Climatology Of Tornadoes Research Articles

Monte Carlo modeling of tornado hazard to wind turbines in Germany.

Using a Monte Carlo hazard modeling approach, this study assesses the damage and losses to wind turbines caused by tornadoes over Germany. The model combines observed climatology of tornadoes, exposure map of wind turbines and their capacities, vulnerability curve (first developed in this study), and costs of wind turbines to estimate the likelihood of financial losses of different magnitudes. The losses are presented in terms of aggregated and highest annual losses as a function of the return period. Deterministic modeling of the vulnerability function produced larger variability of the most severe losses (rare, but high-intensity events) compared to the pseudorandom sampling of the damage from the vulnerability curve. Doubling the number of current wind turbines results in smaller expected losses than installing fewer but more powerful units (repowerment). Tornadoes are most frequent in the summer months when the capacity factors of wind farms are the lowest and the electricity consumption is also lower than in the winter months. By repeatedly placing a tornado track of a fixed size over the same wind farm, we further investigated the sensitivity of our model to different parameters. The probability of tornadoes of different intensities hitting a wind turbine over Germany is also calculated.

Climatology of Significant Tornadoes within China and Comparison of Tornado Environments between the United States and China

Abstract A climatology of significant tornadoes [SIGTOR, tornadoes rated (E)F2+ on the (enhanced) Fujita scale] within China and in three subregions, including northern, central, and southern China, is first presented for the period 1980–2016. In total, 129 SIGTOR are recorded in China, with an average of 3.5 per year. The tornado inflow environments of the south-central and southeast regions of the United States (USC and USSE) are compared with those of China and its subregions based on sounding-derived parameters including shear, storm-relative helicity, convective available potential energy (CAPE), lifting condensation level (LCL), etc. Soundings are extracted from the ERA5 reanalysis dataset. The results confirm that the SIGTOR in USSE are characterized by high shear, low CAPE, and low LCL whereas those in USC are characterized by moderate-to-high shear, high CAPE, and high LCL. The thermodynamic conditions of tornadic cases are favorable for China, with moderate-to-high CAPE and low-to-moderate LCL, but their kinematic conditions are much less favorable than in the United States, a fact that is believed to be primarily responsible for the lower tornado frequency and intensity in China. The high CAPE in China is due mostly to high humidity. For three subregions in China, the central China cases account for 60% of total samples, and its environmental features are similar to those of China. The average shear with northern China cases is stronger than that with the other two subregions, and the midlayer is relatively dry. The southern China SIGTOR have the most conducive humidity conditions, but the CAPE and shear there are the lowest. The northern, central, and southern China environments can be considered as representative of midlatitude, subtropical, and tropical regions. Significance Statement We document the climatological characteristics of significant tornadoes (SIGTOR) within China and compare the inflow environments of SIGTOR in China and its subregions with those in the U.S. central and southeastern regions. The availability of hourly high-resolution ERA5 data makes the environments based on extracted proximity soundings much more accurate than possible with earlier reanalyses. The environmental characteristics show systematic differences in the tornado environments of different regions of China and the United States and suggest different roles played by thermodynamic and kinematic conditions for tornado formation. Overall, the environmental differences are consistent with the resulting frequency and intensities of SIGTOR. The findings are helpful toward improving tornado forecasting and warning or even understanding of potential impacts of climate change on SIGTOR, especially in China, where such studies are rarer.

Climatology of Long-Track Tornadoes

A 40-year climatology (1979–2018) is presented for long-track tornadoes in the United States using the Storm Prediction Center tornado database. Path length (PL) stratification thresholds are defined using characteristics of supercell storm evolution, and are categorized as: all (ALL), PL >0 mi or 0 km; short (S), PL <30 mi or 48.3 km; long (L), [30, 60) mi or [48.3, 96.6) km; very long (V), [60, 90) mi or [96.6, 144.8) km; extremely long (X), PL ≥90 mi or 144.8 km; and long-track sum (LVX), PL ≥30 mi or 48.3 km. Results show LVX tornadoes: a) made up <1% of all tornadoes; b) occurred east of the Rocky Mountains; c) were generally wider; d) caused disproportionate numbers of deaths and injuries; e) typically had damage ratings ≥F/EF2 (peak F/EF3); f) occurred more often with more deaths and injuries in the Southeast than in the Midwest or Great Plains; g) had larger area scale and Destruction Potential Index; h) occurred mostly in April and May versus May and June for S tornadoes; i) occurred primarily from midafternoon to early evening; j) had a peak formation hour at 1600 local solar time (also true for ALL S, V and X), though L tornadoes had a peak and secondary peak at 1800 and 1500, respectively; k) were less common during nighttime than S tornadoes; l) were more frequent during nighttime in the Southeast than nighttime in the Midwest or Great Plains; and m) occurred more often with tornado outbreaks.

