Summer Season Forecasts: Can you believe them?

Forecasting the summer season in Minnesota is about as easy as winning that really big stuffed animal on the midway. You’re more likely to walk away with that little plastic thingy and a few less quarters in your pocket.

Case in point.

Take a look at the National Oceanic and Atmospheric Administration's "Heidke skill scores" for summer season forecast across the US.

Note that the lowest forecast skills, (worse than climatology) occur over the Upper Midwest and Great Lakes regions. The best chance for nailing a summer forecast? The southern Rockies and Southwest.

Create a More Connected Minnesota

MPR News is your trusted resource for the news you need. With your support, MPR News brings accessible, courageous journalism and authentic conversation to everyone - free of paywalls and barriers. Your gift makes a difference.

summer skill scores
NOAA

University of Washington Professor Cliff Mass has an interesting take on summer forecasts. I pulled a couple of the most salient clips.

I should note that this forecasts are manual/subjective products, based on forecaster judgement, a variety of statistical tools, the output from extended-range models,the current state of El Nino/La Nina and the cycles like the Pacific Decadal Oscillation,  and other sources of information.  Sort of the meteorological version of sausage making---you might be surprised what goes into it.

But can you believe such seasonal forecasts, even this close to summer?   Do they have any real skill?

The answer:  skill is marginal at best.

Editorial:  You would think that the National Weather Service would have good verification statistics available on their web site  for their long-range predictions, but as with most product verification, their offerings are weak or non-existent.  They have an interactive verification tool that does not work ( I have tried on several platforms).

Providing the public with good verification information about their forecasts should be a priority for the National Weather Service; they seem to give this task little resource and don't maintain what they have.

latest_sst
Latest sea surface temps show building warmth in the tropical Pacific. NOAA

Summer of 2014: Any trends?

A developing El Nino has yet to fully manifest in the tropical Pacific. The links to seasonal weather are much stronger in winter (milder) for El Nino events in Minnesota. There’s a much lower statistical correlation and forecast skill with El Nino / Southern Oscillation events for our summer weather patterns.

NOAA leans toward a cooler summer at this point for the Upper Midwest. I’m not buying it just yet.

[image]

My hunch is we’ll see a pretty typical summer. That means a good mix of heavy rainfall early in June, mixed in with our fair share of severe weather this summer.

  • 19 days at or above 90 degrees in 2013 at Minneapolis-St. Paul International Airport

  • 31 days at or above 90 degrees in 2012 at MSP

  • 13 days – average number of 90 degree days annually at MSP

Last summer we sweated through 19 days of 90-plus degree heat after sweltering in 31 days of 90-degree heat in 2012.

This summer?

Who knows. Last year some forecasters confidently predicted we were done with 90 degrees in early August during a cool spell. We went on to log 10 more days at or above 90 in late August and September.

If you've lived in Minnesota long enough you learn not to bet against 90s during State Fair time.

My best guess? We end up somewhere between 13 to 18 days at or above 90 this summer, near or slightly above average. Overall near normal temps and a slightly wetter summer would not surprise me. Recent years have show a strong trend toward wetter early summers, and flash drought later in summer and into fall.

As we say in the weather biz,  stay tuned.