NSSL NOAA National Severe Storms Laboratory

NSSL Research: Tornadoes

Much about tornadoes remains a mystery. They are rare, deadly, and difficult to predict, and they can deal out millions or even billions of dollars in property damage per year. The U.S. typically has more tornadoes than anywhere else in the world, though they can occur almost anywhere. NSSL's tornado research targets ways to better understand how they form, and use that understanding to improve tornado forecasts and warnings to help save lives.

Tornado Research Areas

Tornadogenesis

One of NSSL’s core missions is to understand severe weather and the hazards that accompany it, like tornadoes. As such, NSSL routinely participates in field work designed to better understand them. Most recently, the LIFT project sought to measure winds in tornadoes using a variety of remote sensing, including radars, lidars, and photogrammetry. The PERiLS project gathered data on tornadic storms and their environments in the southeast United States. The goal is to study and better observe features near the ground that are thought to play a key role in tornado formation. We continue to study the vast amounts of data collected from projects like these to learn more about tornado intensity, what specific ingredients thunderstorms need to form a tornado, what causes tornadoes to die, and why some rotating thunderstorms produce tornadoes and others do not.

Tornado Dynamics

NSSL researchers use computer models that simulate tornado-producing thunderstorms in 3-D, and even tornadoes themselves. We use these models to study how terrain, the land surface, and buildings impact tornado intensity, what changes in the environment cause a thunderstorm to produce a tornado, and how the tornado and storm behaves as they encounter different weather conditions.

Most tornadoes come from rotating thunderstorms, called supercells. However, nearly 20% of all tornadoes are associated with lines of strong thunderstorms called “quasi-linear convective systems” (QLCS). QLCS tornadoes frequently occur during the late night and early morning hours when it can be more difficult to stay weather aware of severe hazards. NSSL researchers are looking for ways to detect QLCS tornadoes more effectively, which is a particular problem is the Southeast United States.

Tornado Detection

The national network of weather radars now use dual-polarization technology, and NSSL continues to be a leader and major contributor to its ongoing scientific and engineering development. NSSL researchers discovered dual-polarization radars can detect debris from a tornado, helping forecasters pinpoint its location even at night or if it is wrapped in rain.

NSSL has a research phased array radar that also incorporates dual polarization technology, and can scan the entire sky for severe weather in less than a minute, five times faster than current weather radars. Researchers are collecting high-resolution data on developing tornadoes both in QLCS's and supercells to look for clues in radar data that a tornado is forming. Phased array radar has strong potential to aid the NWS in the forecast and warning decision process by providing new radar data more quickly. Forecasters have already identified this more rapid update time as a crucial benefit in experimental tests

TORP: NSSL's New Tornado Probability Algorithm

Researchers at NSSL have developed a novel Tornado Probability algorithm, or TORP, to help NWS forecasters better detect tornadoes. This work was part of the larger Probabilitic Hazard Information (PHI) effort, which is revolutionizing ways that forecasters can use machine-learning algorithms to issue real-time, probabilitic hazard forecasts. National Weather Service forecasters currently use a Tornado Detection Algorithm which was also developed at NSSL, but as with all technology, it needed an update. TORP uses machine learning to evaluate storm criteria and calculates the probability of whether a tornado is present with each detection. It was trained to find tornado probabilities by looking at storm radar data from thousands of storms taking into account multiple storm characteristics, like dual-polarization signals, and reviews the statistics related to each evaluated element. All of these factors are then combined by TORP to yield a probability of a tornado presence. TORP continues to be tested in NOAA’s Hazardous Weather Testbed on its performance and how NWS forecasters like the look and feel of the product; results so far are very encouraging!

Tornado Warning Decision Support

NSSL continues development of an automated multi-radar, multi-sensor (MRMS) system that quickly integrates data streams from multiple radars, surface and upper air observations, lightning detection systems, satellite and forecast models, and more. The MRMS system was developed to produce severe weather and precipitation products for improved decision-making capability within NOAA.

The NSSL MRMS project provides a web-based tool that displays products in real time. This includes a "rotation" product that helps confirm when and where tornadoes may have occurred by mapping circulations detected by radar on Google Earth satellite images. NWS forecasters can quickly review warnings and check their accuracy with this system. Emergency responders and damage surveyors have also used this product to produce high-resolution street maps of affected areas, so they can more effectively begin rescue and recovery efforts and damage assessments.

NSSL and the NOAA National Weather Service collaborate to streamline moving research into practical operations. NSSL has developed severe weather warning applications and decision support systems that will make the forecasters job easier. The result will be improved NWS warning services for the public, increased detection accuracy, and longer lead times.

Tornado Forecasting

NSSL's Warn-on-Forecast project aims to create highly detailed computer weather forecast models that predict what the atmosphere will look like in the future. These models are unique because they use the latest weather observations and radar scans to continuously re-compute forecasts. We want these forecasts to accurately predict when and where tornadoes will occur in the next hour so forecasters can issue warnings guided by that forecast and give people more time to find shelter.

Human forecasters continue to be essential in the tornado warning process. An essential part of that process is the translation of tornado conceptual models into a forecast or warning to guide decision making. NSSL performs integrative analyses that incorporate field observations and computer modeling into improved conceptual models of tornadoes and their parent storms. We take that a step further and translate that knowledge into improvements to concept-based tornado forecasting methods.

