By Rod Hill on 2017-10-26
Like many forecasters that attempt long-range, seasonal forecast, I rely heavily on the projected Enso Cycle, which is a reference to projected water temperatures in the equatorial region of the Pacific Ocean. A forecast for a period of NEUTRAL conditions, LA NINA or EL NINO plays a significant role in weather prediction. NOAA's projection on October 17th, favors a 55-65% of a developing La Nina this Fall and Winter seasons. The outlook does leave the door open for present NEUTRAL conditions to continue.
Other weather patterns I have examined for my prediction include winter's following hot summers in terms of 90 degree heat, years following 50" water seasons and winters following big snow seasons. Last season's long list of big weather events has made my research for 2017-2018 my most difficult call, since I began seasonal outlook prediction back in 2001.
Rod's Winter / Seasonal Outlook 2017-2018
1. Total Precipitation: 32 - 39" /Odds favor by 67% a normal to below normal year.
Would be 11-20" drier than last season. Normal Water Year at PDX is 36 inches.
2. Valley Temperatures: 1-3 degrees below normal / Coldest months Dec. & Feb.
3. Valley Snow: No Confidence / data shows a 50% of a quiet year or a big season.
(My Hunch is that we slightly favor a quiet snow year with a trace to 2" of total snow)
4. Mt. Hood Snowpack: A Great Season, 105% of Average or Higher!
Timberline 600-700" of total snowfall, Meadows at least 600", both amounts would better last year's 95% of normal snowpack.
5. Wind Storms: No Reason to expect more than a few 50 mph gusts events
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My forecast accuracy for seasonal prediction dating back to 2001 is 66%. Last winter I correctly predicted at least 5-6" of valley snow and called for a heightened chance of one big storm. Although I called for an above normal water year, I did not see our 51" of moisture that came raining down. Industry standard for seasonal forecasting is closer to 55%.
Meteorologist Rod Hill
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