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| #1148989 (Received by flhurricane at: 4:54 PM 22.Aug.2023) TCDAT3 Tropical Storm Franklin Discussion Number 9 NWS National Hurricane Center Miami FL AL082023 500 PM EDT Tue Aug 22 2023 Franklin is not a healthy tropical cyclone--and there is still some question if it even is a tropical cyclone. A NOAA Hurricane Hunter aircraft investigating the system found a broad low-level cyclonic wind field exposed to the west of the deep convection, but this feature is well to the west of where we would have expected the center to be. At the same time, developing deep convection with some mid-level turning is noted about 90 n mi to the east, which would more closely follow persistence from previous forecasts. Either way, Franklin is not well organized, and for now the initial position is held closer to the convection in case a new center re-forms in that area. In fact, a dropsonde recently released by the NOAA crew near the convection measured a surface pressure of 1003 mb with winds of 32 kt, giving additional credence that a new center could be forming. The crew also reported that the SFMR winds were running too high, and the highest 850-mb flight-level wind was 41 kt, suggesting that Franklin`s initial intensity is probably down to about 35 kt. The smoothed 12-hour motion remains northwestward (320 degrees) at 6 kt. The track model guidance continues to insist that Franklin will move slowly northward and then northeastward during the next 3 days or so, toward broad troughing located over the western Atlantic. This track should take Franklin northward across Hispaniola during the next 12-36 hours, with the system then turning northeastward over the western Atlantic. By days 4 and 5, a shortwave trough is expected to amplify near the northeastern U.S. while a stronger mid-level ridge develops over the central Atlantic, likely causing Franklin to turn back to the north by the end of the forecast period. Despite the possibility of center re-formations, which could cause Franklin`s track to jump around, the model guidance is in good agreement on this general forecast scenario, even if all the details are not yet ironed out. The new intensity forecast probably has the biggest change from the previous advisory, at least in the short term. Little change in strength is expected during the next 48 hours or so due to Franklin`s current disheveled state and its expected crossing of the high terrain of Hispaniola on Wednesday. Once Franklin moves over the western Atlantic waters, a more diffluent upper-level environment could foster some intensification, and the NHC forecast continues to show the system becoming a hurricane by the end of the 5-day forecast period. This forecast remains close to the HCCA and IVCN consensus aids. KEY MESSAGES: 1. Heavy rainfall from Franklin is expected across portions of Hispaniola and Puerto Rico into Thursday. The heavy rainfall may produce areas of flash and urban flooding as well as river rises and mudslides. Across Hispaniola, significant and potentially life-threatening flash flooding is possible Tuesday into Wednesday. 2. Franklin is expected to bring tropical storm conditions to portions of the Dominican Republic and Haiti, where Tropical Storm Warnings are in effect, beginning later tonight and continuing through Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 15.8N 71.4W 35 KT 40 MPH 12H 23/0600Z 17.0N 71.3W 40 KT 45 MPH 24H 23/1800Z 19.1N 70.9W 35 KT 40 MPH...OVER HISPANIOLA 36H 24/0600Z 20.9N 70.3W 35 KT 40 MPH...OVER WATER 48H 24/1800Z 22.0N 69.3W 40 KT 45 MPH 60H 25/0600Z 22.5N 68.2W 45 KT 50 MPH 72H 25/1800Z 22.9N 67.3W 50 KT 60 MPH 96H 26/1800Z 24.3N 66.7W 60 KT 70 MPH 120H 27/1800Z 27.6N 67.7W 75 KT 85 MPH $$ Forecaster Berg |
