000 AXPZ20 KNHC 091514 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1414 UTC Thu Nov 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 1200 UTC surface analysis and satellite imagery through 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...High pressure surging southward behind a cold front moving across the western Gulf of Mexico will push a cooler air mass towards the eastern slopes of the Sierra Oriental mountains along eastern Mexico. This will further intensify the pressure gradient already in place allowing for northerly winds to increase to minimal gale force across the Gulf of Tehuantepec by early this afternoon. Seas are expected to build to the range of 10-15 ft with these gale conditions. A gale warning is already in effect for the Gulf of Tehuantepec through 48 hours. Winds may briefly diminish just below gale force during the afternoon hours after today. Model guidance suggests that this event will last through early next week, with winds increasing to 35-40 kt by early Monday morning. At that time, seas are forecast to build to 14-16 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N84W to 09N100W to 1010 mb low pressure near 10N122W to 09N140W. Scattered moderate convection is N of 06N E of 82W...including the Gulf of Panama, and from 07N to 10N between 82W and 87W. Scattered moderate to isolated strong convection is from 08N to 10N between 102W and 107W, and from 08.5N to 11N between 120W and 124W in association with the above mentioned low. Scattered moderate convection is from 10N to 12N between 124W and 128W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on a Gulf of Tehuantepec Gale Warning. A ridge will dominate the waters W of Baja California through the rest of the week, while a trough will meander between the coast of NW Mexico and the Gulf of California. Moderate to locally fresh NW to N flow will prevail across the waters W of Baja California, increasing to fresh to locally strong offshore of the northern waters this evening through Fri as the pressure gradient slightly tightens between a high pressure center over the northern forecast waters and the aforementioned trough. A cold front is expected to weaken before reaching the area on Fri, but the associated long period NW swell inducing seas in the range of 8 to 10 ft will propagate southeastward across the waters N of 23N and to the W of Baja California on Fri, then spread southward through all of the waters W of Baja on Sat, subsiding to less than 8 ft by early Sun. Looking ahead, the pressure gradient W of Baja California will tighten even more Mon through Tue, with increasing of 20-25 kt and building seas of 8 to 9 ft across the waters N of 24N or 25N. Gulf of California: A relatively tight pressure gradient is supporting moderate to fresh NW flow across the central and southern Gulf, with gentle to moderate NW flow to the N. Seas are 2 ft or less in the northern Gulf, and 4 to 6 ft elsewhere. The gradient will slacken with winds diminishing to light to gentle throughout for the end of the week through Sat, with seas subsiding to 2 ft or less, except 4 to 6 ft near the entrance of the gulf. The pressure gradient will tighten back a bit for the end of the weekend into early next week with gentle to moderate NW winds across the entire gulf. Elsewhere, mainly gentle to moderate NW flow and 4 to 6 ft seas will prevail for the next several days. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Nocturnal drainage flow will support pulsing moderate to fresh winds during the overnight hours for the next several days, with seas occasionally building to 5 or 6 ft downstream of the Gulf near 11N87W. Light and variable winds and 4 to 6 ft seas are expected elsewhere to the N of 09N, while moderate to locally fresh southerly winds and 5 to 7 ft seas are forecast S of 09N through the next several days. REMAINDER OF THE AREA... A cold front is moving across the northern forecast waters and extends from 30N130W TO 27N140W. A new set of long period NW swell follows the front, with seas up to 12 ft or 13 ft. This swell event will propagate SE across the area reaching the waters W of Baja California as previously mentioned. The front will weaken and eventually stall from 30N128W to 26N140W early on Fri. Seas of 8 ft or greater will cover the waters N of 15N W of 115W by Fri evening, then begin to subside to near 8 ft throughout the waters by Sun evening. A transient and weak low pressure remains along the monsoon trough near 10N122W, and will continue to move westward through the upcoming weekend and into early next week. Model guidance indicates a tightening pressure gradient between the low and and building high pressure to the N during the weekend into early next week. This may allow for trades to increase to fresh to strong across the waters S of 20N and N of the monsoon trough/ITCZ, supporting fresh seas of 8 to 10 ft. $$ GR