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Weather Forecast Uncertainty Information

An Exploratory Study with Broadcast Meteorologists

Julie L. Demuth, Betty Hearn Morrow, and Jeffrey K. Lazo
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Julie L. Demuth, Jeffrey K. Lazo, and Rebecca E. Morss

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Past research has shown that individuals vary in their attitudes and behaviors regarding weather forecast information. To deepen knowledge about these variations, this article explores 1) patterns in people’s sources, uses, and perceptions of everyday weather forecasts; and 2) relationships among people’s sources, uses, and perceptions of forecasts, their personal characteristics, and their experiences with weather and weather forecasts. It does so by performing factor and regression analysis on data from a nationwide survey of the U.S. public, combined with other data. Forecast uses factored into planning for leisure activities and for work/school-related activities, while knowing what the weather will be like and planning how to dress remained separate. Forecast parameters factored into importance of precipitation parameters and of temperature-related parameters, suggesting that these represent conceptually different constructs. Regression analysis showed that the primary drivers for how often people obtain forecasts are what they use forecasts for and their perceived importance of and confidence in forecast information. People’s forecast uses are explained in large part by their frequency of obtaining forecasts and their perceived importance of temperature-related and precipitation forecast information. This suggests that that individuals’ frequency of obtaining forecasts, forecast use, and importance of forecast parameters are closely interrelated. Sociodemographic characteristics and, to a lesser extent, weather-related experience also influence some aspects of people’s forecast sources, uses, and perceptions. These findings continue to build understanding of variations among weather forecast users, which can help weather information providers improve communication of forecasts to better meet users’ needs.

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Julie L. Demuth, Mark DeMaria, and John A. Knaff

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Previous work, in which Advanced Microwave Sounding Unit (AMSU) data from the Atlantic Ocean and east Pacific Ocean basins during 1999–2001 were used to provide objective estimates of 1-min maximum sustained surface winds, minimum sea level pressure, and the radii of 34-, 50-, and 64-kt (1 kt ≡ 0.5144 m s−1) winds in the northeast, southeast, southwest, and northwest quadrants of tropical cyclones, is updated to reflect larger datasets, improved statistical analysis techniques, and improved estimation through dependent variable transforms. A multiple regression approach, which utilizes best-subset predictor selection and cross validation, is employed to develop the estimation models, where the dependent data (i.e., maximum sustained winds, minimum pressure, wind radii) are from the extended best track and the independent data consist of AMSU-derived parameters that give information about retrieved pressure, winds, temperature, moisture, and satellite resolution. The developmental regression models result in mean absolute errors (MAE) of 10.8 kt and 7.8 hPa for estimating maximum winds and minimum pressure, respectively. The MAE for the 34-, 50-, and 64-kt azimuthally averaged wind radii are 16.9, 13.3, and 6.8 n mi (1 n mi ≡ 1852 m), respectively.

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Samuel J. Childs, Russ S. Schumacher, and Julie L. Demuth

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Eastern Colorado is one of the most active hail regions in the United States, and individual hailstorms routinely surpass millions of dollars in crop loss and physical damage. Fifteen semistructured interviews with eastern Colorado farmers and ranchers were conducted in the summer of 2019 to gauge perceptions of the severity and vulnerability associated with hailstorms, as well as to understand how forecasts and warnings for severe hail are received and acted upon by the agricultural community. Results reveal a correspondence between perceived and observed frequency of hailstorms in eastern Colorado and highlight financial losses from crop destruction as the greatest threat from hailstorms. In contrast to the National Weather Service defining severe hail as at least 1.0 in. (25.4 mm) in diameter, the agricultural community conceptualizes hail severity according to impacts and damage. Small hail in large volumes or driven by a strong wind are the most worrisome scenarios for farmers, because small hail can most easily strip crop heads and stalks. Larger hailstones are perceived to pose less of a threat to crops but can produce significant damage to physical equipment and injure livestock. Eastern Colorado farmers and ranchers are avid weather watchers and associate environmental cues with hailstorms in addition to receiving warning messages, primarily via alerts on mobile telephones. Hailstorms elicit feelings of dejection and anxiety in some respondents, whereas others accept hailstorms as part of the job. Increasing awareness of the agricultural perceptions of hailstorms can help the meteorological community direct hail prediction research efforts and improve risk communication to the agricultural sector.

