Dry & Mild November; Beginning of an “El Nino Winter”?

November 14, 2018

8pm Wednesday…

Sure seems like a slow start to our “storm season” doesn’t it?  November is typically a wet and windy month featuring numerous weather systems moving onshore.  Not this year!  We’re halfway through November and most of the Willamette Valley has seen less than a quarter inch of rain.  It’s the 2nd driest 1st half of the month in Portland’s history and #1 driest in Eugene.

Across the USA it has been a cold start to November with only the Pacific Northwest a bit warmer than average, mainly due to unusually warm temps the first week.

We know about the California wildfires; they are being fueled by a late start to the wet season.  It’s been very dry across the West, including all of Oregon and a good part of Washington.

We’ve been unusually dry because of a persistent ridge of high pressure near, or just offshore the past two weeks.  It doesn’t appear that is going to change in the next week or two either.  Take a look at the 500 mb (around 18,000′) height anomaly for this coming weekend from the GFS & ECMWF. You see the anomalous ridging centered over and north of us, with slightly below normal “heights” in the southwestern USA.

Look further ahead…these two models are slightly different, but neither produces significant precipitation during the Thanksgiving Weekend.  The ECMWF & GFS meteograms for the next 10 days.

Looking to the end of both model operational runs, the 500mb height anomaly lingers in the same general location.  The GFS is a bit different showing a classic El Nino setup with unusually low heights across the southern USA.  That can lead to a wet California but drier than average Pacific Northwest.

As I look at these runs I wonder if it is the beginning of our “typical” drier than normal El Nino pattern (as opposed to a stormy/wet El Nino).  As mentioned in an extensive post about this coming winter (also in WINTER 2018-2019 THOUGHTS tab above), sometimes these years are dominated by this pattern of splitting systems, wet California weather, and just plain boring weather for weather geeks like me.

It’s VERY interesting to note the latest November seasonal runs of the ECMWF, UKMET, & JAMSTEC feature this pattern.  These are 500mb height anomaly for December-January-February.  The ECMWF has been showing this winter pattern for at least the last 3 months!  We get these seasonal runs once per month.

CASCADE SKIING OUTLOOK

You can probably guess that this is bad news for ski areas for now.  There will be no early start to the ski season this year and Thanksgiving Weekend skiing is unlikely.

I quickly perused El Nino Novembers for Cascade snowfall.  The real shut-out years (less than 20″) most of the time seem to end up as rough ski seasons.  Although 1965-66 was a huge snow year after only 15″ at Government Camp in November.  Same thing happened in 1963-64;  Only 27″ at Govy in all of November and December.  Then 155″ fell in January!  A more recent example (although not an El Nino year) would be 2008.  Ski areas had little/no snow through the first week of December.  Then the big freeze plus tons of lowland snow hit.  Ski areas opened about the same time snow fell in the lowlands.  It ended up being a big snow year in the Cascades.  Lesson?  Things can change quickly; FOR NOW there is no reason to freak out. 

Chief Meteorologist Mark Nelsen