Highlighting possible D.C. region tornado hotspots using warnings and tracks

Tornado warning hot spots and tornado tracks, 2002-2013 in the D.C./Baltimore region.  (Jordan Tessler)

Tornado warning hot spots and tornado tracks, 2002-2013 in the D.C./Baltimore region. (Jordan Tessler)

Are certain parts of the broader region more prone to tornado warnings and tornado touchdowns than others? Both the density of recent warnings as well as actual tornado tracks suggest that’s possible.

The map above shows the frequency of tornado warnings broken down by small gridded boxes, and also the tracks of tornadoes recorded since 2002. That was the year storm-based polygon warnings were introduced.

Overall, most of the tornado warnings issued — and the verified tornadoes in our region — occur between the Blue Ridge and the Chesapeake Bay, with a sharp drop off east of the bay. The location with the most tornado warnings issued over the period is southern St. Mary’s county. 21 warnings covered an area near California, Md.

When examining confirmed tornadoes, Frederick and Fauquier counties lead the pack at 13. Charles and St. Mary’s came in with 12, Other hotspots for recent tornadoes include Harford, Stafford, Montgomery, and Prince George’s counties.

There are two predominant zones of tornado warning frequency and actual tornadoes forming something of a “V” shape around the D.C.-Baltimore corridor.

One zone stretches from Culpeper County through Fauquier County into Southeast Frederick County around Mt. Airy and then up through Carroll County into Pennsylvania. The other zone, seemingly more active, is defined by Spotsylvania and Stafford counties through Charles and St. Mary’s counties to the bay.

As for actual tornadoes and their tendencies locally: The majority of them move from southwest to northeast or west to east locally. There are a couple of notable exceptions.

The 2002 La Plata tornado, as one example, tracked more toward the southeast. There’s also a group that move nearly straight north through Northern Virginia, and they’re associated with the tornado outbreak that accompanied the remnants of Hurricane Ivan in 2004.

There hasn’t been a tornado warning covering downtown D.C. since 2002 when storm-based polygon warnings were phased in over county-based warnings. There is also a low frequency area around and in metro Baltimore.

Given the relatively short period of record covered here, it’s hard to draw conclusions about those facts. We must remember no spot is tornado proof.

Jordan Tessler is CWG’s intern for spring and summer 2014.

Also on Capital Weather Gang

Grading our 2013-14 winter outlook: it's ugly