Climate Highlight

June 10, 2003

    The intention of this Climate Highlight is to predict future weather by analyzing past weather conditions.  In particular, I will be analyzing the historical record of weather in relation to the unusually cool and wet May of 2003 in Pennsylvania.

    I started by gathering the historical temperature and precipitation data for every climate division in Pennsylvania since 1897.  Then I ranked the Mays of each year from coolest to warmest.  Here's how May of 2003 compared to 106 previous Mays in each of the ten Climate Divisions in Pennsylvania:

    Using these rankings, I chose the six Mays that ranked the closest to the May of 2003.  I will assume that these years did not only have weather conditions most like May of 2003, but the coming June, July, and August also.  This assumption will serve as the basis of my forecast. 

    To predict the actual average temperatures for the next three months in each Climate Division, I averaged the temperature and precipitation data for each of those six years.  I also averaged the average June, July, and August temperatures for all 105 years in each division to understand how this coming summer season  could compare to previous seasons. 

The Results

    According to the forecast produced by this method, cooler than normal temperatures will continue through June, July, and August.  As for precipitation, more than half of the divisions may see a wetter than normal June, and nearly all may have a drier than normal July and August.  Although this trend is relatively consistent among the divisions, there are variations in the magnitude of the departure from normal conditions.  The predictions for individual Climate Divisions can be viewed below.

Climate Division 1

Climate Division 2

Climate Division 3

Climate Division 4

Climate Division 5

Climate Division 6

Climate Division 7

Climate Division 8

Climate Division 9

Climate Division 10