| This basin's first usage of potential tropical cyclone. Track: http://www.nhc.noaa.gov/refresh/graphics_ep4+shtml/?cone#contents Floater: http://www.ssd.noaa.gov/PS/TROP/floaters/14E/14E_floater.html Pacific imagery: http://www.ssd.noaa.gov/PS/TROP/trop-epac.html 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 Potential Tropical Cyclone Fourteen-E Advisory Number 1 NWS National Hurricane Center Miami FL EP142017 300 PM MDT Tue Aug 29 2017 ...HURRICANE WATCH AND TROPICAL STORM WARNING ISSUED FOR PORTIONS OF BAJA CALIFORNIA SUR... SUMMARY OF 300 PM MDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...17.2N 107.2W ABOUT 225 MI...365 KM WSW OF MANZANILLO MEXICO ABOUT 430 MI...695 KM SSE OF THE SOUTHERN TIP OF BAJA CALIFORNIA MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Mexico has issued a Hurricane Watch and a Tropical Storm Warning for the coast of Baja California Sur from Todos Santos to Los Barriles including Cabo San Lucas. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Watch is in effect for... * Todos Santos to Los Barriles A Tropical Storm Warning is in effect for... * Todos Santos to Los Barriles A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. Interests elsewhere in southwestern Mexico and Baja California Sur should monitor the progress of this system. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND 48-HOUR OUTLOOK ------------------------------ At 300 PM MDT (2100 UTC), the disturbance was centered near latitude 17.2 North, longitude 107.2 West. The system is moving toward the northwest near 9 mph (15 km/h) and this general motion with some decrease in forward speed is expected during the next couple of days. On the forecast track, the center of the disturbance will approach the southern tip of the Baja California peninsula by late Thursday. Maximum sustained winds are near 30 mph (45 km/h) with higher gusts. Strengthening is forecast during the next 48 hours and the system could become a hurricane late Thursday. The disturbance is expected to become a tropical storm by Wednesday. * Formation chance through 48 hours...high...near 100 percent * Formation chance through 5 days...high...near 100 percent The estimated minimum central pressure is 1006 mb (29.71 inches). HAZARDS AFFECTING LAND ---------------------- WIND: Tropical storm conditions are expected to first reach the coast within the warning area by late Wednesday, making outside preparations difficult or dangerous. Hurricane conditions are also possible within the watch area by Thursday. Tropical-storm-force wind gusts are possible in rainbands along the coast of Michoacan, Colima and Jalisco tonight and Wednesday. RAINFALL: The system is expected to produce total rain accumulations of 5 to 10 inches in the Mexican states of Michoacan, Colima, Jalisco and Nayarit, with isolated maximum totals of 20 inches possible along the immediate coast. This rain could cause life-threatening flash floods and mudslides. SURF: Swells generated by the disturbance are affecting portions of the coast of southwestern Mexico. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 600 PM MDT. Next complete advisory at 900 PM MDT. $$ Forecaster Blake |