1This study investigates flash flood forecast and warning communication, interpretation, and 2 decision making, using data from a survey of 418 members of the public in Boulder, Colorado, 3 USA. Respondents varied in their perceptions and understandings of flash flood risks in Boulder, 4 and some had misconceptions about flash flood risks, such as the safety of crossing fast-flowing 5 water. About 6% of respondents indicated consistent reversals of U.S. watch-warning alert 6 terminology. However, more in-depth analysis illustrates the multi-dimensional, situationally 7 dependent meanings of flash flood alerts, as well as the importance of evaluating interpretation 8 and use of warning information along with knowledge about warning terminology. Some public 9 respondents estimated low likelihoods of flash flooding given a flash flood warning; these were 10 associated with lower anticipated likelihood of taking protective action given a warning. 11Protective action intentions were also lower among respondents who had less trust in flash flood 12 warnings, those who had not made prior preparations for flash flooding, and those who believed 13 themselves to be safer from flash flooding. In addition, the analysis elucidates the complex, 14 contextual nature of protective decision making during flash flood threats. These findings 15 suggest that warnings can play an important role not only by notifying people that there is a 16 threat and helping motivate people to take protective action, but also by helping people evaluate 17 what actions to take given their situation. 18 19 Keywords: Flash flooding, warnings, risk perception, communication, decision making 20 4 impacts, and thus present distinct challenges for communicating and responding to threats. To 41 help address these challenges, this study investigates people's perceptions, understandings, and 42 interpretations of flash flood risks and alerts 1 and their anticipated responses to flash flood 43 warnings. The analysis focuses on members of the public in the U.S., utilizing data from a survey 44 of 418 residents of Boulder, Colorado, conducted in 2010. 45 The article examines three research questions: 1) How do members of the Boulder public 46 perceive and understand flash flood risks? 2) How do they perceive and interpret flash flood 47 warnings and other alerts?; and 3) How do they anticipate responding to flash flood alerts, and 48 what influences their anticipated responses? This includes investigating people's knowledge, 49 attitudes, and beliefs about flash flood risks and alerts and their anticipated decisions when a 50 flash flood threatens. For time-sensitive hazards such as flash floods, people's interpretations and 51 decision processes during a real threat are complex and difficult to measure, especially among 52 people at high risk. By examining people's anticipated interpretations and behavior in 53 hypothetical contexts, this study seeks to develop knowledge that can help understand what 54 people think and do during more complicated real-worl...

Uncertainty information in natural hazard forecasts is increasingly being communicated explicitly. This study was designed to determine whether different ways of communicating uncertainty graphically affects the decisions and interpretations of forecasts and if expertise was a factor in the decisions and interpretations from forecasts explicitly showing uncertainty. In a hypothetical decision‐making task regarding ice thickness and shipping, 138 experts and non‐experts received ice‐thickness forecasts in four different presentations expressing uncertainty: worded probability, spaghetti plot, fan plot and box plot. These forecasts contained no measures of central tendency. There was no consistent difference in decision or best‐guess forecast (deterministic ice thickness forecast based on the forecast representation) between the different forecast representations. However, participants interpreted different amounts of uncertainty across the different forecast representations. Experts made significantly more economically rational decisions than non‐experts, interpreted lower best‐guess forecasts and inferred significantly more uncertainty than non‐experts. These results suggest that care be taken in choosing how uncertainty is represented in forecasts, especially between expert and non‐expert audiences.

During volcanic eruptions, Volcanic Ash Advisory Centres issue ash advisories for aviation showing the forecasted outermost extent of the ash cloud. During the 2010 Icelandic volcano Eyjafjallajökull eruption, the Met Office produced supplementary forecasts of quantitative ash concentration, due to demand from airlines. Additionally, satellite retrievals of estimated volcanic ash concentration are now available. To test how these additional graphical representations of volcanic ash affect flight decisions, whether users infer uncertainty in graphical forecasts of volcanic ash, and how decisions are made when given conflicting forecasts, a survey was conducted of 25 delegates representing U.K. research and airline operations dealing with volcanic ash. Respondents were more risk seeking with safer flight paths and risk averse with riskier flight paths when given location and concentration forecasts compared to when given only the outermost extent of the ash. Respondents representing operations were more risk seeking than respondents representing research. Additionally, most respondents’ hand-drawn no-fly zones were larger than the areas of unsafe ash concentrations in the forecasts. This conservatism implies that respondents inferred uncertainty from the volcanic ash concentration forecasts. When given conflicting forecasts, respondents became more conservative than when given a single forecast. The respondents were also more risk seeking with high-risk flight paths and more risk averse with low-risk flight paths when given conflicting forecasts than when given a single forecast. The results show that concentration forecasts seem to reduce flight cancellations while maintaining safety. Open discussions with the respondents suggested that definitions of uncertainty may differ between research and operations.

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

On 23 November 1981, a strong cold front swept across the United Kingdom, producing tornadoes from the west to the east coasts. An extensive campaign to collect tornado reports by the Tornado and Storm Research Organisation (TORRO) resulted in 104 reports, the largest U.K. outbreak on record. The front was simulated with a convection-permitting numerical model down to 200-m horizontal grid spacing to better understand its evolution and meteorological environment. The event was typical of tornadoes in the United Kingdom, with convective available potential energy (CAPE) less than 150 J kg−1, 0–1-km wind shear of 10–20 m s–1, and a narrow cold-frontal rainband forming precipitation cores and gaps. A line of cyclonic absolute vorticity existed along the front, with maxima as large as 0.04 s−1. Some hook-shaped misovortices bore kinematic similarity to supercells. The narrow swath along which the line was tornadic was bounded on the equatorward side by weak vorticity along the line and on the poleward side by zero CAPE, enclosing a region where the environment was otherwise favorable for tornadogenesis. To determine if the 104 tornado reports were plausible, first possible duplicate reports were eliminated, resulting in as few as 58 tornadoes to as many as 90. Second, the number of possible parent misovortices that may have spawned tornadoes is estimated from model output. The number of plausible tornado reports in the 200-m grid-spacing domain was 22 and as many as 44, whereas the model simulation was used to estimate 30 possible parent misovortices within this domain. These results suggest that a number of 90 reports was plausible.

This paper describes the rationale, development and testing of a quick guide leaflet on the presentation of data and uncertainty. While tools for capturing, analysing and presenting data become more advanced, the fundamentals of presenting data with adequate context and clarity remain unchanged. The leaflet, aimed at scientists generating and presenting data, was created as part of an interdisciplinary collaboration (meteorologists, information designers, psychologists) working within the PURE Network project RACER, funded by the UK Natural Environment Research Council. A copy of the leaflet is included in this article.

No abstract

No abstract