Severe Weather Research Papers - Academia.edu (original) (raw)

Forecasting severe convective weather remains one of the most challenging tasks facing operational meteorology today, especially in the mid-latitudes, where severe convective storms occur most frequently and with the greatest impact. The... more

On the evening of 5 April 2003, three supercells traversed northern portions of Dallas-Fort Worth, Texas causing nearly one billion dollars in hail damage, making the event the sixth costliest storm in Texas history to date (ICT 2003).... more

A protocol has been developed by the authors for assessing hail-impact damage to steep-sloped roofing systems. The protocol includes a definition of hail-caused damage to roofing, a detailed field inspection procedure, and a calculation... more

A protocol has been developed by the authors for assessing hail-impact damage to steep-sloped roofing systems. The protocol includes a definition of hail-caused damage to roofing, a detailed field inspection procedure, and a calculation method for determining repair or replacement of hail-damaged roofing based on economics.

Although the Fujita Scale has been in use for 30 years, the limitations of the scale are well known to its users. The primary limitations include a lack of damage indicators, no account of construction quality and variability, and no... more

Although the Fujita Scale has been in use for 30
years, the limitations of the scale are well known to its
users. The primary limitations include a lack of
damage indicators, no account of construction quality
and variability, and no definitive correlation between
damage and wind speed. These limitations have led
to inconsistent ratings of tornado damage and, in
some cases, overestimates of tornado wind speeds.
Thus, there is a need to revisit the concept of the
Fujita Scale and to improve and eliminate some of the
limitations. This paper summarizes our work in developing the EF (Enhanced Fujita) scale which involves determining the degrees of damage (DoDs) to various damage indicators (DIs).

On 22 May 2011, a large and destructive tornado traveled through southern portions of Joplin, MO, a city of approximately 50,000 people. According to the Storm Data, the tornado killed 158 people and injured more than 1000. Total property... more

On 22 May 2011, a large and destructive tornado traveled through southern portions of Joplin, MO, a city of approximately 50,000 people. According to the Storm Data, the tornado killed 158 people and injured more than 1000. Total property damage exceeded two billion dollars. This paper summarizes the results of our damage survey. The EF-scale was utilized on several building types.

Severe convective storms occasionally result in loss of life and property in Turkey, a country not known for its severe convective weather. However, relatively little is known about the characteristics of Turkish severe weather... more

Severe convective storms occasionally result in loss of life and property in Turkey, a country not known for its severe convective weather. However, relatively little is known about the characteristics of Turkish severe weather environments. This paper documents these characteristics using European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data on tornado and severe hail days in Turkey from 1979 to 2013. Severe storm environments are characterized by larger convective available potential energy (CAPE) in Turkey compared to the rest of Europe, but the CAPE values are less than those in typical U.S. severe storm environments. Severe hail is associated with large CAPE and vertical wind shear. Nonmesocyclonic tornadoes are associated with less CAPE compared with the other forms of severe weather. Deep-layer vertical wind shear is slightly weaker in Turkish supercell environments than in U.S. supercell environments, and Turkish tornadic supercell environments are chara...

Easterly waves (EWs) are prominent features of the intertropical convergence zone (ITCZ), found in both the Atlantic and Pacific during the Northern Hemisphere summer and fall, where they commonly serve as precursors to hurricanes over... more

Easterly waves (EWs) are prominent features of the intertropical convergence zone (ITCZ), found in both the Atlantic and Pacific during the Northern Hemisphere summer and fall, where they commonly serve as precursors to hurricanes over both basins. A large proportion of Atlantic EWs are known to form over Africa, but the origin of EWs over the Caribbean and east Pacific in particular has not been established in detail. In this study reanalyses are used to examine the coherence of the large-scale wave signatures and to obtain track statistics and energy conversion terms for EWs across this region. Regression analysis demonstrates that some EW kinematic structures readily propagate between the Atlantic and east Pacific, with the highest correlations observed across Costa Rica and Panama. Track statistics are consistent with this analysis and suggest that some individual waves are maintained as they pass from the Atlantic into the east Pacific, whereas others are generated locally in the Caribbean and east Pacific. Vortex anomalies associated with the waves are observed on the leeward side of the Sierra Madre, propagating northwestward along the coast, consistent with previous modeling studies of the interactions between zonal flow and EWs with model topography similar to the Sierra Madre. An energetics analysis additionally indicates that the Caribbean low-level jet and its extension into the east Pacific-known as the Papagayo jet-are a source of energy for EWs in the region. Two case studies support these statistics, as well as demonstrate the modulation of EW track and storm development location by the MJO.

On average 1-2 tropical cyclones form over the Arabian Sea each year, and few of these storms are intense enough to be classified as very severe or super cyclonic storms. As such, few studies have explicitly identified the seasonal to... more

On average 1-2 tropical cyclones form over the Arabian Sea each year, and few of these storms are intense enough to be classified as very severe or super cyclonic storms. As such, few studies have explicitly identified the seasonal to interannual changes in environmental conditions that are associated with Arabian Sea tropical cyclogenesis. However, over the last 30 yr several intense Arabian storms did form and make landfall, with large impacts, which motivates this new study of the basin. The conclusions of earlier studies are visited by utilizing modern observational and reanalysis data to identify the large-scale features associated with Arabian tropical cyclone variability on seasonal time scales. Then year-to-year changes in environmental conditions that are related to interannual variability in Arabian storms during the pre-and postmonsoon periods are elucidated. The analysis of the relationship between large-scale environmental variables and seasonal storm frequency supports conclusions from work completed more than 40 yr prior. Investigation of the year-to-year changes in premonsoon storm frequency suggests that May (June) storms are associated with an early (late) onset of the southwest monsoon. The findings also demonstrate that November cyclones (the month when the majority of postmonsoon cyclogenesis occurs) primarily form during periods when the Bay of Bengal experiences a broad region of high sea level pressure, implying that November storms form in either the Arabian Sea or the Bay of Bengal but not in both during the same year. Finally, the analysis of changes in a genesis potential index suggests that long-term variability in the potential for a storm to form is dictated by changes in midlevel moisture.

