000 AXPZ20 KNHC 151603 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Dec 15 2016 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...A Gale Warning remains in effect for the Gulf of Tehuantepec from this evening to around midday Friday. Northerly winds of 20 to 30 kt this morning will further increase to minimal gale force this evening. A cold front moving across the Gulf of Mexico today will allow northerly winds behind the front to begin to spill through the Isthmus of Tehuantepec and across the Gulf of Tehuantepec. Winds across these Pacific waters are forecast to reach 30-35 kt this evening through Friday morning, while seas are expected to build to 9-11 ft with this gap wind event. A stronger cold front could produce a more significant northerly gale wind event beginning on Monday. Gulf of California...A Gale Warning has been issued for the Gulf of California with the morning forecast package. A cold front is forecast to reach northern Baja California on Friday evening and move across the area, including the northern part of the Gulf of California on Friday night. Expect increasing winds ahead and behind this front. Model guidance suggests strong southwest to west winds ahead of the front and strong to minimal gale force west to northwest winds behind the front over the northern Gulf of California Friday night into Saturday morning. Fresh to strong NW winds will affect the offshore zones N of 25N on Saturday and N of 23N Saturday evening, with seas building as high as 10 ft near 30N behind the front. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 07N78W to 09N85W to 10N98W to 1010 mb low pressure near 09N102W. The ITCZ continues from 09N102W to 07N110W to 09N125W to 07N136W to beyond 08N140W. A surface trough extends from low pres center to 15N101W. Scattered moderate isolated strong convection is noted from 08N to 13N W of trough to 106W. Similar convection is within 90 nm N of ITCZ axis between 108W and 112W, and 120 nm N of ITCZ axis between 120W and 122W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gale warnings are in effect for the Gulf of Tehuantepec and Gulf of California. Please, see Special Features section above for details. Currently, gentle to moderate northerly winds and seas of 3-4 ft continue over the offshore waters W of Baja California this morning, under the influence of a weakening ridge extending southward from 1019 mb high pressure centered near 30N121W. The high and ridge will continue weakening during the next couple of days as a cold front moves eastward toward the Baja California peninsula. The front now extends from an occluded low pressure system of 1008 mb located near 30N134W to 30N132W TO 27N140W. Seas of 8-10 ft in N swell follow the front while seas of 8 ft are noted ahead of the front, particularly N of 29N to 130W. The front will begin to move eastward today and reach northern Baja California and the northern part of the Gulf of California by Friday evening. Outside of the Gulf of Tehuantepec area, mainly light to gentle winds prevail south of Los Cabos, with seas of 3-5 ft in mixed NW and SW swell. A low pressure located along the monsoon trough SW of the Tehuantepec region is producing moderate to fresh easterly winds across parts of forecast zone PMZ027. These marine conditions will diminish on Friday as the low pressure continues to move away from the area. Much of the forecast zone PMZ027 still will experience moderate to locally fresh winds due to the ongoing gap wind event. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... As previously mentioned, a 1010 mb low pressure is currently centered southwest of the Gulf of Tehuantepec near 09N102W. The low will continue weakening as it moves westward away from the offshore waters. The low is expected to become a trough by tonight. The convective activity associated with this system and described above in the ITCZ/Monsoon trough section should decrease as the low weakens. Fresh to strong NE winds are expected across the Gulf of Papagayo mainly during the overnight and early morning hours with the assistance of the nocturnal drainage flow. Seas should remain below 8 ft due to the limited fetch length. A larger gap wind event appears to be in store for most of zone PMZ113 on Tuesday morning as strong trade wind flow in the SW Caribbean funnels across Central America. REMAINDER OF THE AREA... As previously mentioned, a 1019 mb high pressure is centered near 30N121W and extends a ridge across the NE waters. The high is forecast to move S to a position near 23N123W in about 24 hours as the aforementioned cold front moves eastward. Expect increasing trade winds and building seas across the west- central waters during the upcoming weekend as strong high pressure builds N of area. $$ GR