Strong Tornadoes Research Articles

Tornado Occurrence in the United States as Modulated by Multidecadal Oceanic Oscillations Using Empirical Model Decomposition

Studies have analyzed U.S. tornado variability and correlated F1–F5 tornado occurrence with various natural climate oscillations and anthropogenic factors. Using a relatively new empirical mode decommission (EMD) method that extracts time-frequency modes adaptively without priori assumptions like traditional time-series analysis methods, this study decomposes U.S. tornado variability during 1954–2022 into intrinsic modes on specific temporal scales. Correlating the intrinsic mode functions (IMFs) of EMD with climate indices found that 1. the U.S. overall tornado count is negatively (positively) correlated with the Atlantic Multidecadal Oscillation (AMO) index (the Southern Oscillation Index (SOI)); 2. the negative (positive) correlation tends to be more prevalent in the western (eastern) U.S.; 3. the increase in weak (F1–F2) and decrease in strong (F3–F5) tornadoes after around 2000, when both the AMO and the Pacific Decadal Oscillation (PDO) shifted phases, are likely related to their secular trends and low-frequency IMFs; and 4. the emerging Dixie Tornado Alley coincides with an amplifying intrinsic mode of the SOI that correlates positively with the eastern U.S. and Dixie Alley tornadoes. The long-term persistence of these climate indices can offer potential guidance for future planning for tornado hazards.

Total lightning signatures in a tornadic thunderstorm over the Pearl River Delta of Southern China

Tornado rises rotating air columns extending from the bottom of cumulonimbus clouds to the ground, often accompanied by strong convection with thunderstorms, hail, and short-term heavy precipitation, which seriously threaten people's lives and property safety. Studying the characteristics of thunderstorm activity during a tornado is crucial for comprehending the atmospheric electrical mechanisms involved in its generation process and developing cooperative methods for tornado warning and forecasting. Based on the VLF/LF total lightning location system and radar echo data, this paper analyzes the spatial-temporal evolution, frequency, polarity, and height of total lightning during a strong tornado (EF3) in the Pearl River Delta region on June 3, 2014. The lightning activity lasted for about 3.5 h, with a total of 41,117 total lightning flashes, of which intra-cloud (IC) flashes accounted for 74.7%, cloud-to-ground (CG) flashes accounted for 21.6%, and narrow bipolar events (NBEs) accounted for 3.7%. Connected-Component Labeling (CCL) algorithm was used to divide the thunderstorm into four stages: initiation, development, maturation, and dissipation, and it was observed that the occurrence of tornadoes was closely related to total lightning activities. The observed characteristics of lightning activity in the tornado are summarized through comparison with other studies.

The Violent Tornado on 24 June 2021 in Czechia: Damage Survey, Societal Impacts, and Lessons Learned

Abstract A violent tornado occurred in Czechia on 24 June 2021, killing six and causing at least 576 injuries. There were more indirect than direct injuries. The tornado was rated 4 on the international Fujita scale (IF4) using a draft version of the IF scale. This was the first violent tornado in Czechia and one of only 17 violent, i.e., (I)F4 or higher, tornadoes that occurred in Europe since 1950. The tornado reached a width of 3.5 km, the widest on record in Europe. The case presents an important opportunity to investigate the impacts of such a strong tornado in the area, where they are rare, no tornado warnings are issued, and where the building standards are different from the typically investigated tornadoes in the United States. We discuss challenges in organizing the damage survey, which took 3 days and involved meteorologists from three countries. A wind damage survey guide to aid mitigating these was written by the European Severe Storms Laboratory and initiated the development of a wind damage surveying app. The damage survey showed that most of the inhabited buildings built using heavy masonry and rigid ceilings did not collapse in IF2/3 winds, but only with IF4 winds. Eyewitness reports collected after the tornado show that many people were not aware of the risk associated with the tornado. Eventually, most people tried to shelter in the most secure part of the house, but it was often too late. This case highlights the need for better communication of tornado risk to the public in Europe.

