000 AXPZ20 KNHC 281740 AAA TWDEP Tropical Weather Discussion...Updated NWS National Hurricane Center Miami FL 1740 UTC Mon Jan 28 2019 Updated ITCZ/Monsoon Trough section for convection 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 1715 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: North to northeast gale force winds across the Gulf of Tehuantepec region will diminish to strong to near gale force winds early this afternoon as high pressure over southeastern Mexico weakens. Ship with call sign "PCHM" reported gale force winds at locations near 14.8N94W at 10Z, location near 15N94W at 12Z, near 15.1N95W at 13Z and near 15.3N95W at 14Z along with seas of 10-13 ft. These seas will subside to 8 to 11 ft by early this afternoon. The gradient will remain on the rather light side through Tue, then intensify again Tue night as new high pressure ridging builds southward along the eastern slopes of the Sierra Madre mountains. The resultant strong north to northeast winds through the Isthmus of Tehuantepec will increase to minimal gale force by late Tue night as they then span outward over the Gulf. The gradient will weaken once again early on Wed allowing for these winds to diminish back to strong to near gale force. 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 more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...Updated A surface trough extends from northwest Colombia near 08N75W and continues southwestward to the coast at 05N77W, then to 04N81W, to 06N90W and to 05N100W, where latest scatterometer data indicated the ITCZ begins and continues to 04N112W, to 05N120W, to 05N131W and to beyond the area at 07N140W. Scattered moderate to strong convection is within 120 nm south of the ITCZ between 105W and 109W, and within 90 nm north of the ITCZ between 119W and 123W. Similar convection is within 60 nm north of the ITCZ between 106W and 109W, and within 60 nm south of the ITCZ between 119W and 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of California: Moderate to fresh northwest will diminish to mainly light to gentle winds tonight, with seas of 3-4 ft. Seas will lower to 1-2 ft early on Tue and 1 ft or less on early on Wed. Winds will be light and variable from Tue afternoon into Tuesday night. Winds will become light from the southeast early on Wed and continue through Fri. A surface ridge extends from near 32N127W to near 20N119W. The gradient between it and relatively lower pressure over Baja California supports light to gentle northwest to north winds and seas in the range of 4-5 ft in northwest swell over the waters to the west of the Baja California Peninsula. These winds will increase to moderate speeds north of 27N Tue afternoon and continue through Wed, with seas building to 5-7 ft. A weak cold front is expected to clip the far northeast waters and far northern Gulf of California late on Thu. Winds over the far northern Gulf of California are expected to become southwest at strong speeds late Thu ahead of the front from 30N to 31N. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong northeast winds will begin to pulse at night, across the Gulf of Papagayo, beginning tonight and continuing through Fri morning. Seas resulting from these winds will build to 8 ft early Tue and to 10 ft early on Thu and through Fri. These winds may reach near gale force late Wed night into Thu and again late Thu night into Fri. Gulf of Panama: Gentle to moderate north to northeast winds will change little through this evening, then increase to fresh to locally strong speeds late tonight and diminish to mainly fresh speeds on Tue. These winds then increase again to fresh to locally strong speeds late Tue night into early Wed north of 05N and between 79W and 81W before diminishing on Wed afternoon and developing again Wed night as strong winds are expected to funnel through the Isthmus of Panama through Thu night. Seas are forecast to reach 8 ft with these winds early on Thu. REMAINDER OF THE AREA... A tight pressure gradient between broad low pressure and associated frontal system just west of the forecast waters and the high pressure ridging that extends into the area from 32N127W to near 20N119W had recently induced strong east to southeast winds across a portion of the northwest part of the area. These winds have since become southerly at fresh speeds while mixed southeast and northwest swell produce seas of 8-10 ft west of a line from 32N132W to 24N134W to 18N140W. The gradient will again tighten, similarly to the recent event, by early Tue as the frontal system west of the area and a leading trough shift some more eastward closer to 140W. The interaction between these systems and the high pressure ridging is expected to once again lead to strong east to southeast winds, with seas of 8 ft over the area from 15N to 20N and between 134W and 138W. The 8-10 ft seas w of the above mentioned line will slowly subside through early Tue as the area of swell shrinks. By late Tue night, the east to southeast strong winds are forecast to be confined roughly from 15N to 20N west of 137W along with seas of 9-12 ft and change little into mid-week as the gradient there remains rather tight as a blocking type-pattern, with the ridging over the northern and central waters and the low pressure and frontal system just west of 140W will not allow much change to occur with the gradient in place that will support the aforementioned strong east to southeast winds. With the soon to occur blocking pattern set-up, swell generated by the frontal system to the west of the area and related troughiness will send additional swell, from the northwest in direction, to propagate into the far western part of the area from about 10N to 28N and west of 134W, with resultant seas of 8- 11 ft by mid-week. $$ Aguirre