Climatological, Composite, and Case Study Analyses Linking Rossby Wave Breaking to Potential Vorticity Streamer and Cutoff Cyclone Formation in the Subtropical North Atlantic Basin

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Extreme weather events, although having a low probability of occurrence, can exert very high adverse socioeconomic impacts. The goal of the funded research is to investigate the climatology, seasonality, and their interactions with background flows of a variety of extreme weather events that impact parts of the United States, Central America, and the Western Caribbean. Candidate extreme weather events to be investigated include heavy, flood-producing rainstorms during the cooler half of the year and tropical disturbances that can bring flooding rains, damaging winds, and devastating storm surges during the warmer half of the year. These candidate extreme weather events often occur in conjunction with upper tropospheric disturbances known as cutoff cyclones. Cutoff cyclones that form in higher latitudes can dump chilly air into the subtropics, fueling cold waves initially and big rainstorms subsequently. Cutoff cyclones that form in lower latitudes can enable warm, moist tropical air to reach midlatitudes, fueling tropical cyclone landfalls and/or exceptionally heavy rainfalls. A novel aspect of the research is that it is targeted at the interaction of tropical and midlatitude circulations associated with cutoff cyclones. These cutoff cyclones can govern the timing, occurrence, and location of extreme weather events in the United States, Central America, and western Caribbean. Another innovation of this research project is that historically extreme weather events have been studied in isolation. This historical approach precludes the possibility of detecting the occurrence of multiple geographically separated but dynamically linked extreme weather events that may be occurring near simultaneously in different parts of the world. A sure-fire recipe for the occurrence of extreme weather events is the existence of a wavy, high-amplitude, large-scale flow pattern across the Northern Hemisphere that can break down into a series of cutoff cyclones. A critical science issue is determining the physical causes of flow breakdown that can lead to cutoff cyclone formation. The research project will use state-of-the-art global gridded datasets to identify the frequency of extreme weather events associated with cutoff cyclones. Climatological, composite, and case study analyses will be constructed from these gridded datasets to help quantify the physical processes governing the location and occurrence of these extreme weather events.The broader impacts of the research are substantial, including (1) the education of the next generation of scientists in the field, (2) opportunities to interact with scientists at NOAA's National Hurricane Center to facilitate the transfer of research to operations, and (3) educating meteorologists from Central America and the Caribbean through outreach and training activities to ensure they are current on weather patterns conducive to the occurrence of extreme weather events in their regions.