The La Nina Myth and the Winter Ahead

Warning: this post is pretty heavy on the "weather geek" meter (at least for an amateur).  If you want something simple and vague, go buy a Farmer's Almanac. Alternatively, lose yourself in the utter irresponsibility of AccuWeather's 90-day forecast.

Last year's Rippeology winter preview went about as well as I could possibly expect.  With one of the strongest El Ninos on record dominating weather globally, I made 5 predictions last November:

• Milder temperatures
• Fewer snow events (but not necessarily less snow than normal)
• More ice events
• A brown Christmas
• An active February

Each of these was correct with the exception of "an active February," which I missed by (literally) about 100 miles.  February was indeed a very active month in Wisconsin, but the heaviest precipitation stayed largely to the north/northwest, more on a La Crosse to Green Bay line.  This may have been due to El Nino staying stronger, longer, than most forecasters expected.

Regardless, I consider last year's outlook to be pretty good for a self-taught weather hobbyist who never took a single meteorology class.  So there.

Quick recap on El Nino and La Nina, because it comes into play in this year's winter outlook as well.  Each recurring phenomenon refers to either a warming (El Nino) or cooling (La Nina) of the equatorial waters in the central and eastern Pacific ocean.  To qualify for the label, sea surface temperatures must depart at least a half degree from average for a prolonged period of time.

Last year's El Nino rivaled the strongest occurrence on record, which occurred in 1997-98, and beat that event in duration by a half a year (19 months in 2014-16, versus 13 months in 1997-98).

Generally after a strong El Nino or La Nina occurs, there is a period of stabilization where sea surface temperatures mostly stay within a half degree of the average.  But earlier this spring, it looked as though we would slide directly from a strong El Nino into La Nina -- a rare oceanic feat only accomplished 3 times since we started measuring surface temps in 1950.  Those slides happened in 1972-73; 1988-89; and 1997-98, when a prolonged 32-month La Nina followed what was then the strongest El Nino on record.

Here's the Climate Prediction Center's recording of all sea surface readings since 1950.  These are done in 3-month rolling averages, so "DJF" refers to December/January/February.

We often associate La Nina with colder, snowier conditions in the Midwest.  But it's interesting to note that in those 3 instances above, when El Nino slid directly into La Nina, Madison recorded below-average snowfall in the winters when La Nina finally settled in for the long haul.  Average Madison snowfall for the last 30 winters is about 51 inches.  But here's what we had in those "slide" winters:

1973-74:  42.9 inches
1988-89:  36.2 inches
1999-00:  34.1 inches

But if you love winter, don't be discouraged.  That's because despite the myth of La Nina equating to extreme Wisconsin winters, in actuality, our heaviest snowfall years are associated with little or no sea surface anomalies at all. 

Here are the 8 snowiest Madison winters in the last 30 years, and the the El Nino/La Nina condition during those winters:

2007-08 (101.4 inches):  Weak La Nina
1978-79 (76.1 inches):    No departure
1993-94 (73.7 inches):    No departure
1985-86 (72.4 inches):    No departure
2008-09 (72.0 inches):    No departure
1992-93 (71.2 inches):    No departure
1987-88 (62.2 inches):    Weak El Nino
1995-96 (60.5 inches):    Weak La Nina

So what about the coming winter?  Right now, all indications point to a weak La Nina -- not the stronger one that looked possible just 4 months ago.  Warmer waters off the northwest coast, thousands of miles away, are actually preventing this year's La Nina from rapid cooling.  So, even though the Climate Prediction Center is predicting a La Nina winter, it looks to be relatively weak.  Current ENSO (El Nino Southern Oscillation) anomaly maps shows lighter blues in the Pacific:

If history is any guide, that could lead to a snowy winter in southern Wisconsin.

And that, deep into this post, is my first prediction for Winter 2016-17 in southern Wisconsin: above average snow, probably in the 60-70" range.

Here, then, are your Rippeology headlines for this winter:

1. Above average snowfall (including a very white Christmas);
2. More frequent light to moderate snowfalls and fewer "whoppers" -- as the stronger northern jet resulting from La Nina can favor Alberta Clippers over Texas Panhandle hooks;
3. Early cold and snow (and very possibly a white Thanksgiving);
4. Slightly below to below average temperatures (thanks in part to snow pack and #5...);
5. Up to 3 polar vortex events leading to extreme cold (I won't bore you with solar activity, but let's just say a less active solar flaring pattern can aid the vortex).

About that early cold: there are some solid indications that the last half of September and most of October will feature below-normal temps in the Midwest.  Technically, that's fall, not winter.  But it could certainly be a precursor to an active November.

There are plenty of other factors that could still shape our winter.  Hurricane activity is one of those, and there are still 8 weeks to go in the Atlantic hurricane season.  If anything changes, I'll let you know.  Otherwise, stay tuned to Rippeology for the next 6-7 months for the best amateur winter weather forecasting in New Glarus (disclaimer: small sample size).

And if you prefer to get your medium to long-range weather from an actual pro, there are none better than Jeremy Nelson at WISN-TV12 in Milwaukee.  Follow him on Twitter here.

~Scott

P.S.  New to Rippeology?  See how it all started in my inaugural post.