National Hurricane Center's Tropical Weather Discussion

Eastern Pacific Ocean

640 AXPZ20 KNHC 212108 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2108 UTC Thu Jun 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...TROPICAL WAVES... The axis of a tropical wave is analyzed N of 08N along 98W. Scattered moderate and isolated strong convection is from 07N to 12N between 94W and 104W. Scattered moderate convection is N of 11N between 89W and 95W. Westward progress of this wave has started to slow as anticipated. This wave will be one to watch with interest for potential tropical development this weekend into early next week. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N75W to 11N90W to 14N111W to low pressure near 12N116W to 08N122W. The ITCZ extends from 08N122W to 06N127W to 08N138W. Scattered moderate convection is from 04N to 09N between 78W and 88W, and also from 12N to 15N between 104W and 108W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Moderate NW winds west of the Baja California peninsula will prevail through Fri. A pulse of northerly swell will propagate into the waters off Baja California Norte by the end of the week, building seas to near 7 ft Saturday. Elsewhere, light to gentle winds will prevail over the open waters the next several days. Cross equatorial southerly swell will propagate into the waters off Southern Mexico by the end of the week, which will build seas to near 7 ft by Saturday. Seas will subside Sunday into early next week. Gulf of California: Winds will increase to moderate Friday, then moderate to fresh in the southern Gulf and fresh to strong N of 29N by Saturday morning as the pressure gradient gradually tightens. Seas will build to 4 to 7 ft as the winds increase, except to 8 ft N of 29N. The wind will then diminish to light by Monday with seas subsiding to 2 ft or less. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough will meander between 09N and 11N the next several days. Light to gentle winds will prevail N of the monsoon trough, with gentle to moderate S to SW winds prevailing S of the monsoon trough. A pulse of long period SW swell will reach the waters W of Ecuador today, with combined seas building to 7 to 9 ft late Friday, except in the lee of the Galapagos Islands. The swell will continue to spread across the southern forecast waters, with seas building to 5 to 8 ft S of 08N early Sat. Seas will subside on Sun and Mon. REMAINDER OF THE AREA... Low pressure of 1011 mb is centered near 12N116W. Scattered moderate and isolated strong convection is within 300 nm in the E quadrant and within 150 nm in the S quadrant of the low. This low will linger through the end of the week, then may shift NE thereafter with possible deepening. A trough is analyzed from 13N136W to 06N139W. Scattered moderate and isolated strong convection is from 05N to 09N between 134W and 137W. Seas to 8 ft in mixed northerly swell are noted from 13N to 17N between 133W and 138W. The trough will drift westward, moving west of 140W Fri night. Elsewhere, high pressure of 1025 mb centered near 37N134W extends a ridge SE to near the Revillagigedo Islands. Gentle to moderate trades prevail west of 120W, where seas are in the 5 to 7 ft range. Seas N of 20N have subsided to 4 to 6 ft. A fresh pulse of northerly swell will propagate into the northern waters with seas building to 6 to 9 ft north of 25N between 120W and 130W Friday. Cross equatorial southerly swell will build seas to 6 to 9 ft south of 10N and west of 90W late Friday. Seas associated to this swell will start to subside Sunday into early next week. A large set of northerly swell will push into the waters N of 23N and W of 125W early next week with combined seas building to 8 to 11 ft. $$ Lewitsky