More on the Changes with the F/EF-Scale

     My previous blog talked about the distribution of tornado damage using the F/EF-Scale.  The main point here was how in the modern era (1990-2012) the distribution of violent damage was slow low (0.62%) after the occurrence of two tornadoes in Oklahoma where the damage was labeled EF5.  The tornado damage in Moore, OK after the May 20, 2013 tornado was based on the damage observed, while the El Reno, OK tornado was decided based on damage, but weighted by the measured wind speed using the phased-array radar on a Doppler on Wheels estimated the tornado produced 262 mph winds.  Note: the EF5 wind estimates are listed at 205+ mph.  Thus, the debate was on as two different methods were used to come to the damage rating.

     So, adding to this information and the previous blog, below is the fatalities by F/EF-Scale ratings of tornadoes during the modern era:

Fatalities 1990-2012 associated with F/EF Scale damage ratings.

    So, while the modern era still shows that 0.62% of violent tornadoes (EF4 or EF5), this type of destruction is associated to 61% of the fatalities.

     Let's look at the violent tornado months of April and May, 2011 which were the most active tornado months since 1953.  These months had 1084 tornadoes that resulted in 538 fatalities (see below).

These months included the tornado outbreaks that occurred over MS, AL and parts of GA April 27-29, and also the Joplin, MO tornado of May 22, 2011.  The damage in Joplin was rated as EF5 and resulted in 158 fatalities.

   During the months of April and May 2013, only 2% of the tornado damage was rated EF4 or EF5 (22 of the 1,084 tornadoes reported)

But, these tornadoes were attributed to 83.5% of the fatalities during these months!  This is an alarming figure considering how well-warned people were during many of these events.  Notice that 0.55% of the tornado

damage rated EF5 was linked to 53.5% of the tornado-related deaths!  And, by well-warned, there were moderate and high risks for severe weather issued by the NOAA Storm Prediction Center including several days of highlighted information days in advance, and many NWS Weather Forecast Offices issued hundreds and hundreds of warnings in association with these events.

So, how does this data and the previous data show any change between the F-Scale and EF-Scale?  We have much smaller numbers for EF5 damage than we used to.  We always stated that 1% of all tornadoes were rated the totally damaged EF5.  During the modern era, we have reduced that for the most part, and it's even less when you put aside the 2011 tornado year.  In 2013, we know of 2 tornadoes with EF5 damage: Moore, OK on May 20th and El Reno, OK on May 31st.  Assuming there are 1200 tornadoes on average, that is still 0.01% of all tornadoes that will still play a majority of the tornado fatalities.