Three big snowstorms all ranked in Top 10
The National Weather Service's Sterling, Va. forecast office has disowned the list of Top 20 Snowstorms for Baltimore that was posted on its Web site for many years. In the wake of the Feb. 5-6 storm, concerns were raised about the scientific legitimacy of the criteria long used for inclusion on the list.
Jim Lee, meteorologist-in-charge at Sterling, told me that one of the problems is that the list does not discriminate among 1-day, 2-day and 3-day storms, not to mention those that seemed to rage on even longer. The No. 1 ranked snowstorm, before the list disappeared from the Sterling site, dropped snow on Baltimore over four days, from Feb. 15 to Feb. 18, 2003.
But Lee told me a few weeks back that, meteorologically speaking, no snowfall that lasts four days can be considered the consequence of a single storm. And in truth, that 2003 event really was a combination of at least two storms, with some time during those four days when no snow was falling. (The Baltimore Top 20 snowstorm list includes two others, in 1899 and 1892, that stretched over four days.)
So, because climatologists only accept data on 1-, 2- or 3-day storms, the Sterling office will be reassessing its Top 20 list. What we'll probably get will be several lists, broken down by the length of the storm, and ignoring the snow that fell on the fourth day of three former Top-20 storms.
The Sterling office will also be reassessing storms that may have been measured at BWI-Marshall with hourly measurements - in accordance with FAA standards - rather than with the six-hour measurements required by NOAA for climatological purposes. That could reduce official storm totals for BWI going back as far as 1998, when the FAA took over the job of measuring snowfall at the airport from the weather service. There are six Top 20 storms since 1998 at BWI that could be affected.
I'm not sure how all this will come out in the wash. It seems likely that, if the FAA's contractors really have used hourly measurements since 1998, that all our snowstorms since then will get smaller. When the problem was discovered last month, Lee rejected the 28.8-inch total the FAA contractor reported for the Feb. 5-6 storm based on its hourly measurements. He replaced it with the more conservative 24.8-inch measurement the contractor reported as the storm's "snow depth" - the total measured when the snow stopped falling (and after the snow's weight had compacted it).
On the former issue - revisiting the entire storm record at BWI and Washington and ranking snowfalls in separate categories according to the number of days the snow fell - I suppose they have to abide by the rules set by climatologists.
But, on the latter, it seems to me that those of us who are not climatologists experience snowstorms as discreet events based on how much we have to shovel once the flakes stop falling. I would argue that the February 2003 "storm" - while it may have been two storms - felt like one really long siege to those of us left to dig out from 28 inches of snow.
So, in the interests of continuity ... or nostalgia, or something less than scientific ... here is the old NWS Top 20 Snowstorms list for Baltimore, using the old (now officially discredited) criteria, and updated to include the three big storms from December 2009 and February 2010. Clip and save. You may never see it again after the NWS issues its revised lists.
Some observations: February, while it is not the snowiest month on average at BWI, has seen nine of these Top 20 storms, as many as January and March combined. December has seen just two. But what's most astonishing to me, personally, is that, while the record goes back to the 1880s, my family and I have witnessed 10 of these 20 storms since we moved to Baltimore only 30 years ago. How about you? There should be only three or four that no one living today can recall.
1. Feb. 15-18, 2003: 28.2 inches
2. Jan. 27-29, 1922: 26.5 inches
3. Feb. 5-6, 2010: 24.8 inches*
4. Feb. 11, 1983: 22.8 inches
5. Jan. 7-8, 1996: 22.5 inches
6. Mar. 29-30, 1942: 22.0 inches
7. Feb. 11-14, 1899: 21.4 inches
8. Dec. 18-19, 2009: 21.1 inches
9. Feb. 18-19, 1979: 20.0 inches
10. Feb. 9-10, 2010: 19.5 inches
11. Mar. 15-18, 1892: 16.0 inches
12. Feb. 15, 1958: 15.5 inches
13. Jan. 25, 2000: 14.9 inches
14. Dec. 11-12, 1960: 14.1 inches
15. Feb. 11-12, 2006: 13.1 inches
16. Mar. 5-7, 1962: 13.0 inches
17: Jan. 22, 1987: 12.3 inches
18. Jan. 30-31, 1966: 12.1 inches
19. Feb. 16-18, 1900: 12.0 inches
20. Mar. 13-14, 1993: 11.9 inches
* Snow depth measurement. The "true" depth, had it been measured every 6 hours, likely would have been more.
(TOP: AP Photo/Rob Carr; BOTTOM: Sun Photo/Gene Sweeney, Jr.)