Winter is described from both an astronomical and meteorological standpoint.
Meteorological winter is defined as the three coldest months throughout the winter, or December 1st through March 1st.
MONTHLY AVERAGE TEMPERATURES IN BIRMINGHAM
Astronomical winter is defined as December 21, 2013 through March 19, 2014. Most are pretty familiar with the astronomical-based seasons but if not, they are defined by the rotation of the earth around the sun and the tilt of the earth's axis. Over the course of a year, the earth experiences changes in weather, ecology and hours of daylight. The earth’s axis is an imaginary line that runs through the middle of the earth from the North Pole to the South Pole. The axis of the earth is tilted about 23½ degrees. The tilt of the earth remains the same as the earth follows its yearly path around the sun. This path is known as an orbit.
The beginning of astronomical winter is called the Winter Solstice. On the December solstice incoming solar radiation is at a minimum in the Northern Hemisphere. Since the Northern Hemisphere is tilted away from the sun this time of year, places north of the equator receive significantly less energy from the sun, hence it's colder.
The end of astronomical winter aka the beginning of spring is called the Vernal Equinox. It's when the plane of Earth's equator passes the center of the Sun. At this time the tilt of the Earth's axis is inclined neither away from nor towards the Sun. Around the equinox, night and day are about equal length. More sunlight equals warmer days ahead and plants and trees coming to life!
Here's one sign of spring sent to me by a viewer in Hoover...
This is the farthest south I have worked and been amazed at the fact that some plant and tree life has stayed alive this winter. One of my favorite spring plants are Pansies and it has been so nice to see them live through the coldest months. The pines make me smile each day thanks to their evergreen color.
I just recently noticed some trees and bulbs flowering and honestly think that meteorological winter fits best for Alabama than astronomical.
Spring is my favorite season because I love seeing everything come to life and because I love storms!
What's your favorite season and why?
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Jill Gilardi Fox 6 Meteorologist