How Good Are Severe Weather Forecasts?

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In Warnings, I make the case that warnings of extreme weather have become much more accurate over the last ten years. Let me give you an example from this week.

If you were reading Meteorological Musings Wednesday you viewed this graphic of the National Weather Service's Storm Prediction Center's forecast of tornadoes, large hail, and damaging thunderstorm winds (60 mph or more) with the forecast pertaining to the period from 6am Thursday (yesterday) to 6am CST this morning.

Now, here is a preliminary map of the actual occurrences:

Compare the two maps. There were 238 reports of tornadoes (red), large hail (green) and damaging winds (blue, with winds of more than 75 mph indicated by black squares). All but one were in the area outlined as having a severe weather threat. Every tornado was not only in the outlook, but they were all in the "hatched" area (along with the black squares with the very damaging straight winds) which denotes damaging tornadoes.

Put another way, 237 ÷ 238 = 99.58% accuracy the day before the storms occurred. 

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