The January thaw is an observed but unexplained temperature rise in mid winter found most pronounced mid-latitude North America between 40 and 50 north. Some argue it is not real, others know it is.
For roughly about five days around 25th of January, the temperature spikes climatologically warmer than their colder counter parts in late January or later January or extremely
This occurs during the coldest dip of winter averages roughly around January 23rd. The opposite or warmest part of the year in high summer is roughly July 24th.
But the January thaw is believed to be a weather singularity. Further, a singularity is a characteristic meteorological condition that tends to occur on or near a specific calendar date more frequently than chance would indicate. The spike of the January thaw shows up statistically and is also defined as a period of mild weather, popularly supposed to recur each year in late January in New England and other parts of the northeastern United States and much of eastern Canada....Statistical tests show a high probability that it is a real singularity."
The usual set up is in the third week of January following a strong cold snap, but need not occur every year. In fact, during the very cold winters of the late 1970s, there were no January Thaws in the New England region during 1978 and 1979. And we know that in recent years there have mild winters when the Thaw was not noticeable.
In prime January Thaw country, the ideal weather pattern characteristic of the Thaw period unfolds in this manner. It begins after a cold air mass from northern or western regions has slid over the region (A), eventually moving out over the Atlantic Ocean. As that air mass leaves, the Bermuda High strengthens (B,C,D) and becomes positioned over the southern Atlantic Coast or southeastern US while a broad low pressure trough moves slowly across northern Ontario and Quebec (B-E). This places the northeastern US and southeastern Canada border region into a south-southwesterly flow of warm air originating from northern Mexico orthe gulf of Mexico. This mild intrusion advects over the northern snow and ice fields and begins a thaw.
Often during this time, the upper air wind patterns are in a period of readjustment, and thus surface weather systems stall or creep slowly across the eastern continent's mid-latitude belt. After several days of warmth, the regional weather again comes under the influence of a strengthened polar high (F,G), and cold weather returns.
The period of thaw usually results in a significant reduction of snow cover and ice thickness that is welcomed by many as a release from winter's uncomfortable grip. Those enjoying winter weather recreations -- sports and festivals -- often curse the January Thaw, however, for ruining ice and snow conditions. For them, a respite from bitter cold without the thawing is favored.
All meteorologists would agree that a period of thawing is a common winter weather event in the mid-latitudes of the continent. Why such a thaw should have a preference for the January 20-26 period rather than being a purely random event is still an unknown -- if there is in fact such a preference. Whether there is a preferential calendar slot remains the subject of debate among climatologists.
Analyses by climatologists David Phillips of Environment Canada and Art DeGaetano of the Northeast Regional Climate Center at Cornell University show definite warm spikes in the climate records for many sites across the prime region during this period.
The other side of the debate is characterized by papers such as one to be published this month in the Bulletin of the American Meteorological Society. In it, authors Christopher M. Godfrey, Daniel S. Wilks and David M. Schultz find no unique January Thaw period that is statistically significant, seeing thaws during this month as purely random events. And while they readily admit their analysis is not conclusive proof that no January Thaw exists, they remind us that no dynamic or plausible physical mechanism has yet been advanced to explain why a winter thaw should favor any specific narrow period year to year.
Godfrey, et al. do suggest one probable explanation for folklore and popular perceptions of so-called weather singularities such as the January thaw. "It is a recognized characteristic of human psychology that people will find patterns in the world around them, whether or not those patterns result from coherent underlying causes." This characteristic to see patterns in the surrounding environment, whether they exist or not, has served our species and many individuals well in the past and will continue to do so. Better we see the face of a non-existent tiger in the bushes and be wary than not see the face of a real tiger and be killed.
That we see a pattern in the winter cycling of weather across certain regions which gives rise to a welcomed respite from the cold is a given. If it were not there, scientists would not have spent over a century trying to prove or disprove its existence. Is the January Thaw real?
Excerpts were taken from the Weather Doctor
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