Vertically Integrated Moisture Flux Convergence (VIMFC) alone and in combination with the lifted stability index of the most unstable layer (SMUL) is evaluated as a thunderstorm predictor. By using six-hourly standard pressure weather... more

Vertically Integrated Moisture Flux Convergence (VIMFC) alone and in combination with the lifted stability index of the most unstable layer (SMUL) is evaluated as a thunderstorm predictor. By using six-hourly standard pressure weather analysis data from the European Centre for Medium-range Weather Forecasts (ECMWF) during 30 days in the summers of 1992 and 1994 containing several severe weather events along with quiescent events in northwestern Europe 17,206 events are obtained. The location and time of a lightning discharge are obtained from the Arrival Time Difference (ATD) sferics lightning location system from the UK Meteorological Office. Using the Heidke Skill Score (HEIDKE) to determine the best threshold we conclude that VIMFC alone, does not perform well as a dichotomous thunderstorm predictor compared to the stability index. However, the Thundery Case Probability (TCP) tested as function of VIMFC results in a high correlation with thunderstorms. By combining SMUL and VIMFC the surplus value as a thunderstorm predictor of VIMFC was established. TCP percentages up to 95% were found in an unstable environment with high positive values of VIMFC. In a marginally unstable environment with a high positive VIMFC the thunderstorm probability is higher than in a very unstable environment with no or negative VIMFC. These results are illustrated with a study of the case of the disastrous flash flood at Vaison-La-Romaine (southeastern France) on September 22, 1992. Although latent instability was present in a large area surrounding Vaison-La-Romaine, nearly all and especially the most severe thunderstorm activity occurred within the smaller area with positive VIMFC and latent instability.

On May 22, 2011, a large and violent tornado struck southern portions of Joplin, MO. The tornado killed 158 people and injured more than 1000 people. The tornado was rated EF-5 on the Enhanced Fujita Scale, with maximum winds exceeding 89... more

On May 22, 2011, a large and violent tornado struck southern portions of Joplin, MO. The tornado killed 158 people and injured more than 1000 people. The tornado was rated EF-5 on the Enhanced Fujita Scale, with maximum winds exceeding 89 ms-1 (200 mph). During the week following the tornado, the author conducted aerial and ground surveys of the damage. Surveying the damage was a challenge due to the large numbers of damaged or destroyed buildings (about 8,500 structures) as well as the rapid clean-up that was ongoing. Certain buildings were being demolished with heavy equipment within days after the tornado. Therefore, the author decided to select a sample of 14 buildings constructed with concrete masonry unit (CMU) walls.

During the evening of 27 April 2014, an EF4 tornado struck the communities of Mayflower and Vilonia, Arkansas. The tornado traveled 66 km, passing just northwest of the Little Rock Metropolitan area, and had a maximum path width of about... more

During the evening of 27 April 2014, an EF4 tornado struck the communities of Mayflower and Vilonia, Arkansas. The tornado traveled 66 km, passing just northwest of the Little Rock Metropolitan area, and had a maximum path width of about 1200 m. During its 56 minute lifespan, the tornado killed 16 people, including one person who sought refuge in an above ground storm shelter. The fatality occurred when a hard object struck the storm shelter door causing it to deform excessively into the shelter. This was the first known fatality in an above ground storm shelter.

There has been a dearth of systematic comparative studies of environmental and natural events during the Early and High Middle Ages. Using new analytic concepts and methods, this study examines multiple and highly diverse sources in... more

There has been a dearth of systematic comparative studies of environmental and natural events during the Early and High Middle Ages. Using new analytic concepts and methods, this study examines multiple and highly diverse sources in relation to extreme natural events. It represents the first precise study of the reliability of contemporary perception concerning such events, and also considers their instrumentalization.
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Die Umwelt wird zunehmend als vierte Grundkategorie der Geschichtswissenschaft neben Politik, Wirtschaft und Kultur wahrgenommen, aber gerade zum Früh- und Hochmittelalter fehlten bislang systematisch vergleichende Untersuchungen der Naturereignisse. Da die bisher angewandten Arbeitsweisen am frühmittelalterlichen Material versagen, mussten neue methodische Konzepte der Auswertung entwickelt werden, bei denen die überlieferten extremen Naturereignisse im Fokus stehen. Diese wurden aus historiographischen Quellen gefiltert, kategorisiert und analysiert. Dabei stellt sich einerseits heraus, dass mittelalterliche Autoren teilweise über unerwartet genaue Beobachtungsmöglichkeiten verfügten, sie aber andererseits ihre Beobachtungen nicht unreflektiert niederschrieben und keiner empirischen Genauigkeit verpflichtet waren. Insgesamt konnten anhand von Parallelüberlieferung oder Vergleichen etwa 1175 Ereignisse bezüglich ihrer intentionalen Nutzung analysiert werden. So bietet die Arbeit einen genauen Einblick in die Zuverlässigkeit der Wahrnehmung und die mögliche Instrumentalisierung der Darstellung extremer Naturereignisse und ihrer Folgen in den Quellen des 6. bis 11. Jahrhunderts.