Climatology and Formation Environments of Severe Convective Windstorms and Tornadoes in the Perm Region (Russia) in 1984–2020

Severe convective windstorms and tornadoes regularly hit the territory of Russia causing substantial damage and fatalities. An analysis of the climatology and formation environments of these events is essential for risk assessments, forecast improvements and identifying of links with the observed climate change. In this paper, we present an analysis of severe convective windstorms, i.e., squalls and tornadoes reported between 1984 and 2020 in the Perm region (northeast of European Russia), where a local maximum in the frequency of such events was previously found. The analysed database consists of 165 events and includes 100 squalls (convective windstorms), 59 tornadoes, and six cases with both tornadoes and squalls. We used various information to compile the database including weather station reports, damage surveys, media reports, previously presented databases, and satellite images for windthrow. We found that the satellite images of damaged forests are the main data source on tornadoes, but their role is substantially lower for windstorm events due to the larger spatial and temporal scale of such events. Synoptic-scale environments and associated values of convective indices were determined for each event with a known date and time. Similarities and differences for the formation conditions of tornadoes and windstorms were revealed. Both squalls and tornadoes occur mostly on rapidly moving cold fronts or on waving quasi-stationary fronts, associated with low-pressure systems. Analyses of 72-h air parcel backward trajectories shows that the Caspian and Aral Seas are important sources of near-surface moisture for the formation of both squalls and tornadoes. Most of these events are formed within high CAPE and high shear environments, but tornadic storms are generally characterised by a higher wind shear and helicity. We also differentiated convective storms that caused forest damage and those did not. We found the composite parameter WMAXSHEAR is the best discriminator between these two groups. In general, storm events causing windthrow mainly occur under conditions more favourable for deep well-organised convection. Thus, forest damage can be considered as an indicator of the storm severity in the Perm region and in adjacent regions with forest-covered area exceeding 50%.

Severe Convective Storms across Europe and the United States. Part I: Climatology of Lightning, Large Hail, Severe Wind, and Tornadoes

AbstractAs lightning-detection records lengthen and the efficiency of severe weather reporting increases, more accurate climatologies of convective hazards can be constructed. In this study we aggregate flashes from the National Lightning Detection Network (NLDN) and Arrival Time Difference long-range lightning detection network (ATDnet) with severe weather reports from the European Severe Weather Database (ESWD) and Storm Prediction Center (SPC) Storm Data on a common grid of 0.25° and 1-h steps. Each year approximately 75–200 thunderstorm hours occur over the southwestern, central, and eastern United States, with a peak over Florida (200–250 h). The activity over the majority of Europe ranges from 15 to 100 h, with peaks over Italy and mountains (Pyrenees, Alps, Carpathians, Dinaric Alps; 100–150 h). The highest convective activity over continental Europe occurs during summer and over the Mediterranean during autumn. The United States peak for tornadoes and large hail reports is in spring, preceding the maximum of lightning and severe wind reports by 1–2 months. Convective hazards occur typically in the late afternoon, with the exception of the Midwest and Great Plains, where mesoscale convective systems shift the peak lightning threat to the night. The severe wind threat is delayed by 1–2 h compared to hail and tornadoes. The fraction of nocturnal lightning over land ranges from 15% to 30% with the lowest values observed over Florida and mountains (~10%). Wintertime lightning shares the highest fraction of severe weather. Compared to Europe, extreme events are considerably more frequent over the United States, with maximum activity over the Great Plains. However, the threat over Europe should not be underestimated, as severe weather outbreaks with damaging winds, very large hail, and significant tornadoes occasionally occur over densely populated areas.

