The temperature and precipitation forecasts for August & September 2004 are compiled using an analog forecasting approach. This analog approach compares regional surface temperature and precipitation deviations from normal for July 2004 to years with similar regional deviations throughout the United States. The following years experienced Julys with anomalies resembling the temperature and precipitation anomalies described below: 1956, 1967, 1996 and 2000. These four years serve as the basis of the August/September analog forecast.
Temperature anomalies utilized for July 2004 included the following:
· Warm anaomaly throughout the Pacific Northwest and northern Nevada
· Cold anomaly in northern Arizona and southern Colorado
· Cold anomaly in the Northeast
· Cold anomaly in the north/south corridor just east of center, which included Minnesota, Wisconsin, eastern Nebraska, Iowa, Illinois, Missouri, Tennessee, Oklahoma, Arkansas, and northeast Texas
The August 2004 temperature anomaly map predicts warm conditions for most of
the western US, particularly in the Pacific Northwest where the departure from
normal is around +1 standard deviation. The map predicts cold anomalies throughout
the eastern US. The temperature outlook throughout Pennsylvania is below normal.
Precipitation anomalies utilized for July 2004 included the following:
· Wet anomaly along the northern Atlantic corridor
· Wet anomaly in southern California and throughout Colorado, Wyoming and eastern Idaho
· Dry anomaly along the Pacific coast in northern California, Oregon and Washington
The August 2004 precipitation anomaly map predicts dry conditions for most of the northwest and central US as well as New England. Above normal precipitation is predicted for western Pennsylvania and western New York. Precipitation predictions for Pennsylvania suggest normal precipitation for eastern PA and above normal precipitation for western PA.
Pennsylvania Temperature Forecast
Using 15-day medium range forecast temperature guidance and the likely monthly departures based on analog years, the following is a daily temperature forecast for May and June 2004 for western, central and eastern Pennsylvania. This forecast predicts the daily average temperature departure from the 30-year average temperature (dotted line) and the five day running mean of the temperature departure (solid line).
