iPhone says 80s next week? Careful where you get your Minnesota weather

Many Twin Cities residents awoke Monday to their iPhone weather forecasts telling them it’d be in the 80s next week. This would be quite the “weather whiplash.” It’s also highly unlikely.

Forecast with caution

Twitter and text messages on my phone were blowing up Monday morning with people asking: “Is it really going to be in the 80s next week!?”

I wish I could give you an emphatic “Yes!” However, it’s not likely. That’s probably a good thing, too, considering our flooding situation across Minnesota.

Let’s dive into the world of computer models and weather forecasting a bit.

First, a weather app on your phone is not a forecast made by a human usually but rather heavily based on computer models or even just one model, as appears to be the case in this recent viral episode.

The forecasts in question look to be heavily reliant on one model, the commonly named ‘American model,’ or more officially the National Oceanic and Atmospheric Administration’s Global Forecast System model.

As you can see above, the GFS forecast from its 7 p.m. run Sunday evening forecasts a high of 87 degrees for next Wednesday, April 12. The exact same model, just six hours later has a more tempered 72-degree high.

The very same model six hours earlier, midday Sunday, had a high of 48 degrees for next Wednesday. That’s a 39-degree spread among the models within the same 12-hour period for the same day.

I’ve thrown in two other medium range models we use for forecasting; the European Centre for Medium-Range Weather Forecasts model and the Environment Canada model. They are forecasting highs of 55 and 62 degrees respectively.

At this point, it’s time for your local meteorologists to toot their own horn.

We quality control computer forecasts, knowing their biases, weaknesses, and strengths. A good forecast also looks at trends — not just one model run but what examining how all the models trending toward over time.

As we get closer to an event, whether it’s a snowstorm or a high temperature, are the models being consistent and in agreement? This gives us an idea of confidence. We also have to look at climatology, or statistics.

The first red flag of an 87-degree high for April 12 in the Twin Cities is that this would be an all-time record for the date. The earliest we’ve reached 87 or warmer was April 10, 1977, so it’s not entirely impossible, but highly improbable.

One of the ways we can measure volatility in our temperature data is by measuring standard deviation.

For April 12, the median high temperature is 53 degrees with a standard deviation of 11 degrees. This equates to a high temperature of even 80 degrees on April 12 specifically being a 1 percent chance climatologically.

About 10 percent of the time we see our first 80 by April 12 or earlier. Given that we just finished March with temperatures averaging more than 4 degrees colder than normal and we just finally had our first 50, 80s this soon would be remarkable, though we’ve seen stranger things in this state.

In case you’re curious, when we look at all the models into next week, the median forecast high is about 63 in the Twin Cities for next Wednesday.

The probability in those models of hitting 70 is 12 percent. The trend is indeed for much warmer temperatures this weekend into next week but you may just need to be patient for summer temperatures quite yet.