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Rebecca E. Morss, Julie L. Demuth, and Jeffrey K. Lazo

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Weather forecasts are inherently uncertain, and meteorologists have information about weather forecast uncertainty that is not readily available to most forecast users. Yet effectively communicating forecast uncertainty to nonmeteorologists remains challenging. Improving forecast uncertainty communication requires research-based knowledge that can inform decisions on what uncertainty information to communicate, when, and how to do so. To help build such knowledge, this article explores the public’s perspectives on everyday weather forecast uncertainty and uncertainty information using results from a nationwide survey. By contributing to the fundamental understanding of laypeople’s views on forecast uncertainty, the findings can inform both uncertainty communication and related research.

The article uses empirical data from a nationwide survey of the U.S. public to investigate beliefs commonly held among meteorologists and to explore new topics. The results show that when given a deterministic temperature forecast, most respondents expected the temperature to fall within a range around the predicted value. In other words, most people inferred uncertainty into the deterministic forecast. People’s preferences for deterministic versus nondeterministic forecasts were examined in two situations; in both, a significant majority of respondents liked weather forecasts that expressed uncertainty, and many preferred such forecasts to single-valued forecasts. The article also discusses people’s confidence in different types of forecasts, their interpretations of the probability of precipitation forecasts, and their preferences for how forecast uncertainty is conveyed. Further empirical research is needed to study the article’s findings in other contexts and to continue exploring perception, interpretation, communication, and use of weather forecast uncertainty.

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300 Billion Served

Sources, Perceptions, Uses, and Values of Weather Forecasts

Jeffrey K. Lazo, Rebecca E. Morss, and Julie L. Demuth

Understanding the public's sources, perceptions, uses, and values of weather forecasts is integral to providing those forecasts in the most societally beneficial manner. To begin developing this knowledge, we conducted a nationwide survey with more than 1,500 respondents to assess 1) where, when, and how often they obtain weather forecasts; 2) how they perceive forecasts; 3) how they use forecasts; and 4) the value they place on current forecast information. Our results indicate that the average U.S. adult obtains forecasts 115 times per month, which totals to more than 300 billion forecasts per year by the U.S. public. Overall, we find that respondents are highly satisfied with forecasts and have decreasing confidence in forecasts as lead time increases. Respondents indicated that they use forecasts across a range of decision-making contexts. Moreover, nearly three-quarters stated that they usually or always use forecasts simply to know what the weather will be like. Using a simplified valuation approach, we estimate the value of current weather forecast information to be approximately $286 per U.S. household per year, or $31.5 billion total per year value to U.S. households. This compares favorably with total U.S. public and private sector meteorology costs of $5.1 billion a year. To better support the provision of societally beneficial weather information, we advocate for well-designed periodic evaluations of the public's sources, perceptions, uses, and values of weather forecasts. These should include investigations of other important topics such as interpretations of hazardous weather warnings and presentation of uncertainty information.

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Cara L. Cuite, Rachael L. Shwom, William K. Hallman, Rebecca E. Morss, and Julie L. Demuth

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Evacuation before severe coastal storms is a critical tool for keeping coastal residents safe. Effective messaging of evacuations could help save lives, but there is little evidence-based guidance on the advantages or disadvantages of specific messaging. Ideally, evacuation messages would convince those most at risk to evacuate and those who do not need to evacuate to stay in their homes. Using an online survey of 1716 coastal residents in Connecticut, New Jersey, and New York, this study randomly assigned respondents to message conditions in each of two hypothetical storm scenarios. Results from the first scenario indicate that those who saw mandatory evacuation messages had higher evacuation intentions than those who saw advisory messages, and both of those messages resulted in slightly higher evacuation intentions than voluntary evacuation messages. However, voluntary messages resulted in lower evacuation intentions for those that did not live in evacuation zones compared to those who did live in evacuation zones, which may help reduce shadow evacuation. In the second scenario, identifying an evacuation area by the municipality name or the individual’s street name resulted in similar evacuation intentions across all participants. Messages identifying an evacuation area by “flood zone” or “flood-prone area” resulted in equally high evacuation intentions for those who believe they live in a flood zone, but these messages suppressed evacuation intentions for those who do not believe they live in a flood zone. This indicates that such messages could also be an effective approach for reducing shadow evacuation. Implications for risk communicators and emergency managers are discussed.

