November/December 2003 Experimental Forecast for Pennsylvania

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

For verification of the November and December 2003 forecast, visit the Verification Page.

October 2003 Conditions

The primary technique employed to produce the predictions below is an analog method. First, we compared the 500mb anomalies in October 2003 with previous October flow patterns using the NCEP reanalysis data set. We found that the October 1952, 1964, 1980, 1987, and 1988 were the most similar to this past October's geopotential height pattern (images below).

The next 2 images show the temperature and precipitation anomalies in November when the data of those 5 similar October months are compiled.

The next 2 images show the temperature and precipitation anomalies in December when the data of those 5 similar October months are compiled.

Predictions

The following products to guide in predicting the temperature and precipitation anomalies for November and December 2003 applied a second analog approach. This method compared years in which regional surface temperature and precipitation deviations from normal were similar to those experienced this past October throughout the United States. Using these years (1917, 1925, 1937, 1952, 1964, 1976, 1980, 1987 and 1988) the composite temperature and precipitation trends of the Novembers and Decembers that followed were calculated. 

November

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

The November temperature anomaly map predicts that it will be cool in the Southwest, East, and South, especially along the Gulf of Mexico and Atlantic Ocean coasts.  Warmer than normal conditions are expected in the Northern Central Plains, Northern Rocky Mountains, and Northwest regions. Especially warm conditions are possible along the Canadian border.

The November precipitation anomaly map predicts a drier than normal month throughout most of the country.  Areas that can expect the most unusually dry conditions are those along the Canadian border, the Northern Central Plains, the Ohio Valley, and the Northeast. The only areas with a significantly wetter than normal forecast are isolated in Arkansas and Florida.

December

The following two images show the analog forecast for December 2003.  The first image predicts how the average temperature for the month may compare to the average temperature for the Decembers of 1895 – 2000.  The second image predicts how the precipitation amounts for the month may compare to the long-term average amount.

The temperature anomaly map predicts that this December will have below average temperatures east of the Mississippi River and above average temperatures west of the Mississippi River. The Rocky Mountain region is predicted to have the most significantly warm weather.

The precipitation anomaly map predicts a wetter than average December in the Northwest and Northern Rocky Mountain region.  A drier than normal month is predicted throughout the rest of the country. Particularly dry conditions may occur along the Appalachian Mountains chain.

Pennsylvania Forecast

Using 15-day medium range forecast temperature guidance and the likely monthly departures based on the analog years, the following is a daily temperature forecast for November and December in western, central and eastern Pennsylvania.  This forecast predicts the daily average temperature departure from the 30 year average temperature.