Summer 2004 Outlook

Temperatures in Pennsylvania remained below normal throughout January and precipitation was near normal.  February and March brought normal to slightly above normal temperatures to all of Pennsylvania.  The purpose of this investigation is to use the analog method, used in our monthly experimental forecasts, to get a first glance at what is to come this summer. 

The analog method compares years in which regional surface temperature and precipitation deviations from normal were similar to those experienced this past January through March throughout the United States. Using these years (1986, 2000, 1981, 1999, 1921, 1931, 1992, 1935, 1990, 1938, 1953, 1976, 1934, 1907, and 1954) the composite temperature and precipitation trends of the Mays that followed were calculated. 

The two images below show the predicted May temperature and precipitation deviations from normal. 

                                            Fig 1:  Temperature anomalies for May, 2004. 

Most of the US should experience normal temperatures throughout the month of May, with the exception of the Rocky Mountain states which should be warmer.  Colorado and Nevada are the mostly likely to observe warmer than normal temperatures. 

                                            Fig 2:  Precipitation anomalies for May, 2004. 

Pennsylvania and much of the US should observe normal precipitation amounts.  Wetter weather is expected in the southern US, especially western Louisiana, extending southwest through New Mexico and Arizona. 

The second part of this investigation used Western Regional Climate Center's website to find years that experienced cold Februarys and Aprils.  The common years were then used to determine what the summer months (June, July, and August) temperature and precipitation patterns were like for Pennsylvania.  Using these years (1904, 1907, 1936) the temperature and precipitation composites were calculated.

                                            Fig 3:  Predicted temperature anomalies for June through August, 2004. 

The temperature composite shows colder than normal temperatures to occur throughout the Northeast, southern Texas, southern Florida, and much of the western half of the US.  Nevada, Utah, and southern Florida will experience the greatest departure from the average summer temperatures. 

                                            Fig 4:  Predicted precipitation anomalies for June through August, 2004. 

The summer (June, July, and August) precipitation composite shows the western half of the US, southern Florida, and the mid-Atlantic seaboard experiencing above normal rainfall.  The Midwest is predicted to have a slightly drier summer than normal.  Pennsylvania doesn't seem to trend towards a wet or dry summer. 

This investigation shows that even though Pennsylvania should experience normal conditions throughout May, temperatures are expected to fall below normal throughout the rest of the summer.  The summer precipitation outlook for Pennsylvania is normal.