The Climatology of Significant Tornadoes in the Czech Republic

In the Czech Republic, tornadoes may reach an intensity of F2 and F3 on the Fujita scale, causing “considerable” to “severe” damage. Documentary evidence is sufficient to allow the creation of a chronology of such events, from the earliest recorded occurrence in 1119 CE (Common Era) to 2019, including a total of 108 proven or probable significant tornadoes on 90 separate days. Since only 11 significant tornadoes were documented before 1800, this basic analysis centers around the 1811–2019 period, during which 97 tornadoes were recorded. Their frequency of occurrence was at its highest in the 1921–1930, 1931–1940, and 2001–2010 decades. In terms of annual variations, they took place most frequently in July, June, and August (in order of frequency), while daily variation favored the afternoon and early evening hours. Conservative estimates of human casualties mention 8 fatalities and over 95 people injured. The most frequent types of damage were related to buildings, individual trees, and forests. Tornadoes of F2–F3 intensity were particularly associated with synoptic types characterized by airflow from the western quadrant together with troughs of low pressure extending or advancing over central Europe. Based on parameters calculated from the ERA-5 re-analysis for the period of 1979–2018, most of these tornadoes occurred over a wide range of Convective Available Potential Energy (CAPE) values and moderate-to-strong vertical wind shear. The discussion herein also addresses uncertainties in tornado selection from documentary data, the broader context of Czech significant tornadoes, and the environmental conditions surrounding their origins.

Climatology of tropical cyclone tornadoes in China from 2006 to 2018

We surveyed the occurrence of tropical cyclone (TC) tornadoes in China from 2006 to 2018. There were 64 cataloged TC tornadoes, with an average of five per year. About one-third of the landfalling TCs in China were tornadic. Consistent with previous studies, TC tornadoes preferentially formed in the afternoon shortly before and within about 36 h after landfall of the TCs. These tornadoes mainly occurred in coastal areas with relatively flat terrains. The maximum number of TC tornadoes occurred in Jiangsu and Guangdong provinces. Most of the TC tornadoes were spawned within 500 km of the TC center. Two notable characteristics were found: (1) TC tornadoes in China mainly occurred in the northeast quadrant (Earth-relative coordinates) rather than the right-front quadrant (TC motion-relative coordinates) of the parent TC circulation; and (2) most tornadoes were produced by TCs with a relatively weak intensity (tropical depressions/storms), in contrast with the United States where most tornadoes are associated with stronger TCs. Further analyses showed that TC tornadoes in China tend to be spawned in an environment with large low-level storm relative helicity and large convective available potential energy taking entrainment effects into account. TC tornadoes were particularly active in 2018, with 24 reported tornadoes accounting for 37.5% of the total surveyed samples. The first recorded tornado outbreak in the modern history of China occurred in the envelope of TC Yagi (2018), in which 11 tornadoes were reported in association with significant midlevel intrusions of dry air and the interaction of Yagi with an approaching midlatitude midlevel trough.

Using the standard deviational ellipse to document changes to the spatial dispersion of seasonal tornado activity in the United States

Recent studies have documented possible ongoing changes to the climatology of tornadoes in the United States. Observed changes include increasing tornado counts in the Southeast and Midwest Regions, decreasing tornado counts in the Great Plains, and increased clustering of tornadoes on fewer days of the year. This study illustrates that the spatial dispersion of tornadoes in the United States is also changing. The dispersion of tornadoes decreased between 1954 and 2017, most notably in spring, summer, and fall. Furthermore, tornadoes tended to be less spatially dispersed in seasons with more tornadoes and with multiple days on which 20 or more tornadoes occur. This suggests that the increased occurrence of tornado outbreaks is contributing to the decrease in dispersion.

