Meteorological Annual Report for 1997

Abstract

An analysis of meteorological data collected at the Savannah River Site (SRS) in 1997 shows that overall weather conditions for the year were relatively cool and wet. The average temperature for 1997 was 63.7 degree F which is about 1 degree F below the annual average for the 30-year period 1968-97. June 1997 had the lowest average temperature of any June in the 34 years for which temperature records are available at SRS ; moreover, the average temperature for the summer months (June, July, and August) was the third lowest for any summer on record. Conversely, the average temperature for March 1997 was the highest for any March in the 34-year record. Temperature extremes for 1997 ranged from a minimum of 18.6 degree F on January 18 to a maximum of 99.1 degree F on August 15.Wet weather during the last three months of the year was due to the development of a strong El Nino event (NOAA, 1998). Total rainfall for December 1997, 10.19 inches, was the highest for a December in the 46 year period of record for precipitation. Monthly rainfall was above average each month except March, May, and August. The greatest 24-hour rainfall during the year was 2.82 inches on December 24. Daily rainfall in excess of 2 inches occurred on April 28, June 28, and September 25. No snow was recorded.The annual average wind speed at the Central Climatology meteorology tower near N Area was 5.8 mph which is very nearly equal to the average wind speed at that station for the 7-year period 1991-97. The 1997 data also showed a slightly higher frequency of west to northwest winds and a slightly lower frequency of northeast winds than was observed in the 5-year period 1992-96. A winter storm which developed over the Mid-Atlantic States March 30-31 produced the most notable period of sustained strong winds. Daily and 15-minute average wind speeds of 15.3 miles per hour (mph) and 25.1 mph, respectively, were recorded at Central Climatology.Monthly average relative humidity for the year was lowest during the spring months (52 percent in April) and highest in the summer and fall (79 percent in October). The average relative humidity for the year was 70 percent and the average daily minimum relative humidity, which typically occurs during the afternoon, was 46 percent.No tropical weather systems affected the SRS region in 1997. Tropical weather activity in the Atlantic basin during the year was below average due to the effects of the developing El Nino (NOAA, 1998)Summary plots of 1997 daily minimum/maximum temperature, 24-hour total precipitation, daily minimum relative humidity, and daily average wind speed are shown in Figure 1.