Hoping for an average U.S. winter? Forget it
By Scott DiSavino (Reuters) - As one of the warmest U.S. winters moves into the new year, nothing will change the pattern unless the polar vortex unexpectedly invades the country from the Arctic, meteorologists said. With home heating demand running 20 percent below normal, January through March would need to be as cold as early 2014 to make this an average winter, according to federal data. Last year the fast moving current of air encircling the Arctic, called the polar vortex, moved down from Canada, causing the coldest U.S. winter in at least 35 years. Instead, Thomson Reuters Analytics forecasts suggest the United States will have the second warmest first quarter in a decade due to the strong El Niño weather pattern. The phenomenon occurs when the Pacific Ocean near the equator is warmer than normal, affecting climates around the world. This sets the course for a full U.S. winter with 14 percent fewer heating degree days (HDDs), a measure of heating demand for homes and businesses, than the norm. Barring an abrupt weakening in the El Niño, "it is very unlikely we will see the season be anything but one of the warmest winters on record," said Brad Harvey, lead forecaster at MDA Weather Services in Gaithersburg, Maryland. "Even if we assume a normal January, February and March, which is not our forecast, this winter would still be one of the five warmest November-March seasons going back to 1950." With such forecasts, U.S. natural gas prices are unlikely to gain much ground over the next few months. Gas prices this year have been the lowest since 1999 as record production from shale formations has outstripped even healthy demand. This U.S. winter is shaping up to be the warmest since 2011-2012 and the second warmest on record, with an estimated 3,000 HDDs for the heating season from November through March, according to Thomson Reuters Analytics. That marks an abrupt reversal from the last two winters when the polar vortex caused temperatures across much of the country to plummet and power plants to scramble for gas supplies in the U.S. Northeast. So far this winter, the lower 48 U.S. states have had only 831 HDDs, the fewest since 2010, according to Thomson Reuters Analytics. That is 198 days short of the 30-year average for this period. To make up for the deficit, the first quarter would need 276 more HDDs than usual to reach the 30-year norm of 3,485 by the end of March. MID-WINTER REVERSAL? Freak changes have happened, though. In the 1989-1990 winter, for instance, November and December were 20 percent colder than usual, based on the HDD data. But the first quarter was 15 percent warmer than usual as the jet stream shifted north and changed the North Atlantic Oscillation, which measures surface sea-level pressure differences, from negative to positive. Strong positive phases of the oscillation tend to be associated with above-normal temperatures in the eastern United States, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). The latest NOAA data shows the North Atlantic Oscillation was positive in November 2015 and is expected to remain so in December and into early January. (Reporting by Scott DiSavino; editing by Jonathan Leff and Richard Chang)