The Super Outbreak of tornadoes over the central and eastern United States on 3-4 April 1974 remains the most outstanding severe convective weather episode on record in the continental United States. The outbreak far surpassed previous... more

The Super Outbreak of tornadoes over the central and eastern United States on 3-4 April 1974 remains the most outstanding severe convective weather episode on record in the continental United States. The outbreak far surpassed previous and succeeding events in severity, longevity, and extent. In this paper, surface, upper-air, radar, and satellite data are used to provide an updated synoptic and subsynoptic overview of the event. Emphasis is placed on identifying the major factors that contributed to the development of the three main convective bands associated with the outbreak, and on identifying the conditions that may have contributed to the outstanding number of intense and long-lasting tornadoes. Selected output from a 29-km, 50-layer version of the Eta forecast model, a version similar to that available operationally in the mid-1990s, also is presented to help depict the evolution of thermodynamic stability during the event.

Over the western United States, the hazards posed to aviation operations by convective storm-generated downbursts have been extensively documented. Other significant hazards posed by convective downbursts over the intermountain western... more

Over the western United States, the hazards posed to aviation operations by convective storm-generated downbursts have been extensively documented. Other significant hazards posed by convective downbursts over the intermountain western U.S. include the rapid intensification and propagation of wildfires and the sudden generation of visibility-reducing dust storms (haboobs). The existing suite of GOES downburst prediction algorithms employs the GOES sounder to calculate potential of occurrence based on conceptual models of favorable environmental thermodynamic profiles for downburst generation. Previous research has demonstrated the effectiveness of the Dry Microburst Index (DMI) as a prediction tool for convectively generated high winds. A more recently-developed diagnostic nowcasting product, the Microburst Windspeed Potential Index (MWPI) is designed to diagnose attributes of a favorable downburst environment: 1) the presence of convective available potential energy (CAPE), and 2) the presence of a deep surface-based or elevated mixed layer with a large temperature lapse rate. This paper presents an updated assessment of the MWPI algorithm, case studies demonstrating effective operational use of the MWPI product, and recent validation results. MWPI data were collected for downburst events that occurred during the 2014 convective season and were validated against surface observations of convective wind gusts as recorded by wind sensors in high-quality mesonetworks. Favorable validation results include a statistically significant correlation (r > 0.6) and low mean error (< 1 kt) between MWPI values and confirmed downburst wind speeds measured in situ.

As the climate warms, stressors are developing that challenge the adaptive capabilities of Arctic peoples. In Nunavut, one of Canada’s Arctic territories, increased weather variability and changes in physical and climatic conditions are... more

As the climate warms, stressors are developing that challenge the adaptive capabilities of Arctic peoples. In Nunavut, one of Canada’s Arctic territories, increased weather variability and changes in physical and climatic conditions are having profound
effects on residents. One problem is that while these changes have magnified risks associated with travel and land-based activities, individuals lack sufficiently reliable and useful
information on which to base decisions. In this paper, we argue that weather-related risk assessment can be improved by integrating local and scientific weather knowledge and
making this information accessible to residents through the creation of weather hazards impact advisory groups. We present a qualitative case study of Iqaluit, the capital of Nunavut, using data from participant observation and semi-structured interviews conducted with indigenous and non-indigenous long-term residents in summer 2009. We examine how long-term residents of Iqaluit acquire, perceive, and use both local and scientific weather knowledge. We find that various barriers, such as a lack of land-based experience, cultural and linguistic differences, and an absence of social networks, prevent most people from
obtaining all the information required to make fully informed decisions about the risks associated with land-based activities at different locations. Experienced hunters are perceived
to be a reliable source of weather-related information, while scientific weather knowledge is not as accessible or informative as it could be. Increasing the potential use of traditional and scientific hazardous weather knowledge, by making both more universally accessible, can enhance strategies for adapting to climate change in the Arctic.

On 31 May 2013, an intense, multiple-vortex tornado meandered through sparsely populated areas near El Reno, Oklahoma. This exceptionally wide tornado had a complex path, changing rapidly in both speed and direction. The tornado killed... more

On 31 May 2013, an intense, multiple-vortex tornado meandered through sparsely populated areas near El Reno, Oklahoma. This exceptionally wide tornado had a complex path, changing rapidly in both speed and direction. The tornado killed eight people, all in vehicles, including three severe storm researchers. This paper summarizes our findings from conducting a damage survey using the EF (Enhanced Fujita) scale developed by the Wind Science and Engineering Center. Survey teams also documented damage to 344 non-standard DIs which included 112 oil tank batteries. The maximum damage rating was determined to be EF3. Total path length was 26.2 km.

On 4 May 1999, the Wind Science and Engineering Research Center at Texas Tech University dispatched three survey teams to the Oklahoma City area to conduct a tornado damage survey. The author was the leader of one of the teams whose... more

On 4 May 1999, the Wind Science and Engineering Research Center at Texas Tech University dispatched three survey teams to the Oklahoma City area to conduct a tornado damage survey. The author was the leader of one of the teams whose purpose was to survey tornado damage in and around the suburb of Moore, Oklahoma. The survey team was given five tasks: 1) to map out the damage path and assign F-scale numbers to damaged buildings, 2) to document the performance of housing, 3) to interview witnesses, 4) to document projectiles, and 5) to assess the performance of any above-or belowground shelters within the damage path. This paper will present the methodology utilized for conducting the tornado damage survey and will summarize the observations and findings of the survey team. Wind speeds necessary to cause the observed damage to residences were found to be significantly lower than the established F-scale wind speeds. The author returned to the disaster area three months later and discovered that, in general, the quality of new home construction had not improved.

