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Increased flash drought awareness in recent years has motivated the development of numerous indicators for monitoring, early warning, and assessment. The flash drought indicators can act as a complementary set of tools by which to inform flash drought response and management. However, the limitations of each indicator much be measured and communicated between research and practitioners to ensure effectiveness. The limitations of any flash drought indicator are better understood and overcome through assessment of indicator sensitivity and consistency; however, such assessment cannot assume any single indicator properly represents the flash drought "truth." To better understand the current state of flash drought monitoring, this study presents an intercomparison of nine, widely used flash drought indicators. The indicators represent perspectives and processes that are known to drive flash drought, including evapotranspiration and evaporative demand, precipitation, and soil moisture. We find no single flash drought indicator consistently outperforms all others across the contiguous United States. We do find the evaporative demand- and evapotranspiration-driven indicators tend to lead precipitation- and soil moisture-based indicators in flash drought onset, but also tend to produce more flash drought events collectively. Overall, the regional and definition-specific variability in results supports the argument for a multi-indicator approach for flash drought monitoring, as advocated by recent studies. Furthermore, flash drought research-especially evaluation of historical and potential future changes in flash drought characteristics-should test multiple indicators, datasets, and methods for representing flash drought, and ideally employ a multi-indicator analysis framework over use of a single indicator from which to infer all flash drought information. SIGNIFICANCE STATEMENT: Rapid onset or "flash" drought has been an increasing concern globally, with quickly intensifying impacts to agriculture, ecosystems, and water resources. Many tools and indicators have been developed to monitor and provide early warning for flash drought, ideally resulting in more time for effective mitigation and reduced impacts. However, there remains no widely accepted single method for defining, monitoring, and measuring flash drought, which means most indicators that are developed are compared with other individual indicators or conditions and impacts in one or two flash drought events. In this study, we measure the state of flash drought monitoring through an intercomparison of nine, widely used flash drought indicators that represent different aspects of flash drought. We find that no single flash drought indicator outperformed all others and suggest that a comprehensive flash drought monitor should leverage multiple, complementary indicators, datasets, and methods. Furthermore, we suggest flash drought research-especially that which reflects on historical or projected changes in flash drought characteristics-should seek multiple indicators, datasets, and methods for analyses, thereby reducing the potentially confounding effects of sensitivity to a single indicator. [ABSTRACT FROM AUTHOR]

The 2018 exceptional drought over the Colorado Plateau motivated unprecedented responses by individuals and organizations. Some of these responses made clear that proactive adaptive measures were fundamental to drought resilience. Climate service organizations (CSOs) supporting and observing these responses realized the utility of a network to share and document successful drought responses. In February 2020, a small group of CSOs and resource managers (RMs) met to envision the Southwest Drought Learning Network (DLN) to align with other existing efforts, but with the specific goal of enabling peer-to-peer learning to build resilience to future droughts. Since then, the network has grown into five organized teams focused on specific aspects of building drought resilience. Team activities include sharing case studies to help others learn from past experiences, hosting monthly drought briefings that introduce drought data and management tools, identifying information needed to support critical management decisions, innovating and sharing new and traditional drought monitoring technologies, and building drought resilience with indigenous communities. The network allows for collaboration and leveraging partner resources and strengths. The DLN website (https://dln.swclimatehub.info/) hosts more information about network teams and activities. This innovative network continues to grow in response to management needs and water scarcity in the region. For the benefit of others who may be considering a similar network and supporting peer-to-peer learning, we document the history, process, and lessons learned regarding the Southwest DLN. [ABSTRACT FROM AUTHOR]

Anthropogenically forced-warming and La Niña forced-precipitation deficits caused at least a sixfold risk increase for compound extreme low precipitation and high temperature in California–Nevada from October 2020 to September 2021. [ABSTRACT FROM AUTHOR]

In this paper, we report on the frequency of false onsets of wet season rainfall in the case of the Northern Australian wet season and investigate the role of large‐scale tropical climate processes such as the El Niño–Southern Oscillation, Indian Ocean Dipole (IOD) and Madden–Julian Oscillation. A false onset occurs when a wet season rainfall onset criterion is met, but follow‐up rainfall is not received for weeks or months later. Our analysis of wet season rainfall data from 1950 through 2020 shows a false onset occurs, on average, between 20 and 30% of wet seasons across all of northern Australia. This increases at a regional and local level such as at Darwin, the Northern Territory (NT), and parts of Queensland's north coast to over 50%. Seasonal climate influences, such as a La Niña pattern and a negative IOD that typically expedite the wet season rainfall onset, also increase the likelihood of a false onset over northern Australia. Our analysis also finds that periods of false onsets can sometimes, but not always, coincide with periods of rapid soil moisture depletion. The false rainfall onsets that develop into flash drought can be potentially disruptive and costly and are of potential significance for agriculture and fire management in northern Australia, and in other monsoonal climates that also typically experience a slow build‐up to the seasonal monsoon. In conclusion, effective rainfall indicates that many seasons experience 'false onsets' with dry conditions after early rainfall. We propose that false onsets are a physical characteristic of the climate of northern Australia which occurs with relatively high frequency. In addition, these false onsets may sometimes co‐occur with a flash drought. [ABSTRACT FROM AUTHOR]

