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| #978861 (Received by flhurricane at: 10:36 PM 20.Aug.2019) TCDAT4 Tropical Storm Chantal Discussion Number 1 NWS National Hurricane Center Miami FL AL042019 1100 PM AST Tue Aug 20 2019 Recent scatterometer wind data and passive microwave satellite images indicate that the small low pressure system that the NHC has been monitoring for the past few days has developed a well-defined surface wind circulation and contains tropical-storm-force winds south of the cyclone's center. Therefore, the low has become Tropical Storm Chantal. The initial motion estimate is 085/19 kt. NHC model guidance is in excellent agreement that Chantal will move eastward around the northern periphery of the Bermuda-Azores high and gradually slow down during the next 48 hours. Thereafter, the cyclone is forecast to drop southward around the eastern portion of the ridge, possibly stalling over warmer waters. The NHC forecast track lies close to the consensus models HCCA and TVCN. Chantal is expected to remain in a moderate southwesterly to westerly vertical wind shear regime for the next 48 hours or so, followed by a significant decrease in the shear through 120 h. After 48 hours, the southward motion is also expected to move Chantal over warmer water with SSTs around 27C. However, mid-level moisture is expected to be quite sparse with humidity values forecast to be less than 40 percent based on the GFS and ECMWF SHIPS intensity guidance. Therefore, little or no significant intensification is expected throughout the forecast period, and the official intensity forecast closely follows a blend of the HCCA and IVCN consensus models. Although the official forecast calls for Chantal to remain a tropical cyclone through the 120 h, the abundance of dry air that the cyclone will be moving through could result in erosion of the deep convection sooner than currently expected. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 40.2N 56.2W 35 KT 40 MPH 12H 21/1200Z 40.3N 52.6W 35 KT 40 MPH 24H 22/0000Z 40.2N 48.5W 35 KT 40 MPH 36H 22/1200Z 39.0N 44.7W 35 KT 40 MPH 48H 23/0000Z 37.4N 42.3W 35 KT 40 MPH 72H 24/0000Z 34.9N 42.5W 35 KT 40 MPH 96H 25/0000Z 34.6N 44.8W 35 KT 40 MPH 120H 26/0000Z 36.0N 44.8W 35 KT 40 MPH $$ Forecaster Stewart |