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Cara L. Cuite, Rebecca E. Morss, Julie L. Demuth, and William K. Hallman

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Both hurricanes and nor’easters can be destructive and deadly. The current study investigates whether, when all other features of a storm warning message are held constant, people perceive the risks posed by nor’easters and hurricanes differently and whether these differences affect their attitudes and decisions about taking protective action. We conducted an online experiment involving 1,700 Americans residing in Northeastern coastal ZIP codes to test the effects of storm type (hurricane vs. nor’easter). Participants were told that their area was under an evacuation order due to either a predicted hurricane or nor’easter. Reported message comprehension and perceived relevance were similar across storm type; however, storm type had small but significant effects on other dependent measures. Those in the hurricane condition were more likely to believe the storm would be severe (p =. 007). They were also more likely to say that it is important to evacuate, that they would evacuate their homes, and that they would recommend to their neighbors that they evacuate (ps <.001). Additional analysis demonstrated that the effect of storm type on evacuation likelihood is mediated, at least in part, by perceived severity. These findings provide evidence that people perceive hurricanes as more severe and more likely to require taking protective action than nor’easters, even when other attributes of the storms remain the same. Forecasters, broadcast meteorologists, and emergency management professionals should consider these small but important differences in perceptions when communicating about these types of storms.

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Julie L. Demuth, Mark DeMaria, John A. Knaff, and Thomas H. Vonder Haar

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Advanced Microwave Sounding Unit (AMSU) data are used to provide objective estimates of 1-min maximum sustained surface winds, minimum sea level pressure, and the radii of 34-, 50-, and 64-kt (1 kt ≡ 0.5144 m s−1) winds in the northeast, southeast, southwest, and northwest quadrants of tropical cyclones. The algorithms are derived from AMSU temperature, pressure, and wind retrievals from all tropical cyclones in the Atlantic and east Pacific basins during 1999–2001. National Hurricane Center best-track intensity and operational radii estimates are used as dependent variables in a multiple-regression approach. The intensity algorithms are evaluated for the developmental sample using a jackknife procedure and independent cases from the 2002 hurricane season. Jackknife results for the maximum winds and minimum sea level pressure estimates are mean absolute errors (MAE) of 11.0 kt and 6.7 hPa, respectively, and rmse of 14.1 kt and 9.3 hPa, respectively. For cases with corresponding reconnaissance data, the MAE are 10.7 kt and 6.1 hPa, and the rmse are 14.9 kt and 9.2 hPa. The independent cases for 2002 have errors that are only slightly larger than those from the developmental sample. Results from the jackknife evaluation of the 34-, 50-, and 64-kt radii show mean errors of 30, 24, and 14 n mi, respectively. The results for the independent sample from 2002 are generally comparable to the developmental sample, except for the 64-kt wind radii, which have larger errors. The radii errors for the 2002 sample with aircraft reconnaissance data available are all comparable to the errors from the jackknife sample, including the 64-kt radii.

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John A. Knaff, Stacey A. Seseske, Mark DeMaria, and Julie L. Demuth

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Axisymmetric temperatures and gradient-balanced winds associated with tropical cyclones derived from the Advanced Microwave Sounding Unit are stratified by the 24-h averaged vector difference of the horizontal wind between 200 and 850 hPa (or vertical wind shear). Using 186 total cases that are limited to tropical cyclones with intensities greater than 33 m s−1 (or mature) and are located over sea surface temperatures greater than 26.4°C, vertical wind shear–based composites are created. Results show that as the vertical wind shear increased, the upper-level warm-core structure associated with the tropical cyclone descended, resulting in a shallower balanced vortex. These observationally based results are presented in the context of recent mesoscale modeling results of the effect of shear on tropical cyclone structure.

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