Tomorrow marks the 40th anniversary of the historic "Super Outbreak" of tornadoes that tore a path of destruction from Alabama to Michigan. The outbreak was the the most violent ever recorded — producing 7 F5s, 11 F4s, and 35 F3s, and killing over 300 people — and to this day remains the ultimate analog by which all tornado outbreaks are measured.
The Storm Prediction Center (SPC) recently ran a model simulation of the 1974 Super Outbreak to see how close the simulated forecast would come to how the outbreak actually played out. To accomplish this task, the SPC used the North American Model (NAM), which is a regional weather model that is capable of simulating thunderstorm activity.
The result is seen at the top of this post. The image on the left shows the tornado paths surveyed by meteorologists in 1974, and the image on the right shows the simulated streaks of thunderstorm rotation that the NAM measured based on the weather information entered into the model. Warmer colors indicate stronger thunderstorm rotation, which would likely indicate a thunderstorm producing one or more tornadoes.
Even though the model simulation didn't nail each and every area where a tornado occurred, it outlined the main area where the devastation occurred as the hot spot for tornadic activity on that spring day 40 years ago. As many weather weenies find out when severe weather or a major winter storm is about to strike, weather models are guidance for meteorologists to use their experience to issue a forecast.
That being said, meteorologists have it easy today compared to the technology they had back in the '70s.
Weather radar back in 1974 didn't have the Doppler capability that it has today, so forecasters couldn't see the winds within a thunderstorm to see if rotation was present. Meteorologists also had to rely completely on telephones and two-way radios to relay warnings to the media so the media could then, in turn, report them to the public. If a weather service office had telephone issues, it could delay or even prevent timely warnings from reaching the public.
Today, in addition to incredible advances in numerical weather prediction (models), Doppler radar technology, and the existence of the Internet, meteorologists are able to better predict and identify tornado threats before they happen, and people are able to receive warnings almost instantly when they're issued.
[Image via SPC]