Data proves what we all suspected: Alabama’s severe weather is highly unpredictable

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December 5, 2014

Tim Robbins as Andy Dufresne in 'The Shawshank Redemption' (Photo: Screenshot) — Tim Robbins as Andy Dufresne in ‘The Shawshank Redemption’ (Photo: Screenshot)

“Where in the country is the weather truly the most unpredictable?”

That’s the question the statistical wizards at FiveThirtyEight set out to answer this week, and what they found will probably not come as a surprise to most Alabamians: our weather is wild.

Birmingham, Alabama, for instance, has the seventh most unpredictable weather of the country’s 50 largest metros and is a solid reflection of what it’s like across much of the Yellowhammer State.

So how did FiveThirtyEight’s Nate Silver and Reuben Fischer-Baum come to this conclusion?

The explanation of their process is fairly simple:

The data duo compared “daily weather patterns against long-term averages” in 120 U.S. cities and defined the “weather as being more unpredictable when it deviates more from these long-term trends.”

The stats they evaluated fell into three primary categories:

First, temperature:

High temperatures;

Low temperatures;

Daily mean temperatures.

Second, precipitation:

Rainfall, in inches;

Snowfall, in inches of snow (rather than the liquid equivalent⁷);

A binary variable indicating the presence or absence of precipitation (without regard to the type or amount of it). If there’s any precipitation at all over the 24-hour day, we score this variable as one. Otherwise, it’s zero.

Finally, severe weather and the conditions that contribute to it:

Wind speed;

Humidity⁸;

Cloud cover⁹;

A binary variable indicating whether there was a severe weather event (a thunderstorm, tornado or hail) in the city that day.

To reiterate, they were not trying to determine which areas have “better” or “worse” weather, just in which parts of the country is the weather most unpredictable.

Overall, Alabama’s temperature is about middle-of-the-pack when it comes to predictability, with South Alabama’s temperatures being more predictable than the rest of the state.

Alabama’s precipitation is much more unpredictable, though, especially in the South.

But as you may have suspected, it’s Alabama’s severe weather that is particularly unpredictable compared to most of the rest of the country, especially in central and north Alabama.