A review and analysis of possible changes to the climatology of tornadoes in the United States

This review and analysis illustrates that the spatial distribution and temporal clustering of tornadoes in the United States are changing. Tornado activity is increasing throughout the Southeast and in the southern portion of the Midwest and is decreasing throughout the southern and northwestern portions of the Great Plains and in the northern Midwest. This eastward shift is seen in tornado density maps, regional and gridded trends, and in an eastward shift of the mean center of tornadoes at the annual scale and in summer. The mean centers of tornado activity in other seasons are rather insensitive to these changes. Tornadoes are also clustering on fewer days in the year, and days with few tornadoes are becoming less common whereas days with many tornadoes are becoming more common. These concurrent and opposing trends are subsequently altering the frequency distribution of tornado days. The seasonality of these big tornado days also appears to be changing, as their increase in frequency is greatest in the fall and winter. Lastly, the increasing frequency of these big tornado days, which are most common in the Southeast and southern Midwest, contributes to the documented eastward shift in tornado activity.

A satellite-derived climatology of unreported tornadoes in forested regions of northeast Europe

This study presents a novel method of tornado track identification in forested regions in Europe based on remote sensing data. The method enables an objective estimate (i.e. independent of population density and observational networks) of tornado climatology in forested regions. The method is based on the identification of narrow and elongated areas as forest disturbances obtained using Landsat satellite images and Landsat-based Global Forest Change (GFC) data. These areas were subsequently verified with high-resolution satellite images for verification of a tornadic cause of forest damage. Landsat and MODIS satellite images, weather station observations and reanalysis data were additionally involved in order to determine tornado dates. A minimum F-scale tornado intensity was estimated by a Weibull distribution model using information on tornado path lengths and widths. The method is applied to the forested regions of northeast Europe, where 110 tornado tracks were identified between the 2000 and 2014years, 105 of which were previously unreported and discovered for the first time. For some regions, tornado density estimates using the new method is 2–3 times higher than other previously published estimates. The largest number of tornadoes occurred in 2009, and June is the most favourable month for tornado formation (including strong tornadoes and tornado outbreaks). Most identified tornadoes have path length <10km with maximum and mean widths of approximately 200–300m and 100–200m, respectively. A few tornadoes with long and wide paths were found; four of them likely had F3 minimal intensity.

Annual and seasonal tornado trends in the contiguous United States and its regions

ABSTRACTPrevious studies provide evidence of possible changes to the climatology of tornadoes in the United States. These include a decrease in the number of tornado days per year, but an increase in the number of days per year with a large number of tornadoes; an increase in the mean number of tornadoes per tornado day; a spatial shift in tornado activity, generally towards the Southeast United States. Most of these studies, however, tend to examine trends at the annual (or spring) and contiguous United States scales. Using tornado data over the period 1954–2016, this study analyses various tornado metrics to determine whether trends are consistent throughout the year and across the United States. Trends are assessed with the Mann–Kendall test and their slopes with the Theil–Sen estimator. The annual analyses indicate that the number of tornadoes per year declined in the West, North Great Plains, South Great Plains, and Midwest regions, but increased in the Southeast. The decreasing/increasing tendencies in the South Great Plains/Southeast led to a reversal of the most active region – the South Great Plains had the greatest median tornado frequency early in the study period whereas the Southeast had the greatest in the middle and late periods. Annual analyses also indicate that the previously reported decline in the number of tornado days per year and the increase in the mean number of tornadoes per tornado day per year are generally present across the United States. Seasonal analyses suggest that the proportion of tornadoes occurring in the contiguous United States in summer is decreasing whereas the proportion occurring in fall is increasing. This is especially apparent in the Southeast.

