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Hurricane Marie Forecast Discussion Number 8
2020-10-01 04:50:16| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Wed Sep 30 2020 000 WTPZ43 KNHC 010250 TCDEP3 Hurricane Marie Discussion Number 8 NWS National Hurricane Center Miami FL EP182020 800 PM PDT Wed Sep 30 2020 Passive microwave satellite data and satellite intensity estimates indicate that Marie has undergone a brief intensity hiatus since the previous advisory. Date from the 2055Z AMSR and 2306Z SSMI microwave passes indicated that the earlier eye feature has eroded some and opened up on the east side due to dry air entrainment and modest easterly vertical wind shear of about 10 kt. The initial intensity is being held at 65 kt based on subjective Dvorak classifications of T4.0/65 kt from both TAFB and SAB, and UW-CIMSS objective intensity estimates of T4.1/67 kt and 62 kt from ADT and SATCON, respectively. The motion estimate is 280/14 kt. The latest NHC model guidance remains in excellent agreement through about 96 h on Marie moving west-northwestward toward a weakness in the subtropical ridge located to the north of the cyclone. Thereafter, there is considerable divergence in the guidance with the ECMWF and UKMET taking Marie more westward, while the GFS, HWRF, and HMON models take the hurricane northward into a break in the ridge; the latter scenario is preferred by the various simple and corrected consensus models. As a result, no significant changes were required to the previous forecast, and the new forecast track essentially lies down the model of the tightly packed consensus model envelope. Although the eyewall has eroded somewhat, the small inner-core wind field still appears to be intact based on low-level cloud features seen in 36-37 GHz satellite imagery. Once the narrow dry air intrusions mix out in about 6 hours or so, rapid intensification (RI) should resume and continue through 48 hours while the shear gradually decreases to near zero by then. By 60 hours and continuing through the remainder of the forecast period, cooler sea-surface temperatures, along with cold upwelling generated by Marie, should cause the hurricane to weaken, with rapid weakening likely beginning by 72 hours when significant southwesterly vertical wind shear kicks in ahead of a deep-layer trough that will be moving eastward out of the central Pacific. The new official intensity forecast is essentially identical to the previous NHC forecast, and lies along the extreme upper end of the intensity guidance, about midway between the Navy COAMPS-TC model (CTCI) and the NOAA-HCCA corrected-consensus model. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 14.5N 116.5W 65 KT 75 MPH 12H 01/1200Z 14.7N 118.6W 80 KT 90 MPH 24H 02/0000Z 15.3N 121.3W 100 KT 115 MPH 36H 02/1200Z 16.2N 123.6W 115 KT 130 MPH 48H 03/0000Z 17.2N 125.6W 120 KT 140 MPH 60H 03/1200Z 18.2N 127.5W 100 KT 115 MPH 72H 04/0000Z 19.1N 129.1W 85 KT 100 MPH 96H 05/0000Z 20.7N 131.8W 65 KT 75 MPH 120H 06/0000Z 22.6N 134.3W 45 KT 50 MPH $$ Forecaster Stewart
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