Complex sentence: The original National Weather Service report from Milwaukee/Sullivan categorized the tornado to be a F3 to F4, winds of 158-260 mph, although it was later upgraded to an F5, winds greater than 261 mph, the most severe tornado possible.
Split into simpler sentences: The original National Weather Service report from Milwaukee/Sullivan categorized the tornado to be a F3 to F4 tornado on the Fujita scale, with winds of 158-260 mph. It was later upgraded to an F5, winds greater than 261 mph, the most severe tornado possible.