2011-04 · Severe Convective Storms
April 2011 · Around 360 tornadoes in four days, four of them EF5. The 25-28 April 2011 Super Outbreak killed about 321 people and set the roughly $10bn insured benchmark for convective storms.
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Tornado reports
in four days · 235 on 27 April
Strongest
4 EF5 tornadoes (NOAA)
Deaths
NOAA · tornadic, 316 on 27 April
Insured loss
2011 · about $14bn today (Swiss Re / III)
Each line is one tornado report, drawn from its start to its end point and coloured by Enhanced Fujita rating. The scrubber walks the four days; the current day is lit and the earlier days fade back. The long dark lines across Alabama are the EF5 monsters of 27 April.
The outbreak built over four days. Each bar is one day's severe reports, stacked by type.
Reports per day by type. The escalation into 27 April is the story: the record logs 235 tornado reports that day alone.