Category: Winter Outlook

Author: Bill McMillan- Founder and Owner of IndyWx.com

Date: Saturday, October 17th, 2015

2015-2016 IndyWx.com Winter Outlook

Well, here we are again…  The days are growing shorter, leaves are changing, and the air is growing more and more crisp.  Questions around the upcoming winter began last spring and have only increased in frequency over the past several weeks.

Before we get too deep into our reasoning with this year’s winter outlook, we want to make it clear that no long range forecast is ever 100% accurate.  There’s a lot of “guidance” out there, but any winter outlook that doesn’t specifically label temperature and snowfall/ precipitation numbers requires a raise of an eyebrow.

Last year’s winter outlook wasn’t perfect by any stretch of the imagination.  We were pleased with our temperature forecast (colder than normal, but even we weren’t cold enough).  As for snow, a late season rally did help out in a rather lack-luster snowfall forecast.

As a reminder, here was our 2014-2015 Winter Outlook:

• Temperatures: 2 degrees below normal (actual 10 degrees below normal)
• Snowfall: 35″ (actual 26″)

Summary of our 2015-2016 Winter Outlook:

Many factors have to be considered when developing any seasonal outlook.  While the ENSO (El Nino Southern Oscillation) state can, and should, serve as the basis of any particular seasonal forecast, there are several other things to consider:

• PDO- Pacific Decadal Oscillation
• NAO- North Atlantic Oscillation
• Northern Hemisphere Autumn Snow and Ice Cover
• Volcanic activity

There have been several outlooks posted over the past couple months seemingly broad-brushing the upcoming winter based solely off a “typical El Nino” pattern.  First, this isn’t a “typical” El Nino event, but instead a very strong one, and second, you have to consider the various other items mentioned above (and then some).

Case in point, let’s take a look at some other El Nino winters and what those provided across central IN:

Snowfall in Strong El Ninos

• 1982-1983: 5.7″- 8th least snow on record
• 1997-1998: 3.9″- 5th least snow on record*
• 1972-1973: 2.9″- 4th least snow on record
• 2002-2003: 46.9″- 4th most snow on record
• 2009-2010: 33.0″- 9th most snow on record

Snowfall in Weak El Ninos

• 1977-1978: 49.7″- 3rd most snow on record*

* indicates top 10 warmest winter

As you can easily see just based off the data above, using the word “typical” and “El Nino” together is almost laughable.  We took a snap shot of Top 10 least and most snow on record at IND and compared those against strong and weak Nino events.

As previously mentioned, we can’t solely lie on the Nino.  The current state of the PDO (positive) strongly argues for cold, snowy conditions across our neck of the country.  As a reminder, the positive PDO has been a key item in the cold, snowy past two winters.

Positive PDO look:

Sea Surface Temperature as of 10.15.15 profile- note the strong El Nino and positive PDO:

When the PDO is positive, you’d typically expect the eastern and central region to be cold during meteorological winter (Dec., Jan., Feb.):

Interestingly, model data sees a weakening El Nino as we progress deeper into the winter and spring.  Weakening mid and late winter Ninos have been known to be colder, versus the opposite.

Other players:

The NAO, or North Atlantic Oscillation, is a bit of a wild card, as always.  A couple recent El Nino winters teamed up with a predominantly negative NAO to lead to snowy, cold winters (2009-2010 comes to mind).  However, the NAO anomaly is, admittedly, difficult to forecast for winter in October.  Whether negative or positive, the NAO’s impact on our weather is felt most significantly late in the winter- from February into March.  Like a cold late winter?  Root for a negative NAO.

Volcanic activity can also play a role in temperatures across the globe.  Many studies are out there with in-depth research findings around the impact of large eruptions from a global perspective.  Often, years with high volcanism can greatly impact surface temperatures 1-2 years later.

See the Nasa Earth Observation site here.

See the Effects of Very Large Volcanic eruptions here.

See How Volcanism Effects Climate here.

What does this all mean to me?

First, if you read everything above, “bless your heart!”  🙂  A challenging winter lies ahead with conflicting signals of the strong El Nino (associated with top warm and snowless winters) and positive PDO (associated with top cold and snowy winters).

Out of the various forecast models, we like the idea the JAMSTEC has best, and the overall way it handles both the El Nino (shifting towards more of a central-based El Nino event) and PDO.  We feel this model best represents the likely milder than average start to winter before colder conditions mid and late winter.

Model predicted Sea Surface Temperatures Dec., Jan., Feb.

Model predicted Surface Temperatures Dec., Jan., Feb.

Model predicted Precipitation Dec., Jan., Feb.

We think the winter opens warmer than normal and relatively dry before shifting towards a colder than average pattern for mid and late winter.  The idea of a weakening Nino come mid winter and continued positive PDO is key in our idea of a cold mid winter on.  Should the El Nino not weaken as much as currently expected then it would argue for warmer than average conditions continuing deeper into winter.

That said, given the state of the PDO, we also think there will be “bouts” of cold, wintry weather scattered through the first part of the season, as well.  While all-in-all we may come very close to seasonal norms when all is totaled up, the extremes in between may be anything other than normal.  The word “volatile” comes to mind at times.

• IndyWx.com forecasts meteorological winter temperatures (Dec., Jan., Feb.) to average 1 degree below normal (Fahrenheit).
• Average snowfall at IND is 25.9″.  IndyWx.com forecasts 20″ of snow (first flake to last flake).

Remember that we’ll be here all winter long producing daily forecasts and in-depth winter storm discussions. In addition, if your industry is impacted by winter weather, please be sure to shoot us an e-mail at bill@indywx.com to learn ways about how we can help your business with customized winter weather consulting. Also, be sure to follow us on Twitter @IndyWX for more “behind the scenes weather…”

Additional references:

http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/

http://www.metoffice.gov.uk/hadobs/hadisst/data/download.html

http://www.jamstec.go.jp/frsgc/research/d1/iod/sintex_f1_forecast.html.en