Summit County Citizens Voice

A NASA graphic shows a surge of warm water pushing east across the Pacific to reinforce El Niño conditions. Click on the image for an animated version.

Pacific pattern expected to influence U.S. weather through early summer, with wet conditions in the Southwest possible

By Bob Berwyn

SUMMIT COUNTY — After starting to weaken a bit in late January, this year’s El Niño was revived by a giant Kelvin wave sweeping warm water eastward across the Pacific in February.

The surge of tropical water made this El Niño the fifth-strongest on record for this time of year, in a pattern expected to influencing Colorado’s weather for the next few months, according to climate researchers with the National Oceanic and Atmospheric Association.

For the contiguous United States, potential El Niño impacts include above-average precipitation for the Southwest, the south-central states, and Florida, and below-average precipitation in the Pacific Northwest and Great Lakes region. Above-average temperatures are most likely across the northern tier of states (excluding New England and the Northern Plains), while below-average temperatures are favored for the south-central and southeastern states.

Kelvin waves are bumps of warm water in the Pacific that form around Indonesia. They are typically just a few inches high, hundreds of kilometers wide and a few degrees warmer than the surrounding water, according to Bill Patzert, an oceanographer with NASA’s Jet Propulsion Laboratory.

Usually, prevailing easterly trade winds near the equator push sun-warmed water away from the Americas and toward Australia and Indonesia, where the globe’s biggest pool of warm ocean water forms.

During  El Niño, in a complex atmospheric dance, the trade winds falter, enabling pulses of warm water to slide back to the east. The waves can actually increase the height of tides along west-facing shorelines of North and South America by a few inches, as well as warm the water on those beaches. Watch a graphic Kelvin wave animation from NASA here.

More importantly, the warmer water influences the weather. In South America during an  El Niño year, farmers can plant rice and beans in areas that are normally too dry for those crops — but only if they know  El Niño is coming. That’s why scientists study and try to predict the phenomenon. Similarly, in Colorado, an  El Niño year often brings a wet winter and spring to the eastern plains, helping farmers grow more bountiful winter wheat crops.

A powerful El Niño surprised weather scientists in 1982-1983, slamming California with huge storms that crumbled seaside cliffs and closed parts of coastal Highway 1 near San Francisco. After that, researchers from the USA, France and Japan set up a network of 70 buoys across the equatorial Pacific to measure water temperatures to a depth of about 500 meters.

El Niño warnings also come from a U.S.-French TOPEX Poseidon satellite that measures the height of the sea. Warm water expands, so the sea surface is a bit higher where Kelvin waves travel across the Pacific.

According to NOAA’s Climate Prediction Center, the lingering El Niño will result in drier-than-average conditions over Indonesia and enhanced convection over the central and eastern equatorial Pacific Ocean, as well as coastal sections of Peru and Ecuador.

More on El Niño and Kelvin waves here.

Filed under: El Niño, Summit County snow and weather Tagged: | climate, Colorado weather, El Nino, Summit County Colorado, summit county weather, weather