TORNADOES: Record low amount of twisters in July

CLEVELAND - July is about to set a record for the least amount of tornadoes ever.

On Thursday, July 26, a tornado touched down in Elmira New York, a city located in extreme south central New York State just across the Pennsylvania line. Roofs were torn off homes, trees were down power was out for hundreds. It was a small twister, but still remarkable -- because it is one of only 16 tornadoes to touch down in the US during the month of July 2012.

While there are still a few days left to go in the month, no major tornado outbreak is expected. That means July 2012 will shatter the July record for the least amount of US tornadoes ever!

How monumental is this record? Many Julys past have produced more than 100 twisters. The current record holder for fewest July tornadoes is July 1960, when 42 twisters touched down. 2012 is a full two dozen tornadoes behind that record low year!

In fact, this month could end up producing fewer tornadoes than any month on record for meteorological summer (June, July, and August). Among these, the old record is 20, set in August 1957.

What’s going on? According to the National Center for Atmospheric Research, the lack of twisters is related to the intense ongoing drought, which is the nation’s most widespread since the 1950s. If thunderstorms aren’t happening, you can’t get a tornado. Violent tornadoes, in particular, need a complex blend of upper-level winds, unstable air near the ground, and other ingredients still being studied. This month, where thunderstorms have managed to form, they’ve been largely of the scattered, “air mass” variety, driven by local instability and limited by the lack of strong upper-level winds.

The drought’s onset this spring is mirrored in the rapid drop-off of tornado activity shown in the inflation-adjusted graphic at the bottom of this page. After a spate of deadly twisters in early April, tornado counts were at near-record highs for the time of year. After that point, activity plummeted, and 2012 is now in the bottom quarter of years, as ranked by total tornadic activity through mid-July.

When a summer month is unusually hot, it generally means the polar jet stream has been shunted well to the north by domes of high pressure. That means less upper-level energy to fuel tornadic thunderstorms. (h/t NCAR)