Can a Groundhog Really Predict When Spring Will Arrive?
By Renny Vandewege
Groundhog handler Ben Hughes and Punxsutawney Phil at the 125th annual Groundhog Day festivities on Feb. 2, 2011, in Punxsutawney, Pa. (Photo by Jeff Swensen/Getty Images)
Groundhog Day is Saturday, Feb. 2. But can a groundhog really predict when spring will arrive?
We all love Groundhog Day. The idea that a furry rodent can pop out of the earth on Feb. 2 in Punxsutawney, Pa., and tell us, based on whether he sees his shadow, how soon spring will arrive? It doesn't get any more charming than that.
But how accurate is our lovable groundhog, Punxsutawney Phil? According to StormFax Weather Almanac, Phil has been right 39 percent of the time since 1887. It is amazing that he still has a job.
The truth is that there is no science to these predictions. On a day in which the weather features a mix of sun and clouds, it's conceivable that Phil could come up with both predictions depending on the hour.
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So how do scientists really determine when spring will arrive?
Meteorologically speaking, spring arrives on March 1, four weeks after Phil makes his grandiose appearance. In planetary terms, the first day of spring is on March 20 -- the date of the vernal equinox. The equinox is the day when the sun's angle is directly above the equator, making for roughly 12 hours of day and 12 hours of night. After that date, the Northern Hemisphere begins seeing more daylight than night and temperatures begin to warm as a result.
But most folks really just want to know when the cold days of winter will end and warmer days of spring arrive. The answer is far more complicated than the presence of one rodent's shadow.
Meteorologists look to global and regional patterns to find clues. These are known as "teleconnections."
Teleconnections give meteorologists and climatologists key indicators as to how atmospheric pressure and oceanic currents may influence the weather for weeks or months ahead. The most well-known teleconnection that has become a media buzzword is El Niño/La Niña. El Niño has been blamed for many major weather occurrences, most of the time falsely as it doesn't cause singular weather events. El Niño or La Niña is simply a measurement of water temperatures in the equatorial Pacific Ocean. Warmer than normal water temperatures result in an El Niño phase while cooler than normal water temperatures result in a La Niña phase.
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This change in oceanic temperature can inflict large-scale influences on weather patterns over much of the world, including North America. For example, an El Niño pattern typically results in a wet period for southern California and cooler and wetter winter for the southeast United States.
One of the best indicators for seasonal predictions comes from the North Atlantic Oscillation. This teleconnection measures the atmospheric pressure differences in the north Atlantic from the Azores high to the Icelandic High. A negative-phase North Atlantic Oscillation suggests higher-than-normal pressure in the north Atlantic Ocean and represents a blocking pattern that allows cold air to move into the eastern United States. A positive phase North Atlantic Oscillation implies lower-than-normal pressure in the North Atlantic, representing a progressive pattern that allows for a warmer eastern United States.
Currently, the North Atlantic Oscillation is moving from a negative phase to a neutral and weakly positive phase. El Niño/La Niña are both neutral. That means spring could come a little sooner in the southwest and a little later in the upper midwest. As for the rest of the country, spring should arrive right about on time.
Punxsutawney Phil and other local groundhogs represent great traditions celebrating the nearing end of winter. But meteorologists stick with global data in continuing to refine their forecasts for the upcoming seasons.
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