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| #1016068 (Received by flhurricane at: 4:51 AM 11.Sep.2020) TCDAT3 Tropical Storm Rene Discussion Number 17 NWS National Hurricane Center Miami FL AL182020 500 AM AST Fri Sep 11 2020 An AMSR2-GM1 microwave pass revealed that Rene`s surface center is farther separated from the shrinking deep convection. The 0000 UTC FV3 and ECMWF model soundings indicate that east-southeasterly 30-35 kt shear near 300 mb is temporarily undercutting the diffluent southerly flow aloft. The initial intensity is held at 40 kt and is based on the subjective Dvorak estimates from TAFB and SAB, and an ADT estimates yielding 39 kt. The shear is expected to relax during the next 36 to 48 hours which should allow for gradual intensification. By mid-period, Rene is forecast to move into an area of increasing west-northwesterly shear, which should induce a weakening trend. It`s worth noting that the ECMWF and the FV3 Decay SHIPS show very little strengthening through the period and it appears to be due to the cyclone moving into an even more inhibiting thermodynamic environment, in addition to the aforementioned shear. In fact, the relative humidity in the mid portions of the atmospheric is less than 49 percent beyond day 3. The NHC forecast sides with the various intensity consensus models and is above the statistical-dynamical guidance. Rene continues to move west-northwestward, or 290/9 kt within the southwestern periphery of a mid-tropospheric ridge extending from western Africa to the eastern Atlantic. A turn toward the northwest on Saturday, followed by a north-northwestward and northward motion with a decrease in forward speed is forecast Sunday and Sunday night. Early next week, a subtropical ridge is forecast to build to the northwest of Rene, in response to Tropical Storm Paulette moving northeastward over the northern central Atlantic. This change in the steering pattern should cause the cyclone to begin a southwestward to west-southwestward drift through the end of the period. The official track forecast is close to the previous advisory through day 4, then it`s nudged a little south to conform with the HCCA and TVCA multi-model aids. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 19.7N 38.5W 40 KT 45 MPH 12H 11/1800Z 20.4N 40.2W 45 KT 50 MPH 24H 12/0600Z 21.6N 42.4W 50 KT 60 MPH 36H 12/1800Z 23.2N 44.3W 60 KT 70 MPH 48H 13/0600Z 25.0N 45.6W 60 KT 70 MPH 60H 13/1800Z 26.6N 46.1W 55 KT 65 MPH 72H 14/0600Z 27.4N 46.0W 50 KT 60 MPH 96H 15/0600Z 26.9N 46.4W 40 KT 45 MPH 120H 16/0600Z 26.1N 48.8W 35 KT 40 MPH $$ Forecaster Roberts |