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#768552 (Received by flhurricane at: 11:07 AM 08.May.2015) TCDAT1 SUBTROPICAL STORM ANA DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012015 1100 AM EDT FRI MAY 08 2015 Satellite images indicate that Ana is starting to show signs of transforming into a tropical storm, with a more compact structure and tighter convective bands near the center. In addition, aircraft reconnaissance data indicate that the maximum wind band is becoming sharper and migrating inward. The storm still has less-intense convection than most tropical cyclones, however, and is still co-located with an upper-level low; consequently Ana remains best classified as subtropical for now. The maximum winds are estimated to be 40 kt based on the SFMR and flight-level data. Ana has been meandering for the past several hours under a blocking ridge along the U.S. east coast, although recently the storm has drifted eastward toward a convective burst. This ridge will slowly move eastward over the next couple of days, which should steer the storm generally slowly northwestward. Model guidance is in good agreement in bringing Ana to the coast of the Carolinas in about two days. After that, a strong trough should cause Ana to move more quickly to the north and east late Sunday and into early next week. No significant changes were required to the previous forecast track, which remains close to the model consensus. Extratropical transition is anticipated in about four days - in line with the global model guidance. Some strengthening of Ana is possible since the cyclone is embedded within an environment of cold upper-level temperatures, leading to more thunderstorms than one would expect over the marginally warm waters. However, there is quite a bit of dry air around the storm, which could help limit convection. Most of the guidance shows some intensification during the next day or so, and the official forecast does the same. As Ana approaches the coast, some weakening seems probable due to the storm moving over cooler shelf waters. The latest NHC forecast is close to the previous one, although a little higher at 36 and 48 hr to reflect the latest guidance. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 31.5N 77.3W 40 KT 45 MPH 12H 09/0000Z 31.8N 77.5W 45 KT 50 MPH 24H 09/1200Z 32.1N 77.8W 45 KT 50 MPH 36H 10/0000Z 32.6N 78.3W 45 KT 50 MPH 48H 10/1200Z 33.2N 78.9W 40 KT 45 MPH 72H 11/1200Z 35.1N 78.2W 30 KT 35 MPH...INLAND 96H 12/1200Z 39.0N 72.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 13/1200Z 44.5N 57.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake |