Connections among mesoscale extremes are multiscale, from short-time-scale cold-pool outflows triggering neighboring convection to decadal variability of the global circulation that favors concurrent and distant extremes. Tropical and extratropical cyclones, for example, can exhibit temporal clustering, and tropical convection can trigger a global response through Rossby wave trains. Connections can also lead to multihazard events, such as the Thomas fire in California enhancing mudslide and flash flood risk. The full range of physical mechanisms that connect mesoscale extremes and the strength of the connections is only beginning to be explored and may include multiscale wave dynamics, coupled Earth system processes, and persistence of anomalies from days to decades.

Connected mesoscale extremes and their impacts present a challenge and an opportunity for disaster mitigation and risk management. Reinsurance, for example, is based on the premise of independent extremes. This premise is challenged by our new understanding of connected hazards and our increasingly connected society in which impacts from an extreme event may change our exposure and vulnerability in ways that change the likelihood of another high-impact event. For example, the 2012 Mid-Atlantic and Midwest derecho knocked out power to millions, thus exposing many more people to heat risk. Accounting for this connectivity presents opportunities to develop robust disaster mitigation and risk management practices.

This session explores how scientists and risk management experts conceptualize connected mesoscale extremes and impacts. We welcome presentations that explore dynamical and statistical insights into connected mesoscale extremes and impacts, developing statistical and dynamical prediction systems for connected mesoscale extremes and impacts, and challenges and potential solutions to connected events for risk management.

The statistical approaches of conducting extreme event attribution and projection have matured, becoming automated while forming a mainstream methodology; this is largely built upon extreme-value and return-period analysis. However, synoptic–dynamic attribution for extreme weather (i.e. detailed analysis and dynamical diagnosis of an event of interest) and putting it into perspective of future climate projections has not received as much attention. Perhaps one issue is that the generality of results from a single case study is not always clear. Yet, as reanalysis and climate model datasets continue to increase in resolution and begin to resolve mesoscale circulation systems, opportunities exist to apply synoptic–dynamic meteorological reasoning to understand interaction across scales between mesoscale circulation systems and climate.

In this session, we encourage submissions of mesoscale extreme event diagnoses from both the statistical and synoptic–dynamic meteorology approach. Examples of methods for the latter approach include (but are not limited to) climatology and case study analysis of mesoscale circulation systems and their attendant extreme events utilizing high-resolution convection-resolving modeling and/or large global and regional model ensemble simulations. The papers in this session will aim to study and understand the statistics and synoptic–dynamic meteorology of mesoscale meteorological extremes, including the two-way interaction between mesoscale circulations and the larger-scale climate system.

In response to this need, this session is proposed to stimulate discussion and exchange related to statistical methodologies and various relevant areas of environmental science, with a focus on maritime studies. Statistical modeling of complex extreme events has developed rapidly in recent years; theoretical analysis has transitioned to statistical tools with many environmental applications. We hope to examine the state of the art in present statistical tools, to identify challenges and opportunities, and to motivate new research interactions and developments. 

Presentations from all areas of environmental science are welcome. For example, marine mesoscale extreme events are the result of the combination of environmental factors that can be related. Coastal flooding can result from nonlinear interactions of multiple oceanographic, hydrological, geological, and meteorological processes (e.g. tides, sea-level anomalies, storm surge, waves, winds, fluvial discharges, precipitation, and land subsidence). Moreover, although the exceptional extreme variation of a single process (e.g. storm surge) can result in coastal flooding, the more normal situation is that a combination of notably high values of more than one process constitutes the precursor mechanism, thereby making a compound extreme event. Additional topics can consider extremes related to lake-effect (or lake modified) systems and coastal extreme weather.  Moreover, the relevant processes are not stationary, but vary with season, and on time scales of years, decades, etc., with changing climate. Thus, characteristics of an extreme event may be described as the extreme nature of the impact rather than the individual component factors, the multivariate nature of the impact, and the statistical dependence of component factors.

