000 AXPZ20 KNHC 121603 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Mon Mar 12 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong high pressure ridging will surge southward behind a strong cold front along the Sierra Madre Oriental of eastern Mexico and over the western Gulf of Mexico through tonight, then remain in place through Wed night. A tight pressure gradient, typical of such synoptic pattern set- ups, has materialized over southeastern Mexico and just inland the Gulf of Tehuantepec. This has lead to winds abruptly becoming strong to near gale from the north in direction through the Isthmus of Tehuantepec, and out across the Gulf within 30 nm either side of a line from 16N95W to 15N95W. As a cold air mass continues to push southward from eastern Mexico towards Isthmus of Tehuantepec, then gradient will further intensify allowing for the the strong northerly winds to increase to gale force late this afternoon and peak around 40 kt with slightly higher gusts late tonight into early Tue. Gale force winds will likely diminish by midday Thu, with brief lulls below gale force also possible during the afternoon hours Tue and Wed. Seas will reach to a range of 10 to 16 ft late tonight into Tue morning. This latest gap wind event will finally wind down by Thu evening. Please see the latest Pacific Ocean High Seas Forecast product under AWIPS/WMO headers HSFEP2/FZPN03 KNHC, for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 08N82W to 05N95W to 04N104W. The ITCZ axis continues from 04N104W to 02N116W to 01N124W to 04N136W to 05N140W. A second ITCZ axis is S of the equator and extends from just SW of the Galapagos Islands near 02S97W to 02S113W to 04S123W to 05N140W. Numerous strong convection is within 45 nm either side of the trough between 89W and 91W. Scattered moderate convection is within 75 NM N of the trough between 86W and 88W, and also elsewhere within 60 nm of the trough between 88W and 91W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on the Gulf of Tehuantepec developing gale event. High pressure 1019 mb is centered near 25N120W with associated ridging extending southeastward to the open waters W of the Baja California peninsula. The high pres will maintain 15 to 20 kt NW to N winds through Tue. It is forecast to weaken and dissipate by Wed as a decaying cold front approaches. Long period NW swell generated by winds behind the front will allow for seas to build to between 6 and 8 ft W of 110W Wed through Thu, subsiding thereafter. Gulf of California: The pres gradient related to the high pres just NW of the offshore zones will continue to induce moderate to fresh NW winds over the central and southern Gulf, except fresh to locally strong NW winds are expected over the waters S of 26N through the afternoon, especially near Cabo San Lucas. The pres gradient across the region will weaken Tue night through Fri, which will allow winds to diminish to between gentle and moderate. A cold front or remnant trough will approach Baja California Norte Fri night. Winds will become southerly in the northern Gulf of California and increase to fresh to near gale force. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... High pressure ridging over the Caribbean from the SW Atlantic is weakening but is still causing moderate to fresh winds to pulse over the Gulf of Papagayo through Tue. Winds will increase back to fresh to strong Tue night through Fri night as the pressure gradient restrengthens in response to high pressure building SE over the Caribbean from the Gulf of Mexico. Over the Gulf of Panama, gentle to moderate winds will prevail through Wed, increasing to moderate to fresh thereafter. Seas are expected to run between 4 and 6 ft as moderate cross-equatorial SW swell continue to arrive, building to 5 to 7 ft Thu and Fri as the winds also increase. Elsewhere, expect gentle to moderate winds and 4 to 6 ft seas to prevail, except seas of 8 to 11 ft in northerly swells generated from a gale force gap wind event in the Gulf of Tehuantepec, which will propagate into the Guatemala offshore waters tonight through Tue night. REMAINDER OF THE AREA... A remnant surface trough extends from 32N126W to 23N134W. Scattered moderate convection is noted within 240 east and southeast of the trough. A cold front extends from near 32N133W to 25N140W. Fresh to strong SW winds are within 120 nm to the east of the front, with seas of 8 to 11 ft. Scattered moderate is occurring within 30 nm of a line from 32N130W to 28N133.5W to 26N135W. Strong west winds are behind the front, with rather large seas of 10 to 15 ft due to a NW swell. The cold front will gradually weaken as it moves across the northern waters through Tue night, while the NW swell builds and peaks around 16 ft along 30N tonight into early Tue. A weaker cold front will introduce a round of reinforcing NW swell Wed night and Thu, with yet another decaying front dropping S for the end of the week with another set of NW to N swell. Mixed swell are generating an area of seas measuring close to 8 ft generally between 05N and 10N between 120W and 135W. This area of seas will gradually propagate westward and eventually merge with the larger area of NW swell generated by the cold front mentioned in the previous paragraph. $$ Aguirre