000 AXPZ20 KNHC 291530 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1530 UTC Sun Sep 29 2019 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Tropical Storm Narda is centered near 18.1N 102.1W at 29/1500 UTC moving NW at 13 kt. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. A northwestward motion is expected to continue with some decrease in forward speed during the next couple of days. The center of Narda will move over or near portions of the western and southwestern coasts of Mexico through tonight, then emerge over the Pacific on Monday. Weakening is expected as the center moves over land, and Narda is forecast to weaken to a depression tonight. Narda could strengthen to a tropical storm again on Tue once it emerges over water. Numerous strong convection is noted within 60 nm W and 30 nm E semicircles of Narda. Elsewhere, numerous moderate scattered strong convection is occurring from 14N to 22N between 98W and 107W. Narda is expected to produce total rain accumulations of 5 to 10 inches along the southwestern coast of Mexico from Oaxaca to Nayarit, and 1 to 4 inches over Baja California Sur through Monday night. Isolated maximum amounts of 15 inches are possible from Oaxaca to Nayarit. This rainfall will cause life-threatening flash floods and mudslides, especially in mountainous terrain. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N76W to 10N85W to 14N91W, then resumes west of T.S. Narda from 14N109W to 1010 mb low pressure near 12.5N135W to 12N140W. Scattered moderate isolated strong convection is noted from 04N to 08N east of 80W, and within 240 nm south of the monsoon trough west of 130W. Scattered moderate convection is occurring within 180 nm north of the monsoon trough between 125W and 130W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for information about Tropical Storm Narda. Overnight scatterometer data revealed a broad area of strong SW winds well south of Narda over the southern Mexico offshore waters. Earlier altimeter data showed seas of 9 to 16 ft within this enhanced SW wind flow, peaking SW of Puerto Angel within the SE quadrant of Narda. The latest satellite imagery and lightning data indicate numerous showers and scattered strong convection persists off the southwestern coast of Mexico, roughly from 14N to 22N between 98W and 107W. Heavy rainfall potential will continue through Mon across the area. Please refer to statements issued by the Meteorological Service of Mexico for more information. Elsewhere, moderate to locally fresh NW winds prevail across the Baja California Norte offshore waters this morning as a weakening cold front has entered the far northern waters. A high pressure ridge will gradually build into the region later today through Mon. This will freshen offshore winds, with locally strong winds possible near the coast of Baja California north of Cabo San Lazaro. Associated seas will build to 6 to 8 ft within the freshening flow, then subside by mid week as offshore winds are expected to diminish. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough extends from Panama westward across Costa Rica, then continues NW along the coast of Central America to Guatemala. Overnight scatterometer data and recent ship observations indicate offshore winds have shifted to W-NW north of Costa Rica, while moderate W-SW winds prevail south of Panama and off the coast of Colombia. Seas of 8 to 10 ft persist in westerly swell across the waters off Guatemala, El Salvador, and Nicaragua. Seas will subside below 8 ft by Mon night as swell from Narda decays over the region. Fresh SW monsoon flow will resume on Tue between Central America and the Galapagos Islands, with seas building to 8 to 9 ft offshore of Costa Rica and Panama. REMAINDER OF THE AREA... High pressure located well NW of the forecast area is building into the northern waters this morning in the wake of a weakening cold front. Overnight scatterometer data showed moderate to fresh NE winds north of 27N and west of 125W, with corresponding altimeter data indicating seas were 7 to 9 ft in this region. Seas will remain 8 ft through today as a northerly surge pushes southward, then subside tonight as wind speeds gradually diminish. Elsewhere, 1010 mb low pressure analyzed near 12.5N135W along the monsoon trough is supporting fresh to locally strong winds and 8 to 9 ft seas, along with scattered moderate and isolated strong convection. Additional low pressure development is expected along the monsoon trough west of 130W early next week, which will likely maintain fresh SW winds and 8 ft seas over the far SW portion of the forecast waters. $$ Reinhart