000 AXPZ20 KNHC 111551 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1412 UTC Sun Mar 11 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 1445 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Light to moderate onshore winds will prevail through early Mon morning. Strong high pressure ridging will build southward along the Sierra Madre Oriental of eastern Mexico and the western Gulf of Mexico behind a strong cold front through the early part of the week. Winds will abruptly become northerly, then rapidly increase to fresh to strong over the Gulf of Tehuantepec by late Mon morning. Winds will continue to increase to gale force late Mon afternoon and peak around 45 kt Mon night 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 Mon night or Tue morning. 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 09N84W to 05N94W. The ITCZ axis continues from 05N94W to 04N110W to 02N122W to beyond 07N140W. Scattered moderate and isolated strong convection is noted from 04N to 05N between 96W and 99W, from 03N to 05N between 103W and 115W and from 06N to 08N W of 138W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on the Gulf of Tehuantepec developing gale warning. Weakening 1017 mb high pressure centered near 26.5N118W ridges SE across the open waters W of the Baja California peninsula. Mainly light to moderate NW to N winds prevail beneath this ridge. Winds will increase to between 15 and 20 kt this afternoon through Tue as the high gradually builds. The high will then weaken and dissipate by Wed as a decaying cold front approaches. Long period NW swell will cause seas to build to between 6 and 8 ft W of 110W Wed through Thu. Gulf of California: Light to gentle winds will increase to between 10 and 15 kt across the Gulf S of 28N this afternoon through Tue in response to building high pres just NW of the offshore zones. Winds will become fresh to locally strong over the waters S of 26N this afternoon through Mon afternoon, especially near Cabo San Lucas. The pressure gradient across the region will weaken Tue night through Thu, which will allow winds to diminish to between gentle and moderate across the Gulf of California. 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 will be just strong enough to maintain fresh to strong winds over the Gulf of Papagayo this morning. The ridging will continue to weaken but still produce pulsing moderate to fresh winds tonight through Tue, then increasing back to fresh to strong at night as the pressure gradient restrengthens Tue night through Thu night, peaking near 30 kt early Thu morning. 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. Elsewhere, expect gentle to moderate winds and 4 to 7 ft seas to prevail. REMAINDER OF THE AREA... A busy weather pattern remains in place across the NW and N central waters. A cold front extends SW from 1010 mb low pressure centered just offshore of San Diego, California near 32N118.5W to 30N120W to 28N123W to 27N126W. A weakening occluded front enters the discussion area farther W near 32N130W, then continues as a weakening cold front to 30N130W to 27N130W to 24N133W to 21N139W. A plume of deep tropical moisture extends from SE of the Hawaiian Islands northeastward over the discussion waters along and ahead of these frontal boundaries. Scattered moderate convection is present along and up to 60 nm SE of the cold front between 121W and 125W. Scattered moderate convection is seen along and up to 90 nm SE of the weakening cold front S of 27N. Winds associated with these features are light to locally moderate, with corresponding seas in the 4 to 6 ft range. A stronger cold front will approach 30N140W from the NW later this morning. An area of fresh to strong winds will precede the front, as well as follow it, finally diminishing by Mon night. Large NW swell will also accompany the boundary, reaching as high as 14 to 16 ft by Mon evening. The front will weaken as it moves across the waters N of 24N and W of 125W. A weaker cold front will introduce a round of reinforcing NW swell Wed night and Thu. Moderate to locally fresh trades combined with decaying NW swell are supporting combined seas of 7 to 8 ft across the waters from 07N to 10N between 129W and 137W. The pressure gradient in this area will temporarily weaken today and allow seas to subside to less than 8 ft in this area by this afternoon. Seas in this area will rebuild to 8 ft on Mon, then merge with a larger area of NW swell generated by the stronger cold front mentioned in the previous paragraph on Tue. $$ CAM