Evaluation of tornadic environments and their trends and projected changes in Japan

Tornadoes are responsible for several high-impact weather disasters in Japan. However, little is known about how these events have changed over the last several decades or how they may change in future climates. This study examines environmental conditions associated with tornados in Japan using pseudo-soundings from the high-resolution fifth-generation ECMWF reanalysis. We first determine appropriate discriminators of F2+ tornadoes using thermodynamic (convective available potential energy, convective inhibition, lifting condensation level, and the K-index), kinematic (bulk wind difference and storm-relative helicity), and multivariate tornado parameters (energy helicity index, K-helicity index, and the significant tornado parameter), and confirm that F2+ tornadoes occur in environments with higher instability and helicity, but are better distinguished using multivariate parameters. Recent trends indicate that F2+ environments have increased significantly in some regions over the last four decades. We also examined future changes for each parameter using a large ensemble 2-K warming experiment. Robust increases in strong tornado environments are depicted in many regions in Japan, particularly on the Sea of Japan side and the Kanto region. This indicates that despite projected decreases in bulk wind difference and higher convective inhibition, significant increases in atmospheric instability compensate, leading to more days with F2+ tornado potential.

Polarimetric Radar Observations of a Long-Lived Supercell and Associated Tornadoes on 10–11 December 2021

Abstract We present environmental and polarimetric radar observations of a long-lived December supercell that tracked approximately 750 km from Arkansas to northern Kentucky. The storm was associated with two long-track EF4 tornadoes, one of which was among the longest-tracked tornadoes recorded in the United States. The supercell’s life cycle is documented from 2000 UTC 10 to 0700 UTC 11 December 2021, using data from five operational polarimetric weather radars. After convection initiation in central Arkansas, it took nearly 4 h for a supercell to develop. Afterward, the storm’s ZDR column and arc became anomalously large leading up to genesis of the first EF4 tornado. During this time, the storm’s environment had moderate convective available potential energy (CAPE) and strong deep-layer shear. A cell interaction at about 0200 UTC disrupted the supercell updraft, weakening the ZDR arc and column, and initiating the largest radar-implied hailfall event observed with this storm. The remnant circulation associated with the first EF4 tornado did not fully dissipate, and it appeared to merge with the low-level mesocyclone on the nose of a rear-flank downdraft surge likely initiated by the hailfall. It is hypothesized that this merger was important to the intensification of the storm’s second EF4 tornado, which lasted nearly 3 h and traveled approximately 267 km. During the second EF4 tornado the storm experienced decreasing CAPE and increasing storm relative helicity. Increasing interactions with other cells eventually weakened the storm, and its original updraft was obscured before the storm’s remnants dissipated in northern Kentucky. Significance Statement In December 2021, a long-lived supercell thunderstorm produced two long-track, violent tornadoes, including one that produced historic damage across western Kentucky. Radar observations indicate that, once the storm became a supercell, its updraft became anomalously large relative to similar storms studied prior. Simultaneously its storm-relative inflow strengthened markedly, supporting the first long-lived tornado. Interactions with a developing thunderstorm disrupted the supercell’s updraft, leading to hail fallout and updraft weakening. The remnant circulation associated with the first strong tornado merged with the supercell’s updraft and became a rotation source for the second long-track tornado, which persisted for nearly 3 h. Eventually interactions with other thunderstorms weakened the supercell.

Environmental and Radar-Derived Predictors of Tornado Intensity within Ongoing Convective Storms

Analyses of Doppler radar data and environmental parameters for 300 tornado cases are used to propose an alternative framework for tornado intensity prediction during pretornadic stages of ongoing storms, conditional on tornadogenesis. This framework is founded on the robust relationship (R² = 0.69) between pretornadic mesocyclone width and the EF rating of the subsequent tornado. In contrast, the linear relationship between pretornadic mesocyclone intensity and EF scale is much weaker (R² = 0.29). Environmental information for each case was additionally used to explore relationships between environmental parameters and tornado intensity. Such relationships depend in part on how the tornado-intensity categories are distributed [i.e., nonsignificant (EF0–1) versus significant (EF2–5), or weak (EF0–1) versus strong (EF2–3) versus violent (EF4–5)]. Low-level shear parameters discriminate the environments of significant tornadoes from nonsignificant tornadoes, but not the environments of violent tornadoes from strong tornadoes. The converse is true for thermodynamic parameters. Operational implementation of this framework for thepurposes of impact-based warnings will require real-time, automated quantification of mesocyclone width in addition to intensity and other attributes. The information gained from the pretornadic analysis demonstrated in this study would allow an operational forecaster to be aware of—and communicate—information about potential tornado intensity in warning text to the public before a tornado develops to better protect life and property. Currently, these relationships are being utilized in machine learning models for binary prediction of non-significant versus significant tornado intensity where skill is being demonstrated.

