Publications
Kovach, M.M. and C.E. Konrad 2015: Area-Level Risk Factors for Heat-Related Illness in Rural and Urban Locations across North Carolina, USA.
Applied Geography, 60, 175-183.
An improved understanding of heat vulnerable populations and locations is needed, especially in rural communities. The objective of this study was to identify area-level risk factors for heat-related illness (HRI) at the ZIP code level for urban and rural locations. We aggregated ZIP code-level emergency department visits into rural and urban locations based on population density. Area-level risk factors included previously established heat health risk factors (e.g. poverty, minority) and unexamined area-level risk factors common to rural locations (e.g. mobile homes, agriculture). Due to high spatial auto-correlation, a spatial error regression model was applied to identify risk factors with a significant relationship with HRI. Our results suggest that rural locations are also heat vulnerable, with greater rates of HRI compared to urban locations. Previously unexamined heat-health risk factors, including the number of mobile homes, non-citizens, and the labor-intensity of the agriculture, were all associated with increases of HRI in rural locations. In urban locations, previously established risk factors for heat-related mortality, such as decreased vegetation, living in poverty, and low education attainment were associated with increases in HRI.
Kovach, M.M. and C.E. Konrad 2014: Meteorological impacts of inland moving tropical cyclones. Physical Geography, 27, 245-271.
The southeastern United States is routinely hit by tropical cyclones. As tropical cyclones track inland and dissipate their inland impacts can be substantial. This study examines the spatial patterns of societal impacts associated with tornadoes and high winds with thirty-one inland-moving tropical cyclones that made landfall from 1985 to 2008. Hourly weather information is collected from all available first-order weather stations affected by each storm, as well as tropical cyclone preliminary reports issued from the National Hurricane Center. Societal impacts are identified through selected newspapers across the region and the National Climatic Data Center’s Storm Data. Geographic Information System (GIS) software is employed to make geometric measurements of the distance and direction of the impacts relative to storm center. From these measurements, the spatial distribution of the societal and meteorological impacts is plotted relative to the track (e.g. left vs. right) and location (forward vs. rear sector) of the cyclone center. Various tropical cyclone attributes, including size, strength, and forward speed of movement are then related to the occurrence of different impacts and their location relative to the cyclone track. The majority of tropical cyclone tornado and high wind impacts occur in the right forward sector of the tropical cyclone. However, many tropical cyclones produce impacts that occur in other sectors far from the center of circulation. These abnormalities are associated in many cases with interactions between the TC circulation, topography, peripheral dry air, and extratropical synoptic weather features.
Fuhrmann, C.M., C.E. Konrad, M.M Kovach, J.T. McLeod, W.G. Schmitz, and P.G. Dixon: 2014: Ranking of tornado outbreaks in the United States and their climatological characteristics. Weather and Forecasting, 29, 684-701.
The calendar year 2011 was an extraordinary year for tornadoes across the United States, as it marked the second highest annual number of tornadoes since 1950 and was the deadliest tornado year since 1936. Most of the fatalities in 2011 occurred in a series of outbreaks, highlighted by a particularly strong outbreak across the southeastern United States in late April and a series of outbreaks over the Great Plains and Midwest regions in late May, which included a tornado rated as a category 5 event on the enhanced Fujita scale (EF5) that devastated the town of Joplin, Missouri. While most tornado-related fatalities often occur in outbreaks, very few studies have examined the climatological characteristics of outbreaks, particularly those of varying strength. In this study a straightforward metric to assess the strength, or physical magnitude, of tornado outbreaks east of the Rocky Mountains from 1973 to 2010 is developed. This measure of outbreak strength, which integrates the intensity of tornadoes [Fujita (F)/EF-scale rating] over their distance traveled (path length), is more highly correlated with injuries and fatalities than other commonly used variables, such as the number of significant tornadoes, and is therefore more reflective of the potential threat of outbreaks to human life. All outbreaks are then ranked according to this metric and their climatological characteristics are examined, with comparisons made to all other tornadoes not associated with outbreaks. The results of the ranking scheme are also compared to those of previous studies, while the strongest outbreaks from 2011 are ranked among other outbreaks in the modern record, including the April 1974 Super Outbreak.
