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Tropical Storm NICOLE Forecast Discussion Number 25
2016-10-10 10:39:52| National Hurricane Center (Atlantic)
Issued at 500 AM AST MON OCT 10 2016 000 WTNT45 KNHC 100839 TCDAT5 TROPICAL STORM NICOLE DISCUSSION NUMBER 25 NWS NATIONAL HURRICANE CENTER MIAMI FL AL152016 500 AM AST MON OCT 10 2016 Nicole's overall convective pattern has changed little since the previous advisory, with most of the convection located in the eastern semicircle. However, during the past hour or two, a small burst of deep convection with tops to -80C has developed just east of the exposed low-level circulation center, signaling that dry air entrainment into the center of the cyclone has abated somewhat. Satellite current intensity (CI) estimates from TAFB and SAB remain 55 kt, and a late-arriving ASCAT-A pass indicated 45-kt surface winds in the western semicircle where no convection was present. Based on these data, the initial intensity remains 55 kt. Nicole is moving slowly northward and the initial motion estimate is 360/05 kt. The cyclone is expected to move slowly at around 5 kt for the next 72 hours, beginning with a motion toward the north today, followed by a turn to the north-northwest tonight, and a turn toward the northwest on Tuesday. By 36-48 hours, a break in the ridge to the north of Nicole is forecast to develop as a shortwave trough moves off of the U.S. east coast and erodes the blocking ridge. This should allow Nicole to move northward by 48 hours and turn toward the north-northeast and northeast by 72 hours. By 96 hours and beyond, the aforementioned shortwave trough is forecast to capture the cyclone and accelerate Nicole to the northeast over the north Atlantic. The global models are now in excellent agreement on this developing track scenario, but have unfortunately shifted farther west and are now much closer to Bermuda. The new NHC track forecast has been shifted westward as a result, but still lies east of the consensus model TVCN and the GFS-ECMWF solutions, which bring Nicole over or just west of Bermuda in about 84 hours. The combination of northerly shear and some additional modest dry air entrainment is expected to inhibit development today. However, by Tuesday the vertical wind shear is forecast by the GFS and ECMWF models to decrease to less than 10 kt, and remain low until about 72 hours. The low shear conditions and developing upper-level outflow pattern as depicted in the global and regional models, along with Nicole's already robust low- to mid-level circulations, should allow the cyclone to strengthen and regain hurricane status during that time. By 96 hours and beyond, southwesterly shear ahead of the shortwave trough is forecast to increase to 30-40 kt, which should induce steady weakening. Extratropical transition is possible by 120 hours, but most of the intensity guidance maintains Nicole as a tropical cyclone, which is reflected in the official forecast. The new intensity forecast closely follows the SHIPS intensity model, which appears to have a good handle on the timing of the reduction of the vertical shear and associated strengthening, and also remains above the intensity consensus model IVCN. The 34-kt wind radius was expanded in the northeastern quadrant based on 31-33 kt winds recently reported by NOAA Buoy 41049. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 25.0N 65.2W 55 KT 65 MPH 12H 10/1800Z 25.8N 65.3W 55 KT 65 MPH 24H 11/0600Z 26.6N 65.7W 60 KT 70 MPH 36H 11/1800Z 27.2N 66.2W 65 KT 75 MPH 48H 12/0600Z 27.8N 66.8W 75 KT 85 MPH 72H 13/0600Z 30.5N 66.0W 85 KT 100 MPH 96H 14/0600Z 34.5N 62.2W 80 KT 90 MPH 120H 15/0600Z 38.5N 56.3W 70 KT 80 MPH $$ Forecaster Stewart
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