000 AXPZ20 KNHC 181546 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Sun Mar 18 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... Gale Warning: An initial cold front will move into the northwest portion of the discussion area today preceded by strong southerly flow with seas building to 9 ft. A deepening surface low pres well northwest of the area will drop southeastward to near 32N140W on Mon night behind this initial cold front, and drag a second cold front into the discussion area accompanied by a strong to near gale southwest-west-northwest wind shift. The pressure gradient will tighten around the southwest semicircle of the low increasing the westerly winds to 25 to 35 kt minimal gale force across the discussion waters from 29N to 30N west of 139W at 1200 UTC on Tue, with the associated seas of 12 to 18 ft forecast from 26N to 32N between 136W and 140W. The low pres will lift north of the area on Tue night with associated winds diminishing to 20 kt or less south of 32N late Wed. The associated northwest swell, in the form of 7 to 10 ft seas, will propagate southeast across the discussion waters covering the area west of a line from the central Baja peninsula to 06N140W on Sat. Please refer to the Pacific high seas forecast for more details on this upcoming event under AWIPS/WMO headers MIAHSFEP2/FZPN03 ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough is analyzed from the Pacific coast of Colombia at 08N82W to 05N104W where scatterometer winds indicate an ITCZ develops, and continues W to beyond 05N140W. Scattered moderate isolated strong convection is noted within 90 nm either side of a line from 05N77W to 06N82W to 03N90W to 08N105W. Similar convection is noted in small clusters within 30 nm of 09N122W and 05N128W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A north-northwest to south-southeast ridge is developing from 30N121W to 17N110W to 13N94W. The ridge will shift slightly southwest on Mon and Tue. Fresh to locally strong northerly winds will set up south of 25N and east of the ridge briefly on Mon with the pressure gradient then relaxing some on Tue. Light to gentle northerly winds and 2 to 4 ft seas are then expected west of the Baja Peninsula through Thu night with large northwest swells arriving at 30N120W on Fri. Gulf of California: A weakening cold front will pass through the far northern gulf waters by this evening. Fresh to locally strong NW flow north of the front will diminish with moderate to fresh northwest flow forecast across the entire gulf waters tonight through Mon, with narrow swaths of strong northwest winds possible across the far southern gulf waters briefly late Mon. Seas may build to 6 ft in the longer fetch waters. Fresh to locally strong northwest to north flow expected across the open Pacific waters from 18N to 23N east of 110W through late Mon night with seas building to 8 ft. Gulf of Tehuantepec: Strong north flow will surge through the gulf waters on Tue evening, increasing to minimal gale force around sunrise on Wed. Gale conditions are then expected to continue through Thu morning, with seas building to 14 ft downstream near 14.5N95.5W on Wed night. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong NE nocturnal winds expected tonight and again briefly on Tue night with seas building to 7 ft downstream. A stronger drainage event is forecast to begin on Wed night and persist into the upcoming weekend. Gulf of Panama: Fresh northerly winds are expected tonight. Fresh to strong north nocturnal winds are expected to resume on Wed night. Elsewhere, gentle to moderate offshore flow will prevail N of 07N while light to gentle SW winds are forecast S of 07N. REMAINDER OF THE AREA... Refer to the Special Features Section above. $$ Nelson