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Tropical Storm Leslie Forecast Discussion Number 24
2018-10-02 10:52:20| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Oct 02 2018 326 WTNT43 KNHC 020852 TCDAT3 Tropical Storm Leslie Discussion Number 24 NWS National Hurricane Center Miami FL AL132018 500 AM AST Tue Oct 02 2018 Infrared and passive microwave satellite imagery indicate that convection has increased and become better organized around the well-defined low-level circulation center. In fact, recent microwave images showed that Leslie has developed a closed, 20- to 25-nmi wide low-level eye. Based on the presence of the distinct low-level eye feature and a Dvorak intensity estimate of T3.5/55 kt from SAB, the cyclone's intensity has been increased to 55 kt. The initial motion is southwestward or 220 degrees at a faster forward speed of 6 kt. For the next 24 h or so, Leslie is forecast to move slowly southwestward to south-southwestward, trapped between a deep-layer ridge to the west and a mid- to upper-level low to the east. After possibly becoming stationary near the 36-h period, a ridge to the southeast and east of Leslie is forecast to become highly amplified, forcing the cyclone northward into the higher latitudes through 72 h. On days 4 and 5, an approaching mid-latitude shortwave trough well to the north of Leslie is forecast to nudge the cyclone eastward, but only slowly at forward speeds of less than 10 kt. The new NHC forecast track has again been adjusted to the left of the previous advisory track in the 36- to 72-h period, and is similar to but slightly east of the various consensus models. Leslie's outflow pattern has become a little more symmetrical during the past 6 h, and further improvement is expected through 72 hours. In addition, lightning data and satellite imagery during the past few hours indicate that convection has been developing in the dry slot to the north and east of the main convective band, suggesting the mid-level environment is finally beginning to moisten. This dry intrusion has been hindering the development of deep eyewall convection and, thus, the lack of intensification of the cyclone. However, given the strong instability that is forecast to develop in the inner-core region region due to very cold air aloft moving over relatively warm waters of near 26C beneath the cyclone, along with increasing outflow and mid-level moisture, slow but steady strengthening seems reasonable for the next 48 hours or so. By 72 h and beyond, gradual weakening is expected as Leslie moves back over cooler oceanic temperatures and dry mid-level air from the mid-latitudes associated with the aforementioned shortwave trough once again gets entrained into the cyclone's circulation. The official intensity forecast is just an update of the previous advisory, and is similar to the weaker IVCN consensus model. Large swells generated by Leslie will continue to affect portions of the southeastern coast of the United States, Bermuda, and the Bahamas. These swells could cause life-threatening surf and rip currents. Although the swells are forecast to abate temporarily in the Bahamas later today, they are expected to increase again on Wednesday and Thursday, and propagate farther southward into the Greater and Lesser Antilles. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 31.6N 55.6W 55 KT 65 MPH 12H 02/1800Z 30.6N 56.1W 60 KT 70 MPH 24H 03/0600Z 29.9N 56.5W 65 KT 75 MPH 36H 03/1800Z 30.2N 56.6W 70 KT 80 MPH 48H 04/0600Z 31.3N 56.4W 70 KT 80 MPH 72H 05/0600Z 35.0N 56.3W 65 KT 75 MPH 96H 06/0600Z 37.1N 54.8W 60 KT 70 MPH 120H 07/0600Z 37.1N 51.9W 55 KT 65 MPH $$ Forecaster Stewart
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