000 AXPZ20 KNHC 251604 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Fri Jan 25 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 1545 UTC surface analysis and satellite imagery through 1200 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: The pressure gradient over southeastern Mexico has weakened slightly during the past several hours as high pressure ridging extending southward from the western Gulf of Mexico to southeastern Mexico shifts eastward. However, high pressure moving southeastward from the Central Plains will bring a tightening of the pressure gradient over southeastern Mexico today allowing for the present strong to near gale force north to northeast winds over the Gulf of Tehuantepec to increase to gale force late this morning into early this afternoon and continue through early on Sat morning. Thereafter, the ridge will shift eastward toward the southeastern United States. Seas currently in the range of 8-11 ft will to around 12 ft during the gale force winds, begin to subside Sat, then will subside more rapidly as the current gap wind event shuts down. The area of 8 ft seas generated by this event will spread well to the S and SW of the Gulf as far as 10N100W tonight and Fri, then subside. Another strong cold front will be entering the Gulf of Mexico on Sunday. Gales will be possible over the basin again by Sun night. Please read the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers FZPN03 KNHC/HSFEP2 or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. Developing Gale Warning: Deep layered upper troughing persisting across the western waters of the discussion area for the past several days has become N to S aligned along about 140W, from 35N southward into the tropics along 08N. This pattern combined with surface high pressure to the north is producing an area abundant low-level moisture from the ITCZ northward to near 25N and between 124W and the trough along 140W. A 1007 mb surface low has developed near 12N133W and is embedded within the large area of convection described below in this very moist region. The low is forecast to lift northward today through Sun and will pull moisture and convection with it to beyond 20N through Sat. Ship with call sign "VRXO6" located bout 150 nm east-northeast of the low reported northeast winds of 30 kt just a few hous ago along with combined seas of 12 ft. As the low moves northward, the pressure gradient will also tighten between the high to the north and the low, and gale force winds are expected within about 270 nm across the NE semicircle of the low beginning Friday evening. Seas will build to 10-15 ft during this time. Please see the latest High Seas Forecast issued by the National Hurricane Center under AWIPS/WMO headers FZPN03 KNHC/HSFEP2 or at website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for further details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 1009 mb low pressure centered over NW Colombia near 08N75W to 07N78W to 08N84W to 04N90W. The ITCZ continues from to 04N90W to 03N95W to 04N100W to 07N110W to 08N116W to 09N128W. Scattered moderate convection is within 60 nm south of the trough between 85W and 89W, and within 30 nm of the ITCZ between 112W and 118W. Scattered moderate isolated strong convection is occurring from 09N to 15N between 114W and 120W. Scattered moderate convection is within 30 nm of 13N111W. Scattered moderate isolated strong convection in association with the low pressure center near 12N133W is noted from 10N to 16N between 127W and 131W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Fresh to strong northwest winds are present across just about the entire length of the Gulf this morning. High pressure over the Great Basin will remain strong through early Sun and combine with lower pressure along the western slopes of the Sierra Madre Occidentales to maintain the current tight pressure gradient and resultant strong northwest winds over the Gulf of California. Seas associated with these winds will peak around 8 ft. Elsewhere, high pressure centered offshore of northern California is supporting a broad ridge extending south to 20N, which is producing moderate to fresh northerly winds west of the Baja California peninsula. Winds will diminish across this area Fri night and Sat morning as the high weakens and shifts northward. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong northeast winds will continue pulsing to at or just below 30 kt each night across the Gulf of Papagayo through Sun. Seas in this area will peak around 9 ft Fri morning. Gulf of Panama: Fresh north to northeast winds will pulse over the Gulf will occur mainly at night and into the early afternoon through Sat. Winds may become locally strong tonight. REMAINDER OF THE AREA... Broad 1032 mb high pressure centered well north of the area near 46N126W ridges across the forecast waters north of 10N. A surface trough extends from the deep tropics near 07N137W to the low pressure described above under "Special Features" near 12N133W to 16N133W. The pressure gradient between the ridge and the surface trough is generating fresh to strong trades between 10N and 20N W of 120W. Seas in this region are running between 8 to 12 ft. Model guidance suggests the area of fresh to strong winds will shift northward during the weekend with the low described above, and while gradually diminishing in areal coverage. The resultant fetch of winds is expected to generate seas as high as 15 ft near the low, while an extensive area of seas 8 to 11 ft in mixed northeast and northwest swell will cover the waters elsewhere generally N of 09N and W of 120W. This area of 8 ft seas will slowly retreat westward to near 130W by Sun evening. $$ Aguirre