El Nino Effects in East Tennessee
Much has been made about the strong El Nino conditions that have been developing across the eastern Pacific over the last several months. Many people have heard about the potential effects from El Nino for such places as California, the gulf coast states and the southwest United States. This has many of us across east Tennessee wondering just what is an El Nino and will it affect the weather across our area? El Nino is the invasion from time to time of warm surface water from the equatorial region of the Pacific basin to the eastern Pacific and along the coasts of Peru, Ecuador and northern Chile. Before 1950 this event was of interest only to local fisherman of these countries due to the biological productivity of these waters. In the mid 1970's international concern shifted to El Nino's proposed connections to climate anomalies (deviations from the average) that occur in other parts of the world either before during or after an El Nino event. The scientific community now seeks to establish relationships between El Nino and events such as droughts of floods that occur around the world.
Signs indicate that the El Nino of 1997-1998 is shaping up to be one of the strongest on record. There have been three other strong El Ninos since 1957 (1957-1958, 1972-1973 and 1982-1983). After examining the data from these strong El Ninos and several weaker ones that have taken place, there appears to be no definite or clear cut effects for the weather across our area due to El Nino. Four out the last six El Ninos (including the three strong events) had above normal precipitation totaled for the entire El Nino period. But there were dry to very dry periods during those years as well. As far as what kind of weather we can expect for this upcoming winter, it remains to be seen. Many different types of winters have occurred during El Ninos. Like any other year there have been colder and dryer than normal winters, warmer and wetter than normal winters and so on. However four out of the last six El Ninos had below normal winter temperatures (with one above normal and one normal). Three our of the last six El Ninos had below normal winter precipitation (with one normal and two above normal).
Snowfall during strong El Nino winters (such as the upcoming winter of 1997-1998) has tended to drop significantly from the previous winter. It appears that the type of weather we can expect this winter and in the months that follow is like any other year across east Tennessee. Anything can happen. The current long range outlook for east Tennessee from the Climate Prediction Center is for near normal precipitation for the October through December period followed by below normal precipitation for January through April. Temperatures are forecasted to be near normal for October though December and slightly below normal during the January to April time frame. More detailed information about the effect of El Nino on east Tennessee weather can be found in the graphs and tables below.
Seasonal Data for Strong El Ninos (averaged for all of East Tennessee)
Temperature and Precipitation Data for El Nino Episodes since 1957 for the Three Metropolitan Areas