Knox, P.N., C.M. Fuhrmann, and C.E. Konrad 2014: Challenges and opportunities for Southeast agriculture in a changing climate: Perspectives from State Climatologists. Southeastern Geographer, 54, 118-136.
Agriculture is one of the most sensitive economic sectors to weather and climate variability. In the Southeastern U.S., agricultural production is widespread and diverse, making it a primary source of commerce. As a result, members of the climate community have garnered extensive experience working with farmers and extension agents to address their sensitivities to climate variability and change. One group of individuals that has established a longstanding relationship with the agricultural community is the state climatologists. In this study, the state climatologists from six southeastern states were interviewed to assess the challenges and opportunities faced by the agricultural sector, particularly in dealing with current climate variability and potential future changes to climate. Based on their experiences, the combination of favorable climatic conditions, ample water resources, and diversity in agricultural production makes the Southeastern U.S. unique in its ability to adapt to current climate variability and potential future changes in climate.
Fuhrmann, C.M. and C.E. Konrad. 2013: A trajectory approach to analyzing the ingredients associated with heavy winter storms in central North Carolina. Weather and Forecasting, 28, 647-667.
Winter storms, namely snowstorms and ice storms, are a major hazard and forecasting challenge across central North Carolina. This study employed a trajectory approach to analyze the ingredients (i.e., temperature, moisture, and lift) associated with heavy snowstorms and ice storms that occurred within the Raleigh, North Carolina, National Weather Service forecast region from 2000 to 2010. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) tool was used to calculate 72-h backward (i.e., upstream) air parcel trajectories from three critical vertical pressure levels at the time and location of heaviest precipitation for each storm. Analysis of composite trajectories revealed the source regions and meteorological properties of air parcels associated with heavy winter storms. Adiabatic and diabatic contributions to air parcel temperature and moisture content were also estimated along each trajectory to assess the physical processes connected with heavy winter precipitation in the region. Results indicate that diabatic warming and cooling contribute significantly to the vertical temperature profile during heavy winter storms and therefore dictate the resulting precipitation type. The main source of diabatic warming is fluxes of sensible and latent heat within the marine atmospheric boundary layer over the Gulf Stream. These fluxes contribute to a warming and moistening of air parcels associated with heavy ice storms. In contrast, heavy snowstorms are characterized by diabatic cooling in the lower troposphere above the marine atmospheric boundary layer. The most significant moisture source for heavy snowfall is the Caribbean Sea, while heavy ice storms entrain moisture from the Gulf of Mexico and Gulf Stream region near the Carolina coast.
Fuhrmann, C.M. Konrad, C.E., Kovach, M., and D.J. Perkins. 2011: The August 2007 Heat Wave in North Carolina: Meteorological factors and local variability. Physical Geography, 32, 217-240.
August 2007 was an exceptionally warm month across North Carolina. Hundreds of daily maximum and daily high minimum temperature records, as well as numerous all-time temperature records, were either tied or broken during the month. At the same time, a drought of historic proportions overspread much of the Southeast United States. A critical aspect of the August 2007 heat wave was the observed variability in heat and humidity across the different geographic regions of North Carolina. The highest maximum temperatures occurred most frequently in the Piedmont and Sandhills regions, while minimum temperatures were exceptionally high along the coast. The broad-scale pattern of heat can be tied to adiabatic warming associated with subsidence downstream of a persistent upper-level ridge centered over the Mississippi River Valley. Regional to local variations in the heat and humidity across North Carolina are linked to upwind sensible heat fluxes associated with major soil moisture deficits, adiabatic warming connected with downsloping winds off the Appalachian Mountains, and the depth of the mixing layer. Along the coast, the pattern of heat and humidity was tied to the positioning of a mesoscale thermal trough and the presence and strength of the sea-breeze circulation. [Keywords: heat wave, North Carolina, back-trajectories, air mass, drought, thermal trough, vertical mixing.]
