Pacific Discussion

  • NHC East Pacific Tropical Weather Discussion
    by (nhcwebmaster) on November 5, 2020 at 4:33 PM

    000 AXPZ20 KNHC 051633 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Thu Nov 5 2020 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 1540 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Northerly gales continue across the Gulf this morning. An overnight scatterometer satellite pass measured peak winds at 40 kt and winds are assumed to continue at 40 kt. Peak seas are estimated to be 19 ft. Swell generated from this Tehuantepec event will produce a large plume of 12 ft or greater seas that will extend about 500 nm southwest of the Gulf of Tehuantepec. High pressure north of the area supporting the gales is starting to weaken, and the gap winds will gradually diminish through Fri, diminishing below gale force Fri morning. Marine interests transiting across or in the vicinity the Gulf of Tehuantepec should be aware of this gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters. Please refer to the latest High Seas Forecast issued by the National Hurricane Center at: for further details. Potential Heavy Rainfall event: Hurricane Eta is moving slowly across central Nicaragua, and producing a surge of moist southwesterly flow across the tropical eastern Pacific that will support heavy to torrential rainfall across portions of Central America through Thu. Eta is likely to cause life-threatening flash flooding and river flooding across portions of Central America, along with landslides in areas of higher terrain. Eta is expected to produce rainfall accumulations of 15 to 30 inches (375 to 750 mm) across central and northern Honduras into NE Guatemala, while SW onshore winds are expected to yield rainfall accumulations of 10 to 20 inches (250 to 500 mm) across coastal sections from NW Costa Rica to Nicaragua to far southern Honduras. Please refer to statements provided by your local national meteorological agency for more details. Farther west, Tropical Storm Odalys is centered near 18.3N 122.9W at 1500 UTC moving WNW at 6 kt. Estimated minimum central pressure is 1000 mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. The center of Odalys is exposed, with SW wind shear keeping scattered isolated strong convection NE of the center, from 150 to 300 nm in the northeast quadrant. A pair of scatterometer satellite passes from around 05 UTC indicated winds to 45 kt in the area of strong convection. Odalys will continue moving WNW then W during the next 24 hours and gradually weaken to a 30 kt post tropical remnant low late Fri afternoon as it reaches cooler waters and drier more stable air. Please read the latest NHC Public Advisory at and Forecast/ Advisory at for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N93W to 11N99W to 10N115W, then resumes south of Odalys near 14N124W to 12N129W. ITCZ extends from 12N129W to beyond 10N140W. Scattered moderate isolated strong convection is observed from 07.5N to the coasts between 84W and 92W, from 09N to 11N between 105W and 110W, and within 90 nm either side of trough and ITCZ W of 125W. OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the Special Features section above for details on the Gulf of Tehuantepec Gale Warning. Overnight ship observations and scatterometer satellite data indicated moderate NW winds across most the offshore waters of Baja California, and gentle SW winds farther south, outside of the Tehuantepec area. A pair of altimeter satellite passes confirmed seas are reaching 8 ft in the waters surrounding the Revillagigedo Islands. These seas are related in part to swell generated by T.S. Odalys which is centered about 465 nm to the west of Clarion Island. Elsewhere 4 to 6 ft primarily in NW swell north of 20N, and SW swell south of 20N. A slightly tighter gradient is in place over the Gulf of California where moderate to fresh NW winds and 3 to 5 ft seas are noted. Meanwhile, mid to upper level low pressure area over the northern Pacific is becoming more organized, and is expected to move along the US west coast through late Fri, bringing a strong cold front into Baja California Norte by late Fri. This pattern will support fresh to strong westerly gap winds into the northern Gulf of California late Fri through Sat, and perhaps into Sun. NW swell will also follow the front, with combined seas in excess of 8 ft encompassing the waters off Baja California through Sun, reaching the area near Socorro Island by late Sun. Peak seas may reach as high as 15 ft off northern Baja California Norte by Sun. Gentle winds will persist south of Cabo Corrientes outside of the Gulf of Tehuantepec plume, with seas of 4 to 6 ft in mostly southerly swell. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, and WITHIN 750 NM OF ECUADOR... Tropical Depression Eta is centered over western Honduras near 15.1N 87.8W at 1500 UTC moving WNW at 7 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained wind speed is 25 kt with gusts to 35 kt. Overnight scatterometer satellite data confirmed the presence of strong westerly winds on the southern periphery of Eta are impacting the waters within 120 nm of the coasts of Nicaragua and El Salvador, from just northwest of the Gulf of Papagayo to just west of the Gulf of Fonseca. A concurrent altimeter pass indicated seas to 10 ft in this area off Nicaragua. Eta has started turning more to the north, which will allow these winds and seas to diminish somewhat later today through tonight. Meanwhile, complex seas of up to 16 ft persist off the rest of the offshore waters of El Salvador and Guatemala, in a mix of swell emerging from the prolonged gale event in the nearby Tehuantepec region, and longer period SW swell. Fresh SW winds and 8 to 9 ft seas in SW swell persist off the coast of western Panama and Costa Rica. Better marine conditions are noted off eastern Panama and the coast of Colombia. Winds and seas will diminish through Fri off Panama and Costa Rica, and the swell from the Tehuantepec gap event will subside as well. However, fresh to occasionally strong onshore SW winds off Nicaragua will persist from late today into Fri, maintaining 8 to 12 ft seas with SW swell. These winds will diminish by Sat, and seas will subside to less than 8 ft by Sun. Moderate SW winds and 4 to 6 ft seas in SW swell will prevail by Mon. REMAINDER OF THE AREA... Please refer to the Special Features section above for details on Tropical Storm Odalys. Ridging dominates north of 20N, anchored by 1029 mb high pressure near 35N136W. Moderate to occasionally fresh NE trade winds persist from 10N to 25N, outside of the immediate area of T.S. Odalys, west of 120W. A large envelope of seas greater than 8 ft surrounds Odalys, reaching up to 480 nm to the southeast of the storm, in a mix of SW swell and shorter period swell generated from Odalys. A belt of seas 8 to 9 ft also persists west of Odalys, from 17N to 21N to beyond 140W, due to a mix of SW swell and a component of waves driven by the trade winds. No significant shower or thunderstorm activity is evident. Odalys will gradually dissipate and it moves westward across the area from 15N to 20N between 125W and 130W tonight through Sat. Meanwhile, a strong cold front will move south of 32N by early Fri morning, push southward, then largely stall and dissipate near 20N by late Sat into early Sun. Fresh to occasionally strong N to NE winds will follow the front, along with NW to N swell. This swell will mix with the lingering swell from Odalys and S to SW will create seas greater than 8 ft for most of the area north of 12N and west of 110W by early next week. Farther east, seas greater than 8 ft in a mix of SW swell and NE swell emerging out of Tehuantepec dominate the waters mainly south of 13N and east of 110W. This area of seas may expand as far west as 115W through today, but then start to subside rapidly Fri through Sat to below 8 ft in primarily SW swell. $$ Stripling