Tornadogenesis Research Articles

Tornado funnel-shaped cloud as convection in a cloudy layer

Abstract. Analytical model of convection in a thick horizontal cloud layer with free upper and lower boundaries is constructed. The cloud layer is supposed to be subjected to the Coriolis force due to the cloud rotation, which is a typical condition for tornado formation. It is obtained that convection in such system can look as just one rotating cell in contrast to the usual many-cells Benard convection. The tornado-type vortex is different from spatially periodic convective cells because their amplitudes vanish with distance from the vortex axis. The lower boundary at this convection can substantially move out of the initially horizontal cloud layer forming a single vertical vortex with intense upward and downward flows. The results are also applicable to convection in water layer with negative temperature gradient.

NWS Tornado Warnings with Zero or Negative Lead Times

Abstract During a 5-yr period of study from 2000 to 2004, slightly more than 10% of all National Weather Service (NWS) tornado warnings were issued either simultaneously as the tornado formed (i.e., with zero lead time) or minutes after initial tornado formation but prior to tornado dissipation (i.e., with “negative” lead time). This study examines why these tornadoes were not warned in advance, and what climate, storm morphology, and sociological factors may have played a role in delaying the issuance of the warning. This dataset of zero and negative lead time warnings are sorted by their F-scale ratings, geographically by region and weather forecast office (WFO), hour of the day, month of the year, tornado-to-radar distance, county population density, and number of tornadoes by day, hour, and order of occurrence. Two key results from this study are (i) providing advance warning on the first tornado of the day remains a difficult challenge and (ii) the more isolated the tornado event, the less likelihood that an advance warning is provided. WFOs that experience many large-scale outbreaks have a lower proportion of warnings with negative lead time than WFOs that experience many more isolated, one-tornado or two-tornado warning days. Monthly and geographic trends in lead time are directly impacted by the number of multiple tornado events. Except for a few isolated cases, the impacts of tornado-to-radar distance, county population density, and storm morphology did not have a significant impact on negative lead-time warnings.

High-Resolution, Mobile Doppler Radar Observations of Cyclic Mesocyclogenesis in a Supercell

Abstract On 15 May 2003, two ground-based, mobile, Doppler radars scanned a supercell that moved through the Texas Panhandle and cyclically produced mesocyclones. The two radars collected data from the storm during a rapid cyclic mesocyclogenesis stage and a more slowly evolving tornadic period. A 3-cm-wavelength radar scanned the supercell continuously for a short time after it was cyclic but close to the time of tornadogenesis. A 5-cm-wavelength radar scanned the supercell the entire time it exhibited cyclic behavior and for an additional 30 min after that. The volumetric data obtained with the 5-cm-wavelength radar allowed for the individual circulations to be analyzed at multiple levels in the supercell. Most of the circulations that eventually dissipated moved rearward with respect to storm motion and were located at distances progressively farther away from the region of rear-flank outflow. The circulations associated with a tornado did not move nearly as far rearward relative to the storm. The mean circulation diameters were approximately 1–4 km and had lifetimes of 10–30 min. Circulation dissipation often, but not always, occurred following decreases in circulation diameter, while changes in maximum radial wind shear were not reliable indicators of circulation dissipation. In one instance, a pair of circulations rotated cyclonically around, and moved toward, each other; the two circulations then combined to form one circulation. Single-Doppler radial velocities from both radars were used to assess the differences between the pretornadic circulations and the tornadic circulations. Storm outflow in the rear flank of the storm increased notably during the time cyclic mesocyclogenesis slowed and tornado formation commenced. Large storm-relative inflow likely advected the pretornadic circulations rearward in the absence of organized outflow. The development of strong outflow in the rear flank probably balanced the strong inflow, allowing the tornadic circulations to stay in areas rich in vertical vorticity generation.

Can a Descending Rain Curtain in a Supercell Instigate Tornadogenesis Barotropically?

