000 WTPZ44 KNHC 292046 TCDEP4 Potential Tropical Cyclone Fourteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP142017 300 PM MDT Tue Aug 29 2017 Satellite images indicate that the large disturbance southwest of Mexico is gradually becoming better organized. While the system still lacks a well-defined center, all indications are that it will become a tropical storm tomorrow. Since the system is forecast to bring tropical-storm-force winds to Baja California Sur within 36 hours, advisories are being initiated on a potential tropical cyclone. The system has 2-3 days over very warm water with decreasing shear. Although the system is quite broad for the moment, the favorable environmental conditions noted above should allow for at least steady strengthening. Thus, the official forecast is higher than the model consensus, but lower than the bullish SHIPS model. The initial motion is a highly uncertain 315/8. A weak ridge over central Mexico should steer the cyclone to the northwest or north- northwest for the next few days. Thereafter, the system should turn toward the west-northwest as it moves around a stronger ridge over the southwestern United States. While there is some spread in the guidance, the models are in reasonable agreement for a first forecast, taking the system near or just west of Baja California Sur. The official NHC track prediction is between the model consensus and the NOAA corrected-consensus model HCCA. It is important to note that outside the watch/warning area, very heavy rain is possible, which could cause life-threatening flooding and mudslides over southwestern Mexico. In addition, wind gusts to tropical-storm force are possible along the coast of Michoacan, Colima and Jalisco states tonight into early Wednesday due to the large circulation. The National Hurricane Center now has the option to issue advisories, watches, and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours. Under previous policy this was not possible. These systems are known as Potential Tropical Cyclones in advisory products and are numbered from the same list as depressions. Because of the threat to Baja California Sur, advisories have been initiated on Potential Tropical Cyclone Fourteen-E and the appropriate watches and warnings have been issued by the government of Mexico. Advisory packages will continue until the threat of tropical-storm-force winds for land areas sufficiently diminishes, although if the system becomes a tropical cyclone, the normal rules for discontinuing advisories would apply. Users should be aware that forecast uncertainty for disturbances is generally larger than for tropical cyclones, especially beyond 48-72 hours. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 17.2N 107.2W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 30/0600Z 18.1N 108.0W 30 KT 35 MPH 24H 30/1800Z 19.3N 108.9W 35 KT 40 MPH...TROPICAL STORM 36H 31/0600Z 20.4N 109.8W 45 KT 50 MPH 48H 31/1800Z 21.4N 110.4W 55 KT 65 MPH 72H 01/1800Z 23.5N 112.0W 60 KT 70 MPH 96H 02/1800Z 25.0N 114.0W 50 KT 60 MPH 120H 03/1800Z 26.5N 117.5W 35 KT 40 MPH $$ Forecaster Blake