| YEAR(S) | JAN | FEB | MAR | APR | MAY | JUN | JUL | AUG | SEP | OCT | NOV | DEC | ANN | |||||||||||||
| 1975 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1976 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1977 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1978 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1979 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1980 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1981 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1982 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1983 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1984 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1985 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1986 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1987 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1988 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1989 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1990 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1991 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1992 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1993 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1994 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1995 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1996 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1997 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1998 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 1999 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2000 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2001 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2002 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z |
| 2003 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | 16.70 | a | 16.70 | k |
| 2004 | 8.55 | 12.62 | 27.16 | 31.10 | 35.77 | 44.73 | 50.48 | 47.90 | a | 39.87 | 32.55 | 21.57 | 13.21 | b | 30.46 | |||||||||||
| 2005 | 18.33 | a | ----- | z | 21.77 | 29.47 | 37.10 | 42.43 | 52.19 | 48.74 | 40.40 | 32.94 | 23.13 | 13.00 | 32.68 | a | ||||||||||
| 2006 | 11.81 | 9.00 | 19.52 | 29.60 | 40.13 | h | 47.78 | c | 54.06 | 50.10 | 39.80 | 32.13 | 20.13 | 10.42 | 29.49 | a | ||||||||||
| 2007 | 2.94 | 15.64 | 24.81 | 30.83 | 36.00 | 43.31 | a | 55.77 | 52.16 | 41.47 | 30.65 | 22.07 | 8.58 | 30.35 | ||||||||||||
| 2008 | 6.10 | 11.21 | 16.70 | a | ----- | z | ----- | z | 42.40 | 52.71 | 50.03 | 41.03 | 31.23 | 26.03 | 10.48 | 28.79 | b | |||||||||
| 2009 | 12.16 | 16.04 | a | 22.07 | c | 27.23 | 38.77 | 42.57 | 52.23 | 48.94 | 44.73 | 28.10 | a | 21.50 | 6.52 | 30.07 | ||||||||||
| 2010 | 13.52 | 15.96 | 20.90 | 27.30 | 31.00 | a | 44.37 | 51.42 | 47.87 | 41.55 | a | 35.29 | 18.60 | 20.84 | 30.72 | |||||||||||
| 2011 | 7.10 | 8.39 | ----- | z | 27.07 | 33.74 | 41.60 | 51.97 | 50.48 | 44.17 | 32.35 | 20.97 | 10.45 | 29.84 | a | |||||||||||
| 2012 | 15.55 | 15.45 | 21.71 | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | ----- | z | 17.57 | i | |||
| Period of Record Statistics | ||||||||||||||||||||||||||
| MEAN | 10.67 | 13.04 | 21.83 | 28.94 | 35.40 | 43.65 | 52.60 | 49.53 | 41.63 | 31.90 | 21.75 | 12.24 | 30.40 | |||||||||||||
| S.D. | 4.90 | 3.20 | 3.16 | 1.74 | 2.72 | 1.97 | 1.64 | 1.45 | 1.87 | 2.06 | 2.19 | 4.35 | 0.27 | |||||||||||||
| SKEW | -0.02 | -0.41 | 0.14 | 0.04 | -0.50 | 1.16 | 0.81 | 0.49 | 0.77 | -0.30 | 0.66 | 0.76 | -0.07 | |||||||||||||
| MAX | 18.33 | 16.04 | 27.16 | 31.10 | 38.77 | 47.78 | 55.77 | 52.16 | 44.73 | 35.29 | 26.03 | 20.84 | 30.72 | |||||||||||||
| MIN | 2.94 | 8.39 | 16.70 | 27.07 | 31.00 | 41.60 | 50.48 | 47.87 | 39.80 | 28.10 | 18.60 | 6.52 | 30.07 | |||||||||||||
| YRS | 9 | 8 | 8 | 7 | 6 | 8 | 8 | 8 | 8 | 8 | 8 | 9 | 4 | |||||||||||||