Severe Weather in the Autumn

Ivan's Severe Weather Outbreak in the Mid-Atlantic Region  (Source: NOAA)

Although most common during spring and early summer, there is a secondary, smaller peak of severe weather in the United States during the fall.  This is largely attributed to the change in seasons, as well as severe weather associated with landfalling tropical systems.  The National Weather Service defines “severe” thunderstorm as one that contains any of the following: wind gusts of at least 58 mph, hail 1” in diameter or greater, or a tornado.

When a tropical storm or hurricane makes landfall, it often spawns weak tornadoes as the circulation of the storm interacts with the topography of the land area.  However, these tornadoes aren’t usually very strong, but are potentially dangerous since their approach can be obscured by heavy rainfall.  The Mid-Atlantic Region has had a variety of fall severe weather during the last 15 years.

For example, on September 8, 2012, a damaging line of thunderstorms passed through the DC Metro Region and brought a multitude of severe wind gusts.  These storms led to a number of downed trees and power lines.  Several funnel clouds were observed, but it was determined that none of the funnel clouds touched down and became tornadoes.  Meanwhile, two tornadoes developed during the same severe weather outbreak in the New York City Metro Area – one in Brooklyn and one in Queens.

 

Washington, D.C. residents recently marked the 15^th anniversary of the deadly severe weather outbreak of September 24, 2001.  On that day several tornadoes touched down in the DC Metro Region, including F3 tornado (with winds of approximately 200 mph) in College Park, MD.  Tragically, it caused two fatalities when a pair of sisters were caught in their car.

The Mid-Atlantic Region has seen the remnants of several tropical systems which have caused significant severe weather outbreaks.  The most significant came in 2004 when the remnants of Hurricane Ivan spawned a large number of tornadoes from North Carolina to Pennsylvania.  The remnants of Hurricane Opal also brought three tornadoes to the state of Maryland on October 5, 1995.

Although uncommon, severe weather can occur in the Mid-Atlantic Region during the autumn.  Fortunately, this month hasn’t featured any significant severe weather outbreaks in this part of the country.  In fact, this month could rank among the driest Septembers on record in the Nation’s Capital.