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Saturday, January 10, 2015

Ocean Snow in Florida Sets Record

News4Jax | Jan 9, 2015 | Blake Mathews

© New4Jax
 [...] According to meteorologist Jason Hess, only three snowfalls have actually accumulated officially in Jacksonville in 103 years (1956, 1986 and 1989) with the greatest 24 hour accumulation of 1.9 inches in February 1899 -- before records officially began.

Thursday's snowfall was a rare phenomenon known as 'ocean effect snow.' It's the same idea as lake-effect snow except it occurs over the ocean.  The idea here is that the water is warmer than the land this time of year allowing moisture to rise and condense to form clouds and rain or snow.

When our winds shifted to the northeast, the moisture began moving towards land. Even though the surface temperatures were above freezing near the surface, the air just above the boundary layer (basically the first few hundred feet above the surface) was below freezing allowing the snowflakes to make it to the ground before melting. Voila! Snow.

It nearly didn't happen though. A powerful arctic front pushed through Florida late Wednesday powered by a mega-high pressure system over the mid west. That high drove in a lot of dry air, evidence by our dew points (measure of moisture in the air) into the teens meaning any flakes would have evaporated before reaching the ground. Through the process of evaporative cooling (wet-bulbing), our atmosphere cooled and moistened just enough to allow for the flakes to hit the ground.

Snow was last observed officially, a trace, in Jacksonville the day after Christmas in 2010 with measurable snowfall in southeast Georgia.

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