000 AXPZ20 KNHC 052205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Fri Jan 05 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 2145 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A very tight pressure gradient over southeastern Mexico continues to induce gale force N-NE winds over the Gulf of Tehuantepec. The gale force winds are expected to continue into Sunday, before diminishing to just below gale force on Sunday afternoon. NE Swell generated from the persistent gale force winds will propagate downstream of the Gulf of Tehuantepec, with seas 8 ft or greater reaching as far south as 05N and westward to near 109W by tonight. The NE swell will begin to mix with NW late tonight between 99W-105W and continue to do so through Sunday. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. A rapidly evolving baroclinic low pressure system is located at 24N131W with a pressure of 1013 mb. Its associated cold front extends from it through 21N130W to near 15N133W. An Ascat pass from 1754 UTC this afternoon highlighted quite an extensive area of strong E-SE gale force winds to the E and SE reaching to near 127W, and strong to near gale force N-NE winds within about 120 nm to its NW. Latest satellite imagery shows areas of rain with embedded scattered showers and isolated thunderstorms from about 21N to 30N between 125W-128W, and also N of 27N between 128W and 136W. The low will deepen as it drifts northeastward over the next couple days. The pressure gradient between the deepening low and high pressure to its W and NW will support gale force winds W and NW of low beginning tonight and last through Saturday afternoon. The current gale force winds to its E and SE will slowly diminish to strong E-SE winds on Saturday afternoon. Seas are expected to be in the range of 10-15 ft within the strong gale force winds E and SE of the low and building from 10-12 ft in the NW quadrant of the low tonight to the range of 12-16 ft on Saturday. By Sunday afternoon the low is forecast to reach a position near 27.5N132W with pressure of 1009 mb, with strong N-NE winds expected between 120 and 180 nm in the NW quadrant of the low along with seas of 9-11 ft. A tight pressure gradient dislodged to the E-SE of the low will support strong E-SE winds over an area from 22N to 24N between 127W-129W late Saturday night and on Sunday with seas in the range of 8-10 ft. Please refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 06N78W to 07N87W to 05N95W to 07N102W to 07N110W, where latest scatterometer data indicates the ITCZ then begins and continues to 08N118W to 11N125W where it briefly ends. It resumes from a 1013 mb low near 10N131W to beyond the area at 08N140W. Scattered moderate convection is noted within 30 nm of the trough between 102W-105W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see Special Features section above for more details about the ongoing gale force wind event in the Gulf of Tehuantepec. Looking ahead another gale force gap wind event is possible in the Gulf of Tehuantepec early next week as high pressure builds behind the next cold front forecast to move into the Gulf of Mexico. NW swell will propagate into the offshore waters off Baja California Norte Tuesday, with seas building to around 13 ft by Tue night. Elsewhere, relatively tranquil marine conditions are expected during the period. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Winds will pulse to near gale force over the Gulf of Papagayo tonight and again on Saturday afternoon and night before diminishing to strong winds on Sunday. Light to gentle NE-E winds will prevail elsewhere to the N of 09N, with gentle to moderate S to SW winds expected S of 09N. REMAINDER OF THE AREA... Please see Special Features section above for details regarding a recently started gale center event. A 1013 mb surface low persists near 10N131W, with a trough extending from it to 13N132W and to 15N132W. Upper divergence aloft between an upper trough along 135W and anticyclonic flow farther S is supporting scattered moderate isolated strong convection within 60 nm of the low in the NE quadrant. The surface low will likely dissipate through Saturday although a surface trough will remain in the area through early next week. An earlier altimeter pass indicated seas of 8 to 10 ft likely in NW swell over the area from 10N to 20N west of 135W. This will subside through early next week, ahead of another round of NW swell 8 ft or greater expected by mid week. $$ Aguirre