On 2 April 2017 Louisiana saw one of its largest tornado outbreaks since 1950. The day saw a total of 21 tornadoes, six of which were classified as significant (EF2+). This extreme event resulted in an estimated 4.2 million dollars in damage and two fatalities. A climatology of Louisiana individual tornado days dating back to 1950 ranked this event second for total number of tornadoes (21) in a day and second for number of significant (EF2+) tornadoes (6) in a day. To assess the overall impact of this outbreak, the Destruction Potential Index (DPI) was used to compare both the overall number and strength of tornadoes to previous events. The 2 April 2017 event had the highest DPI for the state of Louisiana since 1950. Comparisons made to tornado days in nearby states in the region also highlight the significance of this event. The synoptic conditions of 2 April 2017 were compared to a 25-member synoptic scale composite of past Louisiana tornado days with six or more tornadoes. The composite highlighted anomalies in synoptic ingredients that contribute to tornado outbreak environments. Most notably, the synoptic structure consisted of a more meridional flow pattern, which allowed for stronger moisture transport, low level shear, deep layer shear, and increased thermal advection. This produced an optimal mesoscale environment with high instability and storm-relative environmental helicity. The meteorological significance of this event with respect to Louisiana stems from the uncommon combination of a high shear/high CAPE near-storm environment in a southern tornado outbreak. The high shear/high CAPE environment largely responsible for the 2 April 2017 Louisiana tornado outbreak is more commonly observed in Great Plains tornado outbreaks.

We examine the trajectories of four historical markers displaced during an enhanced Fujita scale 2 (EF2) tornado at the Fort Pulaski National Monument located on Cockspur Island, east of Savannah in southeast Georgia. The careful work of National Park Service employees in cataloguing the origin and landing points of the debris allows for an unusually accurate analysis of tornado debris trajectories for heavy objects. These markers, weighing around 68 kg (150 lb) each, traveled intact for distances of up to 220 m (750 ft). One of the historical markers was fractured into at least three pieces, the larger of which traveled 300 m (1,000 ft). Understanding the travel for these relatively heavy items is important, as they are similar in weight to household appliances that could commonly be part of a tornado debris field.

Superstorm Sandy was the second-costliest hurricane in U.S. history, causing catastrophic flooding and prolonged power outages in New Jersey and New York. The public's response to this extreme event on the social network Twitter is examined using statistical analysis and manual inspection of 185,000 "tweets" relating to Sandy. Sentiment analysis of tweets from Manhattan Island reveals a statistically significant trend toward negative perceptions, especially on the southern half of the island, as Sandy made landfall. Inspection of all tweets uncovered scientific misconceptions regarding hurricanes, and a surprising and disquieting anthropomorphic reconception of Sandy. This reconception, divorced from factual information about the storm, dominated the "Twittersphere" compared to official scientific information. The implications of such reconceptions for social media communication during future extreme events, and the utility of the methodology employed for analysis of other events, are discussed.

A 30-yr climatology (1981-2010) of cold-air damming (CAD) events in the southern Appalachians was conducted using hourly surface observations and North American Regional Reanalysis (NARR) data. Analysis of the spatial distribution and frequency of these events reveals that some part of the Southeast is affected by CAD on 50 days out of each year, and even the northern Florida panhandle and much of Alabama experience CAD conditions on about 30 days annually. Spatially, different CAD types tend to exhibit one of two patterns in the southernmost extent of the cold-air dome: a more southerly dome with a ridge axis oriented from north-northeast to south-southwest or a more westerly dome with a ridge axis in a northeast to west-southwest orientation. These patterns may be the result of both splitting around the region of higher terrain in east-central Alabama and Coriolis forcing in stronger CAD types with higher wind speeds. Analysis of the frequency of CAD by type on a month-by-month and year-by-year basis confirms previous work that CAD is much more frequent during the cold season versus the warm season, with CAD occurring on 6.8 days month(-1) during December and only 1.3 days month(-1) during July. Analysis was also stratified by CAD type, revealing that weak/dry events were the most common. Classical type events with stronger and more favorably positioned parent highs exhibited the longest average duration, nearly 45 h, while other CAD types averaged approximately half as long.

Although advances have been made regarding the influence of aerosols on precipitation processes, the ability of power plant aerosol emissions to alter cloud microphysics and enhance atmospheric convection is not yet fully understood. By analyzing the relationship between proximity to coal power plants and lightning flash density in Georgia from 1992–2003, we find that lightning strike frequency is not substantially enhanced near power plants in the long-term warm season climatology. If existent, any signal was likely masked by the more dominant mechanisms of the sea breeze circulation, Sandhills-Fall Line convection, and Atlanta urban environment. Despite the lack of a definitive signal in the climatology, several cases of potential lightning amplification were identified for Plant Scherer. Therefore, power plant lightning enhancement may potentially occur in isolated events, but it is difficult to link such events conclusively to power plant aerosol emissions without a more detailed analysis of the causal mechanisms.

Using publicly available information gleaned from over 1700 found-and-returned objects on the Pictures and Documents found after the 27 April 2011 Tornadoes Facebook page, the authors have created a database of 934 objects lofted by at least 15 different tornadoes during the 27 April 2011 Super Outbreak in the southeast United States. Analysis of the takeoff and landing points of these objects using GIS and high-resolution numerical trajectory modeling techniques extends previous work on this subject that used less specific information for much smaller sets of tracked tornado debris. It was found that objects traveled as far as 353 km, exceeding the previous record for the longest documented tornado debris trajectory. While the majority of debris trajectories were 10 degrees to the left of the average tornado track vector, the longest trajectories exhibited a previously undocumented tendency toward the right of the average tornado track vector. Based on results from a high-resolution trajectory model, a relationship between this tendency and the altitude of lofting of debris is hypothesized, with the debris reaching the highest altitudes taking the rightmost trajectories. The paper concludes with a discussion of the pros and cons of using social media information for meteorological research.