A Devastating Tornado in Moravia in 2021

This article deals primarily with the protection of the population in the Czech Republic, as it is a very important security area of the highest priority. The population protection system in the Czech Republic is briefly explained, which has been fully under the responsibility of the Ministry of the Interior of the Czech Republic since 2001, but a number of other central administrative authorities (ministries, special institutes and institutions, research institutes) are also involved in its implementation. In addition to legal standards and implementation decrees, the Czech Republic security strategy and the concept of population protection are also presented. A separate part is devoted to the last valid Population Protection Concept from 2021, and it is emphasized here that the concept places great importance on the population’s preparedness for dealing with extraordinary events and crisis situations. The Model Action Activity of the Integrated Rescue System in the Czech Republic is presented in the next section. Although many model action activities have already been published in the Czech Republic, unfortunately such a safety management plan has not yet been published for the extremely hazardous natural disaster „Tornado“. This subsection briefly explains how the Intergreted Rescue system intervenes in emergency and crisis situations. A separate part is devoted to the hazardous and strong tornado in Moravia in 2021, where a total of 6 people lost their lives and another 200 were injured, many were hospitalized. Material damage after the tornado’s rampage climbed to dizzying heights. The wave of solidarity with the affected population has reached unprecedented proportions not only in the Czech Republic. At the end of the contribution, the authors present their own proposal for the future, how to continue working in this area, from the preparation and convening of a national security conference in the Czech Republic to the preparation and publication of the Model Action Activity of the Integrated Rescue System in the Czech Republic in the disaster event of a tornado.

Integrated damage, visual, remote sensing, and environmental analysis of a strong tornado in southern Brazil

On 20 April 2015 a strong tornado struck the city of Xanxerê located in western Santa Catarina (SC) state, in southern Brazil. The tornado destroyed several buildings, causing almost 100 injuries, four fatalities, and R$ 104 million in damage (approximately USD$ 34.6 million according to 2015 dollar quotation), making it one of the most damaging tornadoes in Brazil's history. This study provides an integrated damage, visual, remote sensing, and environmental analysis of the tornado event. Medium-resolution satellite imagery and in situ photographs of the damage show that the tornado caused high-end F2 damage on the Fujita scale across a 4.9-km-long path in the northern portion of Xanxerê. Videos of the tornado and its parent storm reveal the existence of a low-level mesocyclone and rear-flank downdraft, indicating that the storm was a supercell. Horizontal vortices, which are occasionally observed in strong tornadoes but rarely documented in Brazilian tornadoes, were also observed in the videos. The supercell developed in a warm and moist air mass characterized by moderate buoyancy and weak mid-level lapse rates. The mid- and upper-tropospheric forcing for synoptic-scale ascent was weak but the prevailing zonal flow was moderately strong, providing sufficient deep-layer shear for supercell development. A key component of the synoptic-scale environment was the presence of a northerly low-level jet stream that promoted warm moist advection into western SC in addition to increasing the low-level vertical wind shear in the region. On the mesoscale, the presence of a broad cloud shield from a decaying mesoscale convective system (MCS) preceding the supercell formation hampered daytime radiative heating over western SC resulting in low dewpoint depression and, thus, lower lifting condensation levels around Xanxerê. Remote sensing and surface data suggest that the MCS-induced outflow boundary may have been responsible for the initiation of the supercell. The complex subtropical environment of the Xanxerê tornado differs in many aspects from well-documented North American tornadic environments and highlights the need for more studies addressing distinctions between the atmospheric conditions that are conducive to tornadic activity in the two continents.

