1950-2015 U.S. Tornado Stats

[vortex95]

Attached is the annual U.S tornado stats updated through 2015.

 

Estimated actual tornado count is 92% of average for 2015 (1253 is average),

which is 200 more than the any of the modern day record low counts of the

previous 3 years.

 

The 34 fatalities is in a 3-way tie for 11th for the lowest fatalities in a calendar

year since 1950.  This is 4th consecutive year of decline of tornado fatalities.

 

The 13 killer tornadoes is in a 4-way tie for the 6th lowest on record since 1950.

This is also the 4th consecutive year of decline of killer tornadoes.

 

3 violent tornadoes (all EF4) in 2015.  This is in a 5 way tie for the 3rd lowest in a

year on record since 1950.  The average is 9-10 a year.

 

Now for a bit of commentary:

 

All that tornado activity in later December I find by some outlets is being portrayed as

"so unusual" or as if it is "not supposed to happen".  Not true.  Don't get me wrong,

what happened in December was tragic, but I think it is important to look at the

event meteorologically and objectively as for its proper context and perspective.

 

I saw some articles talking about how it had been "so moist" and that was the "cause" of

the tornadoes.  A moisture-laden atmosphere is actually *not* favorable for tornadoes,

not when it extends through the full depth of the atmosphere (moist adiabatic lapse rates

result in poor instability).  Throughout the fall through until 12/23, for such a warm moist

pattern across the CONUS starting in the fall, there was a lack of sig svr wx overall. 

Mean trough was in the W with mild conditions in the E would typically favor sig svr

wx outbreaks (November can be a notorious "second season").  The activity as a whole

was not as prevalent and you would think looking at the 500 mean pattern, and not that

there were a lack of sig storminess/excessive rains with the storm track across the

central U.S.  So since it was so moist, where were all the sig tornado outbreaks during

this  time?  Eventually, in this kind of persistent pattern, it is going to produce a sig

tornado outbreak, but that is more likely to occur in the South in very strong El Nino

event.

 

The point here is that you can't just generically say, "it is so moist" and then equate

that to tornado outbreaks.  That is as generic as "extreme contrast of air masses

drives all sig tornado outbreaks".  Tell to the Plains region many years in May and

June.

 

This talk about December having the most tornado fatalities in a year since 1875.

Practically meaningless when looked at what happened the entire year.  What tends to be

omitted is that through 12/23, the 10 fatalities were the lowest on record for so far in any

year since 1950 at least.  So exceeding that count (24 fatalities in one month) is not that

"difficult" (for the lack of a better term).  Double or tripling an amount when that amount

is record low, still gives you a  number that is low (11th lowest out of 66 years).  Having

December with the highest death toll for a year is not "difficult" either when all other

months were very low, and winter tornado outbreaks are well known to be among the

most dangerous b/c 1) shorter daylight make them more likely to occur at night, 2) the

storms often move very fast, 3) the outbreaks are further E in a more hilly, forested,

and densely populated areas compared to the Plains. Also often omitted is that we

went straight 7 months without a single tornado fatality the U.S. in 2015.

 

From a historical perspective and context, 2015 was actually below average as a whole

when it comes to tornadoes.

 

yearlytornadostats19502015.pdf

[andyhb]

Yeah one of the big issues with many spring setups this past year was HP storms owing to oversaturation of the column and high PWATs.

 

Looking forward to perhaps "cleaner" seasons over the next couple of years. This very strong Nino event seems to have led to the weakening of the warm pool off the West Coast, which was one of the primary factors as well in lesser activity (especially earlier in the season over the last few years) since it helped force a +PNA ridge.