Hail is considered to be among the most complex extreme weather phenomena of the atmosphere. Every year, notably in the southern Brazilian States, destructive hailstorms result in serious economic losses and cause a great social impact... more

Hail is considered to be among the most complex extreme weather phenomena of the atmosphere. Every year, notably in the southern Brazilian States, destructive hailstorms result in serious economic losses and cause a great social impact destroying crops, homes, medical facilities and schools. The aim of this study is to document the spatial, annual, and diurnal variation in destructive hailstorm frequency during a 22 year period from1991 to 2012 in Brazil. The analysis is based on a collection of reports released by the Brazilian National Civil Protection Secretariat – SEDEC. Based on reports of emergency assistance given to the population affected by a disaster, the information discussed in this work is assumed as representative only of destructive hailstorms. The analysis reveals a large spatial variability, with the majority of hailstorm occurrences distributed in the three southernmost Brazilian States. Within those states, the number of hail reports was observed to increase with increasing population density in rural areas. Hailstorms were reported most often in the late afternoon and evening of thewinter/spring transition, in agreement with a fewother areas in the subtropics with available studies, but different from the majority of studies for temperate zones, which suggest spring/summer as the hail season. Although the results show some discrepancies compared to satellite hail signatures, the findings of this work confirm that southern Brazil is a region prone to the development of strong convective storms,with high annual numbers of destructive hail events.

In this lesson, students learn that daily weather conditions are not the result of random occurrences, but of global systems that can be predicted on a short-term and a seasonal basis. Through observations and measurements, students... more

In this lesson, students learn that daily weather conditions are not the result of random occurrences, but of global systems that can be predicted on a short-term and a seasonal basis. Through observations and measurements, students investigate the properties of air and other aspects of daily weather. Students learn to interpret public weather reports and investigate the usefulness of various ways of predicting the weather. Understanding the meaning of severe weather forecasts and the preparations to ensure personal safety are emphasized.

A climatology of severe hail (diameter equal to or exceeding approximately 1.5 cm) for Turkey is constructed from official severe weather reports from meteorological stations, newspaper archives, and internet sources. The dataset... more

A climatology of severe hail (diameter equal to or exceeding approximately 1.5 cm) for Turkey is constructed from official severe weather reports from meteorological stations, newspaper archives, and internet sources. The dataset consists of 1489 severe hail cases on 1107 severe hail days (days with at least one severe hail case) from 1925–2014. Severe hail was reported most often in the 1960s, followed by a decrease until the 2000s, and an ensuing increase in the past decade. Severe hail is most likely to occur in the afternoon and evening, and in spring and summer, particularly May and June. The geographical distribution implies that almost all of Turkey is prone to severe hailstorms. In 8.3% of the severe hail cases, very large hailstones (diameter equal to or exceeding approximately 4.5 cm) were observed.

Twenty-eight predecessor rain events (PREs) that occurred over the United States east of the Rockies during 1995–2008 are examined from a synoptic climatology and case study perspective. PREs are coherent mesoscale regions of heavy... more

Twenty-eight predecessor rain events (PREs) that occurred over the United States east of the Rockies during 1995–2008 are examined from a synoptic climatology and case study perspective. PREs are coherent mesoscale regions of heavy rainfall, with rainfall rates ≥100 mm (24 h)−1, that can occur approximately 1000 km poleward of recurving tropical cyclones (TCs). PREs occur most commonly in August and September, and approximately 36 h prior to the arrival of the main rain shield associated with the TC. A distinguishing feature of PREs is that they are sustained by deep tropical moisture that is transported poleward directly from the TC. PREs are high-impact weather events that can often result in significant inland flooding, either from the PRE itself or from the subsequent arrival of the main rain shield associated with the TC that falls onto soils already saturated by the PRE. The composite analysis shows that on the synoptic-scale, PREs form in the equatorward jet-entrance region o...

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... more

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.

In June 2008, the community of Pangnirtung, Nunavut, Canada experienced a rainstorm that caused structural damage to the community’s bridge and extensive permafrost erosion along the Duval River. The local government characterised the... more

In June 2008, the community of Pangnirtung, Nunavut, Canada experienced a rainstorm that caused
structural damage to the community’s bridge and extensive permafrost erosion along the Duval River. The local
government characterised the event as ‘severe’ and focused their attention on the bridge collapse, in contrast to the
residents, who described this particular consequence as inconvenient at worst and at best, exciting. Instead residents
expressed greater concern for the permafrost erosion and the uncertainty this posed for community well-being. This
article follows an 11 week anthropological field trip to Pangnirtung in the summer of 2009 and is based on 31 semistructured
interviews, two focus group discussions, and participant observation. We explore how social processes
influence subjective constructions of what constitutes ‘severe’ weather in the community, and attempt to explain
how such constructions lead to differing perceptions of vulnerability to ‘severe’ weather events. Contributing factors
including the normalisation of threat, local beliefs regarding change and uncertainty, as well as the communication of
risk information are discussed along with the different coping strategies used by government and residents in managing
their perceived levels of vulnerability. The research shows the importance of understanding the role social processes
play in shaping local conceptions of ‘severe’ and perceptions of vulnerability to ‘severe’ weather events. This study
enhances understandings of difference within populations and adds to the growing body of literature that demonstrates
the need to incorporate locally relevant indices when conducting vulnerability assessment.

This study analyzes the relationship between lightning and precipitation in nine convective events. They occurred during the summer season of 2004 in Catalonia (NE Spain) and its coastal area, in the North Western Mediterranean Sea. The... more

This study analyzes the relationship between lightning and precipitation in nine convective events. They occurred during the summer season of 2004 in Catalonia (NE Spain) and its coastal area, in the North Western Mediterranean Sea. The data examined were issued from C-band volumetric radar observations, from radiosoundings, and total lightning detection records, including both cloud-to-ground (CG) and intra-cloud flashes. The overall Rainfall-Lightning Ratio (RLR) found was 38.9 10 3 m 3 /CG flash, which is a value closer to those found in the Southeastern United States than in the Atlantic coast of France. Moreover, the range of variation found in the studied episodes goes from 10.8 to 87.2 10 3 m 3 /CG flash. These variations are analyzed in terms of the synoptic conditions of the events and regarding their spatial distribution, comparing land and sea domains.

