Through the end of last week, this spring had been well behind the average in number of reported tornadoes in the United States. Though we are still running a lower than average year, the recent devastation in Moore, Okla., has brought tornadoes back into the news in a dramatic way.
Why we have been below normal so far is a question prompting ongoing research and may be addressed in a future column.
The Moore tornado was rated an EF5, the strongest tornadic storm, with estimated wind speeds in excess of 200 mph near the core. The other alarming characteristic of the Moore tornado was its exceptional size (over 11/2 miles wide) and the fact that it stayed on the ground for so long (over 40 minutes).
Though we understand the general conditions under which tornadoes are likely to develop, the exact details of tornado formation are still not well known. This makes precise prediction of these storms a near impossibility.
In order to protect the public as best it can in the face of this difficulty, the National Weather Service employs a network of trained tornado spotters along with Doppler Radar data to identify tornadoes as soon as they develop.
In fact, since the Barneveld tornado of June 1984, the average warning time for tornadoes has risen from just under 5 minutes to nearly 15 minutes.
Though not a replacement for point-specific forecasts of tornado occurrence, the combination of vigilance in the face of high likelihood and rapid public alert systems has saved many lives in the past 20 years and probably saved dozens, if not hundreds, of lives last week in Moore.
