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| #799713 (Received by flhurricane at: 4:41 AM 31.Aug.2015) TCDAT1 HURRICANE FRED DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062015 500 AM AST MON AUG 31 2015 Fred's overall cloud pattern has only changed slightly since the previous advisory. However, the inner-core convection has increased markedly, including the development of a well-defined, vertically deep, 15 n mi diameter eye as noted in recent AMSR and AMSU passive microwave satellite data. Upper-level outflow is good in all quadrants. The initial intensity has been increased to 70 kt based on a blend of satellite intensity estimates of T4.0/65 kt from TAFB, a UW-CIMSS ADT value of T4.4/75 kt, and a NHC objective Dvorak T-number of T4.5/77 kt. Fred has maintained a steady northwestward motion but has slowed down some, and is now moving 305/10 kt. The track forecast and rationale remain unchanged from the previous advisory. Water vapor-derived winds indicate that the break in the subtropical ridge to the northwest of the Cape Verde Islands is beginning to fill in based on previous southwesterly winds now having been replaced by east-northeasterly mid- to upper-level winds. Fred is expected to continue its northwestward motion for the next 12-24 hours and pass near or over the Cape Verde Islands of Boa Vista this morning, and over or near Sao Nicolau, Sao Vicente, and Santo Antao late this afternoon and into tonight. As the ridge builds steadily westward to the north of Fred, the hurricane should gradually turn toward the west-northwest by 36 hours and beyond. This will bring the cyclone over progressively cooler waters and into increasing vertical wind shear conditions. The official forecast track is just an update of the previous advisory track, and lies close to the consensus of the GFS and ECMWF model tracks. The vertical shear is expected to remain quite low at less than 5 kt for the next 12 hours as Fred is passing through the Cape Verde Islands archipelago. With ocean temperatures remaining above 27 deg C during that time, some additional strengthening is possible. After the hurricane clears the Cape Verde Islands, however, the combination of decreasing SSTs, decreasing mid-level moisture, and increasing west-southwesterly vertical wind shear should induce a gradual weakening trend. The NHC intensity forecast is similar to the previous advisory and closely follows the IVCN consensus model through 36 hours, and is lower than IVCN from 48-120 hours. Please note that the track/cone graphic, an automatically generated product, does not have the capability of displaying warnings for the Cape Verde Islands. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 15.6N 22.9W 70 KT 80 MPH 12H 31/1800Z 16.6N 24.3W 75 KT 85 MPH 24H 01/0600Z 17.9N 26.1W 70 KT 80 MPH 36H 01/1800Z 19.0N 28.0W 65 KT 75 MPH 48H 02/0600Z 19.7N 29.8W 55 KT 65 MPH 72H 03/0600Z 20.8N 33.4W 45 KT 50 MPH 96H 04/0600Z 22.0N 36.9W 35 KT 40 MPH 120H 05/0600Z 23.0N 40.0W 30 KT 35 MPH $$ Forecaster Stewart |
