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Hurricane Norman Forecast Discussion Number 17
2018-09-01 10:34:06| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Sat Sep 01 2018 873 WTPZ41 KNHC 010834 TCDEP1 Hurricane Norman Discussion Number 17 NWS National Hurricane Center Miami FL EP162018 200 AM PDT Sat Sep 01 2018 Norman continues to weaken due to the effects of moderate northeasterly shear of about 20 kt, as analyzed in SHIPS diagnostics. The hurricane has taken on a traditional IR shear pattern structure, with a tight gradient of brightness temperatures observed up-shear of the estimated center position. Satellite intensity estimates have continued to drop and no longer support keeping Norman at major hurricane strength. The initial intensity has been lowered to 95 kt, just above the latest SATCON estimate, but this still could be generous. The shear affecting Norman is expected to continue for at least the next 24 h. Some of the dynamical models hint that the shear could relax between 24-48 h, which would likely bring an end to Norman's weakening trend. While it is not explicitly reflected in the intensity forecast, a decrease in shear could even allow the hurricane to briefly restrengthen. Recent microwave imagery indicates that the mid- to lower-level inner-core and eye of Norman are still intact. If this structure can survive the next 24 h of shear, reintensification would be more likely. By 72 h, the hurricane will reach drier, more stable air and moderate SSTs, and these factors will likely cause it to steadily weaken through the remainder of the forecast period. The cyclone appears to have finally turned westward, and the initial motion is 265/7 kt. No significant changes have been made to the track forecast. Norman is still expected to move westward to west-northwestward for the next several days, steered primarily by an extensive deep-layer ridge to the north. The models remain in good agreement on the track of Norman throughout the forecast period, and the official track forecast is near the middle of the guidance envelope and very close to the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 01/0900Z 16.3N 123.0W 95 KT 110 MPH 12H 01/1800Z 16.3N 124.4W 85 KT 100 MPH 24H 02/0600Z 16.6N 126.8W 85 KT 100 MPH 36H 02/1800Z 17.3N 129.8W 85 KT 100 MPH 48H 03/0600Z 18.2N 132.9W 85 KT 100 MPH 72H 04/0600Z 19.9N 139.1W 70 KT 80 MPH 96H 05/0600Z 21.0N 143.5W 65 KT 75 MPH 120H 06/0600Z 21.5N 147.0W 60 KT 70 MPH $$ Forecaster Zelinsky
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