000 AXPZ20 KNHC 211611 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Tue Nov 21 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 FEATURE... Gulf of Tehuantepec Gale Warning: Nocturnal northerly drainage flow across the Gulf region is gradually diminishing this morning, with winds beginning to fall below 25 kt and seas 5 to 7 ft. Winds are expected to diminish to 15 kt or less with seas 3- 6 ft by early afternoon. Gale force Nly winds are expected to develop rapidly Wed afternoon, as a cold front moves quickly southward across Mexico and the western Gulf of Mexico. Light winds across the Tehuantepec region Wed morning and afternoon with quickly increase to 20-25 kt by mid-afternoon and then blast 30-40 kt by late afternoon into the evening hours, and continue through Thu morning. Minimal gale conditions will then persist through Fri morning. Expect max seas of 16 ft near 14.5N95.5W late Thu. The resultant NE swell will propagate SW, mixing with long-period cross equatorial swell, with seas 8 ft or higher across the waters well downstream of the Gulf of Tehuantepec, roughly within 120 nm of line from 12N97W to 07N100W early Fri before beginning to subside. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The eastern Pacific monsoonal circulation has weakened in recent days with the monsoon trough currently extending from the semi- permanent low pressure near 10.5N74W across Panama on to 06N94W. the ITCZ then begins from 06N94W TO 06.5N116W TO 12N129W TO low pres near 10.5N138W 1012 MB. Widely scattered moderate convection continues along the Colombian coastal waters from 03N to 06N east of 80.5W. Scattered moderate to strong convection is noted W of a line from 08N140W TO 13N132W TO 16.5N140W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features paragraph above for information on the developing Gulf of Tehuantepec Gale Warning. A weak NW to SE orientated ridge extends across the waters just beyond 250 nm seaward of the Baja Peninsula and will maintain light to moderate NW winds across the offshore waters N of 20N through Wed morning. A weak trough is expected to form extending SW from the central Baja Peninsula to near 23N116W, and continue through early Fri before filling. This will occur as the ridge shifts slightly NW and act to weaken weaken winds through the week, with light to gentle winds prevailing. Expect seas in the 3 to 4 ft range through Thu, building to 4 to 7 ft across the waters N of 25N late in the week. Gulf of California: Moderate NW winds this morning will increase late this afternoon due to daytime heating, reaching around 20 kt through central portions late this afternoon then gradually subsiding overnight. Seas are expected to peak at around 5-7 ft through central portions early tonight. The pressure gradient will relax thu and Fri, with light and variable winds expected through Sun. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Light drainage flow expected during the overnight hours through Thu, with fresh to locally strong nocturnal drainage beginning on Thu night and continuing through the upcoming weekend. Light and variable winds, and 3 to 5 ft seas, are expected elsewhere to the N of the monsoon trough which has been meandering between 09N and 11N, while moderate to locally fresh southerly winds, and 3 to 6 ft seas, are forecast S of the monsoon trough through the upcoming weekend. REMAINDER OF THE AREA... A NE to SW aligned ridge will meander from 32N125W to beyond 18N140W for the next several days. Strong southerly winds, currently across the waters N of 26N W of 136W, will diminish to 20 kt or less on Wed as the ridge weakens allowing a cold front to reach 32N140W on Wed. The cold front will stall from 32N137W to 23N140W on Thu. Seas of 11 to 16 ft W of the front on Wed will subside to 9 to 11 ft on Thu night. The associated long period NW swell, in the form of 8 to 11 ft seas at 12 to 15 seconds, will propagate E across the discussion waters W of 120W through late week, and subside over the upcoming weekend as another round of swell produces 8 to 14 ft seas at 12 to 19 seconds pushing into the NW corner. $$ Stripling