Abstract This paper investigates whether the descending rain curtain associated with the hook echo of a supercell can instigate a tornado through a purely barotropic mechanism. A simple numerical model of a mesocyclone is constructed in order to rule out other tornadogenesis mechanisms in the simulations. The flow is axisymmetric and Boussinesq with constant eddy viscosity in a neutrally stratified environment. The domain is closed to avoid artificial decoupling of a vortex from the storm-scale circulation. In the principal simulation, the initial condition is a balanced, slowly decaying, Beltrami flow describing an updraft that is rotating cyclonically at midlevels around a low pressure center surrounded by a concentric downdraft that revolves cyclonically but has anticyclonic vorticity. The boundary conditions are no slip on the tangential wind and free slip on the radial or vertical wind to accommodate this initial condition and to allow strong interaction of a vortex with the ground. Precipitation is released through the top above the updraft and falls to the ground near the updraft–downdraft interface in an annular curtain. The downdraft enhancement induced by the precipitation drag upsets the balance of the Beltrami flow. The downdraft and its outflow toward the axis increase low-level convergence beneath the updraft and transport air with moderately high angular momentum downward and inward where it is entrained and stretched by the updraft. The resulting tornado has a corner region with an intense axial jet and low pressure capped by a vortex breakdown and a transition to a broader vortex aloft (a tornado cyclone). A clear slot of subsiding air with anticyclonic vorticity surrounds the vortex. The vertical kinetic energy of the entire circulation declines dramatically prior to tornado formation.

The Mechanism of Tornadogenesis

The Mechanism of Tornadogenesis

Coordination, research needed in weather science

At the onset of another hurricane season, Gavin Schmidt’s Quick Study piece on “The Physics of Climate Modeling” (Physics Today, January 2007, page 72) could not be more timely nor on a topic of greater importance. It follows one by Kerry Emanuel in the August 2006 issue (page 74) on thermal aspects of greenhouse gases contributing to hurricane genesis. And in the November 2006 item “Science Board Recommends Major Hurricane Research Program” (page 30), Jim Dawson directed attention both to the devastation wreaked by Hurricane Katrina and to a National Science Board panel convened to investigate the root causes of severe, damaging storms and ways to ameliorate their effects. We’re among the concerned scientists and engineers who have written letters in support of the NSB effort, and we now provide additional information on the topic.First, we underscore the broader need for research funding by pointing out that the topic of weather damage encompasses more than hurricanes developing from severe storms over water. Dawson’s November article stated, “Politicians from the Dakotas and Montana ‘don’t think [research on hurricanes] is their problem.’ “However, tornadoes spawned by severe storms over land are very much an increasing threat to people, infrastructure, and property in the US interior. Tolls associated with these devastating killers are staggering. On average, 800 tornadoes occur nationwide each year. The Environmental Protection Agency states that tornadoes annually cause approximately $1.1 billion in damages and around 80 fatalities. On 3 May 2003, for example, a series of tornadoes ripped through Oklahoma City and its environs, leaving 48 people dead and causing more than $1 billion in damage. The hurricane insurance losses for 2005 were $57 billion, the highest ever before Hurricane Katrina, whose costs are still being counted. And on 5 May 2007, a single tornado with winds up to 205 miles per hour struck and essentially destroyed the town of Greensburg, Kansas. Thus, whether over land or sea, there are more than enough concerns about personnel, infrastructure, and finances to warrant investing in research on severe storms. Second, now appears to be an optimum time for bringing together the previously estranged communities of weather modification practitioners, who are mostly supported by insurance industries, and research academics, who have very limited funds. A considerable amount of data on practical weather modifications has accumulated, and significant advances have occurred in fundamental model descriptions of severe-weather-based instabilities; for example, two of us (Armstrong and Glenn) have reexamined the role of electrification forces in contributing to tornado formation. 1 1. R. W. Armstrong, J. G. Glenn, J. Weather Modif. 38, 77 (2006); available at http://alamaro.home.comcast.net/JWM_armstrong_glenn.pdf. With coordinated efforts, a new, stronger community can be formed to advance the art and science of weather modification. In another case, Jürgen Michele, Vladimir Pudov, and one of us (Alamaro) have been discussing a concept inspired by a 1970s Soviet weather-modification program in the Baltics. 2 2. M. Alamaro, J. Michele, V. Pudov, J. Weather Modif. 38 , 82 (2006); available at http://alamaro.home.comcast.net/WMA_April_2006.pdf. In that program, an array of jet engines was employed to form a vertical air flow that, it was hoped, would be sufficient to cause cloud formation. Even in a stable atmosphere, 9 out of 15 tests led to cloud formation. Alamaro and coworkers presented the hypothesis that the method may be used for such weather modification applications as frost prevention, fog dispersion, and, most ambitiously, hurricane modification. In the case of hurricane modification, a designed array of multiple jets would be used to create atmospheric perturbations that might turn a hurricane back to sea.REFERENCESSection:ChooseTop of pageREFERENCES <<1. R. W. Armstrong, J. G. Glenn, J. Weather Modif. 38, 77 (2006); available at http://alamaro.home.comcast.net/JWM_armstrong_glenn.pdf. Google Scholar2. M. Alamaro, J. Michele, V. Pudov, J. Weather Modif. 38 , 82 (2006); available at http://alamaro.home.comcast.net/WMA_April_2006.pdf. Google Scholar© 2007 American Institute of Physics.

