000 AXPZ20 KNHC 080321 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Wed Nov 08 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 0000 UTC surface analysis and satellite imagery through 0245 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec: N to NE winds of 20 to 30 kt across the Gulf will diminish slightly on Wednesday afternoon and into Wednesday night. This gap flow will then increase and expand in areal coverage by late Thursday morning and into early Thursday afternoon before increasing to minimal gale force by late Thursday evening. These gale force winds are forecast to persist through early Friday morning, with seas then building up to 10 or 14 ft. Seas of 8 to 9 ft in NE swell will propagate SW well away from the Gulf reaching to near 12N between 94W and 98W by Thursday evening and to near 100W from 10N to 13N by Friday evening. As the tight pressure gradient over southeastern Mexico slackens during Friday afternoon, the gale force winds will then diminish to below gale force and associated seas will subside some. The pressure gradient will tighten again by Friday evening ushering in another round of northerly gale force through the Isthmus of Tehuantepec and across the Gulf. Presently, it appears based on the latest NAM/GFS model guidance that this next episode of gale force winds will be small in areal coverage. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 09N84W to 08.5N91W to 09N100W to 10N112W to low pressure near 10N116W 1009 mb to 10N125W to 12N130W to low pressure near 12N133W 1009 mb and to beyond 09N140W. Scattered moderate isolated strong convection is within 60 nm N of the axis between 121W and 123W. Scattered moderate convection is within 60 nm N of the axis between 92W and 94W, and also between 95W and 99W. Similar convection is within 60 nm of the axis between 124W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 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 strong offshore of the northern waters Thu night through Fri. A cold front is expected to weaken before reaching the area on Friday, 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 Friday, then spread southward through all the waters W of Baja on Saturday while subsiding slightly. Gulf of California: moderate to locally fresh NW winds will continue through tonight. The pressure gradient will tighten a little resulting in a narrow swath of fresh to strong NW winds from 25N to 28N on Wednesday. The pressure gradient will relax with moderate NW flow only to the S of 26N by Thursday evening. Mainly light and variable winds and seas of 2 ft or less will then prevail for the end of the week into the upcoming weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: moderate to locally fresh N to NE winds will pulse during the overnight hours through Wednesday, with seas building to 5 or 6 ft downstream 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 remainder of the week. REMAINDER OF THE AREA... In the upper levels, water vapor imagery reveals a deep layer trough that extends from a small upper-level low moving quickly eastward over far southern California southwestward to 32N119W to 25N135W and to an elongated upper low located at 16N140W. A very pronounced jet stream branch along the trough is attendant by strong SW winds that are advecting abundant overcast to broken mid and high level clouds northeastward towards northern and central Baja California as well as across extreme southern California. These clouds extent within 480 nm to the SE of the trough axis. Isolated showers and thunderstorms are possible underneath most of these clouds. A broad upper anticyclone is centered over W central Mexico at 20N103W, with a ridge WSW to near 17N122W. The water vapor imagery indicates strong subsidence aloft covering the area to the SE of aforementioned jet stream clouds roughly from 13N to 23N and E of 120W. The resultant dry air is inhibiting and deep convection from developing over this area. With the exception of isolated showers from 13N to 15N between 100W and 120W, generally fair skies prevail over this portion of the discussion area. At the surface, a 1013 mb low is analyzed near 30N126W, with a dissipating occluded front entering the forecast area near 30N123W and extending SSW to 26N124W to 20N130W. The low is forecast to continue to pull northeastward away from the discussion area through Wednesday. The front is expected to gradually dissipate by Wednesday evening. Another cold front is forecast to reach a position from near 32N138W to 29.5N140W by early Wednesday afternoon followed by a new set of long period NW swell. The front will then reach from near 32N129W to 28N135W and as a dissipating stationary front to 27N140W by early Thursday evening, and dissipate over the far N central and NE waters on Friday. The associated long period NW swell, with resultant seas of 8 to 13 ft will propagate southeastward through the northern and central forecast waters while gradually decaying and shrinking in coverage area Thursday night through Friday night, at which time seas in the range of 8 to 10 ft are expected to be confined within area bounded by 32N131W to along coast of Baja California at 32N116W to 24N114W to 15N123W to 12N133W to 13N140W to 27N140W to 29N132W to 32N116W. $$ Aguirre