000 AXPZ20 KNHC 151631 CCA TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1451 UTC Thu Feb 15 2018 CORRECTED SPECIAL FEATURES SECTION 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 1430 UTC. ...SPECIAL FEATURES... Gulf of Papagayo Gale Warning: Offshore NE to E winds will pulse to minimal gale force in the offshore Gulf of Papagayo waters through early Fri, with a brief lull during the afternoon hours. A surrounding area of fresh to strong winds, including near the Gulf of Fonseca will also persist. Downstream seas will build to 8-11 ft during the strongest winds through tonight and merge with the area of seas downwind from the Gulf of tehuantepec through Fri evening. Pulsing fresh to near gale force winds are then expected each night thereafter through the weekend. Ashfall Advisory: The Fuego Volcano over S Guatemala near at 14.5N 90.9W continues erupting. A plume of volcanic ash may reach to the surface through this evening N of 14N and E of 94W. Low level visibilities may be reduced to 1 nm. Mariners should exercise caution. If mariners encounter volcanic ash, they are encouraged to report the observation to the National Weather Service by calling 305-229-4425. Please refer to the East Pacific High Seas Forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more details on both gale warnings and the ashfall advisory. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 05N84W to 04N94W to 06N112W. The ITCZ reaches from 09N129W to 07N134W to beyond 07N140W. No significant convection is noted. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section above for more details on an ashfall advisory near the far southeast coast of Mexico. Gulf of Tehuantepec: High pressure ridging southward over the western Gulf of Mexico to the east of the Sierra Madre Oriental range, is no longer supporting gale force winds offshore and across the Gulf of Tehuantepec. The gale force winds have diminished as the ridging weakens, with a round of strong to near gale force winds expected in association with nocturnal drainage tonight, and then fresh to strong winds pulsing each night thereafter through Sun night. Light and variable winds and seas of 2 ft or less this morning across the Gulf of California will become northerly while increasing to moderate to locally fresh through Fri as the pressure gradient tightens due to strong high pres to the NW. The gradient will then weaken this weekend as the high weakens, allowing for conditions to once again improve. Looking ahead, a cold front will approach southern California and Baja California Norte by Sun night. SW flow ahead of the front will increase to 20-30 kt over the far northern Gulf Mon and Mon night. Fresh NW swell of 6-8 ft will also propagate into the open Pacific waters of Baja California Norte. Elsewhere across the open Pacific offshore waters of Mexico, light to moderate winds will prevail through the next several days, except pulsing to fresh offshore of Cabo Corrientes Fri night through Sun. Seas will mainly be 4-6 ft in mixed southwest and northwest swell. Scattered showers associated with an inverted trough southwest of the area will continue to advect NE across the waters north of 20N ahead of an associated deep layer trough. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please see the Special Features section above for more details on the gale warning in the Gulf of Papagayo, and on an ashfall advisory near the coast of Guatemala north of 14N. For the Gulf of Panama, fresh to near gale force northerly winds are peaking with seas up to 11 ft. However, fresh to strong northerly flow will still persist through Fri morning before diminishing Fri afternoon. Elsewhere, gentle to moderate offshore flow will prevail north of 09N, and light to gentle SSW winds will generally prevail south of 09N. REMAINDER OF THE AREA... Low pressure measuring 1014 mb is centered near 18N125W with an associated surface trough extending from 22N123W to the low to 11N126W. Scattered moderate and isolated strong convection attending this system is present from 08N to 19N between 120W and 123W. This convection continues to plume off to the NE ahead of a deep mid to upper level trough which extends from 32N125W to 23N125W to 12N119W to 05N112W, and around a large upper level anticyclone positioned over deep South Texas near 26.5N97.5W. A tight pressure gradient between the low and troughing and high pressure centered well NW of the area near 41N137W is supporting fresh to strong NE winds in the NW quadrant of the low within 270 nm, where seas are running 8 to 10 ft. The pressure gradient between the high and lower pressure associated with the ITCZ is also supporting fresh trades elsewhere west of these features to 140W with seas 8 to 9 ft in mixed SE and NW swell. The low is forecast to dissipate within 24 hours. However, the pressure gradient W of the trough will remain tight as the high pressure northwest of the area builds. Fresh to strong trades will expand and cover the waters from 21N to 26N west of 128W by 24 hours. The gradient will then gradually weaken through the upcoming weekend allowing for the trades to diminish along with any residual seas of 8 ft or greater. $$ CAM