000 AXPZ20 KNHC 181604 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Tue Jun 18 2019 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 1545 UTC. ...TROPICAL WAVES... A tropical wave with axis along 91W and north of 04N to inland western Guatemala is moving westward at 10-15 kt. Only isolated showers and thunderstorms are seen within 30 nm either of the wave where it crosses the monsoon trough. A surface to low-level trough extends from 15N102W to 05N104W, moving westward at 10-15 kt. This feature is surrounded in a very moist and unstable atmospheric environment present to the south and southwest of a mid to upper-level anticyclone centered over western Mexico near 21N105W. During the morning, clusters of numerous moderate to strong convection have increased within 210 nm west of the trough from 10N to 15N and also within 270 nm west of the trough from 05N to 10N. A tropical wave with axis along 118W from 04N to 15N is moving westward at 10-15 kt. Scattered moderate to isolated strong convection is within 120 nm east of the wave from 12N to 15N. Isolated showers and thunderstorms are within 300 nm east of the wave from 04N to 10N. A tropical wave with axis along 134W from 04N to 15N is moving westward at an estimated speed over the past 24 hours of 10 kt. Water vapor imagery indicates that upper-level environment over this wave is fairly moist, however stable conditions at the surface and low-levels are allowing for only isolated showers and thunderstorms to develop within 60 nm east of the wave from 10N to 12N. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northwestern Colombia near 10N75W southwestward to 08N78W to 09N90W to 10N102W. It resumes at 11N104W to 12N112W to 10N124W. The ITCZ begins near 09N125W and continues to beyond 07N140W. Outside of shower and thunderstorm activity discussed above under the Tropical Waves section, scattered moderate to isolated convection is noted within 180 nm north of the trough between 116W and 124W. Scattered moderate convection is within 60 nm either side of the trough between 97W and 102W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... The pressure gradient between a high pressure ridge west of Baja California and a low pressure trough along the Baja California peninsula is maintaining moderate northwest to north winds across most of the adjacent offshore waters where seas remain in the 4-5 ft range. Winds and seas off Baja California will change little through next several days. Surface low pressure is expected to cover a rather expansive area over the southwestern United States and California through mid week, and extend a sharp surface trough into the area waters along 123W to the north of 25N. This will prevent the ridge from building a great distance over the offshore waters, with the resultant gradient allowing for gentle to moderate winds through Wed before winds begin to freshen as the surface trough dissipates. Under this pattern, expect pulses of fresh to strong southwest to west gap winds into the northern Gulf of California tonight and again late on Fri. Northwest swell is forecast to propagate through the northern waters off Baja California beginning on Fri night and through at least the earlier part of the upcoming weekend. Otherwise, light to gentle winds will persist farther south over the Mexican offshore waters. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Strong trades across the south central Caribbean are spilling across Central America and producing offshore gap winds from the Gulf of Papagayo region to El Salvador. This scenario is expected to continue across the Caribbean and will support fresh to strong gap winds across the Gulf of Papagayo during overnight hours through the remainder of the week and into the upcoming weekend. Elsewhere, fairly tranquil wind conditions will persist off Central America under a weak pressure pattern. Long-period southwest swell propagating through the southern waters will build the waveheights to 9 ft between Ecuador and the Galapagos Islands through Tue. Wave model guidance suggests that new south to southwest swell will propagate through the southern waters west of 90W Tue night through Thu building waveheights there to a peak of 8 ft again before they begin to subside late on Thu. REMAINDER OF THE AREA... A ridge extends from a 1033 mb high pressure system located well north of the area near 41N141W southeastward to just west of the Revillagigedo Islands. Overnight scatterometer data showed fresh northeast to east winds south of the ridge from 11N to 18N west of 132W, where seas were 7-8 ft. Elsewhere, moderate to fresh northeast to east winds prevail south of the ridge to the ITCZ west of 125W along with generally in the range of 5-7 ft. A series of weak tropical waves will move across the deep tropical waters through Sat, occasionally supporting locally higher winds, seas to 7-8 ft, and shower/thunderstorm activity. Northerly swell related to ongoing gale force winds well north of the discussion area offshore northern California is propagating through the waters north of about 29W and west of 124W. This swell will continue to propagate southward through the remainder of the forecast period. Seas north of 27N and west of 126W will build to 8-9 ft Tue through Wed night, with seas possibly reaching to 10 ft along 30N on Wed afternoon and night as suggested by wave model guidance. Farther south, long-period southwest swell to 8 ft will move in to the waters south of 06N between 91W and 133W through Wed, before decaying below 8 ft by early on Thu evening. Yet another set of long-period swell will bring seas to 8 ft in the same area Fri and Sat. $$ Aguirre