SEATTLE — Winter solstice is still three weeks away, but the season is already underway in a meteorological sense.
Differing from astronomical seasons, meteorologists and climatologists measure them in three-month cycles, based on typical temperature patterns.
As the National Oceanic and Atmospheric Administration explains:
“We generally think of winter as the coldest time of the year and summer as the warmest time of the year, with spring and fall being the transition seasons, and that is what the meteorological seasons are based on. Meteorological spring in the Northern Hemisphere includes March, April, and May; meteorological summer includes June, July, and August; meteorological fall includes September, October, and November; and meteorological winter includes December, January, and February.”
If the last few months have felt unusually wet, it’s not your imagination. As Puget Sound closed the books on meteorological fall Tuesday, Puget Sound set a new all-time record for precipitation. Seattle logged more than 19 inches of rain between September and November. Seasonal totals were even more eye-popping elsewhere in the state.
November is typically the wettest month of the year for Western Washington, and this one was no exception, landing among the top five wettest since 1945 and contributing more than half of the three-month precipitation total in just 30 days.
Looking forward to a ‘double-dip’ La Niña winter
The wetter trend could carry on through the colder months to come, as Western Washington enters its second La Niña winter in a row. Earlier climate forecasts remained on track in November, with the odds continuing to favor a cooler and wetter winter in the Pacific Northwest.
In an update shared in late November, NOAA’s climate office walked through the latest probabilities, accounting for the relative uncertainty over how no two La Niñas behave exactly the same.
According to NOAA, the phenomenon’s influence tends to have more consistent impacts on precipitation, while playing a less reliable role with temperatures. This year, Washington looks to have a slightly better shot at a wetter-than-normal season, with the probabilities slightly lower on the temperate front.
“Probabilities are tiled toward colder-than-normal temperatures along the northern tier from the Pacific Northwest to the Dakotas and across much of Alaska,” wrote Mike Halpert, deputy director of the Climate Prediction Center. “However, the probabilities for below average in these regions are less confident, with none reaching 50%.”
As the Seattle Weather Blog noted Monday, some — but not all — of Washington’s rainiest Novembers heralded snowy winters to come.
Federal climatologists update their seasonal probabilities each month, and the next one is due by mid-December.
Source: Bellevue Patch