April 2014

April was fairly typical from a climatological perspective across the inland NW. Both temperature and precipitation were heterogeneously “normal” with some regions of above normal precipitation in NE Washington and the Idaho Panhandle and below precipitation in the lee of the Cascades and Bitterroots. Water-year to date precipitation (Oct-Apr) reveals somewhat of an east-west gradient in precipitation anomalies with dry conditions in the coastal mountains, the Columbia plateau, much of Oregon and parts of southern Idaho and above normal precipitation across much of Montana and parts of the Clearwater basin. These numbers are far more optimistic than what we were looking at three months ago.

These numbers are largely reflected in the current state of the snowpack across the northwest, with healthy numbers across much of the interior NW from NE Washington state to northern Wyoming. This contrasts with the dismal numbers in Oregon and California of course.

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Seasonal outlook

With summer-like temperature across the entire western US today (90F in Portland, 80F in Spokane and near 80 in Boise and Missoula, and mid 90s in costal Southern California), can we consider this a sneak preview of what this summer might bring? The climate community is tracking what appears to be a decent El Nino event that is about to surface in the eastern tropical Pacific and continue developing over the summer and into next winter.  The animation below shows a longitude by depth slice of ocean temperature anomalies near the equator across the Pacific from the surface to 450m below the surface. The large red-brown blob is the Loch-Ness monster of climate variability surfacing from the mixed layer of the ocean. Except we know far more about El Nino than Nessie. While we typically associate an El-Nino with warm and dry conditions leading some to call El-Nino a bad word in the NW, relationships are more-or-less absent during the summer months and only really apparent in the cool season.

That said, an ensemble of seasonal climate predictions made from numerous models initialized recently are calling for slightly above normal temperatures this summer for much of the region. They are also hinting at enhanced precipitation across the intermountain West emanating from a potentially more active monsoonal flow. Summer seasonal climate prediction generally has lower skill than for winter though.

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The east-west dipole in precipitation anomalies across the NW from this past winter coupled with these seasonal climate outlooks have resulted in fire season outlooks from the Predictive Services of the National Interagency Fire Center that include above normal potential summer fire activity across much of Oregon and suppressed activity across the Northern and Middle Rockies. A lot can change through in terms of how receptive fuels are to fire by the time we get into mid-July.

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And the winner is…

The snowfall forecast 2013-2014 edition has its victor. Recall that the two forecasts were for 1 April SWE at Aneroid SNOTEL station in NE Oregon and total accumulated snowfall in Moscow, Idaho.  You can see the distribution of forecasts and observed values as of 1 Feb below. Note the tight clustering of forecasts for Moscow snowfall between 40-50″ and Aneroid SNOTEL between 18-30″.

SNOWCAST2014_FEB  The accumulated snow through the end of March was 44.5″ or exactly the 1981-2010 normal. Recall, the the Aneroid SNOTEL was slightly above normal due to its healthy start (Oct 1 SWE was >4″).  So the null forecast of predicting climatology for both of these stations was a good approach [maybe a bit more for the Aneroid station given its’ early bump]. Here is a zoom in of that cluster of forecasts with the red dot representing the verified outcome. snowcastfinal201314 While my forecasting skills are not that great [came in 5th out of 6 students in my senior level forecasting class as a undergrad at UC Davis), it appears that regressing to the mean was a good tactic for me (DrThunder).  My prediction for Moscow snowfall was under by -0.4″ and my prediction for Aneroid SNOTEL was slightly over +0.5″.  Both WXWOLF (45.8″, 26.1″) and VSSJ (42″, 27″) were close behind.  Interestingly enough, the 25-person median forecast of 45″ and 27″ would have been just slightly behind my forecast.  This ensemble median approach is actually used quite a bit in consolidating both weather and seasonal climate forecasts and were shown previously in the seasonal forecast maps. The silver medalist was unable to participate in CoCoRAHS (covered balconies would produce serious undercatch) and graciously allowed for the CoCoRAHS trophy to go to the bronze medalist VSSJ. Soon Vincent will contribute to a new data point in the citizen science effort.

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