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Hurricane Chris Forecast Discussion Number 21
2018-07-11 22:47:24| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Jul 11 2018 212 WTNT43 KNHC 112047 TCDAT3 Hurricane Chris Discussion Number 21 NWS National Hurricane Center Miami FL AL032018 500 PM AST Wed Jul 11 2018 The eye of Chris has become a little less distinct and more cloud filled during the past few hours, but the overall cloud pattern remains quite impressive in satellite imagery. The respective wind radii were adjusted outward based on a 1454 UTC ASCAT-A overpass, which included one 65-kt surface wind vector in the southeastern quadrant. The initial intensity has been lowered slightly to 80 kt based on a blend of Dvorak intensity estimates of T4.5/77 from both TAFB and SAB, and an ADT estimate of T5.2/95 kt. The initial motion estimate is now 050/22 kt. Little change was made to the previous advisory track. Chris is now embedded within deep southwesterly flow ahead of a broad trough that is digging southeastward along the U.S. Northeast and Mid-Atlantic coasts. The global models are in excellent agreement that the hurricane should continue to accelerate northeastward for the next 72 hours, passing over or near southeastern Newfoundland in 24-36 hours as a strong extratropical cyclone. In contrast to several previous model runs, the latest NHC guidance shows very little cross-track spread or speed differences, and is tightly packed about the previous advisory track. The new forecast track closely follows the previous forecast and the consensus track models HCCA, TVCN, and FSSE. During next 6 hours or so, Chris will be passing over a ocean thermal ridge consisting of SSTs of more than 28 deg C, which is associated with the Gulf Stream. As a result, little change in strength is expected during that time. However, by 24 hours and beyond, the cyclone will be moving over SSTs colder than 12 deg C and encountering southwesterly vertical wind shear in excess of 30 kt, a detrimental combination that will induce rapid weakening and also result in transition to an extratropical cyclone. The new intensity forecast is a little lower than the various intensity model forecasts to account for stronger shear and colder water. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 37.8N 65.7W 80 KT 90 MPH 12H 12/0600Z 40.6N 61.9W 75 KT 85 MPH 24H 12/1800Z 44.9N 56.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 13/0600Z 48.8N 49.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 13/1800Z 51.9N 40.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 14/1800Z 58.4N 22.6W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 15/1800Z 63.0N 14.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 16/1800Z...DISSIPATED $$ Forecaster Stewart
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