Taming Tornadoes Storm Abatement from Space

Tornadoes represent the most dangerous and destructive of storms. This paper describes a concept for disrupting the formation of tornadoes in a thunderstorm. Beamed microwave energy from a satellite heats cold rain to affect convective forces in the storm cell. This describes a Thunderstorm Solar Power Satellite (TSPS). The TSPS is based on Space Solar Power Program (SSP) concepts and technology. The concept was evaluated in a numerical simulation using the Advanced Regional Prediction System Code at the Center for Analysis and Prediction of Storms (CAPS). Conditions for tornado formation were affected in the simulation. Additional simulation is proposed to determine the specific areas to be heated and the intensity of directed energy to affect tornadogenesis. Benefits from taming tornadoes provide a basis for initial government investment in TSPS. The potential benefits are balanced by reservations about safety. Demonstration of technology and operations may lead to commercial investment in space solar power. We conclude that the TSPS concept merits additional analysis, numerical simulation, and demonstration testing.

Observational Analysis of the 27 May 1997 Central Texas Tornadic Event. Part II: Tornadoes

AbstractThe 27 May 1997 central Texas tornadic event has been investigated in a two-part observational study. As demonstrated in Part I, the 1D environment associated with this event was unfavorable for significant (≥F2) tornadoes. Yet, the storm complex produced at least six significant tornadoes, including one rated F5 (the Jarrell, Texas, tornado). The purpose of this article is to examine the spatiotemporal interrelationships between tornadoes, preexisting boundaries, antecedent low-level mesocyclones, convective cells, and midlevel mesocyclones. It is shown that each of the six observed tornadoes that produced greater than F0 damage formed along the storm-generated gust front, not along preexisting boundaries. Half of these tornadoes formed on the distorted gust front, the portion of the storm-generated gust front whose orientation was deformed largely by the horizontal shear across the cold front. The remaining three tornadoes developed at the gust front cusp (the persistent gust front inflection located at the northeast end of the gust front distortion). Unlike the tornadoes south of the gust front cusp, these tornadoes are found to be associated with antecedent mesocyclones located in the low levels above the boundary layer. Furthermore, these mesocyclonic tornadoes are found to be larger and more destructive than the three nonmesocyclonic tornadoes. The formation of the Jarrell tornado is found to occur as a nearly stationary convective cell became collocated with a south-southwestward-moving low-level mesocyclone near the gust front cusp—a behavior that resembles the formation of nonsupercell tornadoes. It is argued that the back-building propagation/maintenance of the storm complex enabled this juxtaposition of convective cells with vorticity along the distorted gust front and may have therefore enabled tornado formation. Each of the convective cells without midlevel mesocyclones was found to remain farther from the boundaries than the mesocyclonic cells. Since the cells nearest to the boundaries were longer lived than the remaining cells, it is argued that cells near the boundaries were mesocyclonic because the boundaries yielded cells that were more likely to support temporally coherent midlevel rotation.

A Preliminary Survey of Rear-Flank Descending Reflectivity Cores in Supercell Storms

Abstract This paper develops a definition of a supercell reflectivity feature called the descending reflectivity core (DRC). This is a reflectivity maximum pendant from the rear side of an echo overhang above a supercell weak-echo region. Examples of supercells with and without DRCs are presented from two days during the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX), as well as one day with tornadic high-precipitation supercell storms in central Kansas. It was found that in all cases, tornado formation was preceded by the descent of a DRC. However, the sample reported herein is much too small to allow conclusions regarding the overall frequency of DRC occurrence in supercells, or the frequency with which DRCs precede tornado formation. Although further research needs to be done to establish climatological frequencies, the apparent relationship observed between DRCs and impending tornado formation in several supercells is important enough to warrant publication of preliminary findings.

