Tornado season unusually quiet

After two years with unusually high numbers of tornadoes in the United States, the tornado season for this year has proven relatively quiet, with only 741 tornadoes reported, the lowest total since 1989, according to National Weather Service officials. However, they advise all Americans to be prepared for tornadoes because they can happen anywhere at any time.

The 741 tornado reports during the first seven months of 2000 is almost half of those for the same periods in 1999 and 1998, 1,170 and 1,141 tornadoes respectively. Historically, March through July are the busiest months for tornado activity. The number of deaths resulting from tornadoes is significantly lower this year as well, with only 25 deaths compared with seven month totals of 91 in 1999 and 126 in 1998.

In addition, preliminary reports indicate only one of the tornadoes this year has produced damage stronger than F3, which is considered strong but not violent on the Fujita damage scale. A tornado preliminarily rated an F4 struck Granite Falls, Minn. on July 25, killing one and causing more than $20 million in damage to buildings and other property. Violent tornadoes – F4 or F5 – occur about 10 times a year, with most of them in March through July.

“This year is rare, but not unheard of. It’s just one of the natural fluctuations that occur,” said Dr. Joseph Schaefer, director of NOAA’s Storm Prediction Center. “This year, the upper level flow or jet stream has been moving from west to east across the country further north than usual, from the Rockies through the Upper Midwest and the Great Lakes region to the northern mid-Atlantic states.”

In contrast, by this time last year, 62 F3 and greater tornadoes had occurred, a record number of 216 tornadoes were reported in January and 325 tornadoes touched down in May. The deadliest outbreak of 1999 happened on May 3 in Oklahoma and Kansas, with 72 tornadoes and 46 deaths. One F5 tornado that struck Oklahoma City and surrounding suburbs that day became the most expensive single tornado in history, causing about a billion dollars in damage.

Forecasters say this kind of change from year to year is normal.

Normally, during the spring, the predominant upper level flow of weather across the United States is southwest to northeast across the Central Plains, Schaefer said. Without that high level flow through this region, known as tornado alley because of the historically high number of occurrences there, a necessary ingredient for tornado and severe thunderstorm formation is missing, he said.

To help Americans guard against the ravages of severe weather, including tornadoes, the National Weather Service has designed StormReady, a program aimed at arming communities with the communication and safety skills necessary to save lives and property. As part of that initiative, the National Weather Service encourages everyone to equip their homes, schools, businesses and public places with a NOAA Weather Radio to receive information about severe weather watches and warnings directly from their local forecast office.

More information is available online about tornado statistics, http://www.spc.noaa.gov and about the StormReady program at http://www.nws.noaa.gov/stormready.