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| #982146 (Received by flhurricane at: 4:44 PM 13.Sep.2019) TCDAT4 Tropical Depression Nine Discussion Number 5 NWS National Hurricane Center Miami FL AL092019 500 PM EDT Fri Sep 13 2019 An Air Force plane extensively investigated the disturbance near the Bahamas during the past several hours, and in the last portion of the mission, the crew was able to locate a center of circulation, although weak, near the convection. The center was a little bit to the east of the previous estimates. Satellite images also indicate that the cloud pattern has become a little better organized and Dvorak estimates are T2.0 and 1.5 from TAFB and SAB, respectively. On this basis, the disturbance has been classified as a tropical depression with 25 kt winds. Conditions are not ideal for strengthening since the depression is still embedded within a moderate shear environment, but this parameter is not expected to be strong enough to halt additional development. The NHC forecast still calls for this system to become a tropical storm on Saturday with gradual intensification thereafter. Global models insist on further development, and the reliable guidance suggests that the cyclone could even reach hurricane intensity in about 3 days, and so does the NHC forecast. By then, the system is expected to be over the Atlantic waters well southeast of the coast of the Carolinas. Due to the reformation of the apparent center, the initial motion is highly uncertain. The best estimate is toward the northwest or 305 degrees at 7 kt. A weakness in the ridge over the western Atlantic is forecast to develop, and this pattern should steer the system slowly toward the northwest and then northward. In about 3 days, an eastward moving mid-latitude trough will force the system to recurve away from the coast toward the Atlantic. The track guidance has shifted to the east again, and this shift is larger due to the eastward formation of the center. Consequently, the NHC track forecast was adjusted in that direction, but it remains on the western edge of the guidance envelope. Key Messages: 1. The depression is forecast to become a tropical storm within the next 24 hours and will likely bring tropical-storm-force winds and heavy rainfall to portions of the northwestern Bahamas later today and Saturday. Significant storm surge is not expected in the northwest Bahamas from this system. Residents there should follow any advice given by local officials. 2. The system could still bring tropical storm conditions to portions of the Florida east coast. Residents there should monitor the progress of this system and follow any advice given by local officials. 3. Heavy rainfall and scattered flash flooding is possible this weekend in coastal sections of eastern Florida, Georgia, and South Carolina. The chance of heavy rainfall affecting coastal North Carolina early next week continues to diminish. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 25.6N 75.0W 25 KT 30 MPH 12H 14/0600Z 26.2N 76.0W 30 KT 35 MPH 24H 14/1800Z 27.4N 77.6W 35 KT 40 MPH 36H 15/0600Z 28.8N 78.5W 45 KT 50 MPH 48H 15/1800Z 30.0N 78.8W 55 KT 65 MPH 72H 16/1800Z 31.5N 76.5W 65 KT 75 MPH 96H 17/1800Z 32.0N 73.0W 70 KT 80 MPH 120H 18/1800Z 32.5N 68.0W 75 KT 85 MPH $$ Forecaster Avila |
