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1. Synoptic Characteristics of 14-Day Extreme Precipitation Events across the United States

   https://doi.org/10.1175/JCLI-D-19-0563.1  

   Jennrich, Gregory C.; Furtado, Jason C.; Basara, Jeffrey B.; Martin, Elinor R. (August 2020, Journal of Climate)

   null (Ed.)

   Abstract Although significant improvements have been made to the prediction and understanding of extreme precipitation events in recent decades, there is still much to learn about these impactful events on the subseasonal time scale. This study focuses on identifying synoptic patterns and precursors ahead of an extreme precipitation event over the contiguous United States (CONUS). First, we provide a robust definition for 14-day “extreme precipitation events” and partition the CONUS into six different geographic regions to compare and contrast the synoptic patterns associated with events in those regions. Then, several atmospheric variables from ERA-Interim (e.g., geopotential height and zonal winds) are composited to understand the evolution of the atmospheric state before and during a 14-day extreme precipitation event. Common synoptic signals seen during events include significant zonally oriented trough–ridge patterns, an energized subtropical jet stream, and enhanced moisture transport into the affected area. Also, atmospheric-river activity increases in the specific region during these events. Modes of climate variability and lagged composites are then investigated for their potential use in lead-time prediction. Key findings include synoptic-scale anomalies in the North Pacific Ocean and regional connections to modes such as the Pacific–North American pattern and the North Pacific Oscillation. Taken together, our results represent a significant step forward in understanding the evolution of 14-day extreme precipitation events for potential damage and casualty mitigation. 

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2. Synoptic Characteristics of 14-Day Extreme Precipitation Events across the United States

   https://doi.org/https://doi.org/10.1175/JCLI-D-19-0563.1.  

   Jennrich, G. C.; Furtado, J. C.; Basara, J. B.; Martin, E. R. (August 2020, Journal of climate)

   Although significant improvements have been made to the prediction and understanding of extreme precipitation events in recent decades, there is still much to learn about these impactful events on the subseasonal time scale. This study focuses on identifying synoptic patterns and precursors ahead of an extreme precipitation event over the contiguous United States (CONUS). First, we provide a robust definition for 14-day “extreme precipitation events” and partition the CONUS into six different geographic regions to compare and contrast the synoptic patterns associated with events in those regions. Then, several atmospheric variables from ERA-Interim (e.g., geopotential height and zonal winds) are composited to understand the evolution of the atmospheric state before and during a 14-day extreme precipitation event. Common synoptic signals seen during events include significant zonally oriented trough–ridge patterns, an energized subtropical jet stream, and enhanced moisture transport into the affected area. Also, atmospheric-river activity increases in the specific region during these events. Modes of climate variability and lagged composites are then investigated for their potential use in lead-time prediction. Key findings include synoptic-scale anomalies in the North Pacific Ocean and regional connections to modes such as the Pacific–North American pattern and the North Pacific Oscillation. Taken together, our results represent a significant step forward in understanding the evolution of 14-day extreme precipitation events for potential damage and casualty mitigation. 

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3. Synoptic Connections and Impacts of 14-Day Extreme Precipitation Events in the United States

   https://doi.org/10.1175/JAMC-D-21-0174.1  

   Schroers, Melanie; Martin, Elinor (July 2022, Journal of Applied Meteorology and Climatology)

   Abstract Long periods of extreme precipitation can cause costly damages to a region’s infrastructure while also creating a higher risk for the region’s population. Planning for these periods would ideally begin at the subseasonal-to-seasonal time scale, yet prediction of precipitation at this time scale has low skill. In this study, we will use Jennrich et al.’s database of 14-day extreme precipitation events to understand more about the synoptic connections and impacts of these extended extreme events. The synoptic connections of events were examined using the composites of event-day 500-hPa geopotential height and precipitable water anomalies. The combination of these two drivers leads to higher skill in the West Coast and Great Lakes than other regions, with an equitable threat score of 0.137 and 0.084, respectively, and higher conditional probabilities of event occurrence. Therefore, the synoptic patterns associated with events, although significant, are not unique, which poses prediction challenges. Historical impacts of these events, using NCEI storm reports, were assessed to benefit decision-makers in future risk mitigation. A variety of reports were found during events, from winter weather reports in West Coast events to tropical storm reports in Southeast events. Every region has significantly more flooding reports during events than in nonextreme 14-day periods, demonstrating the impacts of such extended events. Although there is still much to learn about extreme precipitation events, this study contributes to the foundational knowledge of synoptic drivers and impacts of events. 

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4. Listening to Stakeholders II: Adapting Research Products on Subseasonal to Seasonal Heavy Precipitation Events by Exploring Options with Users

   https://doi.org/10.1175/BAMS-D-22-0229.1  

   VanBuskirk, Olivia G.; Dickinson, Ty A.; Schroers, Melanie A.; McPherson, Renee A.; Martin, Elinor R. (April 2023, Bulletin of the American Meteorological Society)

   Abstract Extreme precipitation events can cause significant impacts to life, property, and the economy. As forecasting capabilities increase, the subseasonal-to-seasonal (S2S) time scale provides an opportunity for advanced notice of impactful precipitation events. Building on a previous workshop, the Prediction of Rainfall Extremes at Subseasonal to Seasonal Periods (PRES²iP) project team conducted a second workshop virtually in the fall of 2021. The workshop engaged a variety of practitioners, including emergency managers, water managers, tribal environmental professionals, and National Weather Service meteorologists. While the team’s first workshop examined the “big picture” in how practitioners define “extreme precipitation” and how precipitation events impact their jobs, this workshop focused on details of S2S precipitation products, both current and potential future decision tools. Discussions and activities in this workshop assessed how practitioners use existing forecast products to make decisions about extreme precipitation, how they interpret newly developed educational tools from the PRES²iP team, and how they manage uncertainty in forecasts. By collaborating with practitioners, the PRES²iP team plans to use knowledge gained going forward to create more educational and operational tools related to S2S extreme precipitation event prediction, helping practitioners to make more informed decisions. 

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5. Listening to Stakeholders: Initiating Research on Subseasonal-to-Seasonal Heavy Precipitation Events in the Contiguous United States by First Understanding What Stakeholders Need

   https://doi.org/10.1175/BAMS-D-20-0313.1  

   VanBuskirk, Olivia; Ćwik, Paulina; McPherson, Renee A.; Lazrus, Heather; Martin, Elinor; Kuster, Charles; Mullens, Esther (October 2021, Bulletin of the American Meteorological Society)

   Abstract Heavy precipitation events and their associated flooding can have major impacts on communities and stakeholders. There is a lack of knowledge, however, about how stakeholders make decisions at the subseasonal-to-seasonal (S2S) time scales (i.e., 2 weeks to 3 months). To understand how decisions are made and S2S predictions are or can be used, the project team for “Prediction of Rainfall Extremes at Subseasonal to Seasonal Periods” (PRES 2 iP) conducted a 2-day workshop in Norman, Oklahoma, during July 2018. The workshop engaged 21 professionals from environmental management and public safety communities across the contiguous United States in activities to understand their needs for S2S predictions of potential extended heavy precipitation events. Discussions and role-playing activities aimed to identify how workshop participants manage uncertainty and define extreme precipitation, the time scales over which they make key decisions, and the types of products they use currently. This collaboration with stakeholders has been an integral part of PRES 2 iP research and has aimed to foster actionable science. The PRES 2 iP team is using the information produced from this workshop to inform the development of predictive models for extended heavy precipitation events and to collaboratively design new forecast products with our stakeholders, empowering them to make more-informed decisions about potential extreme precipitation events. 

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