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Hurricane Florence Forecast Discussion Number 27
2018-09-06 04:50:14| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Wed Sep 05 2018 550 WTNT41 KNHC 060250 TCDAT1 Hurricane Florence Discussion Number 27 NWS National Hurricane Center Miami FL AL062018 1100 PM AST Wed Sep 05 2018 It appears that southwesterly shear is finally affecting Florence. The cloud pattern has become asymmetric this evening, with the northeastern quadrant growing at the expense of the southwestern one, along with warming cloud tops noted across the central dense overcast. Satellite intensity estimates are a bit lower than before, so the initial wind speed is reduced to 110 kt. The current shear is forecast to persist by the global models during the next day or two until an upper-level low cuts off to south of Florence, which will likely reduce the shear. This, in combination with much warmer waters in the path of the hurricane, should set the stage for restrengthening. At long range, a rather large upper-level anticyclone is forecast to form near Florence, which would provide ample opportunity for the hurricane to regain its former strength and grow in size. Thus, the official forecast shows slow weakening in response to the initial shear, then levels off, with a significant increase in strength predicted by day 5. This solution is very close to the previous NHC advisory, but not quite as high as the HWRF and HMON models at long range. Florence has been moving more to the right during the past several hours, likely due to the vortex attempting to stay vertically aligned in the face of the southwesterly shear, but a longer-term motion is 310 degrees at 10 kt. A mid-level ridge is forecast to strengthen to the north and northwest of Florence, causing the hurricane to turn west- northwestward by Friday and even westward by the weekend. It appears that a mid-latitude trough over the northwestern Atlantic in a few days will likely miss Florence, with the only perceivable effects on the hurricane being a decrease in forward speed. The net result is that the model guidance continues to trend westward at long range, and the official forecast follows suit, lying just north of the model consensus in deference to the ECMWF deterministic model and ensemble mean. It should be noted that there is still considerable model ensemble spread for Florence's track beyond day 5. Given the large uncertainty at these time ranges, it is far too soon to speculate what, if any, impacts Florence may have on the U.S. East Coast next week. Regardless of Florence's eventual track, large swells emanating from the hurricane will reach Bermuda beginning on Friday, resulting in life-threatening surf and rip currents on the island. Swells from Florence could also reach the U.S. East Coast by early next week. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 23.4N 47.2W 110 KT 125 MPH 12H 06/1200Z 24.2N 48.4W 105 KT 120 MPH 24H 07/0000Z 25.0N 49.9W 100 KT 115 MPH 36H 07/1200Z 25.5N 51.6W 95 KT 110 MPH 48H 08/0000Z 25.7N 53.2W 95 KT 110 MPH 72H 09/0000Z 26.1N 55.7W 100 KT 115 MPH 96H 10/0000Z 27.2N 58.1W 105 KT 120 MPH 120H 11/0000Z 29.0N 62.0W 115 KT 130 MPH $$ Forecaster Blake
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