Forecasting Tornadic Thunderstorm Potential in Alberta Using Environmental Sounding Data. Part I: Wind Shear and Buoyancy

Abstract This study investigates, for Alberta, Canada, whether observed sounding parameters such as wind shear and buoyant energy can be used to help distinguish between thunderstorms with significant (F2–F5) tornadoes, thunderstorms with weak (F0–F1) tornadoes, and nontornadic severe thunderstorms. The observational dataset contains 87 severe convective storms, all of which occurred within 200 km of the upper-air site at Stony Plain, Alberta, Canada. Of these storms, 13 spawned significant (F2–F5) tornadoes, 61 spawned weak (F0–F1) tornadoes, and 13 had no reported tornadoes yet produced 3 cm or larger hailstones. The observations suggest that bulk shear contained information about the probability of tornado formation and the intensity of the tornado. Significant tornadic storms tended to have stronger shear values than weak tornadic or nontornadic severe storms. All significant tornado cases had a wind shear magnitude in the 900–500-mb layer exceeding 3 m s−1 km−1. Combining the 900–500-mb shear with the 900–800-mb shear increased the probabilistic guidance for the likelihood of significant tornado occurrence. The data suggest that buoyant energy alone (quantified by the most unstable convective available potential energy) provided no skill in discriminating between tornadic and nontornadic severe storms, or between significant and weak tornadoes.

The 29 June 2000 Supercell Observed during STEPS. Part II: Lightning and Charge Structure

Abstract This second part of a two-part study examines the lightning and charge structure evolution of the 29 June 2000 tornadic supercell observed during the Severe Thunderstorm Electrification and Precipitation Study (STEPS). Data from the National Lightning Detection Network and the New Mexico Tech Lightning Mapping Array (LMA) are used to quantify the total and cloud-to-ground (CG) flash rates. Additionally, the LMA data are used to infer gross charge structure and to determine the origin locations and charge regions involved in the CG flashes. The total flash rate reached nearly 300 min−1 and was well correlated with radar-inferred updraft and graupel echo volumes. Intracloud flashes accounted for 95%–100% of the total lightning activity during any given minute. Nearly 90% of the CG flashes delivered a positive charge to ground (+CGs). The charge structure during the first 20 min of this storm consisted of a midlevel negative charge overlying lower positive charge with no evidence of an upper positive charge. The charge structure in the later (severe) phase was more complex but maintained what could be roughly described as an inverted tripole, dominated by a deep midlevel (5–9 km MSL) region of positive charge. The storm produced only two CG flashes (both positive) in the first 2 h of lightning activity, both of which occurred during a brief surge in updraft and hail production. Frequent +CG flashes began nearly coincident with dramatic increases in storm updraft, hail production, total flash rate, and the formation of an F1 tornado. The +CG flashes tended to cluster in or just downwind of the heaviest precipitation, which usually contained hail. The +CG flashes all originated between 5 and 9 km MSL, centered at 6.8 km (−10°C), and tapped LMA-inferred positive charge both in the precipitation core and (more often) in weaker reflectivity extending downwind. All but one of the −CG flashes originated from &amp;gt;9 km MSL and tended to strike near the precipitation core.

Influence of an island land mass on the frequency of waterspout and tornado formation in its vicinity: Example of the Isle of Wight with regard to waterspouts and tornadoes affecting the English South Coast

This research deals with the incidence of tornadoes and waterspouts along the coasts of Hampshire and Sussex. In particular, the areas north and east of the Isle of Wight are studied and some cases analysed. The severity of the property damage indicates tornado tracks up to 900 m wide (as at Selsey on 7 January 1998) and suggests tornado intensities up to T8 on the International Tornado Scale. On extreme occasions (e.g. 14 December 1810, 28 September 1876, 7–8 January 1998, 28 October 2000, 30 October 2000) many dozens–and sometimes hundreds–of properties were damaged. The work suggests that the presence of the Isle of Wight's land mass in westerly and south-westerly conditions disturbs the atmospheric circulation sufficiently to trigger or to intensify tornadic vortices from storm cells, and implies that in the absence of the island there would be fewer such occurrences.

