Saturday, January 9, 2010

Coldest Night in 14 Years..Could Be Colder Tonight!

With clear skies and calm winds, East Texas was greeted with the coldest temperatures in 14 years last night. Low temperatures were between 10°F and 15°F just about area wide, with a few places dipping below 10 degrees(Winona MADIS station dropped to 9°F and yours truly dropped to 8°F). In addition to the bitter cold, the light winds allowed for a unique type of frost to form last night. Normally here in East Texas when we see frost we have dew form on objects and then freeze as the temperature of the objects fall below freezing. Last night a process called deposition occurred were the water vapor in the atmosphere went from a gas directly to a solid. This occurs when objects are very cold and come into contact with water vapor. Instead of condensation forming on the object, ice crystals begin to grow, just like snowflakes. If you look at the photo above you can see what appears to be small snowflakes. Notice the branching crystal growth. This is called dendritic crystal growth, the way snowflakes form in the atmosphere. The optimal temperature for this to occur is 14°F (-10°C) or colder. Objects around East Texas last night were easily colder than 14°F allowing for the snow like frost to form.

Light winds and sunny skies today will allow for a rapid warm up. Many of us will hit the freezing mark or a little higher. It will fell much warmer today due to the lack of wind. However, another very cold night is in store for East Texas tonight as light winds and clear skies allow the mercury to drop between 10°F and 15°F again in most places.

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