000 AXPZ20 KNHC 152136 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2125 UTC Fri Sep 15 2017 Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis. Based on 1800 UTC surface analysis and satellite imagery through 2130 UTC. ...SPECIAL FEATURES... The center of Tropical Storm Norma at 15/2100 UTC is near 18.9N 110.1W, or about 50 nm E of Socorro Island, moving NW, or 325 degrees at 2 knots. The estimated minimum central pressure is 990 mb. Maximum sustained winds have increased to 60 kt with gusts to 75 kt. Scattered moderate to strong convection was noted within 150 nm in the NW and 75 nm in the SE semicircles of the center. Norma is forecast to gradually strengthen and should become a hurricane later tonight or Saturday as the storm moves NW. Interests in Baja California Sur should monitor the progress of Norma. Please read the latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMEP2/WTPZ22 KNHC for more details. The center of Tropical Depression Fifteen-E at 15/2100 UTC is near 16.0N 125.3W, or about 965 nm W of the southern tip of Baja California, moving W, or 270 degrees at 3 knots. The estimated minimum central pressure is 1006 mb. The maximum sustained winds remain 30 kt with gusts to 40 kt. Scattered moderate isolated strong convection was noted 90 nm in the SW semicircle. The depression may finally strengthen to a tropical storm later tonight or Saturday. Please read the latest NHC Forecast/Advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 KNHC for more details. ...TROPICAL WAVES AND TROPICAL LOWS... A 1010 mb low pressure is near 12N134W embedded in the monsoon trough. S to SW winds of 20 to 25 kt are now confined to an area within 90 nm in the SE semicircle with seas to 9 ft. The low is expected to weaken gradually through Saturday with seas subsiding to less than 8 feet by Saturday night. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... Monsoon trough extends from 09N84W to 08N96W...then resumes from 14N127W to 11N140W. Scattered moderate to strong convection was noted within 180 to 240 NM S of the trough axis E of 98W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the special features section above for more information on Tropical Storm Norma. A NW to SE oriented trough will meander E to W across the Baja California Peninsula and the Gulf of California with a surface low developing intermittently along the trough axis across the far northern Gulf waters. A weak ridge extends along 27N/28N will retreat to the west on Fri night as T.S. Norma approaches the southern tip of the Baja Peninsula this weekend. Gulf of California...Light and variable winds expected through Fri with large southerly swells arriving across the southern waters Fri and Fri night well ahead of Norma. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate southwesterly monsoonal flow is expected through the upcoming weekend with 6 to 8 ft seas primarily due to cross- equatorial swell that is forecast to subside below 8 ft late Friday into Saturday. The monsoon trough has been lifting northward the past few days and will move north of Panama and near the coast of Costa Rica and Nicaragua late Fri...then potentially inland farther north to Guatemala. Abundant moisture converging near the trough will allow for scattered heavy showers and tstms that could produce very heavy rainfall and lead to flash flooding and mudslides across coastal zones and large river discharges early next week. REMAINDER OF THE AREA... A surface ridge extends from a 1025 mb high pressure center located near 36N141W to 27N125W and connects to the ridge off Baja California. Light to locally moderate anticyclonic flow is expected elsewhere N of the monsoon trough and W of 115W through the upcoming weekend. $$ Cobb