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Hurricane Fernanda Forecast Discussion Number 15
2017-07-15 16:34:33| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Sat Jul 15 2017 000 WTPZ41 KNHC 151434 TCDEP1 Hurricane Fernanda Discussion Number 15 NWS National Hurricane Center Miami FL EP062017 800 AM PDT Sat Jul 15 2017 An AMSR2 overpass around 0925 UTC shows that Fernanda is undergoing an eyewall replacement cycle (ERC). Based on the 36 GHz composite image from that pass, the inner core at that time consisted of a very small, 10 nm-wide, inner eyewall surrounded by a 30 nm-wide outer eyewall. An earlier WindSat pass at 0149 UTC suggests that the ERC began about 12 hours ago. This is consistent with a warming trend observed in the cloud top temperatures that began a little before 0000 UTC yesterday. The initial intensity has been decreased to 120 kt, based on a blend of Dvorak estimates from TAFB, SAB, and the UW-CIMSS ADT. Assuming a typical ERC weakening period of about 15 hours, the hurricane could reintensify later today, once the outer eyewall contracts. The environment should support intensification for another 24 hours or so, and the forecast reflects this. Additional ERCs could lead to fluctuations in intensity that aren't explicitly shown in the forecast. After about 36 hours, the hurricane will become embedded in a drier and more stable environment, so steady weakening is anticipated. The new forecast is similar to the previous one, despite the weaker initial intensity, and is above most of the intensity guidance for the first 36 hours. It is close to the intensity consensus by the end of the forecast period. Fernanda is beginning to make a long-anticipated turn toward the west-northwest and the initial motion is now just north of due west, or 275/11. Almost no change has been made to the track forecast, which remains on top of the various multi-model consensus aids. A west-northwest to northwest motion is expected for the next several days while the cyclone moves along the southwestern periphery of a deep-layer ridge. The track guidance is still tightly clustered, and confidence remains high in the track forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 11.0N 123.0W 120 KT 140 MPH 12H 16/0000Z 11.5N 124.8W 130 KT 150 MPH 24H 16/1200Z 12.3N 127.3W 130 KT 150 MPH 36H 17/0000Z 13.0N 129.7W 125 KT 145 MPH 48H 17/1200Z 13.8N 131.9W 120 KT 140 MPH 72H 18/1200Z 15.3N 135.3W 95 KT 110 MPH 96H 19/1200Z 16.5N 138.0W 70 KT 80 MPH 120H 20/1200Z 17.0N 141.0W 50 KT 60 MPH $$ Forecaster Zelinsky
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