ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Norma Discussion Number 5 NWS National Hurricane Center Miami FL EP172017 900 AM MDT Fri Sep 15 2017 Norma has an elongated convective band that curls about three quarters of the way around the low-level center. A well-defined low-level ring was visible in recent 37-GHz SSMIS imagery, indicating that the cyclone's structure continues to improve. The initial intensity is raised to 55 kt based on a blend of Dvorak estimates which range from 50 kt (UW-CIMSS ADT) to 65 kt (TAFB). Norma is essentially drifting toward the north-northwest with an initial motion of 340/2 kt. There's not a whole lot more clarity on Norma's eventual track compared to yesterday. The most that can be said is that Norma will continue to drift northwestward or northward for the next 24-36 hours. After that time, there remains considerable spread in the track guidance. The ECMWF and UKMET models, which maintain a stronger ridge over northwestern Mexico, push Norma northwestward to the west of the Baja California peninsula through day 5. The GFS and HWRF models, as well as the consensus aids, remain closer to the Baja California peninsula and show a northeastward turn by day 5. The NHC track forecast remains close to the TVCN consensus and is a little slower than, but on top of, the previous NHC forecast. Low shear and warm ocean temperatures should foster continued strengthening, with Norma forecast to become a hurricane by this evening. Norma is then expected to continue strengthening through 36 or 48 hours. Some southwesterly shear could begin to affect the cyclone by day 3 as it approaches stronger mid-latitude westerly flow, and some weakening is forecast as Norma approaches the Baja California peninsula. The new NHC intensity forecast mirrors the trend shown in the previous advisory, and is just a little higher due to the updated initial intensity. This forecast is generally close to HCCA and the ICON intensity consensus. A hurricane or tropical storm watch will likely be necessary for portions of the southern Baja California peninsula later today. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 18.7N 109.7W 55 KT 65 MPH 12H 16/0000Z 18.9N 109.9W 65 KT 75 MPH 24H 16/1200Z 19.2N 110.0W 70 KT 80 MPH 36H 17/0000Z 19.9N 110.1W 75 KT 85 MPH 48H 17/1200Z 20.8N 110.3W 75 KT 85 MPH 72H 18/1200Z 23.0N 111.5W 65 KT 75 MPH 96H 19/1200Z 24.5N 112.0W 50 KT 60 MPH 120H 20/1200Z 26.5N 110.5W 35 KT 40 MPH $$ Forecaster Berg NNNN
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Page last modified: Sunday, 31-Dec-2017 12:10:38 UTC