Wednesday, November 11, 2009

The November 11th Blue Norther of 1911

On November 11th, 1911, an intense area of low pressure developed over the Midwest leading to extreme weather across a good deal of the nation. Many areas of the country saw record warmth late that afternoon only to be shocked by the intense arctic blast to follow hours later. In Oklahoma City, a record high of 82°F was set in the afternoon before a cold front raced through the area. Just before midnight, the temperature was 16°F establishing a new record low for the same date. Other Cities such as Springfield, MO set record highs in the 80s that afternoon followed by record lows in the teens just before midnight.

Take a look at some of these temperature extremes from highs on the 11th to lows on the 12th:

Oklahoma City 82°F/14°F
Amarillo, TX 70°F/10°F
Palestine, TX 82°F/28°F
Springfield, MO 80°F/8°F
Fort Worth, TX 86°F/20°F

So why the big difference in temperatures? The image at the top shows the weather map for the morning of November 11th, 1911. You will notice an intense area of low pressure developing across northwest Missouri at this time. This low brought with it a large amount of warm moist air that would lead to severe thunderstorms, as I will discuss farther down, but also brought with it dry air as winds blew down the front range of the Rockies causing a dryline to form from Oklahoma down into Texas. The air mass behind this dry line was still out ahead of the main cold front so temperatures were allowed to soar. Much of southwestern Missouri, Oklahoma, and Texas were in this warm dry air mass with temperatures soaring into the 80s to near 90 in a few locations. Shortly after sunset the arctic front raced through these same areas causing temperatures to plummet, as much as 30°F in one hour. It was the unique combination of warm dry air ahead of a fast moving cold front which allowed such a large range of temperatures to occur on the 11th.

In addition to the significant temperature change, an outbreak of severe weather occurred across parts of the Midwest. Numerous tornadoes were reported across Indiana, Illinois, Michigan, and Wisconsin. An F2 tornado hit Waterloo, IN and 2 people were killed in Michigan with tornadoes. The strongest tornado was in Jamesville, WI where an F4 tornado killed 9 people. Less than an hour later blizzard conditions with wind chill temperatures near 0°F were hampering the cleanup efforts.

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