Top weather events of 2009: D.C. edition
* Winter Weather Advisory starts late tonight: Full Forecast *
It's the end of the calendar year and, as usual, that means 'tis time for those ubiquitous lists of top every this and that one can imagine. These lists include, of course, memorable or otherwise noteworthy weather events. I've got weather lists for you, and the first is the top 5 D.C. metro region events (stay tuned for my top 5 continental U.S. weather events list)...
Here they are (see the end of this post for my criteria for selecting them):
1) Historic snowstorm of December 18-19: Selecting this as THE number one event is a no-brainer, and all else in the list necessarily pales in comparison. The potent east coast storm stemmed from the rare, but not unprecedented convergence of several meteorological factors (see here and here). The official two-day measurement of 16.4 inches at Washington Reagan National Airport set the all time total monthly maximum snowfall record for December. Likewise for Baltimore's 21.1 inches. However, the official record December total of 24.2 inches (1966) at Dulles still stands, not withstanding the Dec. 18-19 two-day total of 21 inches. Whether snow lover or hater, especially after several years without a "big one," this historic storm was truly a memorable extreme and high-impact event of the highest order.
2) Flash floods: Several instances of flash flooding occurred in 2009, the most notable probably being the occurrences on May 6 and 26, June 3 and Aug. 22 and 28 . In each case flooding was associated with rain and thunderstorms producing heavy amounts over short periods and falling on pre-existing saturated ground. The flooding resulted in numerous examples of the usual consequences, particularly the angst caused as high water encroached on roads. Property damage from flooding appears to have been limited.
3) Severe storms: An intense supercell formed on the afternoon of Aug. 19 in southeast Charles Co., Md. As the storm intensified and rolled eastwards there were reports of funnel clouds, but no touchdowns, as well as baseball sized hail. On this one I go along with the expert opinion of Steve Zubrick, Science and Operations Officer at the National Weather Service Forecast Office in Sterling, Va., that this was truly an impressive storm (here). On the previous day (Aug. 18) thunderstorm wind damage occurred across many areas of Baltimore Co. accompanied by hail the size of ping pong balls. (In case you are interested, the largest hailstone on record in the U.S. was nearly the size of a soccer ball).
4) Mini snowstorm: Snowfall totals averaged around 5 to 9 inches locally on March 1-2 (see our post mortem assessment) as a low-pressure system tracked up the mid-Atlantic coast (here) . This was the first and only significant snow last winter and as such then it was considered big time. I label it "mini" only because in hindsight there is no comparison with the December storm in snow amounts, areal coverage, and impacts on routine activities.
5) Drought/No drought roller coaster: February was overall the driest on record in the region (and one of the least snowiest). Collectively the first three months of the year was the 4th driest on record and extended the dry spell of the last three months of 2008. Just when it appeared a severe drought was in the cards, April through June precipitation was well above normal, but was followed by dry conditions lasting through September. One major consequence is that much of the local corn crop in Virginia appears to have dried up on the stalk before harvesting. But, just when it again looked as if drought conditions might prevail, the balance of the year proved wet with the combined total for October and November rivaling the wettest comparable period in 1932.
In selecting this list, it's worth mentioning that the main considerations were whether the event was extreme and/or high impact at some location during some given time period.
Extreme refers to weather phenomena which are relatively rare large departures from what's normally expected. High impact refers to weather which is consequential to life and/or property in some respect. Extreme weather may or may not be high impact, and high-impact events may or may not be associated with extreme weather. A F5 tornado is rare and extreme but unlikely consequential if passing over an uninhabited, non- agricultural region. On the other hand, a run-of-the-mill F0 or F1 tornado can have dire consequences if passing over a residential area. An inch of rain is generally not much of a problem, but a miserly .01" of rain freezing on contact with roads during rush hour can cause mayhem. While one to two feet of snow in December is clearly extreme for the D.C. area, it is not so in Denver, but the impact is high in both locations.
In the end, as with most top-whatever lists, my selections are largely subjective and perhaps unrepresentative with respect to possibly more widely shared judgments. There are certainly more than a handful of possibilities in each category, but I've stuck to just five so there is abundant opportunity to add your suggestions.
Please feel free to comment on my opinions and offer your own choices on the best of 2009.
| December 30, 2009; 10:45 AM ET
Categories: Local Climate, Tracton
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