39.48, 82.98  There is a thread below that asks what we can expect in the year following a drought year. When I researched this I found there is no hard and fast definition of a drought year. NOAA has monthly data going back to 1895 for the contiguous 48 states, which they divide by region based of climatic consistency. I chose (for now) the central region, which includes MO, IL, IN, OH, WV, KY and TN. For a working definition of "drought" I used the mean summer (JJA) Palmer Drought Severity Index of < 3.00. From 1895 to 2011, ten years qualified: 1901, 1914, 1930, 1931, 1934, 1936, 1941, 1953, 1954, and 1988. In some cases, we see backtoback droughts. Other times, dry years were followed by wet years. The graph below shows the results visually, with each point representing two numbers  the mean JJA PDSI of the drought year and that of the year following. The RSQ statistic means that little more than 1% of the subsequent years' PDSI is explained by the drought years' PDSI. For such a small sample, this is insignificant. IOW, the odds of a drought in the central states next year is no greater than chance, which is roughly 10/117 (11/118, if 2012 ends up qualifying) or 9%.
(drought_following_yr.gif)
Attachments  drought_following_yr.gif (9KB  46 downloads)
