These plots show the percentages of tropical storms with peak winds <= 50 knots, <= 45 knots, <= 40 knots and <= 35 knots. In each year the total number of storms is counted and the storms in each category are counted. The counts are inclusive, i.e. the count of peak <= 50 knots includes the storms with peak <= 45 knots, etc. Then the counts in each category are divided by the total storms and hurricanes for the year. Post-tropical winds are ignored. Storms that fail to achieve tropical storm criteria (>= 35 knots) are ignored.

ATLANTIC The trend shows increases particularly from the 1970's when many years had no named storms with winds <= 35 knots (minimal tropical storms, shown by green dots). By the late 80's we start to see named minimal storms. Since 1990 the percentage of minimal storms is flat, but the percentage of moderately weak storms (45 knots or less peak wind) continues to rise. My best guess is, other than natural cycles, there are improvements in measurement such as the scatterometer.


Code: | Data: hurdat.csv | Instructions: README.tropicalstorms