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| #1154153 (Received by flhurricane at: 10:50 AM 23.Sep.2023) TCDAT2 Tropical Depression Seventeen Discussion Number 1 NWS National Hurricane Center Miami FL AL172023 1100 AM AST Sat Sep 23 2023 Visible imagery since sunrise revealed that a small well-defined center has formed on the western edge of an area of disturbed weather located several hundred miles west of the Cabo Verde Islands. Deep convection associated with the system is also sufficiently organized to classify it as a tropical cyclone. Therefore, advisories have been initiated on Tropical Depression Seventeen. ASCAT data valid around 1200 UTC indicated that maximum winds associated with the depression are near 30 kt, and that is the basis for the initial intensity. Since the cyclone`s deep convection and formative mid-level circulation are displaced well east of its surface center, no significant change in strength is anticipated in the short term. Deep-layer shear appears to be very weak, but model soundings suggest some mid-layer shear may be responsible for the current structure. This shear could lessen by early next week, allowing for slow intensification to begin in an environment that should otherwise support strengthening. The NHC forecast is very near the intensity model consensus, with the statistical-dynamical models generally showing a faster rate of strengthening than the dynamical ones. The depression is moving westward, with an initial forward speed near 13 kt. The depression should continue westward for the next several days, slowing down slightly as the subtropical ridge to its north weakens and moves eastward. After about 3 days, a mid- to upper-level trough over the central Atlantic should begin to turn the cyclone northwestward, and then northward by day 5, as long as Seventeen intensifies as forecasted. The NHC track forecast is heavily based on HCCA through the full forecast period. Confidence in the track forecast is somewhat lower than normal based on the model spread and uncertainty as to when the system will be vertically deep enough to begin gaining more latitude, but nearly all available ensemble guidance shows the same general evolution. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 15.6N 38.8W 30 KT 35 MPH 12H 24/0000Z 15.7N 41.0W 35 KT 40 MPH 24H 24/1200Z 15.8N 43.7W 35 KT 40 MPH 36H 25/0000Z 15.9N 46.2W 35 KT 40 MPH 48H 25/1200Z 16.2N 48.5W 40 KT 45 MPH 60H 26/0000Z 16.6N 50.2W 40 KT 45 MPH 72H 26/1200Z 17.1N 51.6W 45 KT 50 MPH 96H 27/1200Z 19.5N 54.0W 50 KT 60 MPH 120H 28/1200Z 23.0N 54.5W 55 KT 65 MPH $$ Forecaster D. Zelinsky |
