The results for two area sizes, 14,000 and 20,000 square miles, illustrate the historical significance. In both cases, the largest 4-day event was Hurricane Harvey and by a large amount. At 20,000 square miles, Florence rainfall averaged about 13 inches (compared to 24 inches for Harvey) and ranks as the 7th largest of the entire 70-yr period of analysis. The 2nd ranked event at 20,000 square miles is Hurricane Georges in 1998 (September 27-30) which produced very heavy rain in the central Gulf Coast. The 3rd through 6th ranked events, none of which were hurricanes, are
#3: March 8-11, 2016, northern Louisiana
#4: August 13-16, 2016, southern Louisiana
#5: October 11-14, 1962, northern California
#6: October 16-19, 1994, southeast Texas
The precipitation in events ranked #2 through #7 are similar in magnitude, in the range of 13-16 inches averaged over 20,000 square miles.
At 14,000 square miles, Florence rainfall averaged over 17 inches and is ranked #2 behind Harvey (which averaged 26 inches). At larger areas, Florence’s rank is considerably lower. For example, at 30,000 square miles, it ranks 19th and at 80,000 sq. miles, it ranks 49th.
The key finding is that Florence’s rainfall was unprecedented for eastern North Carolina and one of the largest on record for the entire United States for areas up to 20,000 square miles.
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