Real-time analyses and forecasts using an ensemble Kalman filter (EnKF) and the Advanced Hurricane Weather Research and Forecasting Model (AHW) are evaluated from the 2009 North Atlantic hurricane season. This data assimilation system... more

Real-time analyses and forecasts using an ensemble Kalman filter (EnKF) and the Advanced Hurricane Weather Research and Forecasting Model (AHW) are evaluated from the 2009 North Atlantic hurricane season. This data assimilation system involved cycling observations that included conventional in situ data, tropical cyclone (TC) position, and minimum SLP and synoptic dropsondes each 6 h using a 96-member ensemble on a 36-km domain for three months. Similar to past studies, observation assimilation systematically reduces the TC position and minimum SLP errors, except for strong TCs, which are characterized by large biases due to grid resolution. At 48 different initialization times, an AHW forecast on 12-, 4-, and 1.33-km grids is produced with initial conditions drawn from a single analysis member. Whereas TC track analyses and forecasts exhibit a pronounced northward bias, intensity forecast errors are similar to (lower than) the NWS Hurricane Weather Research Model (HWRF) and GFDL forecasts for forecast lead times #60 h (.60 h), with the largest track errors associated with the weakest systems, such as Tropical Storm (TS) Erika. Several shortcomings of the data assimilation system are addressed through postseason sensitivity tests, including using the maximum 800-hPa circulation to identify the TC position during assimilation and turning off the quality control for the TC minimum SLP observation when the initial intensity is far too weak. In addition, the improved forecast of TS Erika relative to HWRF is shown to be related to having initial conditions that are more representative of a sheared TC and not using a cumulus parameterization.

The synoptic and mesoscale conditions associated with waterspout occurrence in the Adriatic, Ionian and Aegean Sea are examined in an attempt to quantitatively assess the meteorological environment favourable to the development of... more

The synoptic and mesoscale conditions associated with waterspout occurrence in the Adriatic, Ionian and Aegean Sea are examined in an attempt to quantitatively assess the meteorological environment favourable to the development of waterspouts. For this study, synoptic circulation patterns have been examined for 28 waterspout events in the central-eastern Mediterranean. The waterspouts were reported within the summer and fall of 2002, from July to November, a period of unusually high whirlwind activity. The Adriatic was most active during July, August and September and the Ionian and Aegean during September, October and November. Of the examined waterspout cases, 13 out of the total of 28 were found to be fair-weather waterspouts, while 15 represent tornadic events. For waterspout days, the frequency and distribution of four basic synoptic types, namely, southwest flow (SW), long-wave trough (LW), closed low (CLOSED) and shortwave trough (SWT), were investigated. The particular synoptic features that contributed to the development of waterspout activity were examined, based on five selected waterspout case studies. The mesoscale environment was explored using thermodynamic indices, moisture and wind parameters as derived by operational soundings from the nearest sites (preferably upwind) and closest in time to the waterspout occurrences. The results present an analysis of waterspout types in conjunction to thermodynamic and wind parameters for the purpose of determining synoptic patterns and mesoscale conditions most relevant to waterspout occurrences in these sea areas of the Mediterranean.

On 23-25 March 1998, Norman, Oklahoma, and nearby Tinker Air Force Base hosted a three-day celebration to commemorate the 50th anniversary of the first successful tornado forecast and the advances that have occurred in tornado forecasting... more

On 23-25 March 1998, Norman, Oklahoma, and
nearby Tinker Air Force Base hosted a three-day celebration
to commemorate the 50th anniversary of the
first successful tornado forecast and the advances that
have occurred in tornado forecasting and warning in
the past half-century. The event was a cooperative effort
of the National Oceanic and Atmospheric Administration
(NOAA), the United States Air Force
(USAF), and the University of Oklahoma. Participation
also included the Norman Chamber of Commerce, as
well as the chambers of commerce from surrounding
municipalities in central Oklahoma.

A significant, convectively induced windstorm known as a derecho occurred over parts of Utah, Wyoming, Idaho, and Colorado on 31 May 1994. The event was unusual in that it occurred not only in an environment of relatively limited... more

A significant, convectively induced windstorm known as a derecho occurred over parts of Utah, Wyoming, Idaho, and Colorado on 31 May 1994. The event was unusual in that it occurred not only in an environment of relatively limited moisture, but also one with a thermodynamic profile favorable for dry microbursts in the presence of moderate midtropospheric flow. The development and evolution of the severe wind-producing convective system is described, with emphasis on the synoptic and mesoscale features that may have contributed to its strength and maintenance. A very similar derecho that affected much the same region on 1 June 2002 is more briefly introduced. Questions are raised regarding the unique nature of these events and their potential utility in achieving an increased understanding of the mechanics of derecho-producing convective systems in more moisture-rich environments.

PowerPoint poster on forecasting severe convective storms.

On October 11, 1846, the island of Key West, Florida was struck by a very powerful hurricane. This paper examines the available historical material to gain an understanding of the storm’s broad-reaching effects on the island community and... more

On October 11, 1846, the island of Key West, Florida was struck by a very powerful hurricane. This paper examines the available historical material to gain an understanding of the storm’s broad-reaching effects on the island community and the physical alterations it wrought on the landscape. Many of the experiences of the 1846 hurricane hold lessons for what might be expected in a modern-era storm.

The transmission line insulation breakdown is typically assessed by performing insulator chain tests, and by conducting network modeling and simulation studies incorporating various stress conditions. This paper investigates how... more

The transmission line insulation breakdown is typically assessed by performing insulator chain tests, and by conducting network modeling and simulation studies incorporating various stress conditions. This paper investigates how historical data coming from the lightning detection network and measurement stations capturing associated weather conditions can be utilized to provide a predicted assessment of risk of insulation breakdown for a given exposure and associated weather threats. The proposed analysis is enabled by the space and time correlation of the transient data recorded in the substations at the end of the lines, as well as by the assimilation of data obtained from the lightning detection network and weather stations. The proposed modeling and simulation tools are utilized to facilitate the time and space correlation analysis that leads to predication of the risk.

