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Tropical Storm Hilda Forecast Discussion Number 21
2021-08-04 22:34:47| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Wed Aug 04 2021 000 WTPZ43 KNHC 042034 TCDEP3 Tropical Storm Hilda Discussion Number 21 NWS National Hurricane Center Miami FL EP082021 200 PM PDT Wed Aug 04 2021 Convection associated with Hilda continues to weaken and shrink in areal coverage due to modest northwesterly vertical wind shear, sub-25C sea-surface temperatures (SSTs), and entrainment of stable, cold-air stratocumulus clouds. A 1656Z partial ASCAT-A scatterometer pass revealed two 33-kt vectors in the southeastern quadrant in the radius-of-maximum winds. Even allowing for some undersampling, this indicates that Hilda is barely hanging on to tropical storm status, and the initial intensity will remain at 35 kt for this advisory. Model analyses show virtually no instability in the center of and north of Hilda right now, and with the cyclone forecast to move over even cooler water and into increasing westerly wind shear during the next 12-24 hours, a rapid decrease in both the convection and cyclone's intensity appears to be forthcoming soon. Hilda is forecast to become a depression later tonight and a remnant low on Thursday. Dissipation is expected by late Friday or Saturday well to the east of the Hawaiian Islands. The latest NHC official intensity forecast is similar to the previous advisory, and follows a blend of the HCCA and IVCN consensus intensity models. Hilda continues on a steady west-northwestward course or 295/08 kt. This general motion is expected to continue into Thursday, followed by a more westward motion on Friday and Saturday as a low- to mid-level ridge builds to north of Hilda on days 2 and 3. The official NHC track forecast is essentially just an update of the previous advisory track, and lies along the southern edge of the guidance envelope between the tightly packed consensus track models to the north and the ECMWF model to the south. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 19.4N 128.0W 35 KT 40 MPH 12H 05/0600Z 20.0N 129.4W 30 KT 35 MPH 24H 05/1800Z 21.0N 131.4W 25 KT 30 MPH 36H 06/0600Z 21.8N 133.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 06/1800Z 22.4N 136.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 07/0600Z 23.0N 138.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 07/1800Z...DISSIPATED $$ Forecaster Stewart
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