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Hurricane HILDA Forecast Discussion Number 8
2015-08-07 22:52:31| National Hurricane Center (East Pacific)
Issued at 200 PM PDT FRI AUG 07 2015 000 WTPZ45 KNHC 072052 TCDEP5 HURRICANE HILDA DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP102015 200 PM PDT FRI AUG 07 2015 Hilda has undergone rapid intensification during the past several hours, with a small eye forming in the middle of the central dense overcast. The initial intensity, however, is somewhat uncertain due to a large spread in the satellite estimates. Subjective Dvorak estimates from TAFB and SAB are 55 kt and 65 kt, while the latest AMSU estimates from CIMSS and CIRA are 75 kt and 60 kt. In addition, there is a CIMSS Satellite consensus estimate of about 60 kt. Based on these data, the initial intensity is increased to 70 kt. The shear observed this morning seems to have diminished, as the outflow is increasing in the eastern semicircle. The initial motion is slightly faster at 275/13. For the next 48 hours or so, Hilda should be steered westward to west-northwestward by the deep-layer subtropical ridge to its north. After that time, a mid- to upper-level low is expected to develop north of the Hawaiian Islands, which should cause Hilda to turn generally northwestward. The track guidance again generally agrees on this scenario, and while the GFDL and GFDN models remain right outliers there is better overall agreement on how sharply Hilda will turn than for the previous forecast. The new forecast track is nudged a little to the west of the previous track based mostly on the current position and motion, and it lies near the consensus models and the center of the guidance envelope. It is unclear how long the current rapid intensification will last. The Rapid Intensification Index of the SHIPS model shows about a 30 percent chance of a 25 kt increase in strength during the next 24 hours. However, the cloud pattern of the hurricane still has a ragged appearance, and due to the small size of the system any unfavorable aspect of the environment could stop intensification. The new forecast compromises between these extremes and calls for continued strengthening at a slower rate through 36 hours. After 48-72 hours, the cyclone is expected to encounter strong southwesterly vertical shear and decreasing sea surface temperatures, and this combination should cause significant weakening. The new intensity forecast remains in best overall agreement with the intensity consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 12.7N 138.3W 70 KT 80 MPH 12H 08/0600Z 13.0N 139.9W 75 KT 85 MPH 24H 08/1800Z 13.7N 142.0W 80 KT 90 MPH 36H 09/0600Z 14.4N 144.0W 85 KT 100 MPH 48H 09/1800Z 15.2N 145.6W 85 KT 100 MPH 72H 10/1800Z 17.0N 148.5W 75 KT 85 MPH 96H 11/1800Z 19.0N 150.0W 60 KT 70 MPH 120H 12/1800Z 20.5N 151.5W 40 KT 45 MPH $$ Forecaster Beven
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