Strong El Nino This Winter: What About Cascade Snow?

September 15, 2015

Now that it appears Fall 2015 is here to stay, let’s talk about the big story for the upcoming cool season…EL NINO.

I’m sure you’ve already heard it’s a strong one this year, but what does that mean for skiing/snowboarding/winter sports?  Read on…

First, let’s get two big issues out of the way:

  1. IT’S EXTREMELY LIKELY THAT THIS WINTER WILL BE BETTER FOR SKIING THAN LAST WINTER
  2. EL NINO WINTERS RARELY LOOK LIKE LAST WINTER; THEY GENERALLY ARE NOT “DISASTERS”

Basically we hit bottom last winter, seeing the worst ski conditions in decades, and ANY winter should be better than that right?  That’s the working theory for this winter…

The phrase “EL NINO” often strikes fear into the hearts of Northwest skiers and is a somewhat deserved reputation.  El Nino is a warming of the tropical Pacific Ocean.  All that extra heat causes changes to ocean and atmospheric circulations, affecting weather across the globe in different ways.  As of now, the Oceanic Nino Index (ONI) is at a huge +2.3 deg C.  That puts this event right up with the “Super Ninos” in 1982-83 and 1997-1998.  This is a big one.  IF the current conditions were to continue for the next 5 months (a big IF), this could be the strongest on record since 1950.  But it isn’t for now and at least one model, the CFS, implies this event will peak in the next month or two.

Capture

Regardless, this is a “Strong” El Nino and it’s here to stay for this coming cool season.  In these winters, we tend to see warmer and drier weather than average across the northern half of the Pacific Northwest.  As you’ve also likely heard, California in many of these winters gets slammed by lots of stormy/wet weather.  Taking all moderate/strong El Nino winters since 1950, here is the average precipitation anomaly from November-February…pretty dry:

Moderate_StrongElNinoYears

And temperature anomaly for the same years, warmer than normal:

Moderate_StrongElNinoYearsTemp

 

 

So let’s take a look at Cascade snowfall in the 23 El Nino winters we have seen since 1950 at Government Camp, where average yearly accumulation is 270″ (click for full-size)

ElNino_GovernmentCampSnow

That’s not good news.  A few thoughts:

  1. EVERY EL NINO SINCE 1970 HAS PRODUCED BELOW NORMAL WINTER SNOWFALL AT 4,000′ ON MT. HOOD.
  2. ONLY A FEW YEARS ARE REALLY BAD, MOST JUST HAVE LESS FREQUENT SNOWFALL AND MORE RAIN/SNOW EVENTS.

There is a downward trend as well through the period, although 23 data points is a pretty small sample!  Do you notice the events in the 1960s seemed to do just fine for snowfall, but post-1970 or so things have gone downhill at bit?  It may that a very gradual warmup in the Cascades has produced more warm storms (rain vs. snow) at that elevation.  Notice that I am focusing on the 4,000′ elevation.  That’s because monthly snowfall data is very hard to find.  Records are also taken at Timberline and Mt. Hood Meadows, but aren’t generally publicly available.

Mt. Hood Meadows issued a nice media release earlier this summer that included total winter snowfall at that 5,400′ elevation.  So I plugged in those numbers to see how things vary vs. Gov’t Camp.  Those records only go back to 1982:

ElNino_MeadowsvsGov'tCampSnow

A few thoughts:

  1. Snow accumulation increases dramatically as you go up in elevation.  Looks like that extra 1,500′ or so almost always doubles total yearly snow.  Much of that is in “shoulder seasons” of October/November and mid-March/April/May, I suppose when it’s too warm down at Gov’t Camp.
  2. El Ninos are more reasonable at a higher elevation.  That’s because we tend to be warmer in El Nino winters with warmer storms
  3. At higher elevations a few El Nino winters have actually been snowier than normal.  Another reason to not totally freak out.  You will likely need to spend more time this coming winter on the higher parts of your favorite resort.
  4. 1982-83 is a weird one, Gov’t Camp was well below average yet Meadows was above.  That MAY be because the best snow was in the spring when it was getting too warm down below.  Not sure since I don’t see the monthly data.

That brings up a good point…total snowfall for the season doesn’t matter as much as what happens during the important winter months of December-February when most of us ski/snowboard.  Here are the Gov’t Camp numbers for just that 3 month period during El Nino winters:

ElNino_GovernmentCampDEC_FEBSnow

Thoughts:

  1. Snow during the important December-February period is below normal during every El Nino since 1970.  Some of those years are way below normal as well.
  2. The moderate/strong El Nino years don’t tend to be the “disaster” years (except for 1991-1992)

 

I think I can dispel one myth that I’ve been passing along over the years.  That El Nino winters often start with a “bang”…great snowfall right away in late October/November that then peters out as we get into late winter.  Apparently that’s not true.  Out of the last 10 moderate/strong El Ninos, 5 saw lots of snow by Thanksgiving, 5 did not.  Doesn’t seem like a very clear signal to me.

You may notice I didn’t mention the warm “blob” of water in the Eastern Pacific or the very warm PDO right now.  Those are both long stories for another time, but I don’t believe either one helps the snow situation for this coming winter.  I didn’t see any reason to pile that onto this posting!

I’ll take a look at what El Nino means in the lowlands later this week.

Chief Meteorologist Mark Nelsen