Most surveys of tornadoes are initiated by damage to trees, overturned buildings, or scattered debris across a landscape.
The first indication of this particular tornado (waterspout) was water.
A waterspout formed over the cooling pond at the Braidwood Power Plant in Illinois.
It existed for only a few minutes.
At no time did it cross onto land.
Yet the meteorologists were able to map the path of this waterspout and document the event.
A narrow path stayed entirely over water
A National Weather Service survey determined the feature to be an inland waterspout that developed over the cooling pond at the Braidwood Power Plant.
The beginning of the circulation occurred near the southeastern portion of Godley in Will County, Illinois.
Unlike most other tornadoes documented through surveys, the path of this waterspout remained over the cooling pond for its entire duration.
Surveyors concluded the total distance along the track was 0.32 miles.
They estimated a maximum diameter of 10 yards.
The location had another notable characteristic.
The waterspout developed over an inland body of water directly adjacent to one of Illinois’ nuclear power generation plants.
The track began and ended in close proximity to each other, remaining southeast of Godley in Will County throughout its brief lifespan.
Meteorologists noted that the mapped route was merely an approximation since the circulation stayed entirely above water throughout its existence.
What the National Weather Service documented
Photographs and videos taken while this waterspout developed allowed the National Weather Service Chicago to later complete a storm survey.
The survey located the beginning time at 3:40 PM CDT and the ending time at 3:43 PM CDT.
The entire event was short-lived, lasting roughly three minutes.
Since the circulation was always quite narrow during its journey, there were no reports of damage associated with this event.
Investigators reported no deaths or injuries from the waterspout.
Meteorologists noted that both the location and path of the circulation were estimates.
That is typical if the circulation stays above water and does not leave a damage path.
The survey designated this waterspout an “EFU” rating. An EFU rating is assigned when investigators cannot determine a reliable wind-speed estimate.
The circulation remained entirely over water during its lifespan.
It left no structural damage behind.
Without damage indicators, investigators could document where the circulation traveled but could not establish an estimated peak wind speed.
Why the survey looked different from most tornado reports
One aspect which set this waterspout apart from many others was how little evidence it left behind. Many tornado surveys depend greatly upon what a circulation has left behind.
This waterspout left nearly nothing to examine physically.
Instead of using damage indicators such as collapsed buildings or destroyed homes, surveyors relied on photographic and video documentation taken during the formation and development of this waterspout.
While this allowed them to identify where the waterspout originated and estimate its path and dimensions, it prevented them from estimating wind speeds or determining its peak intensity.
What happened during those three minutes
Meteorologists noted that the circulation did not travel over land at any time during its brief lifetime.
During a period of approximately three minutes, a rotating column of air crossed over the surface of the cooling pond.
At no time did it travel over dry land.
Then it vanished into thin air.
The path measured less than a third of a mile.
The lifespan lasted only a few minutes.
The event received its own storm survey and documentation in National Weather Service records.
Multiple photographs and videos allowed meteorologists to reconstruct a track that existed for only a few minutes over open water.
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