A Numerical Simulation of the “1907” Kaiyuan Tornado Weather Process in Liaoning, Northeast China

From 17:00 to 18:00 local standard time (LST) on 3 July 2019, a rare strong tornado occurred in Kaiyuan, Liaoning Province, northeast China. NCEP/NCAR 0.25° × 0.25° reanalysis data and WRF4.0 numerical prediction models were used to carry out the numerical simulation. Double nesting was adopted, and the horizontal grid distance was 9 km by 3 km. Based on the observation data of China meteorological observation stations, surface and upper charts, Doppler radar data, Himawari(HMW)-8 satellite images and numerical simulation results, the mesoscale structure and mechanism of the tornado were studied. The results show that: (1) At the northwest edge of the subtropical high, and the northeast cold vortex located in Northeast China, when the transverse trough moves southward, cold air is supplied continuously. Under the joint influence of the surface northeast cyclone, these are the main synoptic features of the tornado; (2) The northeast cold vortex cloud system was located at the junction of Heilongjiang and Jilin Provinces, and a squall line cloud system is formed. The tornado occurred at the tail of the squall line, and the strongest echo reached 65 dBZ. A mesocyclone, a 20 km northwest–southeast convergence belt, V-shaped gap, echo overhang structure and tornado vortex feature (TVS) were detected by the Doppler radar; (3) Before the tornado occurred, dry and cold air intruded from the northwest of the cold vortex, and a water vapor convergence zone appeared south of the squall line. The water vapor saturation zone with 80% relative humidity in northeast China was concentrated at 700 hPa, and the 20% dry column dropped down to 500 hPa between 115 and 124° E from the west. On the 850 hPa physical fields, there was a −20 × 10−5 s−1 convergence zone, and a 16 × 10−5 s−1 divergence belt appeared south and north of the squall line. A negative vorticity belt and a positive vorticity belt appeared south and north of the squall line, respectively. Kaiyuan is located at the smallest vertical shear, which is the junction place of three large vertical shear belts; (4) After 10:00 LST, the westerly wind 20 (10) m·s−1 dropped to 400 (800) hPa between 126 and 127° E. The northerly gale at 300 hPa north of 45° N moved southward. The rising center of the low level at 17:00 LST at approximately 45° N moved southward, and a sinking center appeared above it; (5) Several pairs of positive and negative vorticity columns formed between the lower troposphere and the place where the tornado occurred. There was convective instability at the lower level. CAPE increased, 0–3 km vertical wind shear increased, and LCL decreased remarkably during the afternoon.

Examining Terrain Effects on an Upstate New York Tornado Event Utilizing a High-Resolution Model Simulation

AbstractThe complex terrain at the intersection of the Mohawk and Hudson valleys of New York has an impact on the development and evolution of severe convection in the region. Specifically, previous research has concluded that terrain-channeled flow in the Mohawk and Hudson valleys likely contributes to increased low-level wind shear and instability in the valleys during severe weather events such as the historic 31 May 1998 event that produced a strong (F3) tornado in Mechanicville, New York.The goal of this study is to further examine the impact of terrain channeling on severe convection by analyzing a high-resolution WRF model simulation of the 31 May 1998 event. Results from the simulation suggest that terrain-channeled flow resulted in the localized formation of an enhanced low-level moisture gradient, resembling a dryline, at the intersection of the Mohawk and Hudson valleys. East of this boundary, the environment was characterized by stronger low-level wind shear and greater low-level moisture and instability, increasing tornadogenesis potential. A simulated supercell intensified after crossing the boundary, as the larger instability and streamwise vorticity of the low-level inflow was ingested into the supercell updraft. These results suggest that terrain can have a key role in producing mesoscale inhomogeneities that impact the evolution of severe convection. Recognition of these terrain-induced boundaries may help in anticipating where the risk of severe weather may be locally enhanced.

