December 2007 Ice Storm

Oklahoma

An ice storm caused massive damage across Oklahoma, Missouri, and Kansas on Dec. 9-11, 2007. A shallow but strong arctic cold front plowed through Oklahoma on Saturday, dropping temperatures below freezing. Meanwhile, a strong upper-level trough approached only slowly from the southwestern U.S., while ample Pacific and Gulf of Mexico moisture streamed northward above the shallow cold airmass (i.e. strong isentropic lift). From very early Sunday morning through Monday afternoon, temperatures remained below freezing across central and northeastern Oklahoma. Concurrently, an extremely persistent quasi-stationary band of convection (with frequent lightning and thunder) anchored itself along and near the I-44 corridor, from southwest of Oklahoma City to north of Joplin, Missouri. Area soundings showed 500-800 j/kg MUCAPE through much of the event, which contributed to vertical convection and enhanced rainfall rates. 850mb temperatures near 10C were noted on area soundings, which is quite warm for this time of year. Base velocity data from KTLX radar (Oklahoma City) indicated that the cold air was about 3000 feet deep for much of the event, which is shallow enough to prevent the liquid raindrops from refreezing (i.e. freezing rain is the preferred mode, as opposed to sleet or snow).

By Monday afternoon, the shallow cold air dome began to retreat northward as very strong warm-air advection occurred through much of the southern and central Plains. Many locales that were under the quasi-stationary precipitation band recorded very significant glaze ice totals (1-2"), which caused record power outages and catastrophic tree damage. In fact, in the 72 hours proceeding Saturday evening, the Oklahoma City airport received 3.13" of liquid-equivalent precipitation, with more than 2" of that total falling on Sunday and Monday. As of Tuesday afternoon, more than 600,000 customers were without power in Oklahoma, which represents approximately 1.4 million people without power in Oklahoma alone. Many schools and universities canceled classes Monday (and Tuesday), and many shelters have opened to provide food and places to sleep for the more-than-a-million people who are without power in this relatively cold period (temperatures 30-40F).

Roadways were mainly wet or slushy throughout the event as ground temperatures (2" and 4" bare-soil temperatures) remained in the 34-37F range (2" and 4" under-sod temperature were in the upper-30s to low-40s). If nothing else, this helped keep the travel situation open for emergency vehicles and power company officials. In addition, damage could have been worse had winds been stronger. During most of the event, winds were largely weaker than 10 mph. As we've seen with past ice storms, windy conditions can quickly exasperate the power outage and damage situation. Fortunately, in this case, the relatively warm ground temperature and weak winds aided in mitigating the effects of this storm to a degree.

Current power outage numbers from the two largest power providers in Oklahoma:

Some General Information:

Since my house managed to take a glancing blow of the more significant ice accumulations, I've included some links to pictures from those who were hit by the part of the worst of the storm. Some pictures from others in the Oklahoma City area taken by...

Pictures

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