Table 1.

Correlations between July–November surge index and other measures of cyclone activity

Series	Period of overlap	Correlation full period	Correlation 1950–2005	High-frequency correlation	Low-frequency correlation
Cat 0–5	1923–2008	0.56	0.65	0.51	0.64
Cat 1–5	1923–2008	0.55	0.57	0.54	0.56
Cat 2–5	1923–2008	0.50	0.42	0.51	0.50
Cat 3–5	1923–2008	0.51	0.47	0.42	0.58
Cat 4–5	1923–2008	0.53	0.50	0.46	0.62
Cat 5	1923–2008	0.38	0.61	0.41	0.48
US cat 0–5	1923–2008	0.54	0.55	0.55	0.56
US cat 1–5	1923–2008	0.57	0.57	0.55	0.67
US cat 2–5	1923–2008	0.55	0.56	0.51	0.66
US cat 3–5	1923–2008	0.57	0.60	0.55	0.67
US cat 4–5	1923–2008	0.61	0.70	0.57	0.74
US cat 5	1923–2008	0.38	0.62	0.38	0.46
ACE	1923–2008	0.61	0.58	0.54	0.72
US ACE	1923–2008	0.58	0.58	0.51	0.77
NTC	1923–2006	0.58	0.55	0.48	0.54
PDI	1923–2008	0.60	0.58	0.53	0.73
US PDI	1923–2008	0.58	0.61	0.52	0.75
NHD	1923–2005	0.65	0.66	0.59	0.38

Low-frequency correlation is the correlation of the two series after a 5-y moving average. High-frequency correlation is the correlation of the residuals after subtracting this moving average. A US prefix indicates that the metric has been restricted to US-landfalling storms only. Cat, category.