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Subtropical Storm Joyce Forecast Discussion Number 2
2018-09-13 04:45:15| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Wed Sep 12 2018 610 WTNT45 KNHC 130245 TCDAT5 Subtropical Storm Joyce Discussion Number 2 NWS National Hurricane Center Miami FL AL102018 1100 PM AST Wed Sep 12 2018 Joyce still has subtropical characteristics. Although a small area of convection has recent developed near the storm's center, cloud tops are not particularly cold and the cyclone is still co-located with an upper-level low. The initial intensity has been held at 40 kt based on a subtropical intensity estimate of 35-40 kt from TAFB. This could be generous estimate since a recent near-miss of the ASCAT instrument to the west of Joyce suggested that the winds may have decreased somewhat since earlier today. Little change has been made to the track or intensity forecast. Just about all of the intensity guidance continues to indicate that some gradual strengthening is possible during the next day or two while Joyce continues to acquire tropical characteristics. By 72 h, the global and statistical models depict Joyce weakening due to a drastic increase in shear and a decrease in environmental humidity until it is absorbed into a larger mid-latitude trough around 96 h. The HWRF and HMON models show a very different solution where Joyce strengthens to hurricane strength despite the marginal environment. This scenario seems less likely at this time, so the NHC intensity forecast is just below the intensity consensus beyond 36 h. Joyce is caught in fairly light steering currents between strong ridges to its east and west, and the initial motion estimate is 220/5 kt. All of the global models forecast only a slow southwestward motion during the next couple of days, particularly as Hurricane Helene approaches from the southeast. Once Helene passes to the east, Joyce will likely quickly turn northeastward and accelerate ahead of the aforementioned mid-latitude trough before dissipating southwest of the Azores. The official track forecast is basically a blend of the previous advisory and the corrected consensus aids HCCA and FSSE. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 34.1N 42.6W 40 KT 45 MPH 12H 13/1200Z 33.5N 43.3W 40 KT 45 MPH 24H 14/0000Z 32.9N 43.8W 45 KT 50 MPH...TROPICAL STORM 36H 14/1200Z 32.5N 44.0W 50 KT 60 MPH 48H 15/0000Z 32.3N 43.4W 50 KT 60 MPH 72H 16/0000Z 34.2N 40.0W 45 KT 50 MPH 96H 17/0000Z 37.0N 33.5W 40 KT 45 MPH 120H 18/0000Z...DISSIPATED $$ Forecaster Zelinsky
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