You’re Not Seeing Double… It’s Groundhog’s Day!

At daybreak on February 2nd of every year, Phil is awakened from his burrow on Gobbler’s Knob in Punxsutawney, Pennsylvania and is helped to the top of a stump by his handlers. With the recent Polar Vortex hitting Phil’s home with wind chills of -32 F and clouds in the forecast for tomorrow, will Phil see his shadow? If there was no shadow, it would mean an early spring. But, how can a groundhog predict the weather? Groundhog Day is rooted in Celtic and Germanic traditions and has been celebrated since 1887.  Phil may be a popular critter, but he may not always right… 

Last year, for example, Phil saw his shadow suggesting six more weeks of winter. However, February was ranked in the warmest third February’s or about 1.6°F above the 20th Century average, and March was ranked near the median value of a 124-period record. Alaska’s February and March temperatures were 8.3 F and 6.9 F above the long-term average, respectively.  But, results weren’t consistent across the United States. Below average temperatures were observed along parts of the East Coast in February and in the Pacific Northwest and Northern Plains for March 2018.

As of 2018, Phil has made 132 predictions, with an early spring (no shadow) predicted 18 times (~14%). On average, the groundhog’s accuracy has given results somewhere around 39%. After 1969, Phil’s accuracy drops to about 36% with the availability of and accuracy of records to verify with (Wunderground). Even flipping a coin, you’d still be right about 50% of the time, which would still be better odds than going off of Phil’s predictions.

Predicting the weather 6 weeks out would require greater computational power than what is currently available. Even accuracy after about 7-10 days starts to fall of rapidly when introducing model differences. However, climate forecasts are primarily based off sea surface temperature patterns. The three-month CPC outlook for March, April, and May spring currently shows above normal temperatures for the western and southeastern United States, and above normal precipitation for the Rocky Mountains and Great Plain states. We shall see how well the remainder of February matches what would be expected based on what a groundhog named Phil predicted. In the meantime, sit back and enjoy Phil’s promise of an early spring ahead.

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©2019 Meteorologist Sharon Sullivan