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Tropical Storm Hilary Forecast Discussion Number 33
2017-07-29 16:34:54| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Sat Jul 29 2017 000 WTPZ44 KNHC 291434 TCDEP4 Tropical Storm Hilary Discussion Number 33 NWS National Hurricane Center Miami FL EP092017 800 AM PDT Sat Jul 29 2017 Although Hilary has crossed the 25 deg SST isotherm, the inner-core of the tropical storm has remained mostly intact. Recent SSMI and AMSR microwave imagery indicate that deep convection is still present near the center of circulation, and in a band extending to the east and south. IR imagery from GOES-W even briefly showed a warm spot embedded within the shallow to medium convection that surrounds the center. Given that the cloud pattern hasn't changed significantly and an earlier ASCAT-A pass at 0540 UTC showed maximum winds of 49 kt, the initial intensity has been held at 55 kt. Despite Hilary's resilience so far, the SSTs beneath the cyclone will continue to decrease for the next several days, so weakening is inevitable. The intensity forecast has not been changed from the previous advisory, and shows Hilary becoming a remnant low within 48 hours. After days of high uncertainty, the track guidance is finally coming into better agreement. For the next 12 to 24 hours, Hilary should be steered generally toward the west-northwest or northwest by a mid-level ridge located to the north. After that time, a turn toward the west-northwest or west is expected due to a combination of interaction with Irwin and amplification of the ridge. Beyond day 3, the UKMET and ECMWF show the two cyclones dissipating in close proximity to one another, while the GFS still shows the systems merging. The NHC forecast favors the ECMWF and UKMET solutions for now, but both systems are expected to be very weak regardless of how close they actually get. The new track is just a little faster than the previous forecast and is close to the model consensus. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 21.4N 121.5W 55 KT 65 MPH 12H 30/0000Z 22.4N 123.2W 50 KT 60 MPH 24H 30/1200Z 23.6N 125.6W 40 KT 45 MPH 36H 31/0000Z 24.6N 128.0W 30 KT 35 MPH 48H 31/1200Z 25.2N 130.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 01/1200Z 25.4N 132.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 02/1200Z 25.5N 134.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 03/1200Z...DISSIPATED $$ Forecaster Zelinsky
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