The most recent three-month (February through March) weather forecasts from the Climate Prediction Center of the National Weather Service indicate that much of the U.S., including the Southeast, will experience above-normal temperatures. Precipitation forecasts suggest much of the Southeast will be below normal. Most of Kentucky and Tennessee and extreme Northwest Georgia are expected to have above-normal rainfall.
Weather forecasters access an abundance of information to make predictions. The sheer quantity of data as well as the capacity to process it continues to increase. In the last several decades, climatologists and meteorologists have followed ocean surface temperatures in the Pacific Ocean and have identified conditions as La Niña or El Niño. These trends have been associated with somewhat predictable weather conditions in the continental U.S. and are studied to assist in forecasting longer term weather trends.
Apparently, the term El Niño, which means “the little boy” in Spanish, was adopted by Peruvian sailors in the 1800s. A conspicuous warming of coastal waters and southward shift of the Pacific current occurred every few years at Christmas time (hence the “little boy” reference to the baby Jesus). Somewhat later La Niña — "the little girl" — was used to designate an opposite condition of cooling ocean surface temperatures.
After a period of neutral conditions, Pacific surface temperatures in the tropical region have cooled. The Climate Prediction Center, part of the National Oceanic and Atmospheric Administration, is reporting that these La Niña conditions are very likely to persist through the spring. Conditions beyond April are less certain and may become more neutral.
In addition to ocean surface water temperatures, forecasters also have data describing wind speed and direction, so that atmospheric oscillations associated with La Niña are available for interpretation. Climate Prediction Center scientists have described this winter’s La Niña as atypical because of the displacement of the cold air associated with the polar vortex.
The current La Niña is associated with expanding drought in California and the Southwest. Growing conditions have contributed to this winter’s wheat crop as the poorest in several years. Some are suggesting the this La Niña may lead to drought conditions similar to those of 2012. While drought conditions in the Southwest are likely to persist, moisture conditions in the Eastern Corn Belt are adequate or better, limiting the consequences of drying conditions there and neighboring areas.
Weather forecasts, particularly those extending more than a few days, often refer to a departure from normal. Such references provide and opening for jokes about “normal” and critiques of weathermen, meteorologists do use a precise procedure to define normal: they use an average of 30 years of information from each individual station or location where daily readings are observed. Because of the volume of data assembled to produce 30-year averages, these estimates of normal are updated every 10 years. This year represents the beginning of a new decade so normal figures will now be based on observations beginning in 1991 rather than 1981.
While many alternatives to the 30-year average updated each decade are possible, maintaining a consistent procedure may contribute to more understandable references to the standard. The 10-year update also provides accessible information about changes in recorded temperature, precipitation and other observations.
Data available allows comparison of calculated normals for the 1981-2010 period with those generated from the period 1991-2020. A number of official weather recording stations are distributed across Georgia. The station located at the University of Georgia Experiment Station near Calhoun provides long-term data closest to Dalton.
Comparisons could be made for daily maximum or minimum temperature as well as the daily average. Inspecting a diagram of the quantity of daily temperatures depicts a conspicuous increase in the number of calendar days with average temperature between 70 and 83 degrees. There are small decreases for days with average temperatures below about 68 degrees or above 83 degrees. The pattern reflects a general warming over the 30-year periods compared. More warm days and fewer cool ones will be trends that homeowners and farmers will need to be alert to.
Change is gradual, but accumulates over extended time periods.
Roger Gates is the agricultural and natural resources agent for University of Georgia Extension, Whitfield County. Contact him at email@example.com.