Wild Ideas
Global warming continues, but will that affect this winter’s weather?
Noting the mood swings in the weather so far this winter, a couple of weeks ago I started wondering what the rest of the winter held in store.
Then the National Oceanic and Atmospheric Administration (NOAA) came out with its annual report on climate (tinyurl. com/winoaarep), which says that 2016 was the warmest year on record. With El Niño as the catalyst, the globe experienced record warmth from January through August last year. (El Niño is a warming of the water in the equatorial Pacific associated with widespread changes in weather patterns.)
Despite the cooling effects of La Niña in the remaining months of the year, the year ended with the “third warmest December on record for the globe,” with an average temperature 1.42 degrees F above the 20th century average. This put 2016 it in the same club as 2005, 2010, 2014 and 2015, which also broke records from previous years.
The annual climate report from the National Aeronautics and Space Administration (tinyurl.com/wi-nasarep), released at the same time as NOAA’s, echoed the latter’s findings. But what does this say about local weather? As the NASA report pointed out, “weather dynamics often affect regional temperatures,” so not every region on Earth experienced record-breaking warm temperatures last year.
“For example,” the report said, “both NASA and NOAA found the 2016 annual mean temperature for the contiguous 48 states was the second warmest on record. In contrast, the Arctic experienced its warmest year ever, consistent with record low sea ice found in that region for most of the year.”
Details for specific regions in the U.S. are not included in the reports, and the global maps that were included are not much help on the regional level. However, going by the legend, one NOAA map does show that the U.S. generally had “warmer than average temperatures,” while a strip that appears to run along the southern Appalachians (including Virginia) shows higher, “record warming” temps.
While La Niña generally has a cooling effect globally, in the U.S. it typically is associated with winter temperatures that are warmer than normal in the Southeast and cooler than normal in the Northwest, according to NOAA in a its October weather prediction for this winter (tinyurl.com/wi-noaaoct).
NOAA’s maps (see graphic) show that, while the southern part of Virginia has a 30-40 percent chance of having average temps above normal, up here in Northern Virginia, we have an equal chance of experiencing warmer or colder winter this year. Precipitation is also forecast to coincide with this patterns.
But NOAA and NASA are not the only forecasters. Judah Cohen, with the private forecasting firm Atmospheric Environmental Research, uses other models. He is credited on the National Science Foundation website (tinyurl. com/wi-winterweather) with, contrary to NOAA’s models, forecasting colder than normal temperatures for much of the Eastern United States, with warmer than normal temperatures for the Western United States.
As an Oct. 10 “Washington Post” article (tinyurl.com/wi-wpwinter) explains, Cohen has established a “strong track record” by using a model that predicts the phase of the Arctic Oscillation, a climate pattern characterized by winds circulating counterclockwise around the Arctic at around 55 degrees N latitude. “Winters in which the Arctic Oscillation is negative tend to be cold and snowy in the eastern United States,” the article says, and “big areas of ‘blocking’ high pressure develop at high latitudes, which force cold air from the Arctic south.”
In the NSF blurb, Cohen includes a variety of factors in his model as predictors
of weather, one of which is the amount of Siberian snow cover in October. This snow cover “advanced at an above normal rate during the entire month” and indicates “an increased probability of a weakened polar vortex or a sudden stratospheric warming and a predominantly negative Arctic Oscillation during the winter, and cold temperatures, especially east of the Mississippi.” In other words, Virginia is likely to experience a colder-thannormal winter.
The “Washington Post” article cites another forecast, by Joe Bastardi, of the private firm WeatherBell Analytics, that backs up Cohen’s. With the warm northeastern Pacific Ocean waters as a key factor and the Arctic Oscillation strongly negative right now, “Bastardi has called for a cold and snowy winter in the East since July and predicts snowfall 120-150 percent of average in D.C.”
With the launch of a new NOAA satellite, GOES-16, in December, forecast reliability should improve. Scientists are already receiving preliminary data from the outboard magnetometer instrument aboard GOES16, which is five times faster than previous GOES magnetometers. According to the agency’s website (tinyurl.com/wi-goes16), this “increases the range of space weather phenomena that can be measured.”
But for now, with the dueling forecast scenarios, I’m keeping both my down coat and shorts handy for the rest of the winter.