000 AXPZ20 KNHC 072205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Thu Jun 7 2018 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 2145 UTC. ...SPECIAL FEATURES... Recently upgraded Hurricane Aletta is centered near 15.3N 110.0W at 2100 UTC, or about 400 nm WSW of Manzanillo, Mexico, moving WNW or 300 deg at 5 kt. Maximum sustained winds have increased to 65 kt with gusts to 80 kt. Minimum central pressure has lowered to 987 mb. Latest visible satellite imagery shows that Aletta has acquired an eye feature during the day as banding features become more coiled around it. The satellite imagery shows numerous strong convection within 150 nm of the center in the NW quadrant. Scattered moderate isolated strong convection is occurring within 210 nm of the center in the SE quadrant and 180 nm of the center in the E quadrant. Other scattered moderate isolated strong convection is within 30 nm of a line from 11N112W to 13N110W, and within 30 nm of 11N115W. Scattered moderate convection is within 180 nm of the center in the NE quadrant. Aletta will gradually strengthen, with its maximum winds reaching 80 kt with gusts to 100 kt by late Fri night per latest NHC advisory, Aletta is then forecast to be impacted by vertical shear on Sat. This should begin to weaken the cyclone into next week. Please refer to the latest NHC Forecast Advisory under WMO/AWIPS headers WTPZ22/MIATCMEP2, and the NE Pacific High Seas Forecast under WMO/AWIPS headers FZPN03/MIAHSFEP2 for the latest information on this system. A tropical wave is along 95W north of 09N extending inland across southeastern Mexico in the Gulf of Tehuantepec region, moving westward at 10 kt. The southern part of the wave is continues to enhance deep convection present north and south of the monsoon trough as described above. Scattered moderate convection is within 30 nm of 11N95W, and within 30 nm of 11N89W. The wave is forecast to move at about the same speed during the next 24 to 48 hours, at which time low pressure is expected to form along it near 10N98W. Model guidance suggests that upper- level conditions are forecast to become favorable for this system to develop during the upcoming weekend. This system has a medium potential for development during the next couple of days. Fresh easterly flow behind this system is expected to increase to strong Fri through Sat, with some chance of these winds increasing further as the low pressure deepens. This tightening of the gradient will bring fresh northeast to east winds across the Gulf of Papagayo region through the upcoming weekend. Please refer to the latest NHC Tropical Weather Outlook under header ABPZ20/MIATWOEP for the latest potential for development on this system. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northern Colombia to southern Costa Rica/northern Panama to 09N90W to 10N100W, where it has fractured from Hurricane Aletta. It then resumes at 11N116W to 08N125W, where the ITCZ then continues to 07N135W and beyond 07N140W. Scattered strong convection is within 120 nm north and 30 nm south of the trough between 84W and 86W. Scattered moderate isolated strong convection is noted within 120 nm north and 60 nm south of the trough between 115W and 119W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad ridge extends from a 1025 mb high pressure system centered near 31N138W southeastward to near the Islas Revillagigedo. The typical low pressure trough will remain over the Baja Peninsula and Gulf of California through Fri. This pressure pattern will generally support moderate to fresh northwest winds west of the Baja Peninsula through Fri. These winds become mainly fresh on Sat N of 28N. Seas of 5 to 7 ft will build to 6 to 8 ft this evening due to a new pulse of NW swell, with the swell forecast to expand in areal coverage through the next few days. Inside the Gulf of California, generally light to gentle southerly wind flow is expected to continue through the weekend. Afternoon to evening sea breezes are forecast to dominate the Gulf for the next few days and will freshen the winds to around 20 kt along the coasts each day. Variable light to gentle winds are expected across the Gulf of Tehuantepec through tonight, then a brief episode of fresh to strong northerly winds will flow across the Gulf of Tehuantepec Fri as a cyclonic circulation associated with a tropical wave as described above begins to impact the waters downstream from the Gulf of Tehuantepec through Fri and through much of Sat. Latest computer models suggest that this low could become better organized over the weekend as it moves westward and offshore of Acapulco. Please refer to Special Features above for more specific details pertaining to this upcoming next tropical system. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Fuego Volcano in Guatemala may resume venting some ash in the coming days, but remains relatively quite since the major eruption this past Sunday. Moderate to locally fresh nocturnal drainage flow across and downstream of the Gulf of Papagayo will be prolonged through Fri as a tighter pressure gradient develops behind a tropical wave, presently along 94W, keeps these winds mostly in the fresh range. The monsoon trough will meander across the forecast waters near 10N. Gentle to moderate E winds are generally forecast elsewhere north of the monsoon trough through late tonight. Gentle to moderate southwest winds are forecast south of the monsoon trough through Sat. A very large batch of SW cross equatorial swell will move into the regional waters over the upcoming weekend and raise seas to 6 to 8 ft by Sun. REMAINDER OF THE AREA... The surface ridge extending across the northern waters will gradually shift westward during the next few days. Fresh trades will continue across the tropics to the south of the ridge, generally from 08N to 18N west of 125W through Fri. Model guidance indicates that these winds increase in coverage late Fri as the Aletta tracks in a general west to northwest motion. NW to N swell producing seas to around 8 ft will propagate through the northeast waters N of 28N between 117W and 122W beginning tonight, and reach south to near 24N between 117W to 124W early on Sat, building maximum waveheights to the range of 7 to 9 ft. Long period cross equatorial SW swell will build seas near the Equator between the Galapagos Islands and 100W to 8 ft tonight. The long period SW swell will continue to propagate northward and merge with swell associated with Aletta by Sat, with expected seas in the 8 to 10 ft range. The area of 8 ft seas will impressively expand to include almost all of the basin to the south of 24N between 100W and 135W over the upcoming weekend. Seas are expected to become more churned over these waters as the SW swell begins mix with swell from other directions, especially near Aletta. $$ Aguirre