Synoptic climatology of tornadoes in the northeast USA

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 72:19-27 (2017) - DOI: https://doi.org/10.3354/cr01444 Synoptic climatology of tornadoes in the northeast USA Andrew E. Benjamin*, Daniel J. Leathers Department of Geography, University of Delaware, Newark, Delaware, USA *Corresponding author: abenj@udel.edu ABSTRACT: A tornado climatology is constructed for the northeast USA (hereafter, Northeast) for the period 1950-2014. This region is highly susceptible to tornado damage as it includes dense populations in several major cities. This study provides a general climatology of tornadoes in the Northeast by exploring the spatial and temporal characteristics of the region’s tornadoes. Additionally, 86 days defined as active tornado days (5+ reports per day) are used to examine the synoptic patterns associated with Northeast tornado environments. Tornadoes in the Northeast were most frequently reported in the late spring and summer months (May to July), during the late afternoon and early evening hours, between 18:00 and 23:00 h UTC (14:00 and 19:00 h local sidereal time [LST]). Tornadoes were reported most frequently along the densely populated Interstate 95 corridor, which connects several of the largest cities in the USA. Approximately 79% of all Northeast tornadoes were given an Enhanced Fujita Scale intensity rating of ≤1. Composite synoptic maps indicate that Northeast tornado outbreaks are commonly associated with a 500 hPa trough and a surface low pressure system over the Great Lakes. Differential positive vorticity advection and warm advection contribute quasi-geostrophic forcing, modifying thermodynamic profiles making them favorable for convection. These lifting mechanisms and associated instability (represented by high equivalent potential temperature and an unstable lifted index), along with sufficient lower tropospheric wind shear, provide the ingredients necessary for severe convection. KEY WORDS: Tornado · Climatology · Northeast USA · Severe weather Full text in pdf format PreviousNextCite this article as: Benjamin AE, Leathers DJ (2017) Synoptic climatology of tornadoes in the northeast USA. Clim Res 72:19-27. https://doi.org/10.3354/cr01444 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 72, No. 1. Online publication date: March 15, 2017 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2017 Inter-Research.

Climatology, Storm Morphologies, and Environments of Tornadoes in the British Isles: 1980–2012

Abstract A climatology is developed for tornadoes during 1980–2012 in the British Isles, defined in this article as England, Scotland, Wales, Northern Ireland, Republic of Ireland, Channel Islands, and the Isle of Man. The climatology includes parent storm type, interannual variability, annual and diurnal cycles, intensities, occurrence of outbreaks (defined as three or more tornadoes in the same day), geographic distribution, and environmental conditions derived from proximity soundings of tornadoes. Tornado reports are from the Tornado and Storm Research Organization (TORRO). Over the 33 years, there were a mean of 34.3 tornadoes and 19.5 tornado days (number of days in which at least one tornado occurred) annually. Tornadoes and tornado outbreaks were most commonly produced from linear storms, defined as radar signatures at least 75 km long and approximately 3 times as long as wide. Most (78%) tornadoes occurred in England. The probability of a tornado within 10 km of a point was highest in the south, southeast, and west of England. On average, there were 2.5 tornado outbreaks every year. Where intensity was known, 95% of tornadoes were classified as F0 or F1 with the remainder classified as F2. There were no tornadoes rated F3 or greater during this time period. Tornadoes occurred throughout the year with a maximum from May through October. Finally, tornadoes tended to occur in low-CAPE, high-shear environments. Tornadoes in the British Isles were difficult to predict using only sounding-derived parameters because there were no clear thresholds between null, tornadic, outbreak, and significant tornado cases.

Tornado Climatology of Poland

Abstract Very few studies on the occurrence of tornadoes in Poland have been performed and, therefore, their temporal and spatial variability have not been well understood. This article describes an updated climatology of tornadoes in Poland and the major problems related to the database. In this study, the results of an investigation of tornado occurrence in a 100-yr historical record (1899–1998) and a more recent 15-yr observational dataset (1999–2013) are presented. A total of 269 tornado cases derived from the European Severe Weather Database are used in the analysis. The cases are divided according to their strength on the F scale with weak tornadoes (unrated/F0/F1; 169 cases), significant tornadoes (F2/F3/F4; 66 cases), and waterspouts (34 cases). The tornado season extends from May to September (84% of all cases) with the seasonal peak for tornadoes occurring over land in July (23% of all land cases) and waterspouts in August (50% of all waterspouts). On average 8–14 tornadoes (including 2–3 waterspouts) with 2 strong tornadoes occur each year and 1 violent one occurs every 12–19 years. The maximum daily probability for weak and significant tornadoes occurs between 1500 and 1800 UTC while it occurs between 0900 and 1200 UTC for waterspouts. Tornadoes over land are most likely to occur in the south-central part of the country known as the “Polish Tornado Alley.” Cases of strong, and even violent, tornadoes that caused deaths indicate that the possibility of a large-fatality tornado in Poland cannot be ignored.

