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Tropical Storm Hilda Forecast Discussion Number 3
2021-07-31 10:36:34| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Sat Jul 31 2021 000 WTPZ43 KNHC 310836 TCDEP3 Tropical Storm Hilda Discussion Number 3 NWS National Hurricane Center Miami FL EP082021 200 AM PDT Sat Jul 31 2021 A prominent convective band now wraps about halfway around the southeast to west side of Hilda's center, and another band is taking shape to the north of the center. With the improved organization, Dvorak estimates increased to a consensus T3.0/45 kt from TAFB and SAB, and a 0520 UTC ASCAT-B pass confirmed that indeed maximum winds are about 45 kt. This is being set as Hilda's initial intensity, although it could be a little conservative since objective ADT estimates have trended higher than that since 0600 UTC. A mid-tropospheric ridge currently extends from northern Mexico westward across the Baja California peninsula to about 120W and is steering Hilda west-northwestward at 290/12 kt. Although this ridge is expected to build westward and keep Hilda on a west-northwestward course, potential interactions with Tropical Depression Nine-E to the west and another low pressure area to the east could cause the storm to slow down over the next 3 days and oscillate a bit around that general heading. There is slightly more spread among the track models than is typical, with the HWRF a notable southern outlier and the GFS and HMON models having some of the faster solutions due to greater interaction with T.D. Nine-E. That being said, the overall track guidance has trended a little slower and farther south on this cycle, and the updated NHC track forecast has therefore been adjusted in that direction from the previous forecast, lying close to the TVCE multi-model consensus but not nearly as far south as the HCCA consensus aid. Hilda is currently in a light-shear regime and over sea surface temperatures of about 29 degrees Celsius, so continued strengthening is anticipated in the short term with Hilda likely to reach hurricane strength by tonight or early Sunday. However, global models are suggesting that the shear may increase out of the east during the next 24 hours, and then Hilda will be near cooler waters in 2 to 3 days. Therefore, Hilda is likely to reach its peak intensity in about 48 hours, and the NHC intensity forecast at that time is near the upper end of the guidance suite. Hilda is expected to move over even cooler waters after 48 hours, which should cause a gradual weakening trend through the end of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 31/0900Z 13.3N 115.7W 45 KT 50 MPH 12H 31/1800Z 13.6N 117.3W 55 KT 65 MPH 24H 01/0600Z 14.1N 119.1W 65 KT 75 MPH 36H 01/1800Z 14.6N 120.8W 70 KT 80 MPH 48H 02/0600Z 15.1N 122.3W 75 KT 85 MPH 60H 02/1800Z 15.7N 123.7W 70 KT 80 MPH 72H 03/0600Z 16.3N 124.8W 65 KT 75 MPH 96H 04/0600Z 17.8N 127.6W 55 KT 65 MPH 120H 05/0600Z 18.9N 131.5W 45 KT 50 MPH $$ Forecaster Berg
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