The Environmental Pollution Following COVID 19

Over the last 30 years, the pollution of the environment has increased progressively with the growth of the economy worldwide. Polluting substances such as Co2, So2, Freon, etc., on one hand, and on the other hand, the clearing of forests increased the greenhouse effect and this led to a gradual increase of the temperature in the world. This has led to extreme phenomena around the globe: fires, floods, extremely strong tornadoes, even the displacement of seasons. There are, however, events that cause pollution to decrease. Such a phenomenon is COVID 19.

The Impact of Home Gardening amidst Climate Change

Today’s climate is unpredictable there are so many natural calamities which took place in our country which is the Philippines, two weeks ago because of the sudden changes of the weather in the Province of Zambales, the Philippines a strong tornado hits the town of Castillejos, Zambales which some of the electrical wirings were severely damaged because of the sudden change of the climate. The researcher is thinking of implementing a home gardening to each Municipality in our Province. By doing this it can help lessen the pollution in the air and it will help heal our Ozone Layer faster. The empirical evidence for the benefits of gardening and the advocate of the development and testing of socio-ecological models of community resilience through the impact of community gardens, especially in urban areas is highly effective(Okvat & Zautra, 2011). As lessening the air pollution will have a greater impact on our Ozone Layer no to deplete but it will heal the would faster. The present study revealed that local experiences in the face of climate change adaptation have merits that need special consideration(Anik & Khan, 2012). Also, the Researcher will implement this project in the Municipality of Subic, Zambales.

Analysis of Debris Signature Characteristics and Evolution in the 24 May 2016 Dodge City, Kansas, Tornadoes

AbstractOn 24 May 2016, a supercell that produced 13 tornadoes near Dodge City, Kansas, was documented by a rapid-scanning, X-band, polarimetric, Doppler radar (RaXPol). The anomalous nature of this storm, particularly the significant deviations in storm motion from the mean flow and number of tornadoes produced, is examined and discussed. RaXPol observed nine tornadoes with peak radar-derived intensities (ΔVmax) and durations ranging from weak (~60 m s−1) and short lived (<30 s) to intense (>150 m s−1) and long lived (>25 min). This case builds on previous studies of tornado debris signature (TDS) evolution with continuous near-surface sampling of multiple strong tornadoes. The TDS sizes increased as the tornadoes intensified but lacked direct correspondence to tornado intensity otherwise. The most significant growth of the TDS in both cases was linked to two substantial rear-flank-downdraft surges and subsequent debris ejections, resulting in growth of the TDSs to more than 3 times their original sizes. The TDS was also observed to continue its growth as the tornadoes decayed and lofted debris fell back to the surface. The TDS size and polarimetric composition were also found to correspond closely to the underlying surface cover, which resulted in reductions in ZDR in wheat fields and growth of the TDS in terraced dirt fields as a result of ground scouring. TDS growth with respect to tornado vortex tilt is also discussed.

Satellite-Based Study and Numerical Forecasting of Two Tornado Outbreaks in the Ural Region in June 2017

Strong tornadoes are common for the European part of Russia but happen rather rare east of the Urals. June 2017 became an exceptional month when two tornado outbreaks occurred in the Ural region of Russia, yielded $3 million damage, and resulted in 1 fatality and 14 injuries. In this study, we performed detailed analysis of these outbreaks with different data. Tornadoes and tornado-related environments were diagnosed with news and eyewitness reports, ground-based meteorological observations, sounding data, global numerical weather prediction (NWP) models data, synoptic charts, satellite images, and data of specially conducted aerial imaging. We also estimated the accuracy of short-term forecasting of outbreaks with the WRF-ARW mesoscale atmospheric model, which was run in convection-permitting mode. We determined the formation of 28 tornadoes during the first outbreak (3 June 2017) and 9 tornadoes during the second outbreak (18 June 2017). We estimated their intensity using three different approaches and confirmed that, based on the International Fujita scale (IF), one of the tornadoes had the IF4 intensity, being the first IF4 tornado in Russia in the 21st century and the first-ever IF4 tornado reported beyond the Ural Mountains. The synoptic-scale analysis revealed the similarity of two outbreaks, which both formed near the polar front in the warm part of deepening southern cyclones. Such synoptic conditions yield mostly weak tornadoes in European Russia; however, our analysis indicates that these conditions are likely favorable for strong tornadoes over the Ural region. Meso-scale analysis indicates that the environments were favorable for tornado formation in both cases, and most severe-weather indicators exceeded their critical values. Our analysis demonstrates that for the Ural region, like for other regions of the world, combined use of the global NWP model outputs indicating high values of severe-weather indices and the WRF model forecast outputs explicitly simulating tornadic storm formation could be used to predict the high probability of strong tornado formation. For both analyzed events, the availability of such tornado warning forecast could help local authorities to take early actions on population protection.