Perry, L. B., Konrad, C. E., Hotz, D. G., and Lee, Lawrence. 2010: Synoptic classification of snowfall events in the Great Smoky Mountains, USA. Physical Geography, 31,156-171.
Mean annual snowfall in the Great Smoky Mountains National Park (GSMNP) exhibits considerable spatial variability, ranging from 30 cm in the valleys to 254 cm at higher elevations. Snowfall can be tied to a variety of synoptic classes (e.g., Miller A or B cyclones, 500 hPa cutoff lows), but these frequency and significance of different synoptic classes have not been fully assessed, particularly at higher elevations. In this paper, we manually classify all snowfall events during the period 1991 to 2004 according to a synoptic classification scheme, calculate mean annual snowfall by 850 hPa wind direction and synoptic class, and develop composite plots of various synoptic fields. Hourly observations from nearby first-order stations and 24 hr snowfall totals from five sites within the GSMNP are used to define snowfall events. NCEP/NCAR reanalysis data are used to develop composite plots of various synoptic fields for cyclones passing south and then east of the area (e.g., Miller A cyclones). Results indicate that over 50% of the mean annual snowfall at higher elevations occurs in association with low-level northwest flow, and that Miller A cyclones contribute the greatest amount to mean annual snowfall at all elevations. [Key words: synoptic classification, snowfall, Great Smoky Mountains.]
Konrad C.E. and L. B. Perry, 2010: Relationships between tropical cyclones and heavy rainfall in the Carolina region of the United States. The International Journal of Climatology, 30,522-534.
A strong association exists between exceptionally heavy rainfall and the movement of tropical cyclones (i.e. tropical depressions, tropical storms, and hurricanes) across the Carolina region of the USA. There is much variability, however, in the precipitation totals associated with each tropical cyclone. This variability is at least partially tied to various interactions between mid-latitude features and the moisture plume that is advected around the tropical cyclone. In the first part of this study, a 55-year precipitation events climatology is constructed that quantifies the influence of tropical cyclones on precipitation events with varying return intervals. In particular, it shows that the majority of the heaviest precipitation events in the eastern three-quarters of the region are associated with tropical cyclones. In the second part of this study, a synoptic climatology is developed that reveals the relationships between precipitation totals and various atmospheric variables. The variables include the speed of movement, size, and strength of the tropical system as well as the relative position and strength of various synoptic features surrounding the tropical system. These synoptic features include the location of fronts, regions of upper level divergence and areas of high water vapor contents in the atmosphere. A tree regression model is used to develop a classification that summarizes these multivariate relationships. Four classes of tropical cyclones are identified that effectively differentiate tropical cyclones that produce relatively light versus extraordinarily heavy rainfall.
Keighton, S., Lee, L., Holloway, B., Hotz, D., Zubrick, S. Hovis, J. Votaw, G, Perry, L.B., Konrad, C. E., Miller, D., and Etherton, B. 2009: A collaborative approach to study northwest flow snow in the southern Appalachians. Bulletin of the American Meteorological Society, 90, 977-991.
Upslope-enhanced snowfall events during periods of northwesterly flow in the southern Appalachians have been recognized as a significant winter forecasting problem for some time. However, only in recent years has this problem received noteworthy attention by both the academic and operational communities. The complex meteorology of these events includes significant topographic influences, as well as a linkage between the upstream Great Lakes and resultant southern Appalachian snowfall. A unique collaborative team has recently formed, working toward the goals of improving the physical understanding of the mechanisms at work in these events, as well as developing more accurate forecasts and more detailed climatologies. The literature shows only limited attention to this problem through the 1990s. However, with modernization of the National Weather Service (NWS) in the mid-1990s came opportunities to bring more attention to new or poorly understood forecast problems. These opportunities included the establishment of new forecast offices, often co-located with universities, the deployment of the WSR-88D radar network, expansion of the surface observational network in both space and time, improved access to sophisticated numerical models, and growth of the spotter and cooperative observer networks.
