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Hurricane Hilda Forecast Discussion Number 8
2021-08-01 16:50:31| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Sun Aug 01 2021 000 WTPZ43 KNHC 011450 TCDEP3 Hurricane Hilda Discussion Number 8 NWS National Hurricane Center Miami FL EP082021 800 AM PDT Sun Aug 01 2021 Hilda is a bit of a mess this morning with an elongated cloud pattern from southeast to northwest and no signs of an eye in conventional satellite imagery. However, microwave data near 1155 UTC from GPM still shows a well-defined low-level eye, although the mid-level structure remains degraded from easterly shear. The current wind speed is held at 75 kt, with this being an uncertain estimate due to a large spread in the various intensity techniques. Hilda is moving west-northwestward at about 7 kt, with microwave data helping to pinpoint the slower movement. The track forecast is no piece of cake this morning with some interaction anticipated with Invest 91E to the east in a day or two. While a mid-level ridge persists to the northwest of Hilda, the southern periphery of the ridge weakens due to 91E, causing Hilda to take a northwestward turn in a couple of days. Hilda then should turn back toward the west-northwest and west by midweek due to the ridge remaining in place and 91E weakening. This is a tricky forecast because the guidance is shifting to the right, which at some point will bring Hilda over cold waters and closer to 91E, changing which atmospheric layers will dominate steering the tropical cyclone. In addition, interactions between two systems this close together aren't easy to forecast in the best of circumstances, and the latest guidance isn't in great agreement on the future strength of 91E either. As a compromise, the NHC track forecast is more conservative in shifting the track to the northeast than the guidance (remaining on the westerly side of the track envelope), then gradually comes close to the previous NHC forecast by the end of the 5-day period. This forecast is obviously rather uncertain, and a lot of generally better performing aids are to the northeast of the latest NHC track. The hurricane still has some chance to intensify during the next day or so with moderate easterly shear and good inner-core structure. Still, it is becoming more likely that Hilda is close to its peak intensity with no signs of the easterly shear abating until the hurricane moves over cool waters in a few days. Model guidance generally is lower than the last cycle, and only a few show strengthening. I'm going to keep the chance for slight strengthening in the near term, then show a steady drop in intensity due to persistent (or stronger) easterly shear and marginal water temperatures. The new intensity forecast is 5 kt lower than the last one at 36 hours and beyond and that could still be too high, especially if the track shifts any farther to the north. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 14.6N 120.2W 75 KT 85 MPH 12H 02/0000Z 14.9N 121.2W 80 KT 90 MPH 24H 02/1200Z 15.4N 122.4W 80 KT 90 MPH 36H 03/0000Z 16.1N 123.4W 75 KT 85 MPH 48H 03/1200Z 16.9N 124.2W 70 KT 80 MPH 60H 04/0000Z 18.0N 125.5W 60 KT 70 MPH 72H 04/1200Z 19.0N 127.0W 50 KT 60 MPH 96H 05/1200Z 20.2N 131.2W 40 KT 45 MPH 120H 06/1200Z 20.5N 135.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Blake
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