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Subtropical Depression SEVEN Forecast Discussion Number 1
2014-10-10 16:47:11| National Hurricane Center (Atlantic)
Issued at 1100 AM AST FRI OCT 10 2014 000 WTNT42 KNHC 101447 TCDAT2 SUBTROPICAL DEPRESSION SEVEN DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072014 1100 AM AST FRI OCT 10 2014 Satellite images indicate that the area of low pressure located several hundred miles north of the northern Leeward Islands has developed a large area of deep convection in a long curved band north and west of the center. First-light visible satellite imagery also indicates that the low-level center of the low has become better defined since yesterday. Satellite classifications are a subtropical 1.5 from TAFB and SAB at 1200 UTC, and the system's involvement with a nearby upper-level low and roughly 100 n mi radius of maximum winds also argue for a subtropical designation. An Air Force Hurricane Hunter aircraft will investigate the depression this afternoon to better assess its intensity and structure. The protective cover of the nearby upper low will provide a relatively low vertical wind shear environment in the short term, with the cyclone over warm sea surface temperatures of 28- 29 deg C. The model guidance indicates that the depression should become embedded in increasing southerly vertical shear east of the same upper-level trough after 24 hours, so the system has a short window for intensification or transformation into a tropical cyclone. Global models depict the cyclone becoming absorbed by a frontal zone over the north-central Atlantic before 72 hours. The NHC intensity forecast is close to the statistical-dynamical guidance. The depression is moving northwestward or 320/09 around the southwestern perhiphery of a mid-level ridge over the central Atlantic. The deep-layer steering flow around this feature should cause the cyclone to turn northward within 24 hours, after which it will turn northeastward in increasing southwesterly flow at the base of a longwave trough prior to absorption by the front. The NHC track forecast is very close to the multi-model consensus, TVCA, through- out the period and between the ECMWF and GFS model solutions. The Bermuda Weather Service has issued a tropical storm watch for Bermuda. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 23.8N 63.7W 30 KT 35 MPH 12H 11/0000Z 25.1N 64.6W 35 KT 40 MPH 24H 11/1200Z 26.8N 65.1W 40 KT 45 MPH 36H 12/0000Z 29.4N 64.7W 40 KT 45 MPH 48H 12/1200Z 31.5N 62.9W 40 KT 45 MPH 72H 13/1200Z...DISSIPATED $$ Forecaster Kimberlain
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