000 AXPZ20 KNHC 092118 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2118 UTC Wed Aug 9 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 2100 UTC. ...TROPICAL WAVES... A tropical wave axis is along 90W moving W at around 10 to 15 kt. Convection is present near the southern portion of the wave axis SW of the monsoon trough as described below. The interaction of energy associated with this tropical wave and the monsoon trough axis is forecast to gradually develop a broad cyclonic gyre over the far eastern part of the area to the SW of Central America by the end of the week and into the upcoming weekend. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pressure over northern Colombia near 09N75W to 07N89W to 10N95W, then resumes from 14N101W to 09N130W to 12N140W. Scattered moderate and isolated strong convection is within 270 nm S of the axis E of 95W, within 180 nm S of the axis between 114W and 127W, and also within 240 nm S the axis between 129W and 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Ridging W of the Baja California peninsula and troughing along the Baja California peninsula is supporting moderate NW flow across the waters W of 110W, along with 4 to 5 ft seas. Mainly light to moderate onshore winds prevail elsewhere outside of the Gulf of California. Gentle to occasionally moderate southerly winds and seas of 2 ft or less prevail in the Gulf of California, except 3 to 4 ft near the entrance. Winds will become northerly in the southern Gulf by the end of the week. By Friday morning, weak low pressure may develop SW of Mexico between 100W and 106W. Fresh to strong E to SE winds will develop and parallel the coast within 60 nm building fresh seas to 8 ft. These conditions may then spread NW during the upcoming weekend along the coast dependent on the possible development of the low. Uncertainty remains with regards to the strength and impacts of any associated marine conditions. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate southerly winds are expected S of the monsoon trough, with gentle and variable winds N of the monsoon trough. Seas are expected to be in the range of 4 to 6 ft. Long period southerly swell reaching the coastal areas of Costa Rica and Panama will decay through the end of the week. A new and extensive set of cross-equatorial swell is forecast by wave model guidance to cross 03.4S east of 120W, on Friday afternoon. This swell is forecast to reach the coastal waters of Panama and Costa Rica between 80W and 88W late on Sunday night, then from between El Salvador and Mexico by sunrise Monday. Seas will range from 7 to 10 feet across these offshore waters, except in the lee of the Galapagos Islands. REMAINDER OF THE AREA... A weak and broad ridge dominates the waters N of the convergence zone with a few exceptions. A weak trough disrupts the ridge from 28N133W to 23N129W. Scattered showers are possible in the vicinity of the trough axis. The trough will dissipate tonight. A weak 1012 mb low pressure area is near 13N106W. Scattered moderate and isolated strong convection is from 12N to 16N between 105W and 110W. This low is forecast to linger over the same general area during the next few days. Otherwise, moderate trades and seas of 4 to 6 ft prevail N of the convergence zone under the ridging, with moderate to fresh southerly flow and 4 to 7 ft seas S of the convergence zone. Little overall change in these marine conditions is expected into the upcoming weekend. $$ Lewitsky