000 AXPZ20 KNHC 232149 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2033 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 1800 UTC surface analysis and satellite imagery through 2100 UTC. ...SPECIAL FEATURES... A broad circulation a few hundred miles off the Oaxaca coast of Mexico is becoming a little better organized this afternoon. Clusters of showers and thunderstorms remain disorganized along and north of the monsoon trough, and to the east of a tropical along roughly 102W. The pattern is becoming slightly more favorable for development, and the convection is building in an area where deep layer easterly shear remains light, south of an upper anticyclone over Mexico. Recent scatterometer data sampled this area well, and shows very broad gentle to moderate cyclonic flow. A coherent low pressure center is expected form by Mon, with gradual further development anticipated as the low pressure moves west- northwest through mid week, parallel to the coast of Mexico and toward the Revillagigedo Islands. At a minimum, if this scenario happens, the low pressure will bringing strong winds, building seas, and increased thunderstorm activity to the offshore waters of southern Mexico between Punta Angel and Cabo Corrientes through the forecast period. Please refer to the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. ...TROPICAL WAVES... A weak tropical wave with axis along 87W north of 06N to the Gulf of Fonseca is moving westward at 10-15 kt. Numerous moderate to strong showers and thunderstorms are active mainly where the wave intersects the monsoon trough. This wave may eventually encroach on a low pressure area possibly forming off southern Mexico in the next day or two. A tropical wave has its axis along 114W from 04N to 14N. It is moving westward at 15-20 kt. No significant convection is noted with this tropical wave currently, although the wave continues to move through a very moist and unstable atmospheric environment. Convection is likely to increase along and near this wave over the 24 hours. A poorly defined tropical wave had been analyzed near 125W, but no clear sign of the wave is evident at this location at this time. The wave may have dissipated, or is possibly a little farther west than earlier thought. Scatterometer data and precipitable water imagery, along with model diagnostics, indicate a trough along the monsoon trough/ITCZ closer to 132W. This may or may not be the continuation of the earlier wave, as there is also increased influence of sharp upper trough and cutoff low west of 135W, which may be supporting development of a surface to low level trough a little farther east. At any rate, aside from the weak trough is scatterometer data along 132W and isolated thunderstorms nearby, there is little impact at this time. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 06N77W to 12N105W to 10N130W. The ITCZ continues from 10N130W to beyond 08N140W. Numerous moderate to scattered strong convection is noted within 180 nm either side of the monsoon trough east of 105W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features section above for details regarding gradual development of low pressure near a tropical wave, with potential to develop into a tropical cyclone during the next few days. Farther north, an earlier scatterometer satellite pass indicated moderate to fresh NW winds funneling off the coast of Cabo San Lucas. This was on the eastern periphery of a ridge reaching southwestward across the waters west of Baja California through the Revillagigedo Islands. Various altimeter satellite passes indicated seas of 4 to 6 ft over open offshore waters of Mexico. Aside from the potential impact of the developing low pressure over the outer offshore waters of southern Mexico, strong gap winds are possible in the wake of the low pressure in the Gulf of Tehuantepec by Wed night. 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 to strong northeast to east gap winds will impact the Papagayo region through Thu night. Seas are being dominated by long period south to southwest swell from the southern hemisphere. Recent altimeter satellite passes indicated seas of 5-7 ft adjacent to Central America, with seas of 6-8 ft noted along the coasts of Colombia and Ecuador. The swell will maintain seas in these areas for at least the next several days. The southern portion of the tropical wave along 85W is triggering numerous moderate to strong convection over the offshore waters E of about 88W. This activity will most likely be attended by strong gusty winds and locally higher seas through at least tonight or longer. REMAINDER OF THE AREA... A 1032 mb high pressure center is well north of the area near 39N138W. A ridge extends southeastward from this high to the Revillagigedo Islands. To the south of the high, the pressure gradient between the ridge and lower pressure in the tropics is supporting moderate northeast to east trades to the north of the ITCZ and west of about 120W. Little change in the position of the high or the speed of trades is expected for the next several days. Waveheights in this area will generally run between 5-7 ft. Farther south, long-period cross-equatorial swell is maintaining waveheights of 8 to 9 ft to the south of 09N between 100W and 120W. This area of seas will begin to subside this evening. $$ Christensen