000 AXPZ20 KNHC 230228 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 228 UTC Sun Jun 23 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 0000 UTC surface analysis and satellite imagery through 0200 UTC. ...TROPICAL WAVES... A weak tropical wave reaching from the Pacific coastal waters of southern Costa Rica northward to the Caribbean coast of Nicaragua will continue to drift westward along the Pacific coasts of Costa Rica and Nicaragua through Sun. The wave may follow a low pressure area possibly forming off southern Mexico in the next day or two. A tropical wave persists off southern Mexico along roughly 98W, drifting west at 5 kt. Scattered showers and a few thunderstorms are ongoing east of the tropical wave axis in the area where southwest wind converge into the monsoon trough. Earlier scatterometer satellite data show generally light winds on the northern periphery of the tropical wave, outside of shower and thunderstorm activity. The convection around this tropical wave is still fairly disorganized, but some global model output continues to show a surface low pressure area forming near the tropical wave over the next couple of days and drifting west- northwest away from the coast of Mexico through mid week. A tropical wave has its axis along 108W from 04N to 12N. It is moving westward at 10-15 kt. Scattered moderate convection evident near the tropical wave and along the adjacent portions of the monsoon trough. A tropical wave has it axis along 120W from 04N to 15N, moving westward near 15 kt. Recent scatterometer satellite data shows no clear surface impact from this wave, and no significant convection is associated with the wave as well. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N84W to 11N105W to 08N120W. The ITCZ continues from 08N120W to beyond 08N140W. Scattered moderate to isolated strong convection is ongoing from 06N to 12N east of 120W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Earlier scatterometer satellite data continued to show light to gentle winds off southern Mexico, and concurrent altimeter data shows seas of 4 to 6 ft, likely with a component of SW swell. But the relatively tranquil conditions may not persist. Sporadic clusters of showers and thunderstorms well off the coast of Chiapas and Oaxaca are likely the early precursors to a broad area of low pressure starting to develop in the area along the monsoon trough. This will be the main weather feature to watch through the waters off southern Mexico through mid week as the low pressure slowly forms and develops. If this scenario happens, expect increasing winds, building seas and increased showers and thunderstorms in the offshore waters from Punta Angel to Cabo Corrientes into mid week. Please see the latest Tropical Weather Outlook for the eastern Pacific on hurricanes.gov for details. Looking ahead, global models indicate strong gap winds into the Gulf of Tehuantepec late in the week in the wake of the developing low pressure. Farther north, a modest pressure gradient will support gentle to moderate winds and slight to moderate seas across the area. The developing low pressure may move near the Revillagigedo Islands later in the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gentle to moderate winds will continue for most areas, although pulses of fresh easterly gap winds will impact the Papagayo region through Tue, then winds could become strong Tue night. Seas are being dominated by long period S to SW swell from the southern hemisphere. Recent altimeter satellite passes indicated seas of 5-7 feet adjacent to Central America, with seas of 6 to 8 feet noted along the coasts of Colombia and Ecuador. The swell will maintain seas in these areas for at least the next several days. A rather vigorous tropical wave located to the southwest of the Tehuantepec region as described above has helped initiate widespread clusters of moderate to strong convection across the offshore waters mainly between 90W and 100W. This activity will most likely be attended by strong gusty winds and locally higher seas through at least Sun. REMAINDER OF THE AREA... A 1034 mb high remains quasi-stationary well north of the area near 42N140W, with a ridge extending southeast from the high to the Revillagigedo Islands. To the south of the high, the pressure gradient between the ridge and lower pressure in the tropics is allowing for northeast to east trades of 10-15 kt. Little change in the position of the high or the speed of trades is expected into early next week. A tight pressure gradient directly to the south of the high is supporting fresh northeast to east winds north of the ITCZ and west of about 125W, along with waveheights in the range of 6-9 ft in northerly swell. Much of the swell is being generated by persistent gale force winds off the coast of California. Wave model guidance indicates that the swell will slowly decay through early next week. Farther south, long-period cross-equatorial swell is resulting in waveheights up to 8 and 9 ft to the south of the Equator. The leading edge of this set of swell will reach northward to near 09N from 100W to 116W on Sun before it begins to subside beginning on Sun evening. Waveheights to 10 ft are possible along and just to the south of 03.4S between 115W and 120W on Sun. $$ Christensen