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Tropical Storm ORLENE Forecast Discussion Number 4
2016-09-11 22:33:33| National Hurricane Center (East Pacific)
Issued at 200 PM PDT SUN SEP 11 2016 000 WTPZ41 KNHC 112033 TCDEP1 TROPICAL STORM ORLENE DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL EP162016 200 PM PDT SUN SEP 11 2016 Visible, infrared, and microwave satellite images indicate that Orlene continues to become more organized. The cyclone has well-defined curved bands, and a recent SSMIS image showed that it has a mid-level eye feature. Dvorak estimates from TAFB and SAB are now T3.0/45 kt while the objective UW-CIMSS ADT is up to T3.5/55 kt. However, ASCAT data only showed maximum winds of 35-40 kt. Given this wide range, the initial intensity is raised to 45 kt for this advisory. Satellite data indicate that Orlene's center is a little bit northeast of the previous estimates, and the initial motion is now 310/12 kt. There are no changes to the forecast track reasoning. Orlene should turn northwestward and then northward and slow down drastically during the next 48 hours when it becomes positioned to the west of the subtropical ridge axis, and south of an amplifying trough over California. After 48 hours, the ridge will gradually restrengthen to the north of Orlene, forcing it toward the west with an increase in forward speed through the end of the forecast period. The official track forecast has been shifted a little northeast of the previous forecast to account for the repositioning of Orlene's center, but otherwise it still closely follows the TVCX multi-model consensus. Given Orlene's improved structure, as well as favorable sea surface temperatures and low shear, rapid intensification still looks like a possibility. The SHIPS guidance continues to indicate a 1-in-3 chance of a 30-kt increase during the next 24 hours, and the raw guidance itself brings Orlene to a hurricane in about 24 hours. The NHC intensity forecast continues to show a peak intensity close to the SHIPS and Florida State Superensemble in about 36 hours, which is at the top end of the guidance envelope. After 36 hours, Orlene's slow motion over sea surface temperatures between 26-27C is likely to lead to upwelling of colder water, and the cyclone is expected to gradually weaken through the end of the forecast period. This new forecast is essentially unchanged from the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 16.3N 117.7W 45 KT 50 MPH 12H 12/0600Z 17.0N 118.8W 55 KT 65 MPH 24H 12/1800Z 17.9N 119.6W 70 KT 80 MPH 36H 13/0600Z 18.6N 119.9W 80 KT 90 MPH 48H 13/1800Z 19.1N 119.9W 75 KT 85 MPH 72H 14/1800Z 19.5N 120.9W 70 KT 80 MPH 96H 15/1800Z 19.0N 124.0W 65 KT 75 MPH 120H 16/1800Z 19.0N 129.5W 60 KT 70 MPH $$ Forecaster Berg
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