The Sensitivity of Tree Rings to ENSO and Climatic Variables in Coastal Alabama

This study investigated the effects of ENSO on annual growth rings of pine trees in coastal Alabama. Tree cores from 28 pines were collected in Mobile County and Baldwin County Alabama, and the ring widths of these cores were measured to the nearest 0.001 mm. Tree ring widths were then cross-dated and standardized using standard procedures. The standardized ring width (SRI) was examined to determine if years of strong ENSO activity were evident. Additionally, SRI values were correlated with other climate variables, including temperature, precipitation, and drought. It appears that strong ENSO episodes are not clearly evident in the tree ring record. Additionally, the climate variables showed inconsistent relationships with SRI. It is possible that a positive annual water balance limits the influences of ENSO on tree ring widths. Furthermore, it is suggested that differences in localized tree environments and mesoscale sea-breeze thunderstorms may obscure the impacts of climatic variables

Regional to Mesoscale Influences of Climate Indices on Tornado Variability

Tornadoes present an undisputable danger to communities throughout the United States. Despite this known risk, there is a limited understanding of how tornado frequency varies spatially at the mesoscale across county or city area domains. Furthermore, while previous studies have examined the relationships between various climate indices and continental or regional tornado frequency, little research has examined their influence at a smaller scale. This study examines the relationships between various climate indices and regional tornado frequency alongside the same relationships at the mesoscale in seven cities with anomalous tornado patterns. The results of a correlation analysis and generalized linear modeling show common trends between the regions and cities. The strength of the relationships varied by region, but, overall, the ENSO had the greatest influence on tornado frequency, followed in order by the PNA, AO, NAO, MJO, and PDO. However, future research is critical for understanding how the effects of climate indices on tornado frequency vary at different spatial scales, or whether other factors are responsible for the atypical tornado rates in certain cities

Perceptions of Hurricane Hazards in the Mid‐Atlantic Region

The mid‐Atlantic region of the United States is susceptible to tropical cyclone hazards. Within the past 15 years this region has experienced Hurricane Isabel in 2003, Hurricane Irene in 2011 and several tropical storms. The region was also impacted by post‐tropical Sandy in 2012. The perception of hurricane hazards among residents of the mid‐Atlantic region has not been directly researched. Furthermore, there is a lack of research on the comprehension of information from hurricane warning graphics that influences hazard perception. This research used a total of eight hypothetical scenarios (four pairs) that varied storm track and storm size to assess risk perception of hurricane hazards and characteristics. Each scenario was represented using a four‐panelled map featuring the National Hurricane Center\u27s cone of uncertainty, a new storm surge map and a new damaging wind map created by the authors. A Qualtrics survey was used to collect responses to questions about concern for personal harm and evacuation intent. Residents of the region perceived falling trees, potential for damaging winds and the size of the storm to be the greatest threats. Scenarios depicting larger storms with track lines that moved inland were seen as more hazardous, resulting in greater concern and evacuation intent. Coastal residents showed greater concern about distance from the track for all scenarios and greater evacuation intent for larger storms compared to inland residents

Changes in Summer Weather Type Frequency in Eastern North America

In this research, the Spatial Synoptic Classification (SSC), a weather type scheme, is used as an alternative method of demonstrating evidence of climate change in the Eastern United States and southern Canada. Changes in frequencies for the seven SSC weather types were assessed for summer trends (May–September) at thirty-eight stations and also at four regions of latitude between 1950 and 2015. Using the SSC, results show significant summer decreases in dry polar (DP) days and transitional (TR) days and significant increases in moist tropical (MT) days. The North region exhibited the greatest breadth of significant results among all weather types. The DP and TR decline was strongest at higher latitudes and weakened approaching the subtropics. The MT gain was strongest across the midlatitudes but statistically significant in all four regions. The four remaining SSC weather types showed more localized statistically significant trends. Results suggest that these trends in weather type frequency are an indicator of summer climate change, with some stations losing over 50 percent of their DP frequency, losing over 40 percent of their TR frequency, and gaining over 30 percent of their MT frequency since 1950

Characteristics of tornadoes associated with land-falling Gulf Coast tropical cyclones

