ASK THE METEOROLOGIST- LONG RANGE FORECAST
“Do you anticipate a lot more snowfall during the rest of the ski season? I heard we were experiencing a week to moderate El Nino, will that make a big difference?”
When we do a seasonal forecast we no longer look at weather models (short-range) but rather teleconnections which are better predictors of long-range forecasts. You may have heard of some including El Nino and La Nina which are part of the El Nino Southern Oscillation or ENSO. Just like last Winter, this year we have a neutral ENSO which makes long-range forecast that much more difficult. La Nina and El Nino are the strongest indicators of what type of Winter the nation will see, and with a neutral set up you can get a “mixed bag” of weather! Just look at last Winter, we had record breaking wet AND dry months! In fact the 1962 Columbus Day storm also occurred during a neutral ENSO. Since ENSO is neutral then we have to look at other teleconnections, and the most influential on the Pacific Northwest is the Pacific Decadal Oscillation or the PDO.
Just like last Winter we are in a cool phase of the PDO in fact we’ve been in a steady cool phase since 2010 but you could argue it’s been at least mostly negative since mid-2007 and PDO phases can last for decades! The cool or negative phase of the PDO means cooler than normal sea surface temperatures in the eastern Pacific. This pattern tends to bring cooler and drier weather to the west coast during the Winter months. Looking back at history, on average December and February trend cooler and drier while January trended warmer and wetter. But remember last Winter? All months were cooler than average and December was much wetter while January was much drier, hence there is variability with this set up.
A neutral ENSO and negative PDO are forecast to stay the same through at least Summer, so then we look at the Madden Julian Oscillation or MJO. The MJO looks at tropical disturbances that move eastward around the tropics on 30-60 day cycle and tends to be most active during a neutral ENSO and can offer long-range forecast assistance. The MJO tends to increase the frequency and intensity of heavy precipitation events along the west coast and increase cold spells in the East….well one of these has happened this winter and it sure isn’t a serious of big storms on the east coast! Now the MJO is strengthening and moving eastward, which means in early February there is some hope that a storm track could move east into our region…but I’m not as hopefully that this is going to bring the active storm track we need.
The Climate Prediction Center just issued their seasonal forecast and they are forecasting through April southern Oregon and California to be warmer than average and California drier than average, but Oregon an equal chance for wetter or drier than normal conditions, though I think Oregon will also be drier than average.
Southern Oregon and northern California are currently in a ‘Severe’ drought without a more active storm pattern wildfire season could be even worse than last year. Even though we aren’t in fire season, keep fire safety in mind!