000 AXPZ20 KNHC 142212 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Fri Dec 14 2018 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 2030 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong northerly winds have begun to spill across the Gulf of Tehuantepec in the past few hours, associated with a cold front crossing the Bay of Campeche this afternoon. Strong high pressure behind this front will initiate gale force northerly winds by 2100 UTC and continue to increase to strong gale force winds by this evening. Computer model guidance suggests that these gales will continue through the weekend and will last until Mon afternoon. Peak winds are forecast to be around 40 kt on Sat as corresponding seas quickly build to near 18 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 07N75W to 07N90W to 06N103W. The ITCZ continues from 06N103W to 09N128W to 08N133W, then resumes from 08N138W to beyond 08N140W. Scattered moderate and scattered strong convection is flaring from 03N to 07N east of 81W. Scattered moderate convection is evident from 07N to 10N between 125W and 132W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Weak high pressure ridging E from 29N126W to near 29N116W is maintaining light to gentle breezes across the Pacific waters off Baja California. Fresh to strong NW flow continues over the Gulf of California along the E shore of the Baja Peninsula between 24N and 27N. Meanwhile the next pulse of long period NW swell has entered the area from the west, and is reaching Baja California Sur this afternoon. NW swell will dominate the offshore waters off the entire Baja California coast through the Revillagigedo Islands with seas up to 9 ft by tonight, followed by reinforcing NW swell through Sun. Looking ahead, a cold front will reach the northern coast of Baja California by Mon night, accompanied by large reinforcing NW swell, bringing seas of 12 to 18 ft to all of the offshore zones of Baja California and into the Revillagigedo Islands by late Tue. Swell of this size and period will present hazardous seas for mariners, cause very powerful and dangerous surf along the Pacific reefs and beaches, and likely produce areas of modest coastal flooding and beach erosion. A mid to upper-level disturbance is approaching the area from the west. This disturbance is currently interacting with a surface trough extending from 09N133W TO 16N128W. The disturbance may bring a few showers to the central and southern portions of the Baja California Peninsula and Gulf of California tonight through Sun. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo...Fresh gap winds will pulse to around 20 kt tonight before ramping back up to between fresh and strong during the overnight and early morning hours Sat night. These conditions will then persist through Mon night as high pressure builds north of the region. Seas are expected to max out near 10 ft Sun morning. Gulf of Panama...Fresh northerly winds across and downstream of the Gulf will slowly diminish through Sat, then become fresh from the north Sat night through Tue. Elsewhere, gentle to moderate winds will persist on either side of the monsoon trough through early next week, as seas remain in the 4 to 6 ft range. REMAINDER OF THE AREA... Weak ridging prevails across the NE waters off of Baja California. A persistent surface trough extends from 09N133W TO 16N128W. Afternoon scatterometer data indicates fresh to strong winds on the W side of the trough between 11N and 19N, and east of the trough to 125W from 16N to 19N. The high pressure ridge to the N will weaken through tonight ahead of an approaching cold front, allowing the winds to diminish to between moderate and fresh by tomorrow morning. A cold front crossing the NW portion of the discussion area extends from 30N132W TO 26N140W, and is introducing a new round of NW swell with seas of 10 to 16 ft following the front. The front will slow then dissipate trough Sat, with the swell propagating ahead of the front and gradually subsiding as well. Elsewhere NW swell in excess of 8 ft will more or less dominate the waters west of 110W through Sun. A stronger cold front will usher in very large NW swell, in excess of 20 ft, which will enter NW portions of the forecast area early Sun. Seas of 12 ft or higher could encompass almost all of the forecast waters N of 07N and W of 115W by Tue morning. $$ Stripling