Characteristics of Precipitation and Wind Extremes Induced by Extratropical Cyclones in Northeastern North America

Abstract

This study investigates important characteristics of extreme (above the 99th local percentile) near-surface wind speed and precipitation hourly events associated with extratropical cyclones (ETCs) over North America, using 20-year ERA5 reanalysis and IMERG satellite-based precipitation data. For seasonal and geographical occurrence frequency, wind extremes prevail in winter over ocean and in autumn over land, while precipitation extremes show relatively weak seasonal variation over ocean and primarily occur in summer over land. For both variables, over 60% of extreme events are associated with ETCs over northeastern North America (NNA) regardless of the season. When one type of extreme is observed, the probability that it is a compound wind-precipitation extreme reaches up to 40% along the coasts and ocean, and about 20% in the NNA region. About 90% of compound wind and precipitation extremes in NNA (which occur most frequently in fall) are associated with ETCs. Significant discrepancies exist between the magnitudes of extremes in ERA5 and IMERG; however, both datasets consistently identify ETCs as the primary drivers of extremes in mid-to-high latitudes. Extratropical cyclones tend to have longer-lasting wind extremes (∼6 hr in ERA5) compared to precipitation extremes (∼3 hr in ERA5 and ∼2 hr in IMERG). Rarer and stronger extremes based on a higher threshold are more likely to be associated with ETCs, exhibiting shorter extreme duration timescales.