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Hurricane GONZALO Forecast Discussion Number 13
2014-10-15 16:54:39| National Hurricane Center (Atlantic)
Issued at 1100 AM AST WED OCT 15 2014 000 WTNT43 KNHC 151454 TCDAT3 HURRICANE GONZALO DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL082014 1100 AM AST WED OCT 15 2014 Data from an Air Force reconnaissance aircraft indicate that Gonzalo has strengthened a little. The maximum 700 mb flight-level wind reported was 123 kt and the highest SFMR wind observation was 116 kt. Based on these data, the initial wind speed is increased to 115 kt, making Gonzalo a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. This is the first category 4 hurricane in the Atlantic basin since Ophelia in 2011. The aircraft data and microwave images clearly show concentric eyewalls, with the inner radius of maximum wind now only about 4-5 n mi from the center. Smoothing through the trochoidal oscillation of the eye yields an initial motion estimate of 320/10 kt. A high amplitude trough over the eastern United States is expected to slowly move eastward during the next couple of days, and will erode the subtropical ridge that is currently steering Gonzalo. This change in the large-scale pattern should cause the hurricane to turn northward by early Thursday and north-northeastward Thursday night and Friday, likely bringing Gonzalo near Bermuda in about 2 days. Beyond 48 hours, the hurricane is forecast to accelerate generally northeastward. The track model guidance remains tightly clustered, and the official forecast is near the GFS and ECMWF solutions and only slightly to the left of the previous one. Given the evidence of concentric eyewalls, and with the inner eyewall already about as small as it can get, the current period of intensification could be about over. The hurricane will likely fluctuate in strength while the environmental conditions remain favorable during the next day or two. After that time, weakening is forecast when the hurricane moves into an atmosphere of increasing southwesterly shear and drier air, and over much colder water. Post-tropical transition will likely occur in 3 to 4 days when the cyclone is forecast to cross the north wall of the Gulf Stream current. Little change was made to the previous intensity forecast, and this one lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 23.5N 68.0W 115 KT 130 MPH 12H 16/0000Z 24.6N 68.7W 115 KT 130 MPH 24H 16/1200Z 26.3N 68.9W 115 KT 130 MPH 36H 17/0000Z 28.6N 68.0W 110 KT 125 MPH 48H 17/1200Z 31.6N 66.2W 105 KT 120 MPH 72H 18/1200Z 40.6N 60.8W 90 KT 105 MPH 96H 19/1200Z 50.5N 46.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 20/1200Z 54.0N 24.0W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Cangialosi
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