Both Argo measurements and satellite sea surface temperature (SST) data revealed that there was less-than-usual surface cooling during the passage of typhoons Kaemi and Cimaron in the tropical Northwest Pacific. In the present study, it... more

Both Argo measurements and satellite sea surface temperature (SST) data revealed that there was less-than-usual surface cooling during the passage of typhoons Kaemi and Cimaron in the tropical Northwest Pacific. In the present study, it is found that SST cooling induced by typhoon can be greatly suppressed by a barrier layer with a thickness of 5-15 m. Such a barrier layer could reduce the entrainment cooling by 0.4-0.8 • C/d during typhoon passage, according to a diagnostic mixed layer model. The pre-existing barrier layer leads to a reduction in typhoon-induced surface cooling, and favors typhoon development. The average SST anomaly under barrier layer condition is 0.4-0.8 • C less than that under no-barrierlayer condition. Due to the reduced cooling, the available maximum potential intensity (MPI) under barrier layer condition are higher 6 and 9.34 m/s than those under no-barrier-layer condition according to SST-dependent MPI formulation for Kaemi and Cimaron. In addition, the results from Price-Weller-Pinkel (PWP) model indicate that stratification due to salinity may significantly influence both entrainment and the upper ocean heat content during typhoon passage in the tropical Northwest Pacific.

A sample of 1185 Rapid Update Cycle (RUC) model analysis (0 h) proximity soundings, within 40 km and 30 min of radar-identified discrete storms, was categorized by several storm types: significantly tornadic supercells (F2 or greater... more

A sample of 1185 Rapid Update Cycle (RUC) model analysis (0 h) proximity soundings, within 40 km and 30 min of radar-identified discrete storms, was categorized by several storm types: significantly tornadic supercells (F2 or greater damage), weakly tornadic supercells (F0-F1 damage), nontornadic supercells, elevated right-moving supercells, storms with marginal supercell characteristics, and nonsupercells. These proximity soundings served as the basis for calculations of storm-relative helicity and bulk shear intended to apply across a broad spectrum of thunderstorm types. An effective storm inflow layer was defined in terms of minimum constraints on lifted parcel CAPE and convective inhibition (CIN). Sixteen CAPE and CIN constraint combinations were examined, and the smallest CAPE (25 and 100 J kg Ϫ1 ) and largest CIN (Ϫ250 J kg Ϫ1 ) constraints provided the greatest probability of detecting an effective inflow layer within an 835-supercell subset of the proximity soundings. Effective storm-relative helicity (ESRH) calculations were based on the upper and lower bounds of the effective inflow layer. By confining the SRH calculation to the effective inflow layer, ESRH values can be compared consistently across a wide range of storm environments, including storms rooted above the ground. Similarly, the effective bulk shear (EBS) was defined in terms of the vertical shear through a percentage of the "storm depth," as defined by the vertical distance from the effective inflow base to the equilibrium level associated with the most unstable parcel (maximum e value) in the lowest 300 hPa. ESRH and EBS discriminate strongly between various storm types, and between supercells and nonsupercells, respectively.

A 5-yr climatology of elevated severe convective storms was constructed for 1983–87 east of the Rocky Mountains. Potential cases were selected by finding severe storm reports on the cold side of surface fronts. Of the 1826 days during the... more

A 5-yr climatology of elevated severe convective storms was constructed for 1983–87 east of the Rocky Mountains. Potential cases were selected by finding severe storm reports on the cold side of surface fronts. Of the 1826 days during the 5-yr period, 1689 (91%) had surface fronts east of the Rockies. Of the 1689 days with surface fronts, 129 (8%) were associated with elevated severe storm cases. Of the 1066 severe storm reports associated with the 129 elevated severe storm cases, 624 (59%) were hail reports, 396 (37%) were wind reports, and 46 (4%) were tornado reports. A maximum of elevated severe storm cases occurred in May with a secondary maximum in September. Elevated severe storm cases vary geographically throughout the year, with a maximum over the south-central United States in winter to a central and eastern U.S. maximum in spring and summer. A diurnal maximum of elevated severe storm cases occurred at 2100 UTC, which coincided with the diurnal maximum of hail reports. The wind reports had a broad maximum during the daytime. Because the forecasting of hail from elevated storms typically does not pose as significant a forecast challenge as severe wind for forecasters and tornadoes from elevated storms are relatively uncommon, this study focuses on the occurrence of severe wind from elevated storms. Elevated severe storm cases that produce only severe wind reports occurred roughly 5 times a year. To examine the environments associated with cases that produced severe winds only, five cases were examined in more detail. Common elements among the five cases included elevated convective available potential energy, weak surface easterlies, and shallow near-surface stable layers (less than 100 hPa thick).

A suite of products has been developed and evaluated to assess hazards presented by convective storm downbursts derived from the current generation of Geostationary Operational Environmental Satellite (GOES) (13-15). The existing suite of... more

A suite of products has been developed and evaluated to assess hazards presented by convective storm downbursts
derived from the current generation of Geostationary Operational Environmental Satellite (GOES) (13-15). The existing
suite of GOES downburst prediction products employs the GOES sounder to calculate risk based on conceptual models
of favorable environmental profiles for convective downburst generation. A diagnostic nowcasting product, the
Microburst Windspeed Potential Index (MWPI), is designed to infer attributes of a favorable downburst environment: 1)
the presence of large convective available potential energy (CAPE), and 2) the presence of a surface-based or elevated
mixed layer with a steep temperature lapse rate and vertical relative humidity gradient. These conditions foster intense
convective downdrafts upon the interaction of sub-saturated air in the elevated or sub-cloud mixed layer with the storm
precipitation core. This paper provides an updated assessment of the MWPI algorithm, presents recent case studies
demonstrating effective operational use of the MWPI product over the Atlantic coastal region, and presents validation
results for the United States Great Plains and Mid-Atlantic coastal region. In addition, an application of the brightness
temperature difference (BTD) between GOES imager water vapor (6.5μm) and thermal infrared (11μm) channels that
identifies regions where downbursts are likely to develop, due to mid-tropospheric dry air entrainment, will be outlined.

