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Tropical Storm ORLENE Forecast Discussion Number 3
2016-09-11 16:41:02| National Hurricane Center (East Pacific)
Issued at 800 AM PDT SUN SEP 11 2016 000 WTPZ41 KNHC 111440 TCDEP1 TROPICAL STORM ORLENE DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP162016 800 AM PDT SUN SEP 11 2016 A central dense overcast has become established over Orlene's center, with very cold temperatures of -86C at cloud top level. There is little to no deep-layer shear, and the cyclone has very good upper-level outflow, especially to the north and west. Because the Dvorak rules don't yet allow the use of an embedded center pattern, estimates from TAFB and SAB are still at T2.5. However, the objective UW-CIMSS ADT is higher, and given the more consolidated structure compared to six hours ago, the initial intensity is raised to 40 kt. Orlene is moving northwestward, or 305/12 kt, to the southwest of a mid-tropospheric high located over northern Mexico. Over the next few days, Orlene is expected to become trapped in an environment of weak steering to the west of the subtropical ridge axis and south of an amplifying trough over California. This should cause the cyclone to turn north-northwestward and slow to a crawl by days 2 and 3. After that time, a re-establishment of the ridge should force an acceleration toward the west on days 4 and 5. There is not much spread among the track models during the entire forecast period. Except for a slight northeastward shift at 36 and 48 hours, the updated NHC forecast is nearly identical to the previous one and lies closest to the TVCX multi-model consensus and Florida State Superensemble. Low shear and warm sea surface temperatures are expected to support additional strengthening, and there are signs that rapid intensification could occur. There is a 1-in-3 chance of a 30-kt intensity increase during the next 24 hours, and several intensity models bring Orlene near or to hurricane strength in about 24 hours. Given the seemingly favorable environment, the NHC intensity forecast is closest to the most aggressive intensity models like the Florida State Superensemble, and it is higher than the previous forecast during the first 48 hours. Orlene's intensity could be limited once it slows down in 48-72 hours due to upwelling of colder water, and thus the official forecast shows gradual weakening after day 2. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 15.4N 116.8W 40 KT 45 MPH 12H 12/0000Z 16.2N 118.2W 50 KT 60 MPH 24H 12/1200Z 17.1N 119.4W 65 KT 75 MPH 36H 13/0000Z 17.9N 120.0W 80 KT 90 MPH 48H 13/1200Z 18.5N 120.2W 80 KT 90 MPH 72H 14/1200Z 19.1N 120.9W 75 KT 85 MPH 96H 15/1200Z 19.0N 123.5W 70 KT 80 MPH 120H 16/1200Z 18.5N 128.5W 65 KT 75 MPH $$ Forecaster Berg
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