A collaborative team, consisting of faculty from five universities and meteorologists from six NWS forecast offices, has established an ongoing, structured dialogue to help advance the understanding and improve the forecasting of these events. The team utilizes a variety of communication strategies to discuss emerging research findings, review recent events, and share data and ideas. The ultimate goal is to continue fostering working relationships between research and operational meteorologists and climatologists as well as students, all with a common motivation of continually improving forecasts and understanding of this important phenomenon. This group may serve as a model for other collaborative efforts between the research and operational communities interested in a common forecast problem.
Fuhrmann, C.M., Konrad, C. E., and L. E. Band, 2008: Climatological perspectives on the rainfall characteristics associated with landslides in western North Carolina. Physical Geography, 29, 289-305.
Landslides are a significant hazard in the mountains of North Carolina. While previous studies have estimated the critical instantaneous rainfall rates that may trigger a landslide, very little is known about the climatology of rainfall events associated with landslides. The rainfall climatology of a sample of landslide events in western North Carolina from 1950 to 2004 is presented in two parts. First, the two-day concurrent and cumulative antecedent (from 4 to 90 days prior to slope movement) rainfall totals are assessed climatologically by ranking them relative to all heavy precipitation events observed in western North Carolina over a 55-year period. Second, the storm types responsible for the rainfall associated with each landslide event are determined using a manual weather map classification scheme. Forty-seven percent (47%) of the landslide events are connected with concurrent rainfall totals that exceed a one-year return period. In almost half of these cases, the heavy rainfall is associated with a tropical cyclone passing through the region. The other major storm types connected with landslide events (i.e., synoptic and cyclonic-type events) generally display lower rainfall intensities and longer durations compared to tropical cyclones. Landslide activity shows the strongest relation- ship with antecedent precipitation totals over a 90-day period, which is the longest time period examined in the study. In many cases, a tropical cyclone produced heavy rainfall over the landslide location between 30 and 90 days before the event. [Key words: land- slide, heavy rainfall, storm types, climatology, western North Carolina.]
Perry L. and C. E. Konrad, 2007: Antecedent upstream air trajectories associated with northwest flow snowfall in the Southern Appalachians, USA. Weather and Forecasting, 22, 334-352.
Northwest flow snow (NWFS) events are common occurrences at higher elevations and on windward slopes in the southern Appalachians. Low temperatures and considerable blowing and drifting of snow, coupled with significant spatial variability of snowfall, substantially increase societal impacts. This paper develops a synoptic classification of NWFS events in the southern Appalachians using 72-h antecedent upstream (backward) air-trajectory analyses. Hourly observations from first-order stations and daily snow- fall data from cooperative observer stations are used to define snowfall events. NCEP–NCAR reanalysis data are utilized to identify NWFS events on the basis of 850-hPa northwest flow (270°–360°) at the event maturation hour. The NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory tool is used to calculate 72-h backward air trajectories at the event maturation hour and composite trajectories are mapped in a geographic information systems format. Analyses of vertical soundings are coupled with NCEP–NCAR reanalysis data to determine the synoptic characteristics associated with each trajectory class. Significant variability of trajectories and synoptic patterns is evident from the analyses, resulting in four distinct backward air-trajectory classes. Trajectories with a Great Lakes connection result in higher composite mean and maximum snowfall totals along portions of the higher-elevation windward slopes when compared with other northwest trajectories, but little effect of the Great Lakes is noted at lower elevations and on leeward slopes.
Martin, J. and C.E. Konrad, 2006: Directional characteristics of potentially damaging wind gusts in the Southeast United States. Physical Geography, 27, 155-169.
