Characteristics of precipitation associated with post-tropical cyclones in the North Atlantic

Abstract

Precipitation brought by cyclone systems has long been known as a major contributor to devastating flood events.Recent post-tropical cyclones (PTCs), which transform from tropical cyclones (TC) to extratropical cyclones (ETC) in the mid-latitudes, are among the strongest cyclones in the mid-latitude European region. Understanding PTCs and their precipitation behavior, particularly in the context of recent observations, is crucial for assessing and mitigating hazards effectively. Here, we couple precipitation data and best track data to examine different aspects of PTCs, such as track characteristics and the associated precipitation behavior. Using the International Best Track Archive for Climate Stewardship (IBTrACS) data from 2001 to 2020, we find that TCs and ETCs peak during fall months, especially in October, with cyclogenesis and extratropical transition (ET) locations varying seasonally. ETCs share characteristics with frontal cyclones, such as faster translation velocities and larger radii than TCs. Hourly precipitation data from Integrated Multi-satellitE Retrievals for Global precipitation measurement (IMERG) (2001–2020) shows lower intensity during ETC phases compared to TC phases but with broader areal coverage – precipitation shields -, with ETCs consistently producing more total rainfall over 24 h. The centroid of precipitation regions during ETC phases shifts northeast of the cyclone centers for short-duration rainfall and west-southwest for longer durations, indicating widespread precipitation further from the cyclone centre. We found asymmetric precipitation distributions favoring the left side of the cyclone track during ETC phases, especially for lower-intensity events. Our results provide valuable insights into the evolving nature of PTCs, and their impact on precipitation patterns, which are crucial for hazard assessment models and mitigation strategies to safeguard communities and minimize the risks associated with these potential hazards.