ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM HURRICANE SANDRA DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL EP222015 200 PM MST FRI NOV 27 2015 Geostationary and microwave imagery indicate that the low-level center of Sandra has begun to separate from the mid-level circulation. This is due to vertical shear of 30 to 35 kt, which is forecast to increase further tonight. Dvorak estimates continue to decrease as the deep convection wanes and separates from the center, and the initial intensity has been conservatively lowered to 70 kt based on a blend of the latest Final-T and CI numbers from TAFB and SAB. Quick weakening is forecast, and Sandra should weaken to a tropical storm in the next 12 hours and become a tropical depression or remnant low in 24-36 hours before dissipating. The new NHC intensity forecast is close to the latest SHIPS model. The low-level center has wobbled to the left during the past couple of hours, but a long-term initial motion estimate is 020/09. As Sandra shears apart, the guidance envelope has shifted to the left this cycle, with the exception of the HWRF. The new NHC track has been adjusted a little to the left of the previous one now that the cyclone is starting to weaken more quickly, and the NHC forecast is close to the latest ECMWF solution. If Sandra decouples faster than anticipated, the low-level circulation could move to the left of the new forecast track and even dissipate entirely before the center reaches the coast. However, the main threat of heavy rainfall over a large part of west-central Mexico will occur regardless of the details of the track and intensity forecast. The remnant mid- and upper-level moisture associated with Sandra will contribute to a significant precipitation event expected to occur over portions of the south-central United States this weekend. For more information, please see products from the NOAA Weather Prediction Center and local NWS Weather Forecast Offices. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 20.4N 108.4W 70 KT 80 MPH 12H 28/0600Z 22.1N 107.8W 50 KT 60 MPH 24H 28/1800Z 23.8N 107.2W 30 KT 35 MPH 36H 29/0600Z 25.5N 106.6W 20 KT 25 MPH...POST-TROP/INLAND 48H 29/1800Z...DISSIPATED $$ Forecaster Brennan NNNN
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Page last modified: Thursday, 31-Dec-2015 12:10:00 UTC