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Tropical Storm Ignacio Forecast Discussion Number 5
2021-08-02 22:34:03| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Mon Aug 02 2021 000 WTPZ45 KNHC 022033 TCDEP5 Tropical Storm Ignacio Discussion Number 5 NWS National Hurricane Center Miami FL EP102021 300 PM MDT Mon Aug 02 2021 Ignacio appears to have peaked in intensity, with moderate-to- strong northeasterly vertical wind shear having displaced most of the deep convection into the southwestern semicircle of the cyclone. The latest subjective satellite current intensity estimates from TAFB and SAB remain at T2.5/35 kt, and objective estimates from UW-CIMSS ADT and SATCON are 37 kt and 38 kt, respectively. Based on these data, the intensity has been held at 35 kt, which could be generous. The center of Ignacio passed 15-20 nmi northeast of Clarion Island, Mexico, where the pressure fell to 1006.5 mb around 1400 UTC and the highest winds measured were sustained 22 kt gusting to 33 kt according to a Mexican navy observing station on the island. A pronounced wind shift from the northeast to the southwest and west was also noted in the wind data. However, wind speeds have been steadily decreasing over the past several hours, an indication that the strongest winds are likely occurring in the northeastern quadrant. Unfortunately, all three ASCAT passes again missed the center and the strongest winds associated with Ignacio. The initial motion estimate is 300/08 kt. No significant changes were required to the previous track forecast. Ignacio is forecast to maintain a west-northwestward motion between a strong mid-/upper-level ridge to the north and Hurricane Hilda to the southwest throughout the short forecast period. The new advisory track forecast is similar the previous forecast track, and lies along the left side of the consensus track models envelope. Ignacio is expected to gradually weaken during the next 48 hours due to steadily increasing northeasterly vertical wind shear in excess of 25 kt by 24 hours and beyond. By 18-24 hours, Ignacio will be moving over sub-26C sea-surface temperatures, which will act to hasten the weakening process, with dissipation expected by 60 hours, if not sooner. The new NHC intensity forecast is similar to the previous advisory and a blend of the NOAA-HCCA and IVCN consensus intensity models. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 18.8N 114.9W 35 KT 40 MPH 12H 03/0600Z 19.5N 116.0W 30 KT 35 MPH 24H 03/1800Z 20.4N 117.2W 25 KT 30 MPH 36H 04/0600Z 21.2N 118.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 04/1800Z 21.2N 118.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 05/0600Z...DISSIPATED $$ Forecaster Stewart
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