Tropical cyclone tornadoes are brief and often unpredictable events that can produce fatalities and create considerable economic loss. Given these uncertainties, it is important to understand the characteristics and factors that contribute to tornado formation within tropical cyclones. This thesis analyzes this hazardous phenomenon, examining the relationships among tropical cyclone intensity, size, and tornado output. Furthermore, the influences of synoptic and dynamic parameters on tornado output near the time of tornado formation were assessed among two phases of a tropical cyclone's life cycle; those among hurricanes and tropical storms, termed tropical cyclone tornadoes (TCT), and those among tropical depressions and remnant lows, termed tropical low tornadoes (TLT). Results show that tornado output is affected by tropical cyclone intensity, and to a lesser extent size, with those classified as large in size and `major' in intensity producing a greater amount of tornadoes. Increased values of storm relative helicity are dominant for the TCT environment while CAPE remains the driving force for TLT storms. (Published By University of Alabama Libraries

Spatial and Temporal Variability of Extreme Precipitation Events in the Southeastern United States

Much of the Southeastern United States (SeUS) has experienced an increasing number of extreme precipitation events in recent decades. Characterizing these extreme precipitation events is critical for assessing risk from future hydroclimatic extremes and potential flash flooding. A threshold of one inch per hour (1IPH) was used to indicate an extreme precipitation event. Non-parametric tests were run to identify trends in 1IPH event frequency and locate time series change points. In the last 20 years, 1IPH events increased by 53 percent in the SeUS, and 21/61 stations recorded significant increasing trends. A change point is identified in 15/61 stations. June, July, and August are generally the peak time for 1IPH events, but Florida, Louisiana, and Mississippi recorded longer peak seasons. For the time between events, 17/61 stations recorded significant decreasing trends, implying that 1IPH events are increasing in frequency. Four teleconnection indices were positively correlated with 1IPH events. The SeUS experiences considerable tropical cyclone-induced extreme precipitation, yet only seven percent of 1IPH events overlapped with tropical cyclones. Therefore, the increasing frequency of 1IPH events is likely the result of a combination of baroclinic frontal zones or regional and mesoscale convective features. Causes for the increasing frequency of 1IPH events require further research

Communication and Hazard Perception Lessons from Category Five Hurricane Michael

Hurricane Michael made landfall on 10 October 2018 as only the third Saffir Simpson Hurricane Wind Scale (SSHWS) category 5 storm in the USA in the named era. The storm’s intensity, rapid intensification, October landfall, high inland winds, and uncommon landfall location all combined to complicate the communication and preparation efforts of emergency managers (EMs) and broadcast meteorologists (BMs), while clouding the comprehension of the public. Interviews were conducted with EMs, BMs, and a small public sample to hear their stories and identify and understand common themes and experiences. This information and previous research was used to inform the creation of questions for a large sample public survey. Results showed that 61% of our sample did not evacuate, and approximately 80% either underestimated the intensity, misinterpreted or did not believe the forecast, or realized the danger too late to evacuate. Hazard perception from a survey of the public revealed that wind followed by tornadoes, and falling trees were the major concerns across the region. According to their counties of residence, participants were divided into Coastal or Inland, and Heavily Impacted or Less Impacted categories. Inland participants expressed a significantly higher concern for wind, tornadoes, falling trees, and rainfall/inland flooding than Coastal participants. Participants from Heavily Impacted counties showed greater concern for storm surge, tornadoes, and falling trees than participants from Less Impacted counties. These results reinforce the continued need for all parties of the weather enterprise to strengthen communication capabilities with EMs and the public for extreme events

A synthesis of Alabama beach states and nourishment histories

Five reaches of Alabama beaches were geomorphologically classified using established techniques from the literature. Different methods of obtaining wave data for the purpose of beach classification were compared. Complete buoy data of wave heights and wave periods were available for only two of five sites, and these were used to test the validity of field and computer model data used in place of buoy data. A nourishment index was created and used to quantify the beach nourishment history of each site, and a relationship between this value and beach state was measured. The classification of beach states found Alabama beaches will most likely remain in the dissipative regime under current climate and tectonic conditions. Using only field and model data to determine beach state was found to produce results similar to buoy data in some instances, but these instances were not enough to indicate the methods used for this study can be used as a sole method of replacing buoy data. Using these selected methods of describing beach state and nourishment history found a strong but not statistically significant relationship between the two variables. (Published By University of Alabama Libraries