Washington, DC (WUSA 9) - Despite its distance from Tornado Alley, Maryland still averages ten tornadoes in a given year. In the last 15 years, Maryland has seen three particularly violent tornadoes in addition to two small tornado outbreaks earlier this month. The majority of Maryland's tornadoes can be attributed to two different factors - a mid-latitude storm system and a decaying tropical system.
The warm and humid weather on June 2, 1998 was quite typical for early June in the Mid-Atlantic Region. Conditions were ideal for thunderstorms to form as an area of low pressure and associated cold front moved into the area. Consequently, a short lived F4 tornado formed in Frostburg, Maryland. Given the relatively rural nature of Frostburg and low population density, damage was minimal and there were no reported fatalities due to sufficient advance warning.
An even stronger F4 tornado struck La Plata, Maryland on April 28, 2002. That tornado formed from what meteorologists call a supercell thunderstorm. A"supercell" is a specific kind of thunderstorm that is larger and longer lasting than average summertime thunderstorms. Supercell thunderstorms also possess "rotation" or spiraling winds around the core of the thunderstorm. These spinning winds are what help create a favorable environment for a tornado to develop. The most powerful tornadoes typically form from supercell thunderstorms. Tornado intensity is measured on the Fujita Scale of F0 - F5. The updated "Enhanced Fujita Scale" has been used since 2007 and its scale goes from EF0 to EF5.
The thunderstorm that the deadly La Plata tornado formed from originated in West Virginia and moved east. It was a prolific hail producer as it continued moving eastward into Virginia and towards Maryland. The storm continued its eastward trek and became stronger as evidenced by its increased size and more pronounced appearance on the radar screen.
When this thunderstorm reached La Plata the strongest tornado on record in the state of Maryland formed. This tornado was a whopping F4 while in La Plata and was on the ground for a total length of 64 miles. Hail up to 4.5 inches in diameter was also concurrently reported in Charles County. Three deaths and 122 injuries were attributed to the 2002 tornado. Property damage was estimated at $100 million -- making it one of Maryland's costliest natural disasters. The La Plata tornado came just 8 months after an F3 tornado had caused two fatalities in College Park, Maryland in September 2001.
The spring and early summer of 2013 has seen a fairly persistent weather pattern with an active branch of the jet stream - a river of air in the upper levels of the atmosphere - that has kept a series of cold front fronts parading eastward across the Midwest and Eastern portion of the United States. The steady stream of storms has led to more than double the average amount of rainfall in June for the Nation's Capital. Also, there were two days when multiple tornadoes were observed in the Mid-Atlantic Region. Four Maryland tornadoes were confirmed on June 10 - including one near downtown Baltimore - and two more on June 13. One of the June 13 tornadoes occurred in central Montgomery County and had an 18 mile track. While it claimed no lives, the EF-0 tornado knocked down a lot of trees that caused damage to houses and cars.
The remnants of tropical systems - such as Hurricane Isabel in 2003 or Irene in 2011 can also spawn tornadoes. However, these tornadoes tend to be weaker than those that form in "supercell" thunderstorms such as the La Plata tornado. Despite the tornadoes we experienced earlier this month, tornadoes remain rare in the Mid-Atlantic Region. Forecasters accurately predicted both the La Plata and Frostburg tornadoes, providing the public with several minutes warning and the opportunity to seek shelter.
The WUSA 9 weather team will continue to keep viewers apprised of the latest weather forecasts on TV or online at wusa9.com.