Fujita's Scale Stands The Test Of Time

Sure, the biggest story for us is the rainfall. April will likely go down as the wettest month of all time…think about that. In the 150 years of keeping data, April 2011 will be the wettest month of them all. Astounding really.

However, I thought I would go in another direction since we’ve covered the rainfall story thoroughly on the air. Here’s what caught my attention today… 559 Tornado Reports across the county in April alone! (Check out the slide show)

With all the recent developments, I thought a refresher on tornado assessment is overdue. We just had three confirmed tornadoes this weekend. Plus, the season’s first EF-4 Tornado hit St Louis just the other day. Let’s talk about tornado classification and the Enhanced Fujita Scale .

You know, it’s already been 4 years since we went to the “E-F” Scale to classify tornadoes.Yet, this “”new” scale continutes to confuse people regarding tornado assessments.

ENHANCED FUJITA SCALE

As background, Dr. T. Theodore Fujita first introduced The Fujita Scale in a research paper published in February 1971 and titled, "Proposed Characterization of Tornadoes and Hurricanes by Area and Intensity". Obviously, groundbreaking research and the basis for everything else since that time.

Dr. Fujita and his staff showed the value of the scale's application by surveying every tornado from the Super Outbreak of April 3-4, 1974 . The F-Scale then became the mainstay to define every tornado that has occurred in the United States. The F-Scale also became the heart of the tornado database that contains a record of every tornado in the United States since 1950. Then, in 1992, Fujita created a modified version.

The Enhanced Fujita Scale continues in that same logic but goes a step further. The EF Scale takes into account expert analysis on damage to various structures and objects based on different wind speeds. While not perfect, the estimated wind speeds likely come a lot closer to reality than those deduced from the older scale.

Most of the levels are really quite similar. However, at the two highest levels, the wind speeds are almost completely different. F4s have winds of 207-260mph, but EF4s have brought that wind speed down to 166 to 200mph. At F5, its dramatic: those were thought to have winds of over 260mph, but now forecasters believe the strongest tornadoes usually have winds closer to 200mph and above.Past tornado events have not be revised and won’t be.

We go forward with the present scale. So, brush up on the “E-F” Scale. There’s still another solid month in our severe weather season.