000 WTNT45 KNHC 182034 TCDAT5 TROPICAL DEPRESSION TEN DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015 500 PM AST FRI SEP 18 2015 The cloud pattern of the depression has continued to improve, with well-defined convective banding wrapping around the center. 1800 UTC Dvorak estimates from TAFB and SAB support tropical storm intensity, but since ASCAT data from earlier this morning only showed 20 kt of wind in the inner core, the initial intensity is only being raised to 30 kt for now. Barring any unexpected changes, the depression will likely be a tropical storm by this evening. The environment appears generally conducive for gradual strengthening during the next few days, but the global models show that the cyclone will be located precariously beneath a narrow upper-level ridge, especially on days 3 through 5. Even a slight deviation from this pattern could put the cyclone in a higher-shear environment and thus limit intensification, or even induce weakening. The NHC intensity forecast continues to show gradual strengthening through the forecast period and is close to a consensus of the SHIPS and LGEM models. The initial motion is 285/7 kt, with the depression being steered by a mid-level anticyclone to its northwest. This anticyclone is expected to move westward at the same pace as the depression during the next few days, maintaining a west-northwestward motion through 48 hours. After that time, the steering currents are forecast to collapse near the cyclone when a deep-layer trough amplifies over the eastern Atlantic. As a result, the models show very slow motion occurring by days 4 and 5, and the updated NHC track forecast shows the cyclone becoming stationary at the end of the forecast period. This forecast is largely unchanged from the previous one and is near the middle of the tightly clustered guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 13.4N 37.3W 30 KT 35 MPH 12H 19/0600Z 13.9N 38.4W 35 KT 40 MPH 24H 19/1800Z 14.9N 40.1W 40 KT 45 MPH 36H 20/0600Z 16.1N 42.5W 45 KT 50 MPH 48H 20/1800Z 17.2N 44.7W 50 KT 60 MPH 72H 21/1800Z 19.5N 47.6W 50 KT 60 MPH 96H 22/1800Z 20.5N 48.5W 55 KT 65 MPH 120H 23/1800Z 20.5N 48.5W 55 KT 65 MPH $$ Forecaster Berg