring tropical-storm-force winds well inland across portions of the southeastern U.S. Tropical storm watches and warnings are in effect for portions of southeastern Mississippi, much of Alabama, and western Georgia. 4. Nate will bring heavy rainfall of 3 to 6 inches with isolated totals of 10 inches east of the Mississippi River from the central Gulf Coast into the Deep South, eastern Tennessee Valley, and southern Appalachians through Monday, resulting in the potential for flash flooding in these areas. 5. Moisture from Nate interacting with a frontal zone will also bring 2 to 5 inches of rain with isolated totals of 7 inches across the Ohio Valley and central Appalachians Sunday and Monday, which will increase the risk for flash flooding across these locations. FORECAST POSITIONS AND MAX WINDS INIT 08/0300Z 29.9N 89.1W 75 KT 85 MPH 12H 08/1200Z 32.1N 88.2W 50 KT 60 MPH...INLAND 24H 09/0000Z 35.7N 85.3W 35 KT 40 MPH...INLAND 36H 09/1200Z 39.3N 80.2W 25 KT 30 MPH...INLAND 48H 10/0000Z 42.1N 73.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 11/0000Z...DISSIPATED $$ Forecaster Berg
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