A Climatology of Tornadoes in Europe: Results from the European Severe Weather Database

Abstract A climatology of tornadoes (over land and water) is presented, based on the European Severe Weather Database (ESWD), which contains reports of 9529 tornadoes. With the exception of a few small countries, tornadoes have been reported from all regions of Europe. The highest density of tornado reports is in western and central Europe. ESWD tornado reports increased strongly from 1995 to 2006 as a result of increased data collection efforts, followed by a decrease that likely has a meteorological nature. There is strong underreporting in the Mediterranean region and eastern Europe. The daily cycle of tornadoes over land (sea) peaks between 1500 and 1600 (0900 and 1000) local time. The Mediterranean annual maximum is in autumn and winter, while regions farther north have a maximum in summer. In total, 822 tornado fatalities have been recorded in the ESWD, which include 10 tornadoes with more than 20 fatalities. The average annual number of tornado fatalities in Europe is estimated to be between 10 and 15. The F2 and F3 tornadoes are responsible for the majority of the fatalities.

Tornado Climatology of Turkey

Abstract A climatology of tornadoes in Turkey is presented using records from a wide variety of sources (e.g., the Turkish State Meteorological Service, European Severe Weather Database, newspaper archives, Internet searches, etc.). The climatology includes the annual, diurnal, geographical, and intensity distributions of both mesocyclonic and nonmesocyclonic tornadoes. From 1818 to 2013, 385 tornado cases were obtained. The tornadoes range from F0 to F3, with F1 being the most frequently reported or inferred intensity. Mesocyclonic tornadoes are most likely in May and June, and a secondary maximum in frequency is present in October and November. Nonmesocyclonic tornadoes (waterspouts) are most common in the winter along the (southern) Mediterranean coast and in the fall along the Black Sea (northern) coast. Tornadoes (both mesocyclonic and nonmesocyclonic) are most likely in the afternoon and early evening hours.

A climatology of tornadic activity over Greece based on historical records

In this study, the climatology of tornadoes, waterspouts and funnel clouds over Greece is presented for the period 1709–2012. The climatology consists of two datasets. An historical dataset (1709–1999) is based on newspaper archives, historical archives, published tornado literature, administrative records and reports of Hellenic National Meteorological Service (HNMS). A recent dataset (2000–2012) is based on newspaper articles, eyewitness reports to the media, HNMS's reports and an open-ended online tornado report database which has been developed and maintained by the Laboratory of Climatology & Atmospheric Environment of the University of Athens. Altogether, 612 Greek tornadic events compose the climatology: 171 tornadoes, 374 waterspouts and 67 funnel clouds. Tornadic events during the past 13 years (2000–2012) have occurred all over the Greek territory and there is frequent tornadic occurrence over north Crete and Corfu Island. Tornadoes are more frequent to occur over NW Peloponnesus followed by south parts of Corfu Island. However, waterspouts are more frequent over north Crete followed by Corfu Island. Tornadic monthly variability depicts a maximum during October, followed by September and November. October is the month with the highest tornado frequency, followed by November and July. The highest waterspout frequency month is September followed by October and December. Tornadoes most commonly develop during the warm time of the day, as more than 75% of all cases occur during 08:00–15:00 hours UTC with a maximum at 12:00 hours UTC. Waterspout frequency of occurrence has two maxima during the day, the first early in the morning (07:00–09:00 hours UTC) and the second after the noon time period (14:00–15:00 hours UTC). The dominant (27.7% of total cases) intensity of tornadoes in Greece is T4 based on the T-scale during the 300-year period (1709–2012); there have been at least 114 injured and 29 deaths.

