Two weather systems keep 2015 on track to be hottest year ever, with current El Niño phenomenon likely to be one of three strongest in half century

Meteorologists have blamed El Niño and the polar vortex for record-breaking warm temperatures across the US this week, saying the pair of weather systems will likely keep 2015 warm enough to be the hottest year on record.

This year’s El Niño, a recurring weather pattern caused by unusually warm water in the Pacific Ocean, is particularly strong and reaching its peak. The high pressure system, now east of Hawaii, sends warm air along the jet stream over the northern Pacific and into the northern and central US.

The system causes storms in the western US, greater precipitation in the south, and warmer air throughout most of the country. The 2015-16 El Niño is expected to rank as one of the three strongest in half a century.

The system has brought desperately needed water to California, delivering three storms in a week to a state that has been parched by a four-year drought. Earlier this year, Mike Halpert, the deputy director of the National Oceanic and Atmospheric Association (Noaa), said the state would need twice its normal rainfall to break free from the drought.

Facebook Twitter Pinterest Temperature forecasts caused by El Niño. Photograph: Noaa

But Halpert ascribes the exceptionally warm weather on the east coast – where Sunday temperatures broke records, hitting 70F (21C) in New York and Philadelphia – to the polar vortex, the same system blamed for numbing the region with cold earlier this year.

“I would not associate the lack of snow in Buffalo with El Niño,” Halpert told CNBC last week, referring to the New York city that usually receives snow by early November. “It is much more likely the Arctic oscillation.”

Halpert explained that the polar vortex, a circular swirl of cold air moving around the north pole, varies in pressure throughout the winter season – changes called the Arctic oscillation.

High pressure expands the system until the bands of cold wind break along the southbound jet stream, spewing icy weather southward into the US. Low pressure holds the vortex winds wrapped in a closer ring around the pole, trapping Arctic air in the region.

In February, high pressure pushed the vortex towards the equator, causing snow and subzero temperatures around the east coast, midwest and as far south as Texas. Unusually low pressure, called a “positive” oscillation, is currently keeping more cold air away from the continental US than normal.

Polar vortex variations: high pressure (cold breaking into the US) on the left, low pressure (cold trapped to the north) on the right. Photograph: Noaa

Not since 1899 has Buffalo gone this late into the season before recording at least a tenth of an inch of snow. With temperatures predicted to be 10 to 20 degrees above freezing through the next week, the city will may have to wait until the new year for snowfall.

“When you combine an Arctic oscillation along with a strong El Niño, this is what you end up with,” Halpert told Time magazine.

About three-fourths of all Americans will see temperatures reach as high as 60F through the next week, following a weekend of record-breaking warmth around the plains, midwest and east coast.

Chicago and cities along the Great Lakes, normally icy by mid-December, are expected to feel temperatures ranging from 30F to 50F. On the east coast, few cities south of Boston should expect a snowy Christmas, according to Noaa predictions. Snow has fallen in some parts of the US: along the Rocky Mountains and Sierra Nevada, where El Niño is driving storms, and in Minnesota and the upper midwest.

Chances of snowfall on Christmas Day. Photograph: Noaa

The unusually warm weather has had a range of consequences, from people lounging barefoot in the park to confusion among plants. The buds of some plants such as Rhododendrons have started to swell as if it were spring, while researchers at Washington State University have documented how some crops are several weeks ahead of schedule due to the warmth.

Early budding of plants could prove to be an issue for some farmers. Crops such as tree fruits and grapes would be vulnerable to frosts if they flower and are then subjected to a drop in temperatures later on in the winter or in spring.

“Warmer temperatures and early budbreak increase the risk of frost damage for growers,” said Lee Kalcsits, assistant professor of tree fruit physiology at Washington State University. “It could be an issue if temperatures become cold again.”

The warmth has proven beneficial to anglers, however, with pike and perch being plundered in central New York by people taking advantage of ice-free lakes.

Meteorologists hesitate to make long-term forecasts about whether the warm streak will continue, since El Niño’s effects are diminishing and the oscillation could turn “negative” and send cold air plunging south.



Autumn 2015 was the warmest on record for the continental US, according to Noaa, about 3.3F above average. The World Meteorological Organization has said that 2015 will be the hottest year in modern observations, with the world entering “uncharted territory” of average temperatures. Climate scientists caution that the fluctuations of the weather – including systems like El Niño and the polar vortex – should not be conflated with climate change, which is the related but separate, long-term warming of the planet.