Tuesday, July 31, 2012

2012 Northeast Ohio Drought Compared to Past Droughts

The National Weather Service in Cleveland has an excellent write up on the current OHIO drought and how it compares to past droughts. The NWS hydrologist Sarah Jamison goes into great detail on what constitutes a drought and the parameters that are used in determining drought severity.


I wanted to take the drought analysis one step closer to home. The NWS analysis was for Ohio as a whole. Why not use the same data (Palmer Drought Severity Index) but for Northeastern Ohio instead?  After all, a hyper local analysis should give a more accurate description of the conditions in locations like Cleveland, Akron, Ashtabula, Lorain and Mansfield.

Online Graphing
Drought Conditions: Lower means drier/higher means wetter

I kept all graphical elements the same as the NWS graph except I used the PDSI numbers for the northeastern Ohio climate region instead of the Ohio numbers. The data is available for free at the NOAA/NCEP/CPC site for drought monitoring. The lower the number the drier the conditions.



Compare the graph above with the NWS Ohio drought graph below.

Several things stand out:   First the drought of 1988 wasn't as severe in NE Ohio as it was in other parts of the state. The 1930-31 and 1934-35 drought didn't recover as fast in NE Ohio as in the rest of the state (red line). Third, the current drought started off far wetter in December/January (presumably due to lake effect snow melt--even with the mild winter conditions) than the rest of Ohio. Finally, the drop in the PDSI from January to July is the largest drop over a 6 months span since the huge drop from December of 1990 to July of 1991.

What does all of this mean short-term?

  • Drought conditions will continue through August and September which will increase the probability of above normal temperatures. Dry air feeds the dry air which makes the ground drier still.  The drier the air, the easier it is to heat up. August of 1988 had 11 days at 90 or better.  We can count on a handful of 90 degree days before Labor Day.

  • This drought came on fast even after an incredibly wet 2011 and early 2012. This summer hasn't been as dry as the summer of 1988.  We need frequent storms that are short in duration producing an inch or less of rain. This will do wonders in alleviating the dry ground conditions heading into the fall.  The pattern would need to significantly change for this to happen. It is showing some signs of this change as of early August.

  • Given the lack of soil moisture in the middle of the continent (which feeds the ridge of heat which has broken apart fronts this summer) the pattern will be very difficult to overcome between now and mid September.

By the way, everyone is trying to draw correlations to winter snowfall and the summer drought.  I'll have more on this in the weeks ahead. Until then, keep watering the garden!