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Hurricane NORBERT Forecast Discussion Number 8
2014-09-04 10:51:22| National Hurricane Center (East Pacific)
Issued at 200 AM PDT THU SEP 04 2014 000 WTPZ44 KNHC 040851 TCDEP4 HURRICANE NORBERT DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP142014 200 AM PDT THU SEP 04 2014 Recent microwave images, including a NASA GPM overpass at 0516 UTC, indicate that Norbert has lost some organization during the past few hours due to easterly vertical wind shear. The low-level center is in the northeastern part of the central convection with a mid-level eye displaced to the southwest of the low-level center. Satellite intensity estimates from TAFB and SAB are unchanged at 77 and 65 kt, and the CIMSS Advanced Dvorak Technique estimates an intensity of 65 kt. Based on these data, the initial intensity remains 70 kt. The microwave data indicate that the center of Norbert made a northward turn since the previous advisory. The initial motion is a somewhat uncertain 325/5. Norbert should continue on a general northwestward motion during the next three days around the southwestern periphery of a mid-level ridge that extends westward across northern Mexico. This part of the forecast track has been nudged to the east based on the current position and motion. After 72 hours, the guidance becomes more divergent due to disagreements in how Norbert interacts with a mid/upper-level trough over the northeastern Pacific. The GFS and NAVGEM forecast Norbert to turn northward, while the ECMWF is forecasting a westward turn and a slower forward speed. The other models are spread between these extremes. The later part of the new track forecast is similar to the previous advisory, and is showing a slow northward motion as a compromise between the extremes. The dynamical models now suggest that moderate shear should continue for the next 24-36 hours, and as a result the intensity guidance shows less strengthening than 6 hours ago. The new intensity forecast is thus nudged downward. Norbert should start weakening by 48 hours as it reaches cooler sea surface temperatures, and the system is forecast to degenerate to a remnant low by the end of the forecast period. The new intensity forecast is in best agreement with the intensity consensus. Moisture indirectly related to Norbert being pulled northward around the eastern side of the cyclone's large circulation is expected to spread across northern Mexico and into the southwestern United States during the next few days. This could result in heavy rains and life-threatening flash flooding in these areas. Please see information from your local weather office for more details. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 20.5N 109.7W 70 KT 80 MPH 12H 04/1800Z 21.2N 110.4W 75 KT 85 MPH 24H 05/0600Z 22.2N 111.4W 80 KT 90 MPH 36H 05/1800Z 23.1N 112.4W 80 KT 90 MPH 48H 06/0600Z 23.9N 113.6W 70 KT 80 MPH 72H 07/0600Z 25.5N 116.0W 55 KT 65 MPH 96H 08/0600Z 27.5N 118.0W 35 KT 40 MPH 120H 09/0600Z 29.0N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven
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