000 AXPZ20 KNHC 191555 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Jun 19 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... The southern portion of western Caribbean Sea tropical wave with axis along 81W extends southward into the far eastern Pacific to near 05N. It is moving westward at about 16 kt. This wave is enhancing deep convection along and south of the monsoon trough as described below. A tropical wave with axis along 94W from 04N to 15N is moving westward at 10-15 kt. Scattered moderate convection is east of the wave within 30 nm of 12N92W. Similar activity is ahead of the wave as described below in the ITCZ/Monsoon Trough section. A tropical wave with axis along 116W from 03N to 15N is moving westward at 15 kt. Active convection associated with the wave continues this morning as the wave is in close proximity to the tail-end of a mid to upper-level trough that is is just to its north, and that is providing additional instability to the environment surrounding the wave. This convection consists of the scattered moderate to isolated strong type within 120 nm east of the wave from 03N to 12N. Scattered moderate convection is within 30 nm of a line from 13N113W to 12N117W. A tropical wave with axis along 124W/125W from 03N to 15N is moving westward at 10-15 kt. Scattered moderate to isolated strong convection exists east of the wave to 120W and from 07N to 14N. Expect for this activity to continue through at least this afternoon. A rather weak tropical wave with axis along 139W from 03N to 15N is moving westward at 10-15 kt. Isolated showers and thunderstorms are seen east of this wave from 08N to 13N. This wave will continue to weaken over the next 24 hours as it moves to just west of 140W. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1007 mb low over northwestern Colombia southwestward to 09N79W to 07N85W to 08N102W and to 13N111W, where overnight scatterometer data indicated that it transitions to the ITCZ to 08N139W. Outside of convection discussed above under the Tropical Waves section, numerous moderate to strong convection is noted within 150 nm south of the trough between 79W and 84AW. Scattered strong convection is within 150 nm south of the trough between 88W and 92W. Scattered moderate to isolated strong convection is within 240 nm south of the trough between 111W and 115W. Scattered moderate convection is within 180 nm north of the trough between 96W and 100W, and also within 120 nm south of the trough between 100W and 103W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Overnight scatterometer data showed gentle to moderate northwesterly winds across the offshore waters as very weak high pressure continues over the area E of 128W. Recent altimeter satellite data confirms wave models guidance of 4 to 5 foot seas. Little change is expected through Thu morning before the ridge strengthens slightly late Thu into the weekend, allowing winds to increase modestly, and seas to build by about 1 ft. Low pressure over the Colorado River Valley will strengthen some toward the end of the week, and a surface trough will continue to extend from this low over Baja California. This will cause winds to increase over the northern Gulf of California at the end of the week. Some northwesterly swell will also build seas off Baja California Norte for the end of the week and into the weekend. Farther south, a weak tropical wave will move west across the southern Mexico offshore waters, with little impact on local weather, aside from enhancing overnight coastal showers and thunderstorms. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Overnight scatterometer data generally showed gentle west to southwest winds across the area south of the monsoon trough, and only moderate offshore gap winds across the Papagayo region. Northeast to east winds across Papagayo increased to 20-25 kt at or just after daybreak this morning. These winds will diminish to fresh speeds by early this afternoon and to moderate to fresh speeds later during the afternoon. With a favorable relatively tight pressure gradient as a result of high pressure north of the Caribbean Sea and lower pressure in the tropics, these winds are forecast to pulse back up to 20-25 kt late tonight till around daybreak on Thu before diminishing to fresh speeds early Thu afternoon and to moderate to fresh speeds later in the afternoon. This scenario of pulsing winds is expected to continue through the remainder of the week and through the upcoming weekend. Seas through this part of the discussion area will continues to be dominated by pulses of moderate cross- equatorial southwest swell. REMAINDER OF THE AREA... A 1033 mb high remains quasi-stationary well north of the area near 42N138W, with a ridge extending southward to the tropical region west of 130W. Overnight scatterometer data showed fresh trades to the south of the ridge, from about 10N to 19N, where seas are running 6-7 ft in mixed swell. The ridge remains blocked from building into the the waters E of 125W due to a weak surface trough that extends from central California to near 32N131W. However this trough will shift east and weaken through Fri, and allow the ridge to build modestly to the Revillagigedo Islands by late Fri. Seas across the area north of about 25N are in the range of 8-9 ft in mixed northwest and north swell, except to 10 ft along 30N. Little change with these waveheights are expected through Fri before new a new set of north swell builds seas to the range of 8-10 ft across the waters N of 27N between 120W and 133W. South to southwest cross-equatorial swell will continue to move into the tradewind belt for the next few days maintaining waveheights in the 6-7 ft range. Farther south, long-period cross-equatorial swell of 8 to 9 ft, with waveheights to 10 ft just to the south of the area are propagating through waters south of 05N and west of 100W, except for south of 08N between 113W and 118W. Waveheights are expected to remain at this level through early Thu, before decaying. Yet another batch of southern hemispheric swell is expected in the area by this weekend. $$ Aguirre