September 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 September 2003 forecast, visit the Verification Page.

Summer 2003 Conditions

A forecast for September of 2003 can be developed by analyzing the weather patterns of the previous month and historical  climate records.  This forecast will be determined by the anomalous weather occurrences in the summer of 2003.  The following figure identifies regions of the United States where abnormal weather conditions occurred in the past summer.

Figure 1:  Summer 2003 Anomalous Temperature Regions

Figure 2:  Summer 2003 Anomalous Precipitation Regions

The Summer of 2003 was unusually warm in the Southwest, while it was unusually cold in the Northeast.  In addition, several parts of the county were unusually wet. these abnormally wet conditions occurred in the Northeast, Florida, and Southwest.

There were several other occurrences of this type of Summer weather pattern in the climate records.  Years that were similar to this year include 1927, 1950, 1982, 1985, and 1992.  A compilation of September weather in these years will form the basis of this forecast for the upcoming September.

Predictions

The following two images show the national analog forecast for September 2003.  The first image predicts how the average temperature in each climate division may compare to the average temperature of all other Septembers from 1895 – 2000.  The second image predicts how the precipitation amounts may compare to the long-term average amount.

These map products that predict the temperature and precipitation anomalies for September 2003 are a compilation of the weather conditions in the Septembers that followed the summers in 1927, 1950, 1982, 1985, and 1992.

Figure 3:  Predicted September 2003 Temperatures Anomalies

Figure 4:  Predicted September 2003 Precipitation Anomalies

The temperature anomaly map predicts that this September will have below average temperatures in a majority of the nation.  The Northwest and West are forecasted to have the most significantly cool temperatures.  The only places where above normal temperatures are expected are South Texas.   Pennsylvania, in general, is expected to have slightly cooler temperatures than normal.

Not many significant precipitation anomalies are expected in September 2003.  The only areas that are predicted to be dry are the Central Plains, the Northeast, and the South.    West of the Mississippi River and the Upper Midwest are expected to be slightly wetter than normal.  The precipitation outlook for Pennsylvania in September is normal.

Using the 15-day medium range forecast temperature trends and the likely monthly departures based on the analog years, the following graphs are daily temperature forecasts for September in Western, Central, and Eastern Pennsylvania.  These predict the daily average temperature departure from the daily normal.