subj/prognostic reasoning for tropical storm 15w warning nr05/ rmks/ 1. For meteorologists. 2. 12 hour summary and analysis. A. Tropical Storm (TS) 15w (Francisco) has intensified over the past 12 hours. The primary steering influence continues to be the low to mid-level subtropical ridge located north of Taiwan and oriented west to east, which has led to a generally westward track over the past 12 hours. B. Ts 15w is located approximately 220 nm southwest of Hong Kong. The current position is based on a enhanced infrared imagery, pgtw 232330z fix, and a 232312z SSMI image. The current intensity is based on Dvorak estimates of 45 knots from pgtw and rjtd. Ts 15w has tracked westward at 10 knots over the past 06 hours. 3. Forecast reasoning. A. The forecast philosophy remains the same as the previous prog reasoning. B. Through tau 72, the subtropical steering ridge will remain north of ts 15w for the next 48 hours. The westward track will con- tinue as the ts crosses northern haninan. The land interaction will cause the storm to weaken until it reemerges in the Gulf of Tonkin. Despite the moderate to strong vertical wind shear, the warm waters and good poleward outflow will allow 15w to remain a tropical storm. After landfall into northern Vietnam around tau 30, ts 15w will weaken to a depression as it completely dissipates by tau 48. The available dynamic aids are in good agreement with this scenario. Forecast team: Alpha//