Annual estimated storm damage in the United States is seven billion dollars. Much of that damage is caused by tree blowover that is induced by high wind gusts. The prevailing directions of these wind gusts dictate the zones around structures in which trees may potentially fall and cause damage. To gain a better understanding of hazardous wind gusts, this research examines the directional component of wind gusts in the Southeast United States. Regional patterns of wind gusts are identified and tied to atmospheric and terrestrial patterns. Results indicate the following: (1) gusts along the northeast coast of the study area are bidirectional, being from the northeast and southwest; (2) the southeast coast has a predominantly westerly component to the gusts with little impact from the east; (3) the Piedmont is strongly influenced by westerly gusts, but an easterly component increases gradually to the northeast; and (4) high gusts in the mountains demonstrate a strong relationship with the regional and local topographic characteristics. [Key words: wind damage, gusts, wind climatology, Southeast.]
Perry L. and C. E. Konrad, 2006: Relationships between northwest flow snowfall and topography in the Southern Appalachians. Climate Research, 32, 35-47.
NW flow snowfall (NWFS) events are common occurrences at higher elevations (1500 to >2000 m a.s.l.) and on windward slopes in the Southern Appalachian Mountain region of the south- eastern USA. The spatial patterns of NWFS are strongly controlled by topography, resulting in pronounced spatial variability. The strong topographic and low-level convective forcing, coupled with low temperatures and strong winds, increases societal impacts. This paper analyzes the relationships between NWFS and various topographic and geographic (TOPO/GEOG) variables in the Southern Appalachians. We identified NWFS events on the basis of low-level wind direction, extracted values for the TOPO/GEOG variables from Digital Elevation Models (DEMs), and developed statistical relationships between NWFS and the TOPO/GEOG variables. Using a multivariate regression model and GIS techniques, we also mapped mean annual NWFS across the region. Results indicate that elevation and NW exposure are most strongly correlated with NWFS; however, the strength of these relationships is mediated by temperature. In the colder NWFS events, the relative importance of elevation is diminished, while NW exposure and distance to a NW slope are relatively more important. Additionally, we demonstrate that multivariate regression modeling in conjunction with GIS techniques can be an effective way to map snowfall patterns associated with specific wind directions, particularly when a strong topographic control is evident.
Chen, F. and C. E. Konrad, 2006: A synoptic climatology of summertime heat and humidity in the Piedmont Region of North Carolina. Applied Meteorology and Climatology, 45, 674-685.
The synoptic patterns and boundary layer conditions over a range of antecedent periods associated with the summertime hot events for the years 1951–93 are examined. A hot event is defined as a single day with the highest average daily temperature within a surrounding 5-day window. Among these events, four event subtypes were determined on the basis of extreme values of temperature and/or dewpoint. Composite synoptic maps and vertical profiles of atmospheric variables are produced to distinguish the hottest and moistest events. The hot events, including the extreme categories, are influenced by similar large-scale circulation features. The region is under the control of the Bermuda high, which is centered off the coast of Florida and in the Atlantic Ocean. An upstream 500-hPa ridge produces subsidence and adiabatic warming in the midlevels of the troposphere. Composite patterns of the hottest and moistest events indicate stronger upstream 500-hPa ridging and upper-level subsidence, which suggest greater suppression of local convection and reduction in the upward turbulence transfer of surface sensible heat and water vapor. The moistest events are tied to considerably greater antecedent precipitation, which suggests increased evapotranspiration and accumulation of water vapor near the ground. The extreme hot and humid events are also associated with greater accumulated precipitation hours in the antecedent periods, especially on a 30-day scale. The hottest events also have less sky cover in the 30-day antecedent period, allowing more insolation and surface heating. The extreme events also have greater atmospheric thickness, lighter winds, and greater westerly component in the winds. Synoptic analysis shows that low-level thermal and moisture advection are not significant contributors to the heat and moisture in the extreme events of the Piedmont region.