Pacific Discussion

  • NHC East Pacific Tropical Weather Discussion
    by (nhcwebmaster) on September 20, 2018 at 8:41 PM

    605 AXPZ20 KNHC 202040 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2040 UTC Thu Sep 20 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 2100 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N84W to 1007 mb low pressure near 09N87W, to 11N100W to 10N117W. Another segment of the monsoon trough continues from 1009 mb low pressure near 14N124W to 11N135W. A segment of the intertropical convergence zone continues from 11N135W to 11N140W. Scattered moderate convection within 90 nm either side of the monsoon trough between 78W and 80W, within 90 nm south of the monsoon trough between 105W and 108W, and within 120 nm either side of the monsoon trough between 110W and 115W. Scattered moderate to isolated strong convection is evident within 90 nm of the low pressure near 11N135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Generally southerly Winds have diminished across the Gulf of California as the remnant low pressure of T.D. Nineteen-E dissipates inland over the mountains of Sonora. Winds will veer more northerly over the Gulf of California Friday through Sunday as an early season frontal boundary moves into northern Mexico east of the mountains. Elsewhere north of 20N, moderate to fresh NW winds persist off the Pacific coast of Baja California, funneling between the coastline and high pressure well northwest of the area. A satellite altimeter pass from 11 UTC showed seas approaching 8 ft north likely due to NW swell entering the discussion area north of 29N and west of 116W. While this is expected to decay below 8 ft today leaving mainly 5 to 7 ft seas, the NW swell and local wind waves will interact with southerly swell off the coast Baja California over the next several days. Farther south, fresh northerly gap winds persist into the Gulf of Tehuantepec, diminishing from stronger winds earlier this morning. Pulses of fresh gap winds will occur again tonight and Fri night. Looking ahead, another strong pulse of gap winds is possible late Sat into early Sun ahead of a tropical wave moving through Central America and southern Mexico. Looking further ahead, there is growing consensus among major models of weak low pressure forming by late Mon into early Tue between Manzanillo and Socorro Island. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fresh offshore nocturnal winds will pulse across the Gulf of Papagayo the next several nights. Cross-equatorial SW swell reaching the Central American coast will slowly subside this weekend. The monsoon trough will meander near 10N the next few days. Looking ahead, an increase in moist southwest flow is advertised by the major global models by early next week, possibly culminating in a Central American gyre pattern by mid week. This may bring increase showers and thunderstorms to the Pacific waters off Central America by early next week, and possibly increased winds and seas thereafter. REMAINDER OF THE AREA... An elongated surface trough extends from roughly Clarion Island to 1009 mb low pressure near 15N123W, then connecting into the monsoon trough. Surface ridging prevails over the waters NW of the trough axis. Moderate to locally fresh trades persist north of the trough west of 120W, supporting seas to 8 ft from 15N-18N W of 130W. The low pressure area will weaken into a trough and move west of the area through early next week, maintaining moderate to fresh winds and at least 5 to 7 ft seas over much of the area north of 15N. A broad circulation is noted along the monsoon trough near 10N112W. There is some disagreement among major models regarding development of this circulation, but at least a weak low may form and drift westward to 130W along 10N through Tue. $$ Christensen […]