000 AXPZ20 KNHC 152206 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Tue May 15 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 1800 UTC surface analysis and satellite imagery through 2115 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 08N76W TO 09.5N87W TO 08N96W TO 13N114W TO 07N122W, where it transitions to the ITCZ to 04N131W. Scattered moderate to strong convection is located from 04N to 10N between 84W and 113W. Widely scattered moderate isolated strong convection is noted within 150 nm either side of the axis between 114W and 124W. ...DISCUSSION... ...TODAY, MAY 15, MARKS THE FIRST DAY OF THE 2018 NORTHEAST PACIFIC HURRICANE SEASON... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A NW to SE oriented high pressure ridge prevails across the offshore waters west of Baja California, producing fresh NW to N winds over those waters. These winds will increase to fresh to locally strong Wed afternoon through Friday as the ridge strengthens slightly. Altimeter data from this morning indicated that seas were subsiding to just below 8 ft, and remain in the 5- 7 ft range. Seas will change little through tonight before building slightly Wed through Thu to 6-8 ft as the winds freshen across the region. Gulf of California: Light and variable winds prevail over the northern Gulf of California this afternoon, while gentle to moderate NW winds continue across the remainder of the Gulf. Little change is expected through Wed, except for fresh NW onshore winds along the coast of Mexico from 24N to 26N late this afternoon through Wed evening. Gulf of Tehuantepec: Gentle to moderate variable winds are expected to prevail across the Gulf region through Fri as a weak pressure pattern remains over SE Mexico and the Yucatan Peninsula. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Light to gentle winds will dominate the gulf most of the forecast period as a weak pressure remains across Central America. Seas of 4-5 ft prevail this afternoon in long period SW swell. A strong pulse of cross equatorial SW swell will move into the regional waters beginning Wed, and build seas to 5-7 ft Thu through Sat. Gulf of Panama: Gentle to moderate S to SW winds are forecast during the next several days, with seas of 4-6 ft in long period southerly swell, building to 5-7 ft Wed night through Sat as long period SW swell reaches the coasts of Panama and Colombia. Elsewhere, gentle to moderate SW winds are expected to the south of the monsoon trough with its axis roughly along 09N/10N, with light to gentle variable winds north of trough as a weak pressure pattern remains over Central America. Seas are forecast to build to 6-7 ft in long period SW swell between Ecuador and the Galapagos Islands late Wed and continuing through Fri, then build slightly higher to 6-8 ft Sat. REMAINDER OF THE AREA... A 1020 mb high has settle across the N waters near 29N124W and extends a ridge southeastward to near the Revillagigedo Islands. The pressure gradient between the ridge and the monsoon trough and ITCZ to the south is presently weak, and yielding moderate NE-E trades between about 09N and 22N to the west of 115W. Seas across this area of trades are 6-8 ft, and should change little through Thu. The ridge will shift slightly southeastward through Wed, with the resultant pressure gradient forecast to induce a slight increase of trades across the tropics. Stronger high pressure is then forecast to build southeastward over the northern portion of the discussion area, and tighten the pressure gradient leading to fresh to strong tradewinds. Seas are expected to increase to 7-9 ft Thu into Fri. Decaying NW swell is propagating through the waters north of 21N W of 118W, where seas are 5-6 ft. Moderate to fresh N to NE winds will continue S through SE of the high over the next few days as the ridge reorganizes. Winds and seas will increase modestly as discussed to the E of 122W through Thu, while little change occurs to the W of 122W. $$ Stripling