Tornado Preparedness

NSSL helped shape the “Weather Ready Nation” initiative to improve the public's preparedness for extreme weather, including tornadoes. Not only are we are looking at ways to improve the forecast and warning system, efforts to conduct and translate social science into improved preparedness have expanded considerably with the VORTEX-southeast and VORTEX-USA program. These efforts include better communicate threats to the public, increase community resilience, and identify gaps in our current understanding of planning, coordination and decision-making in a community.

Tornado Climatology amd Seasonal Trends

Tornadoes can happen at any time of day at any time of the year. NSSL developed the Severe Thunderstorm Climatology to estimate the likelihood of severe weather events such as tornadoes on a given day in the U.S. This can be broken down further to quantify the chance of a tornado at a given location during any hour of the day. For example, around 25% of all tornadoes that occue in the Southeast U.S> happen during the school day. In the Central and Northern Great Plains, that number is around 5%. Climatologies like this can help inform local officials, like elected representatives and emergency managers, as to what preparative actions might be most helpful for their individual communities.

Past Tornado Related Field Programs

2024-present: LIFT

NSSL and Texas Tech University are deploying radars, lidars, mobile mesonets, and UASs to measure the fine-scale structure of tornadoes and the damage they do. The teams are particularly interested in accurately measuring winds near the ground where the damage occurs to improve our understanding of tornadoes and better estimate tornado intensity. This knowledge can guide best practices for sheltering and structural engineering standards for better protecting lives and property and enhancing community resilience.

2022–23: PERiLS

Researchers from multiple universities and institutions teamed with NSSL to conduct the largest tornado field project since VORTEX2, focused on tornadoes in the vulnerable regions of the southeast United States. Large arrays of mobile radars and other ground-based remote and in-situ sensing systems surrounded severe thunderstorm systems to collect detailed observations of the inner-workings of tornadic storms of all shapes and sizes and the conditions that supported them. PERiLS was a primary vehicle to address the goals of the VORTEX project.

2019, 2022-23—TORUS

More than 50 researchers and students deployed a wide-ranging suite of instruments to collect data on supercell thunderstorms and tornadoes across the Great Plains during 2019 and again in 2022 and 2023. The TORUS project aims at better understanding the relationships between severe thunderstorms and tornado formation, particularly the fine-scale storm-internal features that impact tornado protential.

2016–2018—VORTEX-SE

VORTEX is a research program to better understand the physical and social-economic factors that contribute to tornado hazards. In these years the field efforts focused on factors relevant in the southeast United States, including how terrain and the land surface roughness impacts tornadoes, factors controlling tornado development in linear thunderstorms, and the best methods for communicating forecast uncertainty related to these events to the public, and evaluating public response. Visit VORTEX-SE in the field and the VORTEX-SE case encyclopedia for detailed accounts of these missions, and see the VORTEX-SE fact sheet for the overarching goals of this phase of the program!

2009–2010—VORTEX2

NSSL participates in the VORTEX2 experiment, the largest tornado research project in history, to explore how, when and why tornadoes form. The National Oceanic and Atmospheric Administration (NOAA) and National Science Foundation (NSF) supported more than 100 scientists, students and staff from around the world to collect weather measurements around and under thunderstorms that could produce tornadoes.

1999—VORTEX-99

NSSL and OU conduct VORTEX-99, a small follow-on project to the original VORTEX. VORTEX-99 is operating when an F5 tornado tore through parts of south Oklahoma City on May 3, 1999. During the deadly outbreak, NWS forecasters rely on NSSL's Warning Decision Support System (WDSS) to make timely and accurate tornado warnings.

1995–1996—The First VORTEX Project

The Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX) is a two-year project designed to answer a number of ongoing questions about the causes of tornado formation. A new mobile Doppler radar is used and provides revolutionary data on several tornadic storms. You can read more about the history of the VORTEX projects at NSSL and see an interactive, multimedia timeline on the VORTEX @ NSSL page.

1981–1984—Totable Tornado Observatory

NSSL attempts to deploy TOTO, the TOtable Tornado Observatory in the path of an oncoming tornado from 1981-1984. They are unsuccessful.

1976—Joint Doppler Operational Project

NSSL conducts the Joint Doppler Operational Project (JDOP) in 1976 to prove Doppler radar could improve the nation's ability to warn for severe thunderstorms and tornadoes. This led to the decision in 1979 by the National Weather Service (NWS), U.S. Air Force's Air Weather Service, and Federal Aviation Administration (FAA) to include Doppler capability in their future operational radars.

1975—Tornado Intercept Project

NSSL's legacy in organized field experiments begins with the Tornado Intercept Project in 1975 led by NSSL's Bob Davies-Jones. NSSL's Don Burgess provided storm intercept crews with live radar information via radio – and the term “nowcaster” was born.

May 24, 1973—Tornado Vortex Signature identified

An NSSL team intercepts a storm being scanned by the NSSL Doppler radar. The team documents the entire life cycle of a tornado on film. Researchers are able to compare the film images with Doppler radar data and discover a pattern that meant the tornado was forming before it appeared on film. They name this pattern the Tornado Vortex Signature (TVS). This important discovery eventually caused NOAA to begin a nationwide deployment of a national network of Doppler radars.