CHARLOTTE, NC (WBTV) - When we're talking about deficits in weather, we're usually talking about rainfall. It's a lack of rain over a long period of time that results in drought. Today, we're talking about the nation's "tornado deficit."
2012 got off to a busy start. Tornadoes were forming in January across the country, including right here in the Carolinas. The above-normal tornado activity continued into February and March. Then, an outbreak of tornadoes from Iowa to Oklahoma killed several on April 14. Then, it seemingly stopped.
May and June, usually very active tornado months, were slow. Thanks to persistent high pressure plaguing the areas included in Tornado Alley, even showers were out of the question, let alone supercells that spawn tornadoes.
Dr. Harold Brooks, a research meteorologist with NOAA's National Severe Storms laboratory notes that it can take months to confirm whether or not a tornado actually took place. "It can be challenging to answer the question "how many tornadoes occurred" shortly after an event."
First, the National Weather Service will send a crew out to look at damage the possible tornado caused, then will compare that with radar data to determine whether a tornado touched down, or if it was simply a strong downburst wind from a thunderstorm. That evaluation takes time, so we have to estimate the numbers from the past few months.
Early estimates from June indicate only about 100 tornadoes touched down that month. The median number of June tornadoes from 1954-2011 was nearly three times that, at 270.
Particularly remarkable was July. Only 24 preliminary reports of tornadoes were received by the National Weather Service. The fewest tornado reports prior to this year was 42 in 1960. The median number of July tornado reports is about 150.
When we look at what is typically considered "tornado season", from April 15 through the end of July, we expect about 850 twisters to touch down. This year, less than 300. It's a welcome break from the 2011 season, which saw the second highest number of tornadoes during the same time frame we have ever seen.
To see more on the unusually low tornado numbers this year, see Dr. Brooks' blog here.