000 AXPZ20 KNHC 042217 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Mon Dec 4 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... Gulf of California: Strong high pressure is building well N of the area over the U.S. Great Basin and northern Rockies, and has begun to support the development of fresh to strong NW flow in the far northern Gulf N of 29.5N. Winds will increase to minimal gale Tue morning in the northern Gulf as the pressure gradient continues to tighten, then will diminish below gale by Tue evening as it slackens slightly. Meanwhile, the fresh to strong winds will spill southward across the entire Gulf by mid-week. Another area of strong high pressure will build across the region Wed night through Thu and may initiate another round of gales across N and central portions Thu. Seas are expected to build up to 10 ft across the northern part of the basin by late Tue and to 6 to 9 ft across the remainder of the basin Wed through Thu. Also, as the strong winds develop across the Gulf, strong northeasterly gap winds will bleed through gaps in the mountain peaks across the northern peninsula and spill into the Bay of San Sebastian. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pressure near 06N78.5W to 07.5N86W to 07N102W. The ITCZ extends from 07N102W to 10N117W, then resumes from 10N120W to 08N130W to 12N140W. Scattered moderate to strong convection is noted across and south of the Gulf of Panama from 06N to 11N e of 82W to the coast. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: Southerly return flow continues across the W half of the Gulf of Mexico this afternoon and is acting to reduce the northerly flow across and downstream of the Gulf of Tehuantepec. Winds across Tehuantepec have diminished to 15-20 kt this afternoon with seas subsiding to 4-7 ft. Associated seas are 6 to 8 ft in shorter period swell generated from the strong gap winds reaching 200 to 300 nm downstream of the Gulf of Tehuantepec, mixed with longer period NW swell. Moderate to fresh northerly winds will continue across Tehuantepec through Tue, with peak winds pulsing at night, then increase to fresh to strong at night through Thu morning, possibly increasing to gale force by late Wed night as a cold front pushes across the western Gulf of Mexico and through southern Mexico. Looking ahead, strong high pressure building N of the area behind a Gulf of Mexico cold front will supporting a persistent strong gale event across the Gulf of Tehuantepec through late in the week. Elsewhere off the Pacific coast of Mexico, weak high pressure is maintaining gentle to moderate breezes across the region. Long period NW swell is producing seas of 6 to 9 ft swell propagating across all open waters, except within 100 to 200 nm off the coast south of Los Cabos and the central Mexican coast, where seas are 5-7 ft. The swell will gradually decay to less than 8 ft across all offshore waters by Tue. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Moderate to fresh winds across the Papagayo region this afternoon will pulse to strong again tonight with seas downstream building to 6 to 8 ft. Winds and seas will diminish through late week as strong trades winds over the southwest Caribbean diminish and veer SE. Looking ahead, strong high pressure will build N of the region, allowing strong gap winds and building seas to reappear by Sun. Winds may even approach minimal gale force late Sun night through early Mon. Elsewhere, light to gentle N to NE winds are expected N of the monsoon trough, and mainly moderate S to SW winds are expected to the S of the monsoon trough. Seas are in the 4 to 6 ft range, but are expected to build to 5 to 7 ft in SW swell this afternoon and evening to the S of the monsoon trough, subsiding to 4 to 6 ft through mid week. REMAINDER OF THE AREA... A negatively tilted, mid level short wave trough from 10N to 18N between 117W and 125W is supporting a surface trough along the ITCZ between 117W and 121W. Upper divergence on the SE side of the trough along with convergence of moderate to fresh trade winds at the surface are supporting scattered moderate to strong convection from 07.5N to 16N between 114W and 122W. The trough will weaken as it lifts W-NW through mid week. An upper low centered near 31N139W continues to support a stalled frontal trough from 27N138W to 1011 mb low pressure near 22.5N136W, then a stationary front to 20N135.5W to beyond 16.5N140W. A second trough is to the SE from 18N137W TO 14N139W. Jetstream energy and upper divergence across the region continues to enhance scattered moderate to strong convection from 09N TO 22N E of the front TO 126W, and scattered moderate convection N of 22N and E of the frontal trough. A strong ridge prevails across the NE pacific and is producing a tight pressure gradient between the troughs and the high pressure, which supports fresh to strong easterly winds on the eastern periphery of the troughs and fronts to about 129W Elsewhere, NW swell greater than 8 ft covers almost the entire discussion waters beyond 250 nm offshore of Central and South America. These seas will gradually decay through the early part of the week. $$ Stripling