In a prior piece, we had noted that almost all of the top 21 corn and soybean producing states had seen a dramatic improvement in their Palmer Drought Severity Index (PDSI) ratings from the end of December to the end of April.
The fact that many states had end of Dec drought ratings of -4.00 (extreme) to-3.00 (severe) and in the ensuing four months saw readings go to neutral or even positive (excess moisture) is amazing and very beneficial.
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We were curious how these improvements in the PDSI ratings compared to past years. To answer that, this graphic shows the average change in the PSDI from 1961-2012 plus one standard deviation and the maximum PDSI change along with the Dec 2012-Apr 2013 change.
As an example, the 1961-2012 average change for Illinois from December to April is -0.15 with the 1961-2012 standard deviation being 1.74.
Therefore, the average plus the one standard deviation would be 1.59 or an improvement in the PDSI reading of 1.59 and such an improvement is seen about 16% of the time from 1061-2012.
The largest positive Dec ember to April improvement in the Illinois PDSI from 1961 to 2012 was 5.33 and that happened to occur in the most recent period from December 2012 to April 2013.
The chart shows that three other states also saw their best improvement in PDSI ratings in the most recent December to April period including MI, MO, and WI with IA just missing.
There were only two states that saw a deterioration in their PDSI readings over the past four months including OH and PA and these along with TX, MS, KY, and LA saw their Dec 2012 to Apr 2013 PDSI change below their long term average plus one standard deviation.
So not only did almost tall key corn and soybean crop growing states see a big improvement in their PDSI readings but these gains were generally some of the best improvements in moisture seen over the past 52 years.