Arkansas is situated within what meteorologists refer to as “Dixie Alley,” an area recognized for its heightened risk of powerful, long-track tornadoes. The state is regularly subject to the volatile collision of warm, moist air from the Gulf of Mexico and cooler, drier air masses moving from the north. Understanding the frequency and nature of these severe weather events is necessary for residents assessing local risk. This article details the long-term averages, seasonal timing, geographical risk factors, and methods used to classify the intensity of the state’s tornadic activity.
Annual Frequency and Historical Trends
The current long-term average for confirmed tornadoes in Arkansas is approximately 37 per year, a figure based on the 30-year climate period spanning 1991 to 2020. This annual average masks the significant year-to-year variability characteristic of severe weather patterns. For instance, the state experienced a record high of 107 tornadoes in 1999.
Other busy years include 2008 and 2011, which saw 81 and 75 tornadoes, respectively, demonstrating how a single season can drastically skew the long-term average. Conversely, some years are quiet, such as 2007 and 2012, which recorded the lowest counts in recent history with only 16 and 18 tornadoes confirmed. This wide range emphasizes the unpredictable nature of tornadic activity.
Seasonal Patterns and Peak Activity
Tornado activity in Arkansas exhibits a distinct bifurcated season with two peaks, unlike the single pattern seen in the Great Plains. The primary peak occurs during the spring months, specifically from March through May, when the atmosphere is most volatile due to clashing air masses. Historically, April and May are the months with the highest average number of tornado occurrences.
A secondary peak in activity spans November and December. Tornadoes occurring during this cooler season can be dangerous because they often happen after sunset. Across all seasons, the majority of severe events are most likely to occur in the late afternoon and evening, generally between 2:00 PM and 10:00 PM local time.
Geographical Risk Zones within Arkansas
While all 75 counties in Arkansas are exposed to tornadic hazards, the frequency is not uniform across the state. The highest concentration of tornadoes and fatalities tends to cluster in the central, eastern, and southern regions, including the Delta and Gulf Coastal Plain. This area is often associated with the Interstate 30 and U.S. Highway 67/167 corridors, running from the Little Rock area northeast toward Jonesboro. The combination of flat land and the frequent collision of air masses makes the central and eastern sections more favorable for supercell formation.
The topography of the northwestern part of the state, dominated by the Ozark Mountains, generally offers a degree of disruption to the atmospheric flow required for severe storm development. Although tornadoes occur in the mountainous regions, the frequency is relatively lower compared to the flatter terrain of the central and eastern plains.
Understanding the EF Scale and Notable Events
The intensity of a tornado is officially rated using the Enhanced Fujita (EF) Scale, which assesses a storm based on the severity of the damage it causes to structures and vegetation. This scale uses 28 different damage indicators and assigns a rating from EF0, which indicates minor damage, up to EF5, which represents catastrophic destruction. The EF Scale estimates wind speed based on the observed damage, rather than measuring it directly.
The majority of Arkansas tornadoes (about 81%) are classified as weak, falling into the EF0 or EF1 categories. However, the most destructive storms, rated EF3 or higher, account for approximately 80% of all tornado-related fatalities, despite making up only 3 to 4% of the total number of tornadoes. A high-end EF4 tornado tore through Mayflower and Vilonia on April 27, 2014, resulting in 16 deaths. More recently, a high-end EF3 tornado struck the Little Rock metro area on March 31, 2023, illustrating the significant impact a single powerful storm can have.