000 AXPZ20 KNHC 061600 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Wed Jun 6 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURES... Tropical Storm Aletta is centered near ear 14.7N 107.1W at 1500 UTC, moving W or 280 deg at 6 kt. Maximum sustained winds are 40 kt with gusts to 50 kt. Minimum central pressure is estimated at 1000 mb. Latest satellite imagery shows that scattered to numerous strong convection continue to develop in a classic comma pattern. This convection consists of scattered to numerous strong convection, with cold cloud-top temperatures, located within 270 nm of the center in the SW quadrant...120 nm of the center in the SE quadrant 60 nm of the center in the E quadrant. Low-level clouds are seen spiraling in a cyclonic motion in the W and NW quadrants of Aletta where cirrus clouds are thin and minimal. A west- northwestward and then westward motion with a decrease in forward speed is expected during the next several days as the system gradually strengthens to hurricane strength Thursday morning as it moves over very warm waters and under favorable upper-level conditions. Very strong convection is expected to persist across the south and southeast periphery of this system through Thursday. 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. ...TROPICAL WAVES... A tropical wave axis is along 90W north of 10N to inland Guatemala and the central Yucatan Peninsula. It is moving westward near 15 kt. The southern part of the wave is helping to enhance deep convection occurring to the south of the monsoon trough as described above. Scattered moderate isolated strong convection is seen over southern Nicaragua and northern Costa Rica. The wave is forecast to move across the far eastern Pacific waters through the end of the week. Low pressure is expected to form along or near the wave by Thursday. The low may be attendant by strong to near gale force winds and building seas. tighter gradient behind the wave should is producing fresh winds across the Papagayo region. These winds should continue through the rest of this week, with some pulsing of them to moderate intensity expected at times. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from a 1009 mb low that is along the coast of NW Colombia to 10N84W TO 08.5N94W TO 12N102W, where it has fractured from Tropical Storm Aletta. It resumes at 11N110W TO 07N126W, where the ITCZ then continues to beyond 07N140W. Aside from convection near Tropical Storm Aletta, scattered to numerous strong convection is observed from 03.5N to 09N east of 80W. Scattered strong convection is within 60 nm of the trough between 88W-96W, and south of the trough within 30 nm of a line from 07N81W to 08N85W. Scattered moderate isolated strong convection is within 60 nm of the trough between 110W- 113W, and within 60 nm of the ITCZ between 115W-119W. Scattered moderate convection is within 30 nm of the trough between 120W- 124W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A broad ridge extends from a 1026 mb high pressure system centered near 31N139W 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. Seas of 4-6 ft this morning are forecast to gradually build to 5-7 ft Thu and 6-8 ft Thu night and Fri in the waters offshore northern Baja California due to a new pulse of NW swell forecast to propagate through those waters. Inside the Gulf of California, generally southerly wind flow is expected to continue through Thu. Afternoon and 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 Thu night, then a brief episode of fresh to strong northerly winds will flow across the Gulf of Tehuantepec Fri as a cyclonic circulation associated with low pressure is expected to form along or near the tropical wave described above begins to impact the waters downstream from the Gulf of Tehuantepec. 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 on Sunday. Moderate to locally fresh nocturnal drainage flow across and downstream of the Gulf of Papagayo will be prolonged through Fri as a tighter gradient behind a tropical wave, presently along 90W, keeps these winds mostly in the fresh range. The monsoon trough meanders across the forecast waters near 10N. Gentle to moderate E winds are generally forecast elsewhere north of the monsoon trough through Thu night. Gentle to moderate southwest winds are forecast south of the monsoon trough through Sat. REMAINDER OF THE AREA... The surface ridge extending across the northern waters will gradually shift W 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 northwesterly motion. NW to N swell producing seas to around 9 ft propagating through the northeast waters N of 27N between 118W and 125W will gradually subside by early this evening, then a new set of NW to N swell will propagate into the same waters beginning early on Wed afternoon, and reach south to near 26N between 117W-124W on Fri bringing seas to around 8 ft. Long period SW swell crossing the Equator from the southern Hemisphere will cause seas near the Equator between 95W and 136W to build to 8 ft tonight. The long period SW swell will continue to propagate northward and merge with swell associated with Aletta by Fri, with expected seas in the 8-10 ft range. The area of 8 ft seas will expand to include almost all of the basin to the south of 23N between 100W and 130W during this time frame. $$ Aguirre