A numerical investigation of building damage during the 6 May 2012 Tsukuba tornado using hybrid meteorological model/engineering LES method

To validate applicability of the novel hybrid meteorological model/engineering LES method to damage estimation of actual tornado events, simulation is performed focusing on the severely damaged area of the strong tornado on May 6, 2012 in the city of Tsukuba with the realistic tornado structure reproduced in the meteorological model, the actual building distribution, and the topography. The flows over the disaster-affected low-rise residential area show an evident converging character at a height close to the rooftops. Intense strong wind bands are formed by the influence of the buildings. The simulated maximum wind gust is compared with the distribution of actual building damage. It reveals that the hybrid method can reasonably estimate distribution of the building damage over the target area in the tornado event. The track nevertheless exhibits building-scale perturbation that may be attributed to chaotic randomness of the tornado behavior on the complex rough surface. Using the simulated aerodynamic force, simplified case studies on the occurrence and process of damage to two individual buildings is also presented.

Reanalysing strong-convective wind damage paths using high-resolution aerial images

High-resolution aerial imagery may provide very detailed information about strong-convective wind events, which can be very useful to enhance and make more robust severe weather databases. Through an aerial analysis, unknown affected areas can be unveiled, large damaged zones or complex terrain events can be mapped, and in situ damage surveys can be completed. Comparing aerial orthophotographs or high-resolution satellite imagery taken before and after the event, damage to forest associated with EF1 + intensities rated with the Enhanced Fujita scale is easily observable. It is also possible to detect repaired parts on some types of roofs and buildings due to the occurrence of weak events and major damage on human-made structures in case of significant episodes. To illustrate the added value of using orthophotographs in forensic damage survey analysis, the 2 November 2008 strong-convective wind event in Catalonia (NE Iberian Peninsula) is revisited. Confirming previous studies, two different damage swaths, associated with the passage of two supercells during the early morning, are clearly identified in high-resolution aerial images. The additional information provided by orthophotograph analysis allowed extending the two damage paths and increasing the damage intensity of the event. It is concluded that both damage tracks are related to tornadoes, which are rated as an EF2 and an EF3, the second being the strongest tornado ever registered in Catalonia, one of the most tornado-prone regions of southern Europe.

Doppler Circulation as a Fairly Range-Insensitive Far-Field Tornado Detection and Precursor Parameter

AbstractFormulas are obtained for observed circulation around and contraction rate of a Doppler radar grid cell within a surface of constant launch angle. The cell values near unresolved axisymmetric vortices vary greatly with beam-to-flow angle. To obtain reliable standard measures of vortex strength we bilinearly interpolate data to points on circles of specified radii concentric with circulation centers and compute the Doppler circulations around and the areal contraction rates of these circles from the field of mean Doppler velocities. These parameters are proposed for detection of strong tornadoes and mesocyclonic winds. The circulation and mean convergence around the Union City, Oklahoma, tornado of 24 May 1973 are computed. After doubling to compensate for the unobserved wind component, the circulation (1.1 × 105 m2 s−1) agrees with a previous photogrammetric measurement. The mature tornado was embedded in a region, 6 km in diameter, of nearly uniform strong convergence (~5.5 × 10−3 s−1) without a simultaneous mesocyclone. A model of a convergent vortex inputted to a Doppler radar emulator reproduces these results. Moving the model vortex shows that for a WSR-88D with superresolution, the circulation is relatively insensitive to range and azimuth. WSR-88D data of the 31 May 2013 El Reno storm are also analyzed. The tornado formed in a two-celled mesocyclone with strong inflow 5 km away. In the next 8 min the circulation near the axis doubled and the areal contraction rate at 5 km increased by 50%. This signified a large probability of strong tornadoes embedded in powerful storm-scale winds.

