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Hurricane HILARY Forecast Discussion Number 17
2017-07-25 16:39:30| National Hurricane Center (East Pacific)
Issued at 900 AM MDT Tue Jul 25 2017 000 WTPZ44 KNHC 251439 TCDEP4 Hurricane Hilary Discussion Number 17 NWS National Hurricane Center Miami FL EP092017 900 AM MDT Tue Jul 25 2017 Satellite imagery shows that deep, but somewhat asymmetric, convection continues in the inner core of Hilary. The 1-minute visible imagery from GOES-16 indicates strong convective towers are firing in the northeastern eyewall, then attempting to rotate cyclonically around the center. Still, the eyewall remains open in the southwest quadrant, as suggested in the visible imagery and shown in a recent 1340 UTC SSMIS microwave pass. Intensity estimates remain about the same as overnight, so the initial wind speed will stay at 90 kt. Hilary is forecast to remain in a conducive environment for strengthening during the next day or so. However, the northerly wind shear is not far away, as evidenced by cirrus clouds moving toward the center in the northern semicircle, which could cause the hurricane to level off in intensity. Similar to yesterday at this time, the model guidance has really backed down off the peak intensity, with few of the solutions even showing Hilary reaching 100 kt. It was easier to ignore the models yesterday because they seemed unrealistic; today the shear is approaching and should impact the cyclone within 24 hours. It seems best to only gradually reduce the intensity forecast, so the latest NHC prediction is adjusted toward the model consensus by day 3, when more significant weakening is expected due to cooler waters, drier air, and interaction with Hurricane Irwin. The initial motion estimate is a little to the left and faster, 285/10 kt. A mid-tropospheric ridge extending westward from the southwestern United States should cause Hilary to continue on a west to west-northwestward track for the next several days. In a few days, however, Hilary is likely to pass close to Hurricane Irwin. While Irwin won't affect Hilary too much, the bulk of the guidance is showing a slowdown and slight turn to the left of Hilary as Irwin tugs on its circulation. Overall, models are in fairly good agreement considering the complexity of the situation, with even most of the GFS-based guidance now acknowledging the binary interaction. The official forecast has been gradually shifting westward at long range, and this advisory continues that trend, near or just west of the model consensus. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 15.3N 107.8W 90 KT 105 MPH 12H 26/0000Z 15.8N 109.5W 100 KT 115 MPH 24H 26/1200Z 16.3N 111.7W 100 KT 115 MPH 36H 27/0000Z 16.8N 113.9W 100 KT 115 MPH 48H 27/1200Z 17.4N 116.0W 95 KT 110 MPH 72H 28/1200Z 18.5N 120.0W 80 KT 90 MPH 96H 29/1200Z 19.5N 124.0W 70 KT 80 MPH 120H 30/1200Z 20.0N 127.5W 60 KT 70 MPH $$ Forecaster Blake
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