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| #932303 (Received by flhurricane at: 5:00 PM 10.Jul.2018) TCDAT3 Hurricane Chris Discussion Number 17 NWS National Hurricane Center Miami FL AL032018 500 PM EDT Tue Jul 10 2018 Reports from an Air Force Reserve hurricane hunter aircraft indicate that Chris has finally attained hurricane status, making it the second hurricane thus far this season, which is ahead of climatology by more than six weeks. The aircraft found 850-mb flight-level winds of 88 kt in the southeastern quadrant, along with SFMR winds of 73-77 kt. Dropsondes in the the same area found equivalent surface winds of 73-74 kt, and the most recent central pressure observed was 980 mb. Furthermore, satellite intensity estimates are a consensus T4.5/77 kt from TAFB, SAB, and UW-CIMSS ADT, based on a well-defined 20-nmi-diameter clear eye. These data support a solid 75-kt advisory intensity. The initial motion is a slightly faster 050/09 kt. Chris is north of a narrow subtropical ridge, and water vapor imagery also indicates that Chris is beginning to feel the influence of a digging trough over the northeastern U.S. and Mid-Atlantic states. The combination of these two features should gradually accelerate the hurricane northeastward at a faster forward speed through 96 hours. By the time Chris passes well southeast of Nova Scotia in 36 hours or so, the hurricane will be moving at a forward speed of more than 25 kt. On the new forecast track, Chris is still expected to move near or over southeastern Newfoundland in about 48-60 hours. The latest model guidance has a much larger spread in both cross-track and along-track motions. To smooth out these differences, the new forecast track is down the middle of the tighter HCCA, FSSE, and TVCN consensus model suite. Now that Chris has moved away from the cold upwelling region, some additional intensification is forecast for the next 12 hours or so due to 27-28 deg C SSTs beneath the cyclone and the well-established current outflow pattern that is expected to persist during that time. Slow weakening should begin shortly after Chris peaks in intensity due to the cyclone moving over cooler waters, creating some modest upwelling as a result. By 36 hours, Chris will have moved well north of the Gulfstream and be moving over SSTs colder than 15 deg C. The combination of the much colder water and southwesterly vertical wind shear in excess of 30 kt should induce a rapid transition to an extratropical cyclone. The official intensity forecast is above the intensity guidance through 12 hours, and then shows weakening after that similar to the LGEM and IVCN models. Now that Chris is moving away from the United States, the previously scheduled aircraft mission for 11/0600 UTC has been canceled. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 33.7N 72.4W 75 KT 85 MPH 12H 11/0600Z 34.9N 70.7W 85 KT 100 MPH 24H 11/1800Z 37.1N 67.4W 80 KT 90 MPH 36H 12/0600Z 40.5N 62.6W 75 KT 85 MPH 48H 12/1800Z 44.7N 57.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 13/1800Z 51.0N 41.2W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 14/1800Z 55.2N 22.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 15/1800Z 59.0N 12.5W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart |
