000 AXPZ20 KNHC 292145 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2056 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Narda is downgraded to a Tropical Depression at 29/2100 UTC. At this time, Narda is centered near 19.1N 103.5W at 29/2100 UTC moving NW at 17 kt. Estimated minimum central pressure is 1002 mb. Maximum sustained wind speed is 30 kt with gusts to 40 kt. On the forecast track, the center of Narda will move over or near portions of the western and southwestern coasts of Mexico tonight, then emerge over the Pacific waters early Monday. It is then forecast to move near or just offshore the coast of northwestern mainland Mexico through Tuesday. Some additional weakening is expected while the center is over land. Slow strengthening is forecast once the center moves back over the Pacific waters. 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. The Mexican Weather Service reported rainfall amounts of 12 inches in Oaxaca, and 7 inches in Guerrero in 24 hours yesterday. Around 4 inches of rain in 6 hours are reported today in Zihuatanejo, Guerrero. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough crosses Panama and extends along the pacific coast of the remainder of Central America. Then, continues W of tropical cyclone Narda from 14N108W to 1010 mb low pressure near 12.5N134W to beyond 12N140W. Scattered moderate isolated strong convection is noted from 13N to 17N between 123W and 131W, and from 08N to 13N W of 133W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for information about Tropical Depression Narda. 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 13 ft within this enhanced SW wind flow, peaking SW of Puerto Angel. Satellite imagery continues to show a large cluster of moderate to strong convection ahead of Narda affecting the southwestern coast of Mexico, roughly within about 180 nm just off the coast from 19N104W to 21N107W. This convective activity is just S of Las Marias Islands. 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 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 the Pacific coast of the remainder of Central America. 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 9 ft persist in long period SW swell across the waters off Guatemala, El Salvador, and Nicaragua. Seas will subside below 8 ft by Mon night. Fresh to locally strong 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 in the wake of a weakening cold front. 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 tonight as a northerly surge pushes southward, then subside early on Monday as wind speeds gradually diminish. Elsewhere, 1010 mb low pressure analyzed near 12.5N134W 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. Some gradual development is possible while the system drifts slowly eastward or northeastward. 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. $$ GR