Flash droughts, characterized by their unusually rapid intensification, have garnered increasing attention within the weather, climate, agriculture, and ecological communities in recent years due to their large environmental and socioeconomic impacts. Because flash droughts intensify quickly, they require different early warning capabilities and management approaches than are typically used for slower-developing "conventional" droughts. In this essay, we describe an integrated research-and-applications agenda that emphasizes the need to reconceptualize our understanding of flash drought within existing drought early warning systems by focusing on opportunities to improve monitoring and prediction. We illustrate the need for engagement among physical scientists, social scientists, operational monitoring and forecast centers, practitioners, and policy-makers to inform how they view, monitor, predict, plan for, and respond to flash drought. We discuss five related topics that together constitute the pillars of a robust flash drought early warning system, including the development of 1) a physically based identification framework, 2) comprehensive drought monitoring capabilities, and 3) improved prediction over various time scales that together 4) aid impact assessments and 5) guide decision-making and policy. We provide specific recommendations to illustrate how this fivefold approach could be used to enhance decision-making capabilities of practitioners, develop new areas of research, and provide guidance to policy-makers attempting to account for flash drought in drought preparedness and response plans. [ABSTRACT FROM AUTHOR]

The use of social media, such as Twitter, has changed the information landscape for citizens' participation in crisis response and recovery activities. Given that drought progression is slow and also spatially extensive, an interesting set of questions arise, such as how the usage of Twitter by a large population may change during the development of a major drought alongside how the changing usage facilitates drought detection. For this reason, contemporary analysis of how social media data, in conjunction with meteorological records, was conducted towards improvement in the detection of drought and its progression. The research utilized machine learning techniques applied over satellite-derived drought conditions in Colorado. Three different machine learning techniques were examined: the generalized linear model, support vector machines and deep learning, each applied to test the integration of Twitter data with meteorological records as a predictor of drought development. It is found that the integration of data resources is viable given that the Twitter-based model outperformed the control run which did not include social media input. Eight of the ten models tested showed quantifiable improvements in the performance over the control run model, suggesting that the Twitter-based model was superior in predicting drought severity. Future work lies in expanding this method to depict drought in the western U.S. [ABSTRACT FROM AUTHOR]

The last two decades of drought in the Southwest has challenged municipal water providers by decreasing reservoir storage, which acts as a buffer at times of drought. Understanding evolving drought risks in the Southwest The 2020-21 drought in the Southwest set new records for low rainfall and high temperatures. Keywords: Drought; Hydrology; Adaptation; Policy EN Drought Hydrology Adaptation Policy E821 E827 7 04/11/22 20220301 NES 220301 2021 Southwest Drought Forum B I What: i b The Southwest Drought Forum brought together over 100 drought experts, stakeholders, and decision-makers to discuss the long-term implications of drought in the Southwestern United States. [Extracted from the article]

The annual Australian monsoon pattern includes an onset, or the much anticipated first active monsoon period of the season, but defining the monsoon onset has proven to be problematic. Since the first Australian monsoon onset definition by Troup in 1961 there have been many others presented. There appears to be no universally accepted method to define the Australian monsoon onset, and therefore, we present here an analysis of the methods that have been proposed. The aim of this paper is to systematically review the different methods used to define the Australian monsoon onset, adding to the work that has been done by other reviews for monsoon systems around the world. For the first time, we identify the 25 different methods that have been published for the Australian monsoon/wet season onset and compare them to identify how well they align. When considering the 57 seasons where more than one onset definition is provided, the range of dates within the season can range over several months, with an average range of 44 days and the largest range within a season of 78 days. Thus, we show that different onset definitions are capturing different events altogether and pin the 'onset' to different dates throughout the progression of the north Australian wet season. Some capture a 'wet season onset' while others capture the dynamical overturning of the atmosphere (i.e. the monsoon). In conclusion, our analysis finds that there is still a lack in real-time monitoring or prognostic capabilities of monsoon onset dates as well as limited operational applicability despite a plethora of definitions. [ABSTRACT FROM AUTHOR]