This winter is expected to be marked by numerous severe storms affecting the West Coast and southern half of the country, according to the official winter forecast released Thursday by the National Oceanic and Atmospheric Administration. The outlook is dominated by the influence of the El Niño phenomenon, of near-record intensity.
El Niño, which is characterized by above-average ocean temperatures in the tropical Pacific that lead to a domino effect of changes in weather patterns across the globe, is likely to reach peak intensity in December but leave its marks throughout the winter months in the Lower 48 states.
Given the influence of El Niño this winter, much of the country is expected to be milder and wetter than average, but not necessarily less snowy than usual, according to NOAA forecasters.
Given the near-record intensity of the current El Niño and record global ocean temperatures, it is possible that any winter storm could bring unusually heavy rain and mountain snow to areas in its path.
Warmer waters allow for more evaporation and warmer air can carry more moisture, providing storms with additional moisture to work with as they hit land and move across the country.
Although no two severe El Niño winters are the same, most have common trends in temperature and precipitation. This is because El Niño usually indicates the jet stream – the river of air that flows from west to east across the country and directs storms – in the southern United States.
The result tends to be more storms and wetter, cooler weather in southern parts of the country, while northern states become drier and milder than average, according to NOAA. (Yes, snow-loving Northeasterners, that usually means less snow on average during strong El Niño winters, especially in inland regions.)
However, NOAA meteorologist Jon Gottschalck said some of the storms along the Southern Tier could turn northeastward along the East Coast, potentially bringing heavy rain and snow to major cities in the Mid-Atlantic and Northeast, depending on the availability of cold air. “These storms could be very strong,” Gottschalck said.
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In addition to above-average precipitation expected over the West Coast and southern states, precipitation along the East Coast is also expected to be above average.
Across the Southeast and parts of the Southern Plains, where a cooler El Niño trend and increased precipitation sets the stage for snow, sleet and freezing rain. The exact amount of frozen precipitation in these areas will depend on ambient temperature and whether cold air coincides with storms.
Although El Niño is likely the dominant player influencing winter conditions, it is not the only phenomenon at play. Other players, such as the polar vortex, will also influence the amount of cold air and snow that falls, particularly along the northern part of the country.
California could be hit hard by El Niño, as reliable projections from seasonal computer models show the state could see much higher than average precipitation for the winter.
Democratic Gov. Gavin Newsom has already declared a state of emergency as El Niño winter approaches, given the risk of significant inland flooding, high winds, heavy snowfall in the mountains and coastal flooding from waves riding unusually high tides during major storms.
History has shown that strong El Niño events do not guarantee an unusually wet California winter, but they do tip the scales in favor of such an outcome. And El Niño events can be particularly damaging there. A super El Niño in 1997 and 1998 set seasonal rainfall records across the Golden State and caused widespread flooding and mudslides.
“While higher chances of rain and snow can bring relief to drought-affected areas, too much precipitation on dry ground can fuel flash floods and destructive mudslides. Now is the time for communities and individuals to plan for the winter ahead,” Ken Graham, director of the National Weather Service, said in a statement.
El Niño also influences severe thunderstorms, which, after peaking in spring, normally steam up again near and along the Gulf Coast from late fall to early winter.
El Niño puts Florida at particularly high risk in winter. The scenario is reversed in other parts of the Gulf Coast, which are less active than usual, according to Michael Tippett, a climatologist at Columbia University.
Notably, warmer than normal temperatures are possible over more than half of the lower 48 country region. We can’t blame everything on El Niño: global warming from fossil fuel pollution still plays a role. Winter is the fastest warming season across most of the United States, according to an analysis by the nonprofit research group Climate Central..
The areas expected to be drier than normal are not quite in sync with El Niño, but they are confined to the north, where it is also expected to be milder than average. And an exceptionally warm and dry suit is not the suit that will produce snow.
As with winter temperatures, research shows that global warming has also had an impact on snowfall over the decades. Annual snowfall amounts have declined in nearly two-thirds of the United States since 1970, according to Climate Central.
Only time will tell how wintry this winter will be, but El Niño will almost certainly be a major player in global warming.
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