Climate Prediction Center Three-Month Outlooks

Of all the systems created by civilizations to organize time, perhaps none is more relevant to SPU than the water year. Each October 1st, we creatures of the hydrologic cycle affix our service-providing gazes upon the vast Pacific Ocean for signs of rain, then snow, then warmth, and then rain all over again…

Okay, enough poetry. What should we expect this storm season? The following is a summary of SPU’s 2014-15 Winter Weather Outlook:

Warmer than normal, drier than normal. 6-10 days from now, 8-14 days from now, next month, the next three months… The Climate Prediction Center is amazingly persistent right now with that message. That’s mostly due to warmer than normal Pacific Ocean temperatures, i.e. “The Blob,” and later this winter due to a predicted, though likely very weak, El Niño/Southern Oscillation event.

For SPU urban drainage operations, below normal precipitation is generally a good thing, meaning less stormwater volume and greater system capacity. However, warm waters offshore appear to have been fueling recent short-duration, high-intensity rainfall events, and we shouldn’t be surprised if, say, November falls short of its 6.57″ average, but all of it comes in two or three big events. Plus, atmospheric rivers are just as likely during El Niño years as they are La Niña years. Less likely this season are snowstorms and windstorms.

Up in SPU’s watersheds where drinking water is stored behind reservoirs, all the warm-and-dry outlooks are less comforting. That said, SPU has experience managing climate variability and uncertainty. Last season, back when The Blob formed, water supplies throughout the region were looking dire. Then came a series of drought-busting atmospheric rivers and our wettest March on record, and knuckles everywhere regained their color. SPU is watching Pacific Ocean temperatures and other indicators closely.

The other winter weather impact SPU is watching is coastal flooding from King Perihelion Tides. Earth’s eccentric orbit creates a 19-year tidal cycle, or epoch, and this winter we’ll be at a maximum. There are at least four key dates to remember around which predicted tides will be notably high:

References:

 
Climate Prediction Center
2014-15 Winter Weather Outlook (.pdf)