June 13, 2013 Montgomery County tornado track among longest on record in D.C. area

*Approximate* path of the June 13, 2013 tornado in Montgomery County based on preliminary reporting from the National Weather Service. (James Menzies via NWS Baltimore/Washington Facebook page) https://www.facebook.com/US.NationalWeatherService.BaltimoreWashington.gov/posts/507263809340440?comment_id=4512701&offset=0&total_comments=18

*Approximate* path of the June 13, 2013 tornado in Montgomery County based on preliminary reporting from the National Weather Service. (James Menzies via NWS Baltimore/Washington Facebook page)

There’s been some debate as to whether June 13, 2013 was overhyped when it came to the storm threat. A good number of spots did not see much in the way of storminess at all, but those that got storms in the afternoon almost all described them as powerful.

The severe weather star of the day, a preliminary “long track” 17.3 mile tornado, began in North Potomac at 3:41 p.m. and ended in Burtonsville at 3:59 p.m. While the tornado was rated EF0, the weakest of all tornadoes, the length of its track was fairly unusual for the region.

Since 1950, there have been two dozen tornadoes originating or ending in Maryland and Virginia (inclusive of D.C. where there have been none) the same length or longer than the June 13 tornado.  This is roughly 2 percent of all tornadoes in the two states plus D.C.

Maryland itself has now seen nine such tornadoes in the period. (note: the map below shows nine prior to this one, but the two shown crossing from Md. to De. appear more than likely one rather than two events — there is a 5 minute difference in start time, and a slightly different starting point, but all other stats are exactly the same)

Mid-Atlantic and surrounding area tornadoes from 1950-2011. Those with path lengths of 17.3 miles or longer are shown highlighted with intensity coloring. 2012 track data is not yet available, but no additional tornadoes of this length or longer were added to the local area according to the raw data. (Ian Livingston/Storm Prediction Center GIS files)

Mid-Atlantic and surrounding area tornadoes from 1950-2011. Those with path lengths of 17.3 miles or longer are shown highlighted with intensity coloring. 2012 track data is not yet available, but no additional tornadoes of this length or longer were added to the local area according to the raw data. (Ian Livingston, using Storm Prediction Center GIS files)

In the immediate D.C. area (within a one county radius of the District), the June 13, 2013 tornado is now just one of four with path lengths as long or longer. The three tornadoes with lengthier path lengths in the local area occurred on the following dates:

9/5/1979: F3, 17.9 mile track in Fairfax County
6/24/1996: F2, 20 mile track in Fairfax County
9/24/2001: F3, 17.5 mile track through Prince George’s and Howard counties

The La Plata tornado track on the west side of the bay April 28, 2002 is the longest within Maryland at 38 miles. Some sources count the second track on the east side of the bay in addition to the first, with both land portions equaling 56 miles plus the distance over water.

Virginia’s longest-tracked tornado came fairly recently, on April 16, 2011, when an EF3 traveled 46.9 miles across southeast portions of the state.

Tornado tracks from F/EF0 tornadoes and unknown strength tornadoes between 1950 and 2011. I've included unknown ratings as it's likely most of them would have been rated 0 or thereabouts. (Ian Livingston/Storm Prediction Center GIS files)

Tornado tracks from F/EF0 tornadoes and unknown strength tornadoes between 1950 and 2011 with track lengths equal to or longer than the Maryland EF0 of June 13, 2013. I’ve included unknown ratings as it’s likely most of them would have been rated 0 or thereabouts. (Ian Livingston, using Storm Prediction Center GIS files)

On a national scale, getting such a lengthy track from the weakest of all tornadoes is relatively unusual as well.

Only a little more than half of all (55,000+) tornadoes in the record since 1950 have full (and often misleadingly straight) tornado tracks. In that subsection, 108 F/EF0s and 39 unknown strength tornadoes met the 17.3 mile or greater criteria from 1950-2011. That’s less than half a percent of tornadoes with track data and a significantly smaller percent of all tornadoes.

F/EF0s of this length are especially unusual in the region, with one barely entering Virginia from Tennessee, one in North Carolina, and one in New Jersey among a broader sample of local states.

The longest F0/EF-0 on record had a 103.5 mile path length. Another 15 have track lengths of 50 miles or greater. That group is almost entirely made up of Plains and Midwest states, but North Carolina is home to a 64.1 mile F0 in April 1962.

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