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Tropical Storm Hernan Forecast Discussion Number 7
2020-08-27 22:34:16| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Thu Aug 27 2020 000 WTPZ43 KNHC 272034 TCDEP3 Tropical Storm Hernan Discussion Number 7 NWS National Hurricane Center Miami FL EP132020 300 PM MDT Thu Aug 27 2020 Hernan has had a rather ragged appearance today with intermittent convection firing around, but never really over the center. There were no ASCAT overpasses during the day that directly sampled the system's circulation. The latest Dvorak intensity estimates from TAFB and SAB support 35 kt and 30 kt, respectively, while the UW-CIMSS ADT and SATCON numbers range from 30 to 40 kt. Based on a blend of these values, the initial intensity is being lowered to 35 kt. Hernan should at least maintain its current strength through tonight as it remains over very warm waters while battling moderate easterly shear. This shear is not forecast to abate during the forecast period. And by 24 h, the cyclone is expected to begin moving over progressively cooler waters. The combination of these two factors should induce a weakening trend. By 60 h, simulated satellite imagery by global models suggest that the cyclone will become devoid of deep convection. After that time, the remnant low is expected to be absorbed within the broader circulation of Iselle to its west. The latest NHC intensity forecast is in agreement with the various intensity consensus aids. Hernan is now moving northwest at about 5 kt. There is no change to the track forecast reasoning. Hernan is expected to remain caught within a large-scale, eastern North Pacific cyclonic gyre during the next few days, which will result in Hernan moving counter-clockwise around the eastern and northern periphery of the gyre. The cyclone is expected to continue to parallel the coast of southwestern Mexico through this evening and should begin to increase its forward speed tonight. A turn to the west-northwest then west is forecast Friday through Friday night. The westward motion should continue until the system becomes absorbed early next week. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 19.6N 106.5W 35 KT 40 MPH 12H 28/0600Z 20.7N 107.6W 35 KT 40 MPH 24H 28/1800Z 21.6N 109.4W 30 KT 35 MPH 36H 29/0600Z 22.3N 111.1W 30 KT 35 MPH 48H 29/1800Z 22.5N 113.0W 25 KT 30 MPH 60H 30/0600Z 22.6N 114.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 30/1800Z...ABSORBED $$ Forecaster Latto
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