By Rod Hill on 2013-10-03
Neutral enso conditions are projected for the 2nd year in a row. The "neutral" state refers to near normal equatorial Pacific water temperatures. My winter forecast projection is for the months of November, December, January, February and March. The research I have compiled focuses on neutral seasons with high rain totals during the combined months of September and October. Years I am using for comparison begin with the fall months of: 1979, 1981, 1986, 1996 and 2005.
Here is my Portland winter forecast:
1. Precipitation: Wetter than normal by 5.90 inches, which would be an extra month of rain.
2. Valley Snowfall: Odds favor no big events with a season total of 1-3 inches. The data set does include a 20% chance of one 8 inch snow event. Last winter only saw a trace of snowfall.
3. Temperatures: An overall temperature average of 1/2 degree above normal. Month to month data: November near normal; December & January above normal; a cool February and a normal March.
4. Extreme Weather Events: A high chance of 1-3 valley wind events with south peak gusts 50-70 mph. The comparison winter of 2005-2006 had two valley wind events with 50 mph gusts. The fall of 1981 had a mini - Columbus Day storm with 71 mph winds in Salem and Portland.
5. Cascade snowfall: Projecting a good year with 525 inches of snow or more at Timberline Lodge. Normal for the resort is a seasonal total of 400-500 inches. Last year saw 545 inches fall. Mt. Hood has not seen a low snow total since 2004-2005. The last 8 winter seasons have averaged 606 inches at the lodge.
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Keep in mind, seasonal forecasting has a skill roughly 20% better than pure chance. Here is my report card from last winter's forecast:
1. I projected high confidence of no significant valley snow. (Correct)
2. Below normal rainfall for the water year: (Wrong) My projected total was 9.00 inches too low.
3. Mt. Hood snowfall: I projected up to 500 inches of at Timberline. (Correct) The total at the lodge was 545 inches, which is slightly higher than my projection, but still pretty close.
4. I said we were not due for and not expecting any extreme weather events. (Correct)
If my winter forecast is correct, the metro valley will see a wet winter with a few decent wind events and most likely a few brief snowfalls, although one major snow event looks possible.
Happy fall and winter season,
Rod Hill
Wettest Sept. All-Time At PDX