000 AXPZ20 KNHC 210911 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 608 UTC Sat Apr 21 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 0845 UTC. ...SPECIAL FEATURES... N to NE winds over and downstream of the Gulf of Tehuantepec will hover in the 20 to 25 kt range until sunrise as nocturnal drainage flow augments the winds. Seas are slowly subsiding and are now down to 8-10 ft. Winds and seas will begin to more rapidly diminish in areal coverage after sunrise. Supporting high pressure across the southern U.S. behind a stalled cold front over the northern Gulf of Mexico is shifting slowly eastward, and is allowing the pressure gradient across the Isthmus of Tehuantepec to continue weakening. Winds over the Gulf of Tehuantepec will become light and variable and seas will subside below 8 ft by this evening. Another cold front entering the NW Gulf of Mexico could induce the next gap wind event over the Gulf of Tehuantepec Mon through Thu. Gales are not expected during this event. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 07N77W to 06N86W to 05N113W. The ITCZ continues from 05N113W to beyond 05N140W. Scattered moderate and isolated strong convection is present from 06N to 08N between 82W and 84W and from 04N to 10N between 108W and 113W. Isolated moderate and strong convection is found within 60 nm either side of a line from 08N92W to 04N98W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Fresh NW winds and seas of 5 to 8 ft prevail across the offshore waters of Baja California as a tight pressure gradient exists between a ridge building in from the NW and lower pressure over the SW United States and NW Mexico. NW swell following a front that swept through the area last night will maintain seas at 5-8 ft tonight. Winds and seas W of the peninsula will then diminish Sun through Tue as the high to the NW weakens and lower pressure over the SW United States and NW Mexico fills and shifts east. Moderate NW winds prevail over the N Gulf of California, while fresh NW winds are observed through the central Gulf. Winds will subside as well over the Gulf Sun through Tue as the high gradually weakens the area of low pressure weakens and moves east. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh NE to E winds across the region are expected to pulse between nightfall and mid morning to 20-25 kt across and downstream of the Gulf of Papagayo through at least Tue night with seas peaking each episode between 7 and 9 ft. Gulf of Panama: Fresh northerly winds and seas of 5 to 7 ft in SW swell prevail across the Gulf of Panama and offshore of Panama and Colombia to 250 nm today. Very active convection has been developing at night along the coast of Colombia. Convection this morning has less areal coverage but could produce strong gusty winds and very rough seas to near 8 ft this morning. Northerly winds will become gentle to moderate tonight through Mon across the Gulf of Panama, while farther offshore and SW, gentle to moderate SW winds will prevail Sun through Wed. Corresponding seas will generally run between 4 and 6 ft. Elsewhere, mainly light to gentle winds are expected S of 06N through Wed. Cross-equatorial swell will mix with residual swell downwind from Papagayo through Wed, and maintain seas in this area between 5 and 7 ft. Elsewhere seas will subside to 3-5 ft by Sun as long period SW swell from the Southern Hemisphere decay, then rebuild to between 5 and 7 ft on Mon and Tue as another round of SW swell arrive. REMAINDER OF THE AREA... Strong high pressure is centered W of California near 140W. The high ridges SE across the northern forecast waters to near the Revillagigedo Islands. The pressure gradient between the ITCZ and the high to the north will support fresh to strong NE trades N of the ITCZ generally between 05N and 20N W of 125W through Saturday. The combination of these winds, NW swell and SW swell will support combined seas of 8 to 11 ft over these waters into Saturday, expanding N to 30N by Sunday as NW swell propagates into the northern waters. The NW swell will begin to decay below 8 ft Sunday night before becoming reinforced by another pulse of NW swell by Monday night. Cross equatorial SW swell moving into the southern forecast waters continue to decay and seas have subsided to 8 ft or less near the equator. Another round of SW swell could cause waters near the equator to build to 8 ft or above on Mon or Tue. $$ CAM