Issued at 1100 AM AST Fri Sep 15 2023
000 WTNT45 KNHC 151458 TCDAT5 Tropical Depression Fifteen Discussion Number 1 NWS National Hurricane Center Miami FL AL152023 Issued by the NWS Weather Prediction Center College Park MD 1100 AM AST Fri Sep 15 2023 1-min GOES-East visible imagery indicates improved organization of Invest 97, with a well-defined surface center forming since sunrise, along with large curved banding features. Thus the system is designated as a tropical depression, and the initial intensity is set to 30 kt, in closest agreement with the TAFB Dvorak classification. Our estimate of initial motion is northwestward at 10 kt, though this is uncertain due to the recent center formation. A subtropical ridge over the central Atlantic should be the dominant steering mechanism during the next several days, sending the system on a steady northwestward track. For a first forecast, guidance is in remarkably good agreement, and the official forecast lies near or west of the model consensus. Despite the good model agreement, there is still some long-range uncertainty in how far west this system moves, which partially depends on the strength of the subtropical ridge in the wake of Tropical Storm Margot. The depression is forecast to gradually intensify over the next couple of days as moderate northeasterly shear and the initial broad cyclone structure could provide a check on the intensification rate. By early next week, this system is forecast to move over near record warm sea-surface temperatures for the region in light shear conditions. It probably sounds like a broken record at this point in the season, but rapid intensification is a significant possibility, and the official forecast could be conservative below. The intensity forecast is near or above the intensity consensus, only leveling off at 120 hours due to gradual SST cooling and the possibility of eyewall replacement cycles, as suggested by the HAFS model suite. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 14.4N 43.8W 30 KT 35 MPH 12H 16/0000Z 15.5N 44.7W 35 KT 40 MPH 24H 16/1200Z 17.2N 46.0W 40 KT 45 MPH 36H 17/0000Z 18.9N 47.9W 50 KT 60 MPH 48H 17/1200Z 20.5N 49.6W 60 KT 70 MPH 60H 18/0000Z 22.0N 51.2W 70 KT 80 MPH 72H 18/1200Z 23.4N 52.9W 85 KT 100 MPH 96H 19/1200Z 26.0N 56.8W 105 KT 120 MPH 120H 20/1200Z 29.0N 60.0W 100 KT 115 MPH $$ Forecaster Churchill/Blake/Lamers