A new method for predicting the upper tail of the precipitation distribution, based on empiricalstatistical downscaling, is explored. The proposed downscaling method involves a re-calibration of the results from an analog model to ensure... more

A new method for predicting the upper tail of the precipitation distribution, based on empiricalstatistical downscaling, is explored. The proposed downscaling method involves a re-calibration of the results from an analog model to ensure that the results have a realistic statistical distribution. A comparison between new results and those from a traditional analog model suggests that the new method predicts higher probabilities for heavy precipitation events in the future, except for the most extreme percentiles for which sampling fluctuations give rise to high uncertainties. The proposed method is applied to the 24-h precipitation from Oslo, Norway, and validated through a comparison between modelled and observed percentiles. It is shown that the method yields a good approximate description of both the statistical distribution of the wet-day precipitation amount and the chronology of precipitation events. An additional analysis is carried out comparing the use of extended empirical orthogonal functions (EOFs) as input, instead of ordinary EOFs. The results were, in general, similar; however, extended EOFs give greater persistence for 1-day lags. Predictions of the probability distribution function for the Oslo precipitation indicate that future precipitation amounts associated with the upper percentiles increase faster than for the lower percentiles. Substantial random statistical fluctuations in the few observations that make up the extreme upper tail implies that modelling of these is extremely difficult, however. An extrapo-

This study estimates future trends in the characteristics of severe hailstorms that affect the most heavily populated region of Australia, the Sydney Basin, using coupled climate model simulations under both fixed (no change) greenhouse... more

This study estimates future trends in the characteristics of severe hailstorms that affect the most heavily populated region of Australia, the Sydney Basin, using coupled climate model simulations under both fixed (no change) greenhouse gas concentrations and the IPCC SRES A1B future climate scenario. The "future climate", as defined here, is the 50-year period January 1, 2001 to December 31, 2050. First, an assessment is made of the ability of the climate model, in very high-resolution mesoscale model mode, to simulate three of the most severe hailstorms recorded in the Sydney Basin during the "present climate" period, defined here as the years 1990 to 2002. These simulations, nested down to 1 km grid spacing, are compared with the archived hail observations of the storms. The climate model then is used to provide estimates of projected changes in hailstorm frequency, tracks, intensity, duration, and hail size over the Sydney Basin for the "future climate" period.

The paper presents results that shed some more light on the mid-to upper-level dynamics, responsible for development of intense convection, as seen by satellite images in the water vapour channels. The study has also the ambition to help... more

The paper presents results that shed some more light on the mid-to upper-level dynamics, responsible for development of intense convection, as seen by satellite images in the water vapour channels. The study has also the ambition to help forecasters to improve their abilities in nowcasting strong convective events. In addition to the well-known upper-level dynamic structures visible in the 6.2 µm imagery, typical moisture boundaries related to mid-level jet streams can be distinguished in 7.3 µm images. About 20 cases of severe convection developing over southern Europe between 2004 and 2007 were studied. In 80% of the cases, a mid-level jet (MLJ) is present at about 600 or 700 hPa in a south-westerly flow. In these cases, the distinct MLJ boundary in 7.3 µm image grey shades is a signature for the presence of a low-level baroclinic zone-related to the MLJ originthat plays a critical role in destabilisation of the atmosphere for intense convection. Images in the 7.3 µm and 6.2 µm channels are used to detect coupling between low-and midlevel conditions dynamics associated with intense convective developments. As a tool for water vapour imagery analysis in diagnosing this context, "dynamic wind shift"−defined as difference in the position of mid-and upper-level jets over a short distance, seen in the WV images−is considered. Two types of intense convective developments over the Mediterranean are distinguished, associated with "smooth" and "sharp" dynamic wind shift conditions, upstream of the zone of intense convection.

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... more

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.

During the 2005 NOAA Hazardous Weather Testbed Spring Experiment two different high-resolution configurations of the Weather Research and Forecasting-Advanced Research WRF (WRF-ARW) model were used to produce 30-h forecasts 5 days a week... more

During the 2005 NOAA Hazardous Weather Testbed Spring Experiment two different high-resolution configurations of the Weather Research and Forecasting-Advanced Research WRF (WRF-ARW) model were used to produce 30-h forecasts 5 days a week for a total of 7 weeks. These configurations used the same physical parameterizations and the same input dataset for the initial and boundary conditions, differing primarily in their spatial resolution. The first set of runs used 4-km horizontal grid spacing with 35 vertical levels while the second used 2-km grid spacing and 51 vertical levels.

On the night from 1st to 2nd of November 2008, a multi-cell storm coming from the Mediterranean produced severe weather in the coastal area of Catalonia (NE Spain): groundlevel strong damaging wind gusts, a tornadowhich caused F2... more

On the night from 1st to 2nd of November 2008, a multi-cell storm coming from the Mediterranean produced severe weather in the coastal area of Catalonia (NE Spain): groundlevel strong damaging wind gusts, a tornadowhich caused F2 damageand heavy rainfall. A general overview of the synoptic framework, damage observed and a radar analysis is given in the first part of the study. This second part is mostly centered on the detailed analysis of the total lightning behavior, its relationship with radar-derived storm parameters, and total lightning correlation with hazardous weather. The purpose is to bring more evidence about the outstanding role of total lightning in severe weather surveillance tasks. The analysis of the storm cells life cycle has showed similar trends between the total lighting flash rates and radarderived parameters like the area of reflectivity above 30 dBZ at 7-km. Regarding lightning trends, a lightning "jump" patternan abrupt increase of the total lightning rate in a short period of timehas been related to severe weather. On the contrary, cloud-to-ground lightning data did not show any pattern related to severe weather. In comparison to other parameters, like the IC:CG ratio, the lightning "jump" pattern seems more robust to forecast in a short-term basis the possible occurrence of severe weather.

