In a typical El Nino year, storms barrel into the west coast and cross the United States as the Pacific Ocean sends one storm after another careening into the U.S. mainland. The western storm track has been quiet so far this year - California remains drought-stricken and fire-weary, desperately in need of rain.
The Central Pacific, however, has seen a record number of tropical storms in this El Nino pattern, including Hurricane Oho, which made a rare run from Hawaii to Alaska. In New England, warm air has been the autumn rule so far, and an exceptionally dry start to the season has given way to occasional bouts of rain. But what does El Nino have to do with all of this?
El Nino is nothing new. Spanish for "The Christ child," the phenomenon was first observed by South American fishermen in the 1600s, who noticed some years brought unusually warm water to their coast, typically appearing in December around Christmas. It turns out, the South American coast isn't the only area with warm ocean water during El Nino- most of the Pacific Ocean near the equator turns warmer.
Observing technology has given us a new understanding of this important weather pattern: the warm waters across the Pacific can lead to changes in barometric pressure, which can change prevailing winds change and storm paths- not just over the Pacific, but across a large part of the globe.
At home, New England often sees a slightly warmer and wetter than normal winter from El Nino. The frequent storms moving west to east across the country carry warm air with them, limiting arctic air. This means we're nearly certain the winter of 2015-2016 won't come close to rivaling the seasonal record snow of last year in Southern New England, though coastal storms will tap moisture from likely southern United States flooding and severe weather, making frequent mixed precipitation events including snow, sleet, freezing rain and rain a much more likely scenario for the northeast.
This all spells a winter of messy driving, but less snow removal for Boston, Hartford and Providence; lower heating bills in Southern New England; replenished water tables after our fall drought and tricky forecasting of rain and snow lines. On the north side of an El Nino storm track, however, northern New England often can crank out some decent snow and ski areas should be pleased with this year's bounty, as long as the warmer air doesn't push too far north.