Tornadoes in the New York Metropolitan Region: Climatology and Multiscale Analysis of Two Events

Abstract This paper describes the climatology of tornadoes around New York City (NYC) and Long Island (LI), New York, and the structural evolution of two tornadic events that affected NYC on 8 August 2007 and 16 September 2010. Nearly half (18 of 34 events from 1950 to 2010) of NYC–LI tornadoes developed between 0500 and 1300 EDT, and August is the peak tornado month as compared to July for most of the northeast United States. A spatial composite highlights the approaching midlevel trough, moderate most unstable convective available potential energy (MUCAPE), and frontogenesis along a low-level baroclinic zone. Shortly before the early morning tornadoes on 8 August 2007, a mesoscale convective system intensified in the lee of the Appalachians in a region of low-level frontogenesis and moderate MUCAPE (~1500 J kg−1). Warm advection at low levels and evaporative cooling within an elevated mixed layer (EML) ahead of the mesoscale convective system (MCS) helped steepen the low-level lapse rates. Meanwhile, a surface mesolow along a quasi-stationary frontal zone enhanced the warm advection and low-level shear. The late afternoon event on 16 September 2010 was characterized by a quasi-linear convective system (QLCS) that also featured an EML aloft, a surface mesolow just west of NYC, low-level frontogenesis, and a southerly low-level jet ahead of an approaching midlevel trough. The QLCS intensified approaching NYC and generated mesovortices as the QLCS bowed outward. These cases illustrate the benefit of high-density surface observations, terminal Doppler radars, and sounding profiles from commercial aircraft for nowcasting these events.

An Assessment of the Climatology of Florida Hurricane-Induced Tornadoes (HITs): Technology versus Meteorology

Abstract The placement of operational Doppler radar at National Weather Service offices in Florida in 1994 and 1995 has produced a distinct climatological discontinuity in archived records of hurricane-induced tornado (HIT) events. During the period of this study (1979–2010), Florida experienced 91 named tropical cyclones (omitting years 1994 and 1995) that produced a total of 300 HITs, as recorded in the NOAA Storm Data climatological publication. The 30 years of records examined for 1979–2010 consisted of 15 years as the pre-Doppler period (1979–93) and 15 years as the Doppler period (1996–2010) and produced an average of 1.92 HITs per tropical cyclone for the pre-Doppler period and 3.85 HITs per tropical cyclone for the Doppler period. Additionally, the HIT statistics were further compiled as the number of HITs per potential HIT day, which yielded values of 0.52 and 1.14, respectively, for the pre-Doppler and Doppler periods. Normalized statistics are based on the total accumulated number of potential HIT days for each period (96 for pre-Doppler and 219 for Doppler). Further, it has been determined that (a) no HITs were recorded in the pre-Doppler period for hurricanes greater than category-2 intensity, ostensibly because of the inability to separate hurricane wind damage from tornado damage, whereas (b) the Doppler period averaged 5.0 and 11.7 HITs per category-3 and category-4 storms, respectively. Finally, this study has clearly documented the magnitude (and effect) of Doppler technology on HITs reported in Florida Storm Data archives. The Doppler era is much more accurate, whereas the pre-Doppler era HIT occurrences are severely underestimated.

Utilizing synoptic climatological methods to assess the impacts of climate change on future tornado-favorable environments

Previous research into the impacts of climate change on severe mid-latitude weather has been limited by the spatial resolution of many important variables in global climate model output. By utilizing synoptic climatological methods, however, this research takes an entirely different approach. Using a six-step process that includes principal components analysis, cluster analysis, and discriminant function analysis, this study first creates a continental-scale map pattern classification at three levels of the atmosphere, from geopotential height and temperature fields. These patterns are then associated to historic F2 and stronger United States’ tornado days using binary logistic regression. Using output data from two GCMs, spanning five different model emissions scenarios, this synoptic climatology of tornadoes is then utilized in order to project the changes in the frequency and seasonality of tornadic environments due to a changing climate. Results indicate that F2 and stronger US tornado days will increase anywhere from 3.8 to 12.7% by the 2090s. The majority of this increase is likely to be manifested in the earlier part of the tornado season. In addition to the shift in seasonality, a broadening of the peak tornado season is also noticed under some scenarios. Geographically, portions of the Northern and Central Plains, the High Plains, the Lower Great Lakes, the Mid-Atlantic States, and the Southeast are projected to experience an increase in tornado days under some future scenarios. The Upper Great Lakes states and the Southern Plains are projected to experience a decrease in tornado days.