000 WTPZ42 KNHC 170237 TCDEP2 TROPICAL STORM POLO DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL EP172014 800 PM PDT TUE SEP 16 2014 Polo continues to gradually become better organized. The center is located on the northern edge of an area of deep convection, and a curved convective band has become better established in the western semicircle. The initial intensity has been set to 45 kt based on the latest Dvorak estimate from TAFB. The SHIPS model shows the shear decreasing below 10 kt during the next 24 hours, which in combination with very warm SSTs above 29C should allow for intensification in the short term. In fact, the SHIPS RI index shows a 66 percent chance of a 25-kt increase in the next 24 hours. The official forecast has been adjusted upward in the short range, and shows Polo becoming a hurricane by 24 hours. Easterly shear is forecast to increase after that time, which should slow the pace of strengthening. By the end of the period Polo will be moving over cooler waters in a moderate shear environment, and gradual weakening is expected. The new NHC intensity forecast is a a little above the latest IVCN intensity consensus and is close to the SHIPS model through the period. A pair of timely SSMIS passes around 00 UTC were helpful in establishing the initial position and the initial motion of 310/10. The tropical cyclone will be steered northwestward for the next several days by a mid-level ridge centered over northern Mexico. By day 5, the cyclone should turn toward the west as the ridge builds westward to its north. The new NHC track is a little left of the previous one through 24 hours due to the initial position and motion, but is otherwise an update of the previous track. Through the period, the official forecast is close to the TVCE multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 17/0300Z 13.8N 101.3W 45 KT 50 MPH 12H 17/1200Z 14.9N 102.4W 55 KT 65 MPH 24H 18/0000Z 16.2N 103.8W 70 KT 80 MPH 36H 18/1200Z 17.2N 105.2W 75 KT 85 MPH 48H 19/0000Z 18.2N 106.6W 80 KT 90 MPH 72H 20/0000Z 19.7N 108.7W 75 KT 85 MPH 96H 21/0000Z 21.3N 111.0W 65 KT 75 MPH 120H 22/0000Z 22.0N 113.5W 50 KT 60 MPH $$ Forecaster Brennan