Dangerous Storms at Sea

Extratropical and tropical cyclones produce rapidly changing and extreme weather conditions over large areas of the ocean, threatening the safety of life at sea, causing billions of dollars in time lost and ship and cargo damage annually, and damaging coastal communities. However, there remain significant gaps in our understanding of these storms. Rapid intensification of tropical cyclones is an important forecast challenge that is receiving increasing attention in operations and research. Less well-known, but also critical, rapid extratropical cyclogenesis at sea presents a unique forecast problem that requires a greater understanding of air–sea interaction and coupled model improvements, particularly in areas such as the heavily traveled intersection of major coastal storm tracks and the Gulf Stream.

Weather Forecast Needs of the Maritime Industry

The maritime industry would benefit from products and services that extend the forecast horizon beyond the present focus on days 0–4; provide probabilistic forecasts of hazards and high waves; and improve prediction of sea ice development, movement, and decay. Additionally, as cargo and cruise ships continue to get larger, carrying ever more goods and passengers, consideration must be given to providing forecasts and hazardous weather warnings that address the challenges such large ships must face. Stronger public–private partnerships within the maritime weather enterprise will help ensure mariners get the best possible forecasts and warning services.

Weather Observations on the High Seas

Strengthening the global ocean observing system (in situ and satellite based) and achieving optimal spatial distribution is an international challenge highlighted by the WMO Marine Meteorology and Oceanography Programme. A more robust engagement with commercial vessel operators is needed to increase the number and quality of weather observations from ships of opportunity, improving forecasts. Efforts to increase international collaboration and the sharing of remotely sensed ocean surface vector winds and altimeter data are needed to better analyze and predict areas of dangerous winds and waves at sea.

Future of Communication and Dissemination Systems for Mariners

Challenges exist in exchanging information among ships, national hydrometeorological centers, and commercial weather providers. Recent incidents at sea demonstrate that such challenges may adversely impact decision-making by mariners.  This situation is further exacerbated by a maritime weather infrastructure that remains heavily reliant on decades-old technology for dissemination, such as radiofax and text broadcasts.

Dangerous Storms at Sea

Extratropical and tropical cyclones produce rapidly changing and extreme weather conditions over large areas of the ocean, threatening the safety of life at sea, causing billions of dollars in time lost and ship and cargo damage annually, and damaging coastal communities. However, there remain significant gaps in our understanding of these storms. Rapid intensification of tropical cyclones is an important forecast challenge that is receiving increasing attention in operations and research. Less well-known, but also critical, rapid extratropical cyclogenesis at sea presents a unique forecast problem that requires a greater understanding of air–sea interaction and coupled model improvements, particularly in areas such as the heavily traveled intersection of major coastal storm tracks and the Gulf Stream.

Weather Forecast Needs of the Maritime Industry

The maritime industry would benefit from products and services that extend the forecast horizon beyond the present focus on days 0–4; provide probabilistic forecasts of hazards and high waves; and improve prediction of sea ice development, movement, and decay. Additionally, as cargo and cruise ships continue to get larger, carrying ever more goods and passengers, consideration must be given to providing forecasts and hazardous weather warnings that address the challenges such large ships must face. Stronger public–private partnerships within the maritime weather enterprise will help ensure mariners get the best possible forecasts and warning services.

Weather Observations on the High Seas

Strengthening the global ocean observing system (in situ and satellite based) and achieving optimal spatial distribution is an international challenge highlighted by the WMO Marine Meteorology and Oceanography Programme. A more robust engagement with commercial vessel operators is needed to increase the number and quality of weather observations from ships of opportunity, improving forecasts. Efforts to increase international collaboration and the sharing of remotely sensed ocean surface vector winds and altimeter data are needed to better analyze and predict areas of dangerous winds and waves at sea.

Future of Communication and Dissemination Systems for Mariners

Challenges exist in exchanging information among ships, national hydrometeorological centers, and commercial weather providers. Recent incidents at sea demonstrate that such challenges may adversely impact decision-making by mariners.  This situation is further exacerbated by a maritime weather infrastructure that remains heavily reliant on decades-old technology for dissemination, such as radiofax and text broadcasts.