Ranking the strongest tornadoes

 

Photo Credit: NOAA, Oklahoma, 2015

Tornadoes are ranked on the Enhanced Fujita Scale that starts with a minimal EF-0 that has winds of 65 – 85 mph. The strongest tornadoes are ranked an EF-5 with winds of greater than 200 mph. No EF-5 tornadoes have actually occurred in the United States in nearly 12 years since May 20, 2013.

2013:  There were over 400 cases of severe weather reported to NOAA on May 20. Among them was the last EF-5 tornado in the United States that occurred in the town of Moore, Oklahoma. It had a long and destructive track as part of a larger, three-day severe weather outbreak.

The strongest tornadoes often develop from something called a “supercell thunderstorm,” which is a long-lasting thunderstorm that has a rotating updraft. One of the supercell thunderstorms that developed during this outbreak spawned the Moore, OK tornado. According to NOAA, it caused two dozen fatalities and remains the third costliest tornado on record having caused $2 billion in damages (unadjusted for inflation). 

2011:  The town of Joplin, Missouri experienced a devastating EF-5 tornado on May 22.  According to NOAA, the Joplin EF-5 remains the costliest tornado on record having caused $2.8 billion in damages (unadjusted for inflation). With a total of 158 fatalities, it was also the single deadliest U.S. tornado since 1947. The spring of 2011 was an unusually active severe weather season for the United States with a total of six EF-5 tornadoes. That was the highest annual total since 1974.

1999:  The last observed F5 tornado in the United States before the Fujita Scale was updated or “enhanced” in 2007 occurred on May 3. The town of Moore, Oklahoma also saw impacts from this devastating tornado that at the time was the third costliest tornado in the United States.  However, the $1 billion in damages it caused (unadjusted for inflation) makes it “only” the seventh costliest tornado in U.S. history.

1997:  Some might remember the Jarrell, Texas F5 tornado that occurred on May 27. This was the last F5 tornado that developed in the state of Texas and was both destructive and deadly with 27 fatalities. The Jarrell tornado was unusual since it tracked in a south by southwest direction, instead of the more common east by northeast direction in North America.