000 AXPZ20 KNHC 210947 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0945 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: Strong N winds, and seas of 7 to 9 ft, currently across the gulf waters will diminish and subside through late morning. The associated NE swell has been mixing with long-period cross-equatorial swell, with 7 to 9 ft seas currently across the waters from roughly 09N to 11N between 95W and 104W, forecast to subside below 8 ft early this afternoon. Strong N winds are expected to resume on Wed afternoon, with gale conditions developing quickly on Wed evening, with 30 to 40 kt winds by late Wed night, and continuing into Thu afternoon. 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 monsoon trough extends W along 10N across the SW Caribbean to the Pacific coast of Costa Rica at 09N84W, then dips SW to 06N98W where scatterometer winds indicate a transition to an ITCZ, which continues W-NW to beyond 11N140W. A low level trough is analyzed from 09N130W to 15N128W. Isolated moderate to strong convection is noted within 45 nm of 06.5N78W, and within 180 nm either side of a line from 08N122W to 12N130W to 08N139W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features paragraph for Gulf of Tehuantepec Gale Warning. A NW to SE orientated ridge just beyond 250 nm seaward will maintain light NW flow W of the Baja Peninsula through Wed morning when a trough will form extending SW from the central Baja Peninsula to near 23N116W, and continue through early Fri before filling. 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, then subsiding some during the upcoming weekend. Gulf of California: Moderate NW flow expected this morning, becoming a moderate to locally fresh NW breeze tonight, returning to moderate NW flow Thu. The pressure gradient will further relax, with light and variable winds on Fri 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 to near gale force southerly winds, currently across the waters N of 28N W of 138W, 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, in the form of 8 to 14 ft seas at 12 to 19 seconds pushes into the NW corner. $$ Nelson