Space geodetic applications require to model troposphere delays as good as possible in order to achieve highly accurate positioning estimates. However, these models are not capable to consider complex refractivity fields which are likely... more

Space geodetic applications require to model troposphere delays as good as possible in order to achieve highly accurate positioning estimates. However, these models are not capable to consider complex refractivity fields which are likely to occur during extreme weather situations like typhoons, storms, heavy rain-fall, etc. Thus it has been investigated how positioning results can be improved if information from numerical weather models is taken into account. It will be demonstrated that positioning errors can be significantly reduced by the usage of ray-traced slant delays. Therefore, mesoscale and fine-mesh numerical weather models are utilized and their impact on the positioning results will be measured. The approach has been evaluated during a typhoon passage using global positioning service (GPS) observations of 72 receivers located around Tokyo, proving the usefulness of ray-traced slant delays for positioning applications. Thereby, it is possible reduce virtual station movements as well as improve station height repeatabilities by up to 30% w.r.t. standard processing techniques. Additionally the advantages and caveats of numerical weather models will be discussed and it will be shown how fine-mesh numerical weather models, which are restricted in their spatial extent, have to be handled in order to provide useful corrections.

1] A regionalization based on a rotated principal component analysis (PCA) was used to produce six precipitation regions in northwest Mexico and the southwest United States. Monthly precipitation data from 184 meteorological stations for... more

1] A regionalization based on a rotated principal component analysis (PCA) was used to produce six precipitation regions in northwest Mexico and the southwest United States. Monthly precipitation data from 184 meteorological stations for the 1960-1997 period were used in the PCA. The aim of this study was to estimate annual and seasonal trends of 10 daily precipitation indices in the six regions, including four indices related with extreme precipitation. The annual indices show a larger number of statistically significant trends than the seasonal indices, especially in Arizona-New Mexico and in the monsoon region in northwest Mexico (MON). Significant positive trends common to these two contiguous regions are extreme precipitation exceeding the 95th (R95p) and 99th percentiles. The analysis of summer (June-October) daily precipitation indices also reveals the occurrence of significant positive trends in R95p in MON, mainly due to tropical cyclone activity. With the exception of the trends in MON, the most important contribution to the annual trends comes from the winter indices. Four of the six regions in the study area show significant positive trends in extreme winter precipitation (R10mm, R95p or R99p) during the study period. The variability of the annual indices that show statistically significant trends in extreme precipitation are partially linked to natural variations resulting from the combined effects of El Niño/Southern Oscillation and the Pacific decadal oscillation (PDO) and, in most cases, the trends are explained by the PDO.

1] Hurricane storm surge presents a major hazard for the United States. We apply a model-based risk assessment methodology to investigate hurricane storm surge risk for New York City (NYC). We couple a statistical/deterministic hurricane... more

1] Hurricane storm surge presents a major hazard for the United States. We apply a model-based risk assessment methodology to investigate hurricane storm surge risk for New York City (NYC). We couple a statistical/deterministic hurricane model with the hydrodynamic model SLOSH (sea, lake, and overland surges from hurricanes) to generate a large number of synthetic surge events; the SLOSH model simulations are compared to advanced circulation model simulations. Statistical analysis is carried out on the empirical data. It is observed that the probability distribution of hurricane surge heights at the Battery, NYC, exhibited a heavy tail, which essentially determines the risk of New York City being struck by a catastrophic coastal flood event. The peaks-over-threshold method with the generalized Pareto distribution is applied to estimate the upper tail of the surge heights. The resulting return periods of surge heights are consistent with those of other studies for the New York area. This storm surge risk assessment methodology may be applied to other coastal areas and can be extended to consider the effect of future climate change.

The National Environmental Satellite, Data, and Information Service (NESDIS) Center for Satellite Applications and Research (STAR) has developed and evaluated a suite of products that assess convective storm–generated downburst potential... more

The National Environmental Satellite, Data, and Information Service (NESDIS) Center for Satellite Applications and Research (STAR) has developed and evaluated a suite of products that assess convective storm–generated downburst potential derived from Geostationary Operational Environmental Satellite-13–15 (GOES-13–15). The existing suite of downburst prediction algorithms employs the GOES sounder to calculate risk based on conceptual models of favorable environmental thermodynamic profiles for downburst occurrence. A diagnostic nowcasting product, the Microburst Windspeed Potential Index (MWPI), is designed to identify attributes of a favorable downburst environment: 1) the presence of large CAPE and 2) the presence of a surface-based or elevated mixed layer with a large temperature lapse rate. This paper provides an updated assessment of the MWPI algorithm, presents case studies demonstrating effective operational use of the MWPI product, and presents validation results for the Great Plains and mid-Atlantic coastal region of the United States. MWPI data were collected for downburst events that occurred during the convective seasons of 2007–13 and were validated against surface observations of convective wind gusts as recorded by wind sensors in high quality mesonetworks over the southern Great Plains and the Chesapeake Bay region. Favorable validation results include a correlation greater than 0.6 and low mean error [<0.1 knot (kt; where 1 kt = 0.51 m s−1)] between MWPI values and measured confirmed downburst wind speeds over contrasting climate regions of the continental United States. Case studies over the mid-Atlantic region and northern Florida highlight the adaptability of the MWPI algorithm to severe convective storm forecasting and warning operations.