With Equinox Comes 'Roller-Coaster' Spring
By By Gina Cherundolo, AccuWeather.com Staff Writer
March 21, 2011, 4:07:41 AM EDT
Although there are several different ways to classify the seasons, spring will finally be official for the Northern Hemisphere Sunday evening, when the vernal equinox will occur.
The equinoxes and solstices that occur during the year mark the astronomical beginnings of seasons, which is dependent on the Earth's position in relation to the sun.
During the vernal equinox, the Earth's tilt on its axis is neither toward nor away from the sun. This year, the equinox will be 7:21 p.m., EDT.
Astronomical spring occurs the latest among the other two common seasonal classifications. Meteorological spring, which is the three-month period between the coldest and warmest months of the year, began on March 1.
Likewise, solar winter ended on Jan. 31. Solar winter is the three months of the year with the least amount of daylight, while solar summer is the three months of the year with the most. The interim period between these can be considered solar spring.
A Product of Extremes
Although spring begins this Sunday, the change to springlike weather won't be immediate.
"It's a battle going on between winter trying to hold on in the northern latitudes, where the ground is frozen, and the sun, especially in the southern U.S. where spring tends to come about a lot faster," AccuWeather.com Expert Senior Meteorologist Dave Dombek said.
Dombek added that through the course of spring, there are many ups and downs with temperatures, but the trend will eventually make its way toward warmer weather.
"There is a constant battle in transition seasons with wild temperature swings. It's not unusual to have a wild roller-coaster spring. Normals are the product of extremes."
During the spring months, there is a wider gap between normal highs and normal lows than during winter and summer. For example, during January in New York, there is a 12-degree difference between the normal high and normal low temperatures. By the end of April, this increases to 17 degrees.
There is also more of a difference between record highs and lows. On the first full day of spring in New York (March 21), the record low is 10 degrees and the record high is 84 degrees, a difference of 74 degrees. On the usual day of the winter solstice (Dec. 21), the difference is 65 degrees.
Spring 2011 Forecast
Additionally, Paul Pastelok, leader of the AccuWeather.com Long-Range Forecasting Team, has released his Spring 2011 Forecast for the United States, and AccuWeather.com Expert Senior Meteorologist Brett Anderson has released his Spring 2011 Forecast for Canada.
The AccuWeather.com Spring 2011 Forecast for Europe will be released later this week.
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