From the ABC 7 Weather team

The F-4 La Plata Tornado; 11 Years Later (Photos, Video)

April 28, 2013 - 02:03 PM
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A F-4 tornado struck La Plata, MD 10 years ago. Here's a look back at the conditions that caused it and the damage it left behind.

This was captured as the tornado was moving over the Bay. At one point there were two funnels out over the Bay.16 Photos
(Photo: NWS/Alex Liggitt)

On April 28, 2002, a "Moderate Risk" for severe weather was placed over the D.C. area by the Storm Prediction Center. Hours later, the region would be struck by one of the strongest tornadoes ever recorded in the Mid Atlantic and the strongest since another F-4 tornado struck Frostburg, MD just 4 years earlier. The tornado carved a 64-mile path through 4 Maryland Counties and was moving at an astounding 58 miles per hour which is nearly a mile per minute giving residents little time to prepare.

The event occurred on a Sunday, which ended up being lucky as one school was destroyed. As strong as it was, only 3 people perished that day. Another 122 people were injured and 344 homes or businesses were destroyed. Only 6 tornadoes at F-4 strength have been recorded further north and east of La Plata, MD. Keep in mind I am calling them F-4 tornadoes and not EF-4 tornadoes as the Enhanced Fujita scale was not used at the time.

What atmospheric conditions helped it form?

April 28 featured all of the ingredients needed for strong rotating thunderstorms. A strong jet stream existed over the northeast with winds in the upper-atmosphere around 90 mph while an additional 110+ mph jet existed to our west. As the D.C. area sat in the middle of these two jet streams we were in the prime place for rising motion giving a "coupled-jet structure". A cold front lied to the west of D.C. ensuring more vertical motion for thunderstorm initiation and skies cleared in the morning hours leading up to the event which allowed for maximum heating throughout the day.

One more feature really amplified the potential for tornado development as a low-level jetstream set up across the region. The southerly winds were screaming at over 50 mph only a few thousand feet above the ground which raised the dew points into the mid 60s and acted to enhance low-level wind shear. There were extreme levels of instability through the area with the strong coupled jet stream aloft, clear skies allowing for maximum heating and the low level jet at the surface helping feed in the necessary moisture.

Where did the storm travel?

La Plata Supercell Track

This storm formed in West Virginia and Kentucky border and traveled across the state of West Virginia. It moved into Virginia in Rockingham County before developing its first tornado Shenandoah County. This tornado was rated a F-2 and struck around the Mount Jackson area destroying 3 houses, 19 barns and 27 homes. It also flipped a tractor-trailer when it moved over I-81. Once it crossed the mountain ridge just east of Mount Jackson, the storm lifted and didn't produce another tornado until it reached the western short of the Potomac River 75 miles later.

The La plata Tornado touched down near Marbury, MD producing F1 damage. As it reached the western portion of La Plata it began to produce F-3 damage. There were two distinct tornadoes on the ground circling around the parent mesocyclone. The two converged as they crossed through the city creating a widespread path of damage rated as F-2 and F-3 but also isolated areas rated as F-4. Once exiting La Plata, it moved on as a F-1 to F-3 tornado through eastern Charles County.

The storm finally crossed into Calvert County as an F-1 tornado and weakened to a F-0 tornado until it reached the Bay. It actually passed just to the north of the Calvert Cliffs Nuclear Power Plant before heading into the Bay.

The storm wasn't even done when it entered the Chesapeake as it continued into Dorchester County on the eastern side of the Bay before finally dissipating near Royal Oak in Wicomico County, MD.

References:

This blog was completed using a paper by Chris Strong who is the Warning Coordination Meteorologist at the NWS in Sterling as well as Steve Zubrick who is the Science and Operations Officer at the NWS in Sterling. David Manning and Stephen Rogowski also contributed to this work. This paper can be found online and is an incredible overview of the conditions leading up to and during the event. Barbara Watson and Jim Travers also created a website through the NWS which contains pictures and a recap of the event.

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