CLIMATE HIGHLIGHT

April 29, 2004

Temperature Trends for May by Pennsylvania Climate Division

In this Climate Highlight, we attempt to find a correlation in temperature trends to aid in predicting an indication of May temperatures. The first step in doing this was finding previous years with regional surface temperature deviations that were similar to those experienced this past April across the United States. The eight years which best matched April 2004 are as follows: 1913, 1915, 1916, 1926, 1942, 1952, 1977 and 1987. Next, departures from normal temperatures were tabulated across each of Pennsylvania's 10 climate division for these eight common years. Through a careful analysis and investigation, the temperature trend for May was found to be slightly above normal statewide. The table below displays each division's monthly temperature departure from the 30 year mean temperature for the common years.

This graph shows the yearly departure from the mean for each climate division in Pennsylvania. For each division, the departure is either average or slightly above the mean temperature for May. Hence, the signal is that May should be slightly warmer than average.

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This map (courtesy of the Climatic Diagnostic Center) visualizes the temperature trend prediction of slightly above average across Pennsylvania and the Northeast. The map above was generated by using the aforementioned analogous years to produce a composite temperature anomaly. According to this technique, it appears as though the entire state will see temperatures ranging from 0.05 to 0.25 deviations above normal. This composite method also agrees with the analog experimental forecast for May that can be accessed from our homepage.