July 2003 Experimental Forecast for Pennsylvania

At the beginning of each month, the Pennsylvania State Climate Office will present a 30-day experimental temperature forecast for the Commonwealth.  Each week it will be checked with actual data to test its accuracy.

For verification of the July 2003 forecast, visit the Verification Page.

June 2003 Conditions

The primary technique employed to produce the predictions below is an analog method. First, we compared the 500mb anomalies for the 30 days preceding June 16 (seen below) with previous June flow patterns using the NCEP reanalysis data set. We found that the June 1961, 1974, 1977, and 1985 were the most similar to this past June's geopotential height pattern.

The next 4 images show the 500mb heights and the 850mb temperatures for the 4 analog years selected above.

Predictions

The following two images show the analog forecast for July 2003.  The first image predicts how the average temperature for the summer of 2003 may compare to the average temperature for the summers from 1895 – 2000.  The second image predicts how the precipitation amounts for the coming summer may compare to the long-term average amount.

These map products that predict the temperature and precipitation anomalies for July 2003 are a compilation of the weather conditions in the Julys that followed the June of 1961, 1974, 1977, 1985.

The temperature anomaly map predicts that this July will have below average temperatures in the Northeast and South and above average temperatures in the West, Central Plains, and Midwest.

The precipitation anomaly map predicts a slightly wetter than average July in Pennsylvania and the Rocky Mountains.  A drier than normal July is predicted in the Midwest, South, and along the Atlantic Coast.

Using the 15-day medium range forecast temperature trends and the likely monthly departures based on the analog years, the following is a daily temperature forecast for July in Western, Central, and Eastern Pennsylvania.  This forecast predicts the daily average temperature departure from the normal average temperature.