WTNT43 KNHC 141500 TCDAT3 HURRICANE GONZALO DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 1100 AM AST TUE OCT 14 2014 Data from an Air Force Reserve Hurricane Hunter aircraft and the San Juan Doppler weather radar indicate that the earlier intensification process has abated, which is apparently due to some shear-induced disruption of the eye. Maximum 700 mb flight-level winds observed thus far are 112 kt and maximum SFMR winds through most of the morning have been around 93 kt. The central pressure has also leveled off during the past few hours at around 973 mb. A blend of the flight-level surface-wind conversion and SFMR winds support maintaining an intensity of 95 kt. Gonzalo continues to move northwestward with a motion of 315/11 kt. There is no significant change to the previous forecast track or reasoning. The NHC model guidance is in excellent agreement on the hurricane continuing to move northwestward around the southwestern for periphery of a deep-layer ridge the during the next 36 hours. After that, the western portion of the ridge is expected to weaken as a strong mid-latitude trough and associated cold front currently located over the southeastern U.S. moves eastward across the Bahamas by 48 hours. The increasing southwesterly flow ahead of those systems should gradually accelerate Gonzalo toward the northeast, with the cyclone potentially threatening Bermuda in about three days time. Gonzalo is expected to merge with the strong cold front or become extratropical by 120 hours. The new track forecast is similar to the previous advisory track, and lies close to a blend of the GFEX and TVCA consensus models. Recent radar and satellite data indicate that the eye of Gonzalo has been clearing out and gradually becoming better defined with a diameter of about 20 nmi. Once the eyewall stabilizes again, intensification will likely resume, and in fact the reconnaissance aircraft a few moments ago observed an SFMR wind of 99 kt that suggests this intensification is beginning. Buoy data indicate that water temperatures are slightly cooler than what the SHIPS model is indicating, probably due to cold upwelling created by the wake of former Hurricane Fay, but they are still sufficiently warm enough to support a category 4 hurricane. The best vertical shear conditions and upper-level outflow regime are expected to occur on Wednesday and into Thursday morning, and that is when Gonzalo is expected to strengthen into a category 4 hurricane. Afterwards, eyewall cycles and possible cold upwelling beneath the hurricane are likely to cause some fluctuations in the intensity. By 72 hours, increasing southwesterly wind shear ahead of the aforementioned deep trough and strong cold front is expected to induce weakening. By 120 hours, Gonzalo should be over cold waters of the North Atlantic and experiencing vertical shear of more than 50 kt, which should result in the cyclone becoming a extratropical low. The NHC intensity forecast is similar to the previous advisory and is above all of the available intensity guidance. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 20.3N 65.2W 95 KT 110 MPH 12H 15/0000Z 21.7N 66.4W 100 KT 115 MPH 24H 15/1200Z 23.3N 67.8W 110 KT 125 MPH 36H 16/0000Z 24.6N 68.6W 120 KT 140 MPH 48H 16/1200Z 26.1N 68.6W 115 KT 130 MPH 72H 17/1200Z 30.4N 66.5W 105 KT 120 MPH 96H 18/1200Z 37.4N 62.6W 90 KT 105 MPH 120H 19/1200Z 46.8N 53.8W 70 KT 80 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart
Posted on: Tue, 14 Oct 2014 18:13:11 +0000
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