Rochester, NY Area Weather

Many of you have heard of the numerous farmer’s almanacs out there that purport to give long-range weather forecasts out to a full year. Through top-secret proprietary formulae, these publications claim to provide an “80 percent” accuracy rate. Most serious meteorologists consider the farmer’s almanacs to be either too vague to merit serious scrutiny or outright bunk. (For one, you can’t measure forecast accuracy in percentages, unless you use a margin of error– which, conveniently, the almanacs leave out.)

However, taking a look at the way this winter has played out, compared to the past several years of winter, I’m noticing that it seems to play out the same way each year:

• A cold blast comes in either late November or early December, and lasts through January.
• A “January thaw” comes in late January.
• Another winter cold snap arrives at the end of January/early February, and lasts through early March.
• The first warm spell of meteorological spring arrives in mid-March.
• A last shot of winter cold and snow, though not as strong as February, hits in late March.
• In early April, the spring arrives permanently.

The timing of these can vary somewhat, but that is generally the pattern that we in upstate New York experience just about every winter. While I haven’t done much to investigate the climatology of why these phenomena happen at roughly the same time each year, it appears to be a trend. Maybe the farmer’s almanac is on to something– maybe it IS possible to make fairly accurate extreme long-range forecasts, even if we aren’t going to see the 7-day outlook we see on TV go to a full month any time soon. While their methodology is questionable, there are old farmers out there that used to keep their own almanacs and collect rules of thumb that they used to predict the weather, back before meteorologists became commonplace. I’d venture to guess that with a little bit of handed-down lore and several years of trial and error, they too noticed some trends and were able to do some roughly accurate forecasts.

Some of you may ask, “well, why doesn’t this show up in the normals?” In other words, why isn’t the normal for St. Patrick’s Day higher than it is for ten days later, if indeed it is the average for all March 17s in a 30-year span? The answer lies in the fact that what meteorologists call “normal” isn’t a pure average– in fact, it’s an average that is fitted to a sine curve, which smooths out most of the little bumps and valleys that occur within a season. Hence, even though I (and several other meteorologists) like to use the word “average” as opposed to “normal” (due to the semantic arguments that surround what people think “normal” means) it’s not precisely an average– just a smoothed-out estimate.