Soaker, Wet Jan... Turning Colder... Polar Vortex Animation
A nice soaking Mon. night/Tue. morning. If you feel like it's been raining a lot recently, you're right. Jan. rainfall so far stands at 5.76" @ JIA - nearly double the Jan. avg. of 3.30". We were coming off a dry Dec. -- -1.94" -- so good to get the moisture, especially since we're just months away from what is typically the worst of our wildfire season.
Rainfall amounts from Mon. night/Tue.:
Fleming Island - 1.95"
Green Cove Springs - 1.93"
Clay Hill - 1.76"
Mayport - 1.66"
JIA - 1.61"
Arlington - 1.56"
St. Augustine - 1.51"
Orange Park - 1.37"
St. Simons Island - 0.61"
A subtle shift in the upper level winds will result in an extended period of chilly -- generally below avg. -- temps. For much of this winter -- so far -- an upper level ridge has been locked over the E. Pacific or right along the U.S. west coast with a second -- somewhat weaker ridge -- over the W. Atlantic. This has resulted in a persistent upper level trough of low pressure over or near the middle of the U.S. The upshot has been a cold last couple of months for the midwest, parts of the Ohio & Tennessee Valley with mostly just glancing blows of cold for the First Coast.
But now the upper level ridge is shifting eastward some which will push the upper level trough eastward -- see the forecast map for Sat. for an example. This set-up will allow cold air sinking into the Southeast U.S. to have some staying power. The first cold front moves across the First Coast Wed. evening. Deepening low pressure over the W. Atlantic (BUT far enough east to keep any precip. to the east) will make for a windy, cold Thu. Yet another cold front late Fri. will reinforce the cold air for the weekend. An inland freeze can be expected Fri., Sat. & Sun. Indications are that we'll see another shot of cold air about the middle of next week.
NASA has released a video of the polar vortex from Dec. through the first week of Jan. showing the vortex expanding & contracting ending with the severe cold of last week -- click ** here **. From NASA: This movie of temperature observations from NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua spacecraft depicts the first major North American weather event of 2014: cold air moving out of the Arctic and south to cover much of the continent. The temperatures shown are at a pressure of 850 hectopascals (hPa, formerly knows as millibars; sea level pressure is normally around 1000 hPa). Pressures of 850 hPa correspond to an altitude of about 3,000 feet (1 kilometer) above sea level. The temperatures in the movie range from about minus 18 degrees Fahrenheit (245 Kelvin or minus 28 degrees Celsius) to warmer than 66 degrees Fahrenheit (290 Kelvin or about 17 degrees Celsius). The very coldest temperatures in purples and blues are minus 18 to 17 degrees Fahrenheit (minus 28 to about minus 8 degrees Celsius).
The most obvious feature of the movie is the tongue of cold air moving out of Canada and southward to cover much of the eastern United States during early January 2014. This event was covered extensively in the media, and introduced the term 'polar vortex' to a broader audience.
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