000 AXPZ20 KNHC 120904 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 904 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 0600 UTC surface analysis and satellite imagery through 0830 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Light to moderate onshore winds will prevail through early morning. Strong high pressure ridging will build 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. Winds will abruptly become northerly, then rapidly increase to fresh to strong over the Gulf of Tehuantepec by late morning. Winds will continue to increase to gale force late this afternoon and peak around 40 to 45 kt 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 peak in the 15 to 17 ft range 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 08N81W to 04N93W. The ITCZ axis continues from 04N93W to 02N110W to 03N125W to 05N140W. A second ITCZ axis is S of the equator and extends from just SW of the Galapagos Islands near 01S91W to 02S105W to 03.4N117W. Scattered moderate and isolated strong convection is within 90 NM N of the trough between 85W and 89W, and also between 92W and 99W. Similar convection is S of 01S between 100W and 108W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on the Gulf of Tehuantepec developing gale warning. High pressure 1019 mb is centered near 25N120W with ridging extending SE of the ridge across the open waters W of the Baja California peninsula. The high will maintain 15 and 20 kt NW to N winds through Tue. The high will weaken and dissipate by Wed as a decaying cold front approaches. Long period NW swell generated by winds behind the front will cause seas to build to between 6 and 8 ft W of 110W Wed through Thu, subsiding thereafter. Gulf of California: High pres just NW of the offshore zones is generating 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 pressure 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 Atlc 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 reaches from 30N123W to 27.5N130W to 25N140W. Scattered moderate and isolated strong convection is within 300 nm E and SE of the trough to the N of 28.5N, and also within 120 nm SE of the trough to the W of 130W. A cold front extends from 30N136.5W to 27N140W. Fresh to strong SW winds are within 90 nm E and SE of the front, with fresh to strong W winds behind the front. NW swell of 8 to 13 ft also accompanies the front in the area of winds. The 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-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. $$ Lewitsky