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Tropical Storm Eugene Forecast Discussion Number 3
2017-07-08 10:34:30| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Sat Jul 08 2017 000 WTPZ45 KNHC 080834 TCDEP5 Tropical Storm Eugene Discussion Number 3 NWS National Hurricane Center Miami FL EP052017 300 AM MDT Sat Jul 08 2017 Eugene's convective pattern has continued to improve since the previous advisory, with a pronounced band of cold-topped convection now wrapping more than halfway around the center. An ASCAT-A pass at 0432Z indicated peak winds of 37 kt north of the center, but the northeastern quadrant was missed where stronger winds could be occurring. The initial intensity is being maintained at 40 kt for this advisory based on consensus T2.5/35 estimates from TAFB and SAB, and a UW-CIMSS ADT estimate of T2.7/39 kt. The initial motion remains 315/08 kt. There is no significant change to previous forecast track or reasoning. Eugene is expected to continue moving around the southwestern periphery of a deep-layer ridge that extends westward across central and northern Mexico for the next 36-48 hours, and afterwards move into a weakness that is is forecast to develop in the ridge well to the west of the Baja California peninsula. The latest NHC model guidance is tightly packed about the previous forecast track, so only minor along-track speed changes were required. The aforementioned ASCAT pass indicates that the inner-core wind field of Eugene has become better defined and that the radius of maximum winds has also contracted down to about 30 n mi. As mentioned in the previous discussion, this now smaller RMW, in conjunction with a nearly ideal environment, would typically support rapid intensification. However, AMSU microwave and new GOES-16 water vapor imagery indicate that a pronounced tongue of dry air has penetrated into the southwestern quadrant, temporarily disrupting the development of inner-core convection. But should the dry air mix out during the next 12 h or so, then rapid strengthening is still a distinct possibility before Eugene reaches colder water shortly after the 36-h period. Beyond that time, the cyclone will be moving over muh colder SSTs ranging from 21-24 deg C, which should induce rapid weakening despite the low vertical wind shear conditions that will exist throughout the forecast period. The new intensity forecast is similar to the previous advisory, and closely follows the HCCA consensus model. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 12.9N 112.1W 40 KT 45 MPH 12H 08/1800Z 13.7N 113.0W 50 KT 60 MPH 24H 09/0600Z 14.9N 114.1W 60 KT 70 MPH 36H 09/1800Z 16.4N 115.2W 70 KT 80 MPH 48H 10/0600Z 17.9N 116.5W 70 KT 80 MPH 72H 11/0600Z 20.5N 119.0W 55 KT 65 MPH 96H 12/0600Z 22.9N 121.2W 40 KT 45 MPH...POST-TROPICAL 120H 13/0600Z 25.1N 123.3W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart
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