Tornadoes in the Mid-Atlantic Region

 

The Mid-Atlantic Region sees most of its severe weather in May and June, with a secondary peak in the fall as the seasons begin to change.  The remnants of tropical systems also spawn tornadoes when they impact the Mid-Atlantic Region, such as with Hurricane Ivan in 2004 and Hurricane Isaias last August. 

Tornadoes associated with decaying tropical systems are typically weaker than those that develop within supercell thunderstorms.  Tornadic thunderstorms are exceedingly rare within D.C. city limits, but do occasionally occur.  The last such occurrence of tornadoes within the Nation’s Capital was on April 6, 2017 when two EF-0 tornadoes touched down.  They caused only minor damage and, fortunately, no fatalities.   

The 2017 tornadoes occurred as part of a larger, three-day severe weather outbreak.  From April 4 through April 6, 2017, there were 550 reported cases of severe weather from the Midwest to the East Coast, which included 30 tornadoes.  These were the first tornadoes in the Nation’s Capital since September 24, 2001.   D.C.’s strongest tornado on record was an F3 that developed in Rock Creek Park on April 5, 1923.

Maryland has had three significant tornadoes in the last 25 years.  On April 28, 2002, an exceptionally rare F4 tornado developed in Charles County.  This tornado had a track that spanned nearly 70 miles.  It reached peak intensity as it passed through the town of La Plata with winds of nearly 260 mph.  It caused more than $100 million in damage, in addition to five fatalities and dozens of injuries.  The 2002 La Plata tornado remains the strongest tornado on record in Maryland.

The town of College Park, Maryland saw a F3 tornado on September 24, 2001.  Tragically, two sisters who were students at the University of Maryland lost their lives during this tornado, which also caused extensive damage.  In addition, an F4 tornado occurred on June 2, 1998 in Frostburg, Maryland. Wind speeds of the Frostburg tornado were estimated as high as 210 mph.

According to NOAA data, Maryland averages 10 tornadoes annually, while Virginia sees 18.  The two strongest tornadoes on record in Virginia were F4s.  One occurred on August 6, 1993, and the second on September 24, 2001.  

Tornado intensity is measured on the Fujita scale that was named after the late Dr. Ted Fujita of the University of Chicago who designed it in 1971.  It has since been updated and became the “Enhanced Fujita” or EF scale in 2007. 

Post-Hurricane Analysis

 

Hurricane Michael, October 2018  (Source: NOAA)

NOAA scientists study hurricanes for months and sometimes years after the final advisory has been written on them.  Each tropical storm and hurricane often serves as a model with lessons learned for forecasting and emergency preparedness.  Every once in a while a hurricane’s intensity at landfall is updated after the fact to reflect the research done by NOAA.

2019: On this date two years ago, NOAA determined Hurricane Michael was indeed a Category 5 hurricane at its time of landfall on the U.S. Gulf Coast in October 2018.  Originally, it was thought to be an upper end Category 4 hurricane, just below 5 status with sustained winds of 155 mph.  However, according to NOAA’s post-analysis Michael had sustained winds of 160 mph.  While there is little tangible difference between these wind speeds in terms of damage, reclassifying Michael as Category 5 changes a host of historical records.

The upgraded Michael became only the fourth Category 5 hurricane to ever make landfall in the United States and the first since Andrew in 1992.  (The two other Category 5 hurricanes to make landfall are Camille (1969) and the unnamed Florida Keys 1935 hurricane).  While Michael’s sustained winds were the lowest of the three other hurricanes, its minimum central air pressure of 919 millibars was the third lowest air pressure for a hurricane at its time of landfall.  Overall, Category 5 hurricanes are exceedingly rare since they require ideal environmental conditions to develop.

2002: For the 10^th anniversary of Hurricane Andrew, NOAA determined it was actually a Category 5 hurricane when it made landfall in south Florida.  Originally, it was ranked as a Category 4 hurricane with sustained winds of 145 mph on August 24, 1992.  Years of post-analysis study led scientists to reclassify Hurricane Andrew as a Category 5 with sustained winds of 165 mph.

Andrew had the infamous distinction for more than a decade of being the costliest natural disaster in U.S. history.  More recent hurricanes like Katrina, Harvey and Irma have each caused more damage than Andrew, but it still ranks among the Top 10. 

Little did people realize it at the time, but Andrew occurred three short years before a more active cycle began in the tropical Atlantic.  From the 1970s through the early 1990s, the tropical Atlantic was relatively quiet with below average tropical activity.  However, there has been a series of active Atlantic seasons since 1995.  That’s why listening to the latest forecasts from NOAA’s National Hurricane Center and your favorite local meteorologists is of critical importance.

A Warm Up Act?

 

Photo Credit: Ashley Adams

While the Atlantic hurricane season doesn’t officially get underway until June 1, at least one tropical storm has developed before then every year since 2015.  That's the longest such streak on record for the Atlantic Ocean Basin.  Colorado State University recently updated its 2021 Atlantic hurricane forecast and it calls for an above average season.  These are some of the more memorable preseasons storms that have developed in recent years.

2020:  Tropical Storm Arthur was the first of 30 named storms that developed.  It was officially named a tropical storm early on May 17 while off the east coast of Florida.  Arthur slowly tracked northward and reached a peak intensity of 60 mph sustained winds while east of North Carolina.  Tropical Storm Bertha also developed last May and made 2020 the third season in the last decade with two named storms prior to June 1.

2018:  Tropical Storm Alberto reached its peak intensity on May 27 with sustained winds of 65 mph while in the Gulf of Mexico.  It weakened slightly before making landfall in the Florida Panhandle and its impact reached areas well inland.  Rainfall from the remnants of Alberto reached as far north as Michigan on May 31. 

2017:  Tropical Storm Arlene became only the third tropical or subtropical storm to occur during the month of April.  Arlene was the first April storm since Ana in 2003 and an unnamed subtropical storm in April 1992.  Arlene developed in the central Atlantic and had peak sustained winds of 50 mph.   Tropical storms and hurricanes often have higher wind gusts, but the wind speeds meteorologists look at when measuring intensity refer to the maximum sustained winds around the center of circulation.

2016:  Hurricane Alex was the Atlantic’s first January hurricane since Alice in 1955.  At its peak intensity in the Central Atlantic, Alex was a Category 1 hurricane with sustained winds of 85 mph and a minimum central air pressure of 981 millibars (mb).  By comparison, standard sea level air pressure is approximately 1013.25 mb.  Bonnie was also named a tropical storm on May 28, giving the Atlantic Ocean two named storms prior to the official start of the hurricane season.