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Tropical Storm Douglas Forecast Discussion Number 5
2020-07-21 16:38:44| National Hurricane Center (East Pacific)
Issued at 500 AM HST Tue Jul 21 2020 000 WTPZ43 KNHC 211438 TCDEP3 Tropical Storm Douglas Discussion Number 5 NWS National Hurricane Center Miami FL EP082020 500 AM HST Tue Jul 21 2020 A recent SSMIS microwave pass indicated that Douglas's low-level center is located very near the head of a broken band of convection which curls around the southern, western, and northern side of the circulation. This center is also now embedded beneath a Central Dense overcast in infrared imagery, near an area of cold overshooting cloud tops. TAFB and SAB Dvorak classifications have both risen to T3.5, and Douglas's initial intensity is therefore raised to 55 kt. Douglas continues to dip west-southwestward, or 255/13 kt, due to strong mid-level ridging to its north. A mid- to upper-level low located northeast of the Hawaiian Islands is forecast to retrograde westward over the next few days, which will allow the ridge to take on a more east-west orientation. As a result, Douglas is expected to turn westward later today and then move west-northwestward beginning overnight Wednesday into the weekend. The track guidance all agrees on this scenario, but there are some speed differences, bookended by slower GFS and HWRF solutions and a faster ECMWF solution. Overall, however, the new NHC forecast remains very close to the multi-model consensus aids, and no significant changes were made compared to the previous forecast, except maybe a slight northward adjustment on days 4 and 5. The low-shear, warm sea surface temperature environment within which Douglas is moving is a recipe for continued strengthening, potentially at a rapid rate, for the next 48 hours. The intensity guidance has been trending higher, and the latest SHIPS Rapid Intensification (RI) indices are highlighting the increased chance of RI. For example, there is currently a 50/50 shot that Douglas's winds will increase by 25 kt within the next 24 hours, and a 40-50 percent chance of a 30-kt increase during that period. Based on this guidance, the new HCCA and Florida State Superensemble solutions, and the intensity consensus, the NHC intensity forecast has been increased from the previous cycle and now shows Douglas becoming a hurricane later today with a higher peak occurring in about 2 days. Since oceanic heat content falls to zero along Douglas's path by day 3, some gradual weakening is shown in the latter stages of the forecast. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 12.4N 124.2W 55 KT 65 MPH 12H 22/0000Z 12.1N 126.0W 70 KT 80 MPH 24H 22/1200Z 12.1N 128.5W 80 KT 90 MPH 36H 23/0000Z 12.6N 131.0W 85 KT 100 MPH 48H 23/1200Z 13.6N 133.7W 90 KT 105 MPH 60H 24/0000Z 14.9N 136.5W 85 KT 100 MPH 72H 24/1200Z 16.1N 139.4W 75 KT 85 MPH 96H 25/1200Z 18.0N 145.5W 65 KT 75 MPH 120H 26/1200Z 18.5N 151.5W 55 KT 65 MPH $$ Forecaster Berg
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