Early climate predictions for the upcoming winter season indicate Juneau and the rest of Southeast Alaska may be in for weather that is warmer and wetter than normal, with below-average snowfall a possibility.
The National Oceanic and Atmospheric Administration's Climate Prediction Center on Thursday released its updated seasonal outlook for the nation, based on climate trends from the past few decades and the effects of the current El Niño weather pattern.
The outlook, extending from Nov. 1 to March 31, calls for above-average temperatures and precipitation for Southeast Alaska over that five-month period. Chris Maier, warning coordination meteorologist at the National Weather Service's Juneau Forecast Office, said weather records indicate that, in recent El Niño years, such conditions have occurred.
El Niño is a global weather phenomenon, occurring every four or five years, that begins when water temperatures in the Pacific Ocean's tropical regions rise enough to alter ocean currents. Those currents in turn alter the jet stream and lead to changes in weather patterns around the world for up to 18 months.
When warmer winter temperatures do occur in Juneau, records indicate the amount of snow decreases - particularly in November and December.
"The overall climate record for Juneau shows of our top 20 warmest winters, about 80 percent have been in our top 20 (winters with the) least amount of snowfall," Maier said. "There's a strong correlation."
El Niño events have not always meant warmer winters for Juneau. Maier said in the 1960s and 1970s, El Niños actually signaled cooler winter weather here. But since the 1980s, warmer winters have been the rule in El Niño years.
SOUTHEAST ALASKA WINTER WEATHER
Average temperatures, snowfall and precipitation from November through March for selected communities:
Source: National Weather Service
One of the ways in which recent El Niño events have impacted Southeast is the deepening of a weather feature called the "Aleutian low."
The Aleutian low is a persistent area of low pressure near the Aleutian Islands that generates storms that move across the Gulf of Alaska toward Southeast. When the low strengthens, Maier said, "that makes for a more active storm track across the Gulf. ...
"Our cold air comes from the interior of Canada," he said. "To get that cold air, we need to have winds out of the north or northeast for several days. When you have a strong Aleutian low, we're more under the maritime influence of the Gulf throughout the winter. ... We tend to have fewer of the cold, arctic outbreaks (that lead to snow)."
Maier said the weather Juneau has been seeing the past few weeks - mild temperatures and a nonstop series of storm after storm - may be indicative of what is to come.
"The weather pattern we're in now is very similar to what we're looking at for the winter season," he said.
On the Net: Juneau Forecast Office: pajk.arh.noaa.gov. Andrew Krueger can be reached at firstname.lastname@example.org.