Forecast: La Niña Weather Pattern Causing Warmer Fall Temperatures
Northern Virginia's extreme weather started last winter, meteorologists say.
Derechos, blizzards, hurricanes, thunderstorms, extreme heat. Is there any wacky weather Northern Virginia hasn't seen in recent years?
This past summer saw enough 100-plus degree days to make 2012 the most intense in 141 years of record-keeping according to the Capital Weather Gang.
“Starting from this past winter, we had temperatures that were much above normal,” said Ken Widelski of the National Weather Service. “It was an abnormally warm winter, followed by a cooler than normal spring and we definitely had our periods of hot weather over the summer.”
As for this June's derecho, it’s typical climatologically for this area to see a derecho every couple of years, Widelski explained. What was unique about this year's derecho was the extent of the damage, several meteorologists agreed.
Brian van de Graaff, a WJLA meteorologist, said a derecho is not uncommon in Northern Virginia.
"It happens a lot in the Midwest, and it has happened here plenty of times before," said van de Graaff. "This time it was to such a large extent that it really made people wake up."
Widelski said the derecho in June which caused widespread damage may occur only ever 20 or 30 years, and van de Graaff said the extent of damage caused by the derecho in June is not like the more common events.
Warm Temperatures for Fall, Uncertain Winter
This summer has also been quite active with thunderstorms in Northern Virginia, and those severe weather conditions have continued through early fall. For the next few weeks, the National Weather Service expects the temperatures to continue to be abnormal even though it’s already officially fall, said Widelski.
For the fall season, van de Graaff has just started researching when the leaves will peak in Northern Virginia. He said he knows Maryland is seeing the peak of their leaves now and he expects leaves to peak in Northern Virginia around mid-October.
Van de Graaff said the recent warm temperatures and weather conditions in the region can affect the leaf colors, making some colors more prominent when the leaves peak this month.
"Colors of the leaves are sometimes driven, not necessarily by temperature, but sometimes by precipitation," van de Graaff explained. "And because of the lack of rain, sometimes it may affect the colors and timing."
Widelski said for the winter, the region is in a weather pattern called La Niña, which usually leads to a more northern storm track. The La Niña weather pattern kept Northern Virginia in mostly high pressure and warmer-than-normal temperatures this past year.
The La Niña weather pattern has since weakened, however, and Widelski said prognostics indicate that the region will shift into a weak El Niño pattern, which is an irregularly periodic climate pattern that occurs every five years across the tropical Pacific Ocean.
“That could bring at least near-normal precipitation into the first part of the winter,” Widelski said. “But we’re still looking at a good chance that the temperatures will be at least slightly above normal.”
Van de Graaf said it will be a little colder than average and just above average precipitation going into the winter season.
"The average snowfall in the area is somewhere around 18 [inches], when last year it was below that," said van de Graaff. "One big snow can take that away or there may be a bunch of minor events throughout the year. Most likely with this pattern, we'll see that snowfall in the January or February time frame."
The official winter outlook from the National Oceanic and Atmospheric Administration will be complete and accessible on the website Saturday, Oct. 20.