The 30 May 1998 Spencer, South Dakota, Storm. Part I: The Structural Evolution and Environment of the Tornadoes

Abstract On the evening of 30 May 1998 atmospheric conditions across southeastern South Dakota led to the development of organized moist convection including several supercells. One such supercell was tracked by both a Weather Surveillance Radar-1988 Doppler (WSR-88D) from Sioux Falls, South Dakota (KFSD), and by a Doppler On Wheels (DOW) mobile radar. This supercell remained isolated for an hour and a half before being overtaken by a developing squall line. During this time period the supercell produced at least one strong and one violent tornado, the latter of which passed through Spencer, South Dakota, despite the absence of strong low-level environmental wind shear. The two tornadoes were observed both visually and with the DOW radar at ranges between 1.7 and 12.9 km. The close proximity to the tornadoes permitted the DOW radar to observe tornado-scale structures on the order of 35 to 100 m, while the nearest WSR-88D only resolved the parent mesocyclone in the supercell. The DOW observations revealed a persistent Doppler velocity couplet and associated ring reflectivity signature at the tip of the hook echo. The DOW radar data contained tornado strength winds over 35 m s−1 within 100 m AGL approximately 180 s prior to both the first spotter report and visual confirmation of the first tornado associated with this supercell. Following the formation of the second tornado, the DOW radar observations revealed a tornado-strength Doppler velocity couplet within 150 m AGL between two separate tornado tracks determined by a National Weather Service (NWS) damage survey. Based upon the DOW Doppler velocity data it appears that the second and third damage tracks from this supercell are produced from a single tornado. The time–height evolution of the Doppler velocity couplet spanning both tornadoes revealed a gradual increase in vertical vorticity across each tornado's core region within a few hundred meters AGL from near 0.2 to over 2.0 s−1 over a 45-min period. A corresponding reduction in vertical vorticity was observed aloft especially near 1000 m AGL where vorticity values decreased from near 1.0 to about 0.5 s−1 during this same time interval. The shear across the Doppler velocity couplet appears to undergo strengthening both at the surface and aloft during both tornadoes. An oscillatory fluctuation in the near-surface shear across the tornado core developed during the second tornado, with peak shear values as high as 206 m s−1, Doppler velocities over 106 m s−1, and peak ground-relative wind speeds reaching 118 m s−1. The period of this intensity oscillation appears to be around 120 s and was most prominent just prior to and during the passage of the tornado through Spencer. Coincident with the tornado passage through Spencer was a rapid descending of the reflectivity eye in the core of the tornado. A detailed comparison of surveyed tornado damage and radar-calculated tornado winds in Spencer is discussed in Part II.

Mapping lightning channels in a thunderstorm by radar

The state of Georgia has experienced a number of tornados that occur without warning, and, in several cases have caused fatalities. Researchers at the Severe Storms Research Center (SSRC) of the Georgia Tech Research Institute (GTRI), Georgia Institute of Technology are attempting to detect tornado formation within severe thunderstorms occurring in the vicinity of Atlanta, Georgia, using non-radar sensors that may provide early tornado warning and provide cueing to existing National Weather Service (NWS) radars. The goal of these studies is to increase the warning time of tornado formation within the parent thunderstorm. GTRI researchers use real-time S-band Doppler weather radar data from three National Weather Service WSR-88D NEXRAD radars to complement the development of the non-radar tornado sensors. Three NWS Doppler radars provide severe weather surveillance coverage of the north Georgia area to determine if a thunderstorm contains the Doppler signature that indicates tornado formation. The radar data, displayed on a work station developed and optimized for tornado detection by the National Severe Storms Laboratory (NSSL), serves as ground truth data for the non-radar sensor development. GTRI can display cloud to ground (CG) lightning strikes, a capability provided by overlaying data from a national monitoring network onto the radar reflectivity map. GTRI also uses a local lightning direction finder (DF) system that supplies azimuth and range to the lightning strike. This paper discusses the early lightning channel research and the passive parasitic radar system being operated by the SSRC.

A Multiscale Observational Case Study of the Development of an Isolated High Plains Tornadic Supercell

On 21 May 1995, a strong tornado developed with an isolated supercell in southwestern Nebraska. Largescale conditions were not supportive of a tornadic thunderstorm outbreak; however, evidence suggests significant mesoscale enhancements produced a local environment favorable for strong tornado formation. This case study illustrates the importance of ‘‘situation awareness’’ and illustrates how mesoscale enhancements must be anticipated by forecasters in order to properly assess rapidly changing atmospheric conditions.

The 8 June 1995 McLean, Texas, Storm. Part II: Cyclic Tornado Formation, Maintenance, and Dissipation

Abstract On 8 June 1995, scientists participating in the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) collected a unique dataset with the Electra Doppler Radar (ELDORA). The ELDORA observations document the sequential life cycles of storm-scale circulations associated with three large tornadoes in a supercell thunderstorm near McLean, Texas. A qualitative description of the evolution of the storm was provided in Part I of this paper. During the first stage of development of each storm-scale circulation, interaction of the updraft with the environmental low-level horizontal vorticity produced a vorticity column that increased in intensity with height. As the vortex matured, vorticity increased greatly at low levels (i.e., below 2 km AGL) and exceeded that aloft. Each tornadic vortex was located near the rear side of the updraft, where the surrounding low-level horizontal vorticity was modified locally, most likely by weak baroclinity within the storm. Tilting of low-level horizo...

