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Hurricane Sergio Forecast Discussion Number 25
2018-10-05 17:00:20| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Fri Oct 05 2018 000 WTPZ41 KNHC 051500 TCDEP1 Hurricane Sergio Discussion Number 25 NWS National Hurricane Center Miami FL EP212018 800 AM PDT Fri Oct 05 2018 GOES-16 images and a 1054 UTC ATMS microwave overpass indicate that Sergio's 25 n mi eye has become a bit ragged this morning, and has continued to cool. Despite the eye's irregularity, the inner core convection is still intact and is producing very cold (-76C) cloud tops. Primarily due to the eye adjustment temperature, however, the subjective and objective satellite intensity estimates, as well as a recent SATCON analysis, have again decreased to 95-100 kt, and the initial intensity is subsequently lowered to 100 kt. Although due to the possibility of unpredicted inner core structure changes in the short term which could cause Sergio to strengthen again, the current weakening trend is expected to continue through day 5 as Sergio moves toward decreasing oceanic temperatures and into a stabilizing surrounding atmosphere. The statistical intensity guidance as well as the large-scale models show increasing southwesterly shear entering the picture after 72 hours. This should also aid in the forecast weakening trend. The official forecast is just an update of the previous one and follows the NOAA-HCCA consensus and is just above the Florida State Superensemble. Sergio is moving a little left of the previous 6-hr motion...now westward, or 280/7 kt. A gradual turn toward the west-southwest during the next 36 hours is expected as high pressure located north-northeast of the Hawaiian Islands builds to the north of Sergio. Over the weekend, a decrease in forward speed and a turn toward the northwest is forecast as the aforementioned mid-level high retrogrades in response to an amplifying trough over the southwestern United States and Baja California peninsula. Beyond the 72 hour period, increasing southwesterly mid-tropospheric flow should induce a northeastward accelerated motion through the remaining portion of the forecast. The NHC forecast is adjusted a little toward the south of the last advisory through 72 hours to agree more with the various consensus models, but is quite similar in motion and forward speed beyond that period. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 15.9N 121.8W 100 KT 115 MPH 12H 06/0000Z 15.8N 122.7W 95 KT 110 MPH 24H 06/1200Z 15.5N 123.8W 90 KT 105 MPH 36H 07/0000Z 15.2N 125.0W 85 KT 100 MPH 48H 07/1200Z 15.3N 126.0W 85 KT 100 MPH 72H 08/1200Z 16.5N 126.8W 80 KT 90 MPH 96H 09/1200Z 18.5N 125.0W 70 KT 80 MPH 120H 10/1200Z 21.5N 120.8W 60 KT 70 MPH $$ Forecaster Roberts
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