ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Flossie Discussion Number 20 NWS National Hurricane Center Miami FL EP072019 1100 PM HST Thu Aug 01 2019 An 0646 UTC ASCAT-B overpass captured Flossie's entire tropical- storm-force wind field and confirmed that the structure remains asymmetric. Combining the scatterometer data and conventional infrared satellite images shows that Flossie's center is embedded just within the southwestern edge of -70 degree Celsius cloud tops. The initial intensity remains 60 kt, which is a blend of Dvorak CI numbers from TAFB and SAB, and just above the 55 kt shown by the ASCAT data (accounting for possible undersampling). Flossie just won't slow down, as the initial motion is still west-northwestward, or 285/16 kt. The subtropical ridge to the north remains strong, and this should keep Flossie on the west- northwestward trajectory for the next 3 days, although the track models insist that the current speed should decrease a bit. After day 3, a deepening upper-level low north and northwest of the Hawaiian Islands should cause Flossie to turn northwestward and then northward on days 4 and 5. The NHC official forecast depicts such a scenario, but this is where the forecast has the most uncertainty. All of the global models and most of the consensus models show Flossie recurving northeast of the Hawaiian Islands, while the regional HWRF and HMON models, as well as the Florida State Superensemble, are depicting a more southern solution with less recurvature. Despite these southern solutions, the new NHC forecast is relatively unchanged from the previous one and is very close to the HCCA and TVCX consensus aids. Nearly steady shear of 15 kt and ocean temperatures around 27 degrees Celsius should keep Flossie's intensity relatively steady for the next 12 hours or so. After that time, deep-layer shear is expected to steadily increase to at least 30 kt by 48 hours while Flossie also moves over a relative minimum in sea surface temperatures just under 26 degrees Celsius. These factors are likely to contribute to steady weakening, and there is relatively little spread among the intensity models in showing this scenario. The updated NHC intensity forecast has been lowered slightly from the previous one and shows Flossie becoming a tropical depression in 4 days. On the forecast track, Flossie will be moving into the central Pacific basin in 12-24 hours, at which point the Central Pacific Hurricane Center will assume forecast responsibilities. In the meantime, users should continue to consult local forecasts from the National Weather Service Forecast Office in Honolulu, Hawaii, at www.weather.gov/hfo for information specific to the Hawaiian Islands. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 16.8N 136.4W 60 KT 70 MPH 12H 02/1800Z 17.2N 138.7W 60 KT 70 MPH 24H 03/0600Z 17.9N 141.7W 55 KT 65 MPH 36H 03/1800Z 18.5N 144.3W 50 KT 60 MPH 48H 04/0600Z 19.0N 146.6W 45 KT 50 MPH 72H 05/0600Z 20.3N 151.3W 35 KT 40 MPH 96H 06/0600Z 23.5N 155.0W 30 KT 35 MPH 120H 07/0600Z 28.0N 156.0W 30 KT 35 MPH $$ Forecaster Berg NNNN