The 8 June 1995 McLean, Texas, Storm. Part I: Observations of Cyclic Tornadogenesis

Abstract On 8 June 1995 scientists participating in the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) collected airborne Doppler radar data in a storm that produced a family of tornadoes near McLean, Texas. The Electra Doppler Radar (ELDORA) scanned three significant tornadoes during their formative and mature stages; one of the tornadoes was of F4/F5 intensity. Evidence from pseudo-dual-Doppler analyses of the ELDORA data reveals a process of cyclic tornado formation qualitatively similar to that depicted in previous conceptual models. In particular, the rear-flank gust front appears to play a major role in determining the location of the next vortex in the series. When a tornado forms, a small region (3–5 km wide) of outflow surges ahead of the tornado, producing a local bulge in the gust front. A new vorticity maximum may form near the leading edge of the outflow. In contrast to what is suggested by earlier conceptual models, intersection of the rear-flank gust front with a w...

Tornado climatology of Austria

After several decades of little work, a revised tornado climatology for Austria is presented. Tornadoes seldom form in the alpine areas, however, near the eastern flanks of the Alps, favourable conditions for tornado genesis are found. Whereas in the alpine regions less than 0.3 tornadoes per 10,000 km 2 a year touch down (averaged for provinces or major parts of a province), we can count 0.9 in the greater Graz area, 1.0 in the greater Linz area and 1.2 tornadoes per 10,000 km 2 a year in the greater Vienna area, suggesting the existence of so-called tornado alleys. As these regions are the most populated areas of Austria, there is a possible population bias in the dataset. The overall average for Austria is 0.3 tornadoes per 10,000 km 2 a year. The database consists of 89 tornadoes, one landspout and six waterspouts, with a total of 96 events. The seasonal peak is in July with a maximum probability of tornadoes in the late afternoon and early evening hours. Every fifth tornado occurs in the hour after 5 p.m. The maximum intensity determined for a tornado in Austria was T7 on the TORRO-Scale (F3 on the Fujita-Scale), the most common intensity is T2 on the TORRO-Scale (F1 on the Fujita-Scale).

The Tornado Problem: Forecast, Warning, and Response

Research on tornadoes over the last 20 years has been conducted by a combination of universities, research institutions, federal agencies, and more recently by private meteorological companies. Recent advances in scientific technologies and computers have led to an explosion of knowledge in the last decade. This is evidenced by increased accuracy in the detection and prediction of tornadoes as well as increased warning lead time before tornado formation. Most of the research in this area has focused on the physical sciences and technology portion of the warning process. Far less attention has been spent on the warning communication process, behavioral response, and epidemiology of tornadoes. The translation of improved technologies into better tornado forecasting and warning services must also involve the incorporation of physical and social science. This is necessary to develop improved warning communication and coordination processes that will lead to the further reduction of tornado related injuries and fatalities.

Improvement of the WSR-88D Mesocyclone Algorithm

The build 9 Weather Surveillance Radar-1988/Doppler mesocyclone algorithm (B9MA) is designed to locate mesocyclones [rotating thunderstorm updrafts with diameters between 1.8 and 9.2 km (1–5 n mi)]. Because there is less than a one to one correspondence between tornadoes and mesocyclones, the B9MA alerts forecasters when it detects circulations that meet its criteria but tornadoes may not be observed. On the other hand, some tornadoes are not accompanied by large-scale meoscyclonic circulations. Weather radars cannot resolve small-scale tornadic circulations, and the B9MA may fail to alert forecasters that a tornado is present. The B9MA is only one of many tools that forecasters should use to predict tornado formation. This paper describes limitations of the B9MA and how to improve its performance. The correlation between algorithmic detections and severe weather occurrence may be optimized under the premise that storms with strong, deep rotations are more likely to be associated with severe weather. Some tornadic circulations missed by the B9MA can be detected when the value of threshold pattern vector, a B9MA adaptable parameter, is lowered. When a rotational strength filter is added to the program logic, some algorithm detections of nontornadic mesocyclones can be eliminated.