000 AXPZ20 KNHC 110243 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sun Aug 11 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 0230 UTC. ...SPECIAL FEATURES... A broad area of low pressure associated with a tropical wave axis along 103W from 06N to 18N and a 1008 mb low pressure center near 16N103W remains embedded in a very moist environment per the latest TPW satellite animation imagery. The earlier convection observed with this area of low pressure has significantly diminished during the evening. Broad cyclonic turning is noted with this area, with only scattered showers and isolated thunderstorms remaining from 14N to 17N between 102W and 105W. Deep convection is likely to re-develop during the overnight hours. Per latest NHC Tropical Weather Outlook, this system has about a day or two to become a tropical depression as it moves west-northwestward just off the southwestern coast of Mexico. After that time, conditions are forecast to become unfavorable for tropical cyclone formation. Regardless of development, the disturbance will likely bring locally heavy rainfall along portions of the southwestern coast of Mexico during the next couple of days. This area of disturbed weather has a medium chance of becoming a tropical cyclone during the next 48 hours. Refer to the latest NHC Tropical Weather Outlook under AWIPS/WMO headers MIATWOEP/ABPZ20 KNHC for more information. ...TROPICAL WAVES... A tropical wave with axis along 95W north of 05N to inland the Gulf of Tehuantepec region is moving westward at 10-15 kt. Scattered moderate convection has recently formed within 120 nm either side of the wave axis from 08N to 10N as well as along and just offshore the southeastern coast of Mexico between 92W and 94W. Expect for this activity to spread westward during the overnight hours. A tropical wave with axis near 117W from 05N to 18N is moving westward at about 15 kt based on a 24 hour estimated speed. This wave remains embedded in a very moist environment based on the latest TPW satellite imagery animation. Deep convection associated with this wave is occurring near the part of the axis of the wave axis where it crosses the monsoon trough. This convection is described below under the ITCZ/Monsoon Trough section. Environmental conditions are expected to become more conducive for tropical cyclone formation by the middle of next week as this system moves in west-northwestward. Please see the latest eastern North Pacific Tropical Weather Outlook for more information. A tropical wave with axis near 134W from 04N to 16N is moving westward around 15 kt. TPW satellite imagery animation and satellite water vapor imagery are revealing a dry and stable environment existing to the north of 12N. This is inhibiting convection along and near this wave. The only convection occurring in the vicinity of this wave is that which is along and near the ITCZ as described below. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pressure of 1008 mb located over northern Colombia near 09N79W northwestward to 10N88W to 14N96W to low pressure near 16N103W 1008 mb, to another low pressure near 15.5N108W 1009 mb, then to 12N115W to 12N124W and to 11N132W. Scatterometer data from this afternoon suggested that the ITCZ begins at 11N133W and continues to west of the area at 10N140W. Scattered moderate to isolated strong convection is seen within 60 nm north of the trough between 105W and 108W. Scattered moderate convection is within 120 nm south of the trough between 118W and 122W, also within 60 nm north of the trough between 116W and 120W and within 60 nm south of the trough between 131W and 134W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See Special Features section above for details regarding a broad area of low pressure that is along and offshore the southwestern coast of Mexico. The earlier fresh to locally strong southeast winds over the central and northern Gulf of California have diminished to mainly fresh winds this afternoon as the pressure gradient has relaxed some. These winds will diminish further on Sun to gentle to moderate speeds and to gentle speeds during the early to middle part of next week. Fresh east winds along with scattered to numerous showers and thunderstorms, with gusty winds and heavy rainfall, will likely continue along the southwestern coast of Mexico over the next couple days as the broad area of low pressure described above under Special features tracks in a general west-northwestward motion. Elsewhere, gentle to moderate northwest winds continue over the Baja California offshore waters between the typical climatological trough over the peninsula and high pressure of 1021 mb centered well offshore near 30N137W. This high will slowly move northeastward through early next week, with little change in offshore wind and sea conditions expected. Fresh to strong north winds will funnel briefly across the Gulf of Tehuantepec on Mon, then diminish to moderate to fresh Mon night through Tue. Combined wave heights will remain less than 8 ft over the southern waters, despite long-period mixed southeast and southwest swell continuing to propagate through those waters. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The pressure gradient between higher pressure over the western Caribbean Sea and lower pressure over Central America will continue to support the pulsing of strong northeast to east winds across the Gulf of Papagayo through Sun night. These winds will then shift west to over the waters west of the Gulf on Mon night and diminish to moderate speeds late Mon night while fresh northeast to east winds pulse through the Gulf of Papagayo at that time before briefly increasing to fresh to strong early Tue and diminish back to fresh speeds Tue afternoon and through Wed. Wave heights will build to 8 ft within the area of these due to the combination of mixed southerly swell with northeast wind waves. Elsewhere, expect generally moderate southwest winds, with scattered showers and thunderstorms south of the monsoon trough through early next week. Mixed southeast and southwest swell continues spreading northward across the offshore waters between Ecuador and the Galapagos Islands, with seas 8 ft or greater across the waters south of the equator. Combined wave heights of 8 to 10 ft in this area will subside to below 8 ft by Mon night. REMAINDER OF THE AREA... Please refer to the Tropical Waves section above for more information regarding potential tropical cyclone development early next week. Low pressure of 1009 mb is near 14N108W as noted in latest visible satellite imagery. Numerous moderate to isolated strong convection is seen from 14N to 18N between 100W and 102W, and also from 14N to 20N between 102W and 105W. Scattered moderate to strong convection is present from 14N to 17N between 109W and 112W. This low is forecast to move in a general northwestward motion and dissipate by late Sun night. New low pressure is forecast to develop from the tropical wave axis, that is presently analyzed along 115W from 05N to 18N, by or on Mon roughly near 14N120W and track to the northwest. Currently mixed southeast and southwest swell producing wave heights of up to 8 ft are occurring from 08N to 11N and between 111W and 115W, however, by early Mon afternoon the low is forecast to acquire an associated area of strong winds and wave heights of 8-10 ft in its E and SE quadrants. Farther north, the pressure gradient between high pressure centered near 30N137W and the monsoon trough/ITCZ is supporting moderate to locally fresh trades south of 20N. These winds will continue during the next several days as high pressure slowly moves to the northeast. The significant southern-hemispheric swell event of the past few days is gradually lessening up. Recent altimeter data revealed wave heights in the range of 8-10 ft south of the equator roughly between 82W and 120W, with 8 ft seas reaching as far north as 04N. The swell will propagate northward through the weekend, then gradually decay early next week, allowing for wave heights to subside across the region. $$ Aguirre