Predictions
The primary technique used to predict the temperature and precipitation anomalies for May 2004 and the May through June 2004 period is the application of an analog approach. This method compares years in which regional surface temperature and precipitation deviations from normal were similar to those experienced this past April throughout the United States. Using these years (1987, 1915, 1952, 1926, 1913, 1942, 1916 and 1977) the composite temperature and precipitation trends of the following Mays were calculated.
May 2004
The two images below show the analog forecast for May 2004. The first image show the anomalies of May temperature for all of the composite months, with respect to the 1895-2000 average temperature. The second image displays the precipitation anomalies of the same Mays.
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The May temperature anomaly map predicts cooler than average conditions throughout the western half of the US. Nebraska is expected to experience the greatest temperature departure from normal. Warmer than normal conditions are expected throughout the Mid-Atlantic states. Temperatures are projected to near normal to slightly above normal for a majority of Pennsylvania based off these composite years.
The May precipitation anomaly map predicts a slightly wetter than normal month across western and Northcentral United States. The eastern half of the US shows near normal precipitation amounts. A sliver of dry conditions extends from southeast Oklahoma into Arkansas.
May/June 2004
The following two images show the analog forecast for May & June 2004. The first image shows how the average temperature for the 8 composite years compared to the average temperature for the Mays and Junes of 1895 – 2000. The second image displays how the precipitation amounts fared for the same 8 composite years.
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The May & June temperature anomaly map shows that the Southwestern and Northeastern US will remain cool, while the Southeastern US should remain above normal for the two month average.
The May & June precipitation anomaly map predicts slightly above normal rainfall across the Northwestern and Midwestern US. Arkansas is the only state that is expected to have significantly drier than normal conditions. The remainder of the United States should experience near normal conditions based off of this analog approach.
Pennsylvania 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 (solid line).