Climatic changes and their role in emergence and re-emergence of diseases.

Global warming and the associated climate changes are predictable. They are enhanced by burning of fossil fuels and the emission of huge amounts of CO2 gas which resulted in greenhouse effect. It is expected that the average global temperature will increase with 2–5 °C in the next decades. As a result, the earth will exhibit marked climatic changes characterized by extremer weather events in the coming decades, such as the increase in temperature, rainfall, summertime, droughts, more frequent and stronger tornadoes and hurricanes. Epidemiological disease cycle includes host, pathogen and in certain cases intermediate host/vector. A complex mixture of various environmental conditions (e.g. temperature and humidity) determines the suitable habitat/ecological niche for every vector host. The availability of suitable vectors is a precondition for the emergence of vector-borne pathogens. Climate changes and global warming will have catastrophic effects on human, animal and environmental ecosystems. Pathogens, especially neglected tropical disease agents, are expected to emerge and re-emerge in several countries including Europe and North America. The lives of millions of people especially in developing countries will be at risk in direct and indirect ways. In the present review, the role of climate changes in the spread of infectious agents and their vectors is discussed. Examples of the major emerging viral, bacterial and parasitic diseases are also summarized.

The Influence of Tornado Activity, Impact, Memory, and Sentiment on Tornado Perception Accuracy among College Students

A survey consisting of open-ended and closed responses was administered at three universities in the eastern USA. The home counties of survey participants represented climatological tornado risks spanning from rarely impacted to frequently impacted. The first objective of this research was to classify climatological tornado risk for each county so that analyses of tornado perception accuracy could be evaluated. Perception accuracy was defined as the difference between what each participant perceived minus what actually happened. A manual classification scheme was created that uses the Storm Prediction Center’s Convective Outlook framework as county climatological risk categories. Participants from high-risk counties statistically significantly overestimated the numbers of violent tornadoes compared to participants from every risk category but moderate. Furthermore, participants from high-risk counties had significantly greater tornado impacts, thus validating the classification of high-risk. Participants from high, moderate, and slight-risk counties significantly overestimated the number of strong tornadoes compared to participants from enhanced-risk counties. There appeared to be no relationships between tornado memory and tornado sentiment with tornado perception accuracy. Possible explanations for the overestimation of the numbers of violent tornadoes in high-risk counties are discussed.

The College Park, Maryland, Tornado of 24 September 2001

The 24 September 2001 College Park, Maryland, tornado was a long-track and strong tornado that passed within a close range of two Doppler radars. It was the third in a series of three tornadoes associated with a supercell storm that developed in Stafford County, Virginia, and initiated 3–4 km southwest of College Park and dissipated near Columbia, Howard County. The supercell tracked approximately 120 km and lasted for about 126 min. This study presents a synoptic and mesoscale overview of favorable conditions and forcing mechanisms that resulted in the severe convective outbreak associated with the College Park tornado. The results show many critical elements of the tornadic event, including a negative-tilted upper-level trough over the Ohio Valley, a jet stream with moderate vertical shear, a low-level warm, moist tongue of the air associated with strong southerly flow over south-central Maryland and Virginia, and significantly increased convective available potential energy (CAPE) during the late afternoon hours. A possible role of the urban heat island effects from Washington, DC, in increasing CAPE for the development of the supercell is discussed. Satellite imagery reveals the banded convective morphology with high cloud tops associated with the supercell that produced the College Park tornado. Operational WSR-88D data exhibit a high reflectivity “debris ball” or tornadic debris signature (TDS) within the hook echo, the evolution of the parent storm from a supercell structure to a bow echo, and a tornado cyclone signature (TCS). Many of the mesoscale features could be captured by contemporary numerical model analyses. This study concludes with a discussion of the effectiveness of the coordinated use of satellite and radar observations in the operational environment of nowcasting severe convection.