Characteristics and Impacts of Extratropical Rossby Wave Breaking during the Atlantic Hurricane Season

Abstract

This study investigates the characteristics of extratropical Rossby wave breaking (RWB) during the Atlantic hurricane season and its impacts on Atlantic tropical cyclone (TC) activity. It was found that RWB perturbs the wind and moisture fields throughout the troposphere in the vicinity of a breaking wave. When RWB occurs more frequently over the North Atlantic, the Atlantic main development region (MDR) is subject to stronger vertical wind shear and reduced tropospheric moisture; the basinwide TC counts are reduced, and TCs are generally less intense, have a shorter lifetime, and are less likely to make landfalls. A significant negative correlation was found between Atlantic TC activity and RWB occurrence during 1979-2013. The correlation is comparable to that with the MDR SST index and stronger than that with the Niño-3.4 index. Further analyses suggest that the variability of RWB occurrence in the western Atlantic is largely independent of that in the eastern Atlantic. The RWB occurrence in the western basin is more closely tied to the environmental variability of the tropical North Atlantic and is more likely to hinder TC intensification or reduce the TC lifetime because of its proximity to the central portion of TC tracks. Consequently, the basinwide TC counts and the accumulated cyclone energy have a strong correlation with western-basin RWB occurrence but only a moderate correlation with eastern-basin RWB occurrence. The results highlight the extratropical impacts on Atlantic TC activity and regional climate via RWB and provide new insights into the variability and predictability of TC activity.

Relative Impacts of Local and Remote Forcing on Tropical Cyclone Frequency in Numerical Model Simulations

“…This suggests that both the local SST and remote forcing modulate Atlantic TC frequency and that remote forcing exerts a stronger influence than the local SST in the context of the model setup. Further calculations show that RWB occurrence is enhanced in Exp2‐LBC13 (Figure S4), in agreement with the reduced TC activity (Zhang et al, ).…”

“…For example, the 2013 Atlantic hurricane season was characterized by warm sea surface temperature anomalies (SSTAs) in the Atlantic main development region (MDR) and cold SSTAs in the East Pacific, but turned out to be one of the quietest seasons since 1994 (Blake, ). Zhang et al (, ) suggested that the suppressed TC activity in 2013 can be attributed to active extratropical Rossby wave breaking (RWB). Despite a synoptic‐scale process, frequent RWB can induce significant large‐scale circulation anomalies on the seasonal time scale via enhanced tropical‐extratropical mixing and modulate TC activity.…”

Impacts of Extratropical Weather Perturbations on Tropical Cyclone Activity: Idealized Sensitivity Experiments With a Regional Atmospheric Model

“…In some cases, the lack of the extratropical influence allows the Fujiwhara effect to dictate storm motion. The difference might arise because they emphasized lateral boundary forcing from the 2013 season, which featured extratropical anomalies that were exceptionally strong and extended into the deep tropics (Bell et al, 2014;Zhang et al, 2016;Zhang et al, 2017). Finally, storm lysis in the Ncalm simulations occurs farther east and less frequently along the northern boundary than in the Default simulations.…”

“…Based on idealized sensitivity experiments with the 1982 and 1995 hurricane seasons, they suggested that the high-frequency "weather" variations, defined as anomalies relative to seasonal mean fields in the domain interior and at the lateral boundaries, are only of secondary importance for the observed interannual variability in TC statistics. However, there is substantial overall evidence from previous studies suggesting that TCs are sensitive to the weather perturbations contained in the lateral boundary forcing (Hanley et al, 2001;Leroux et al, 2016;Peirano et al, 2016;Zhang et al, 2016Zhang et al, , 2017. They found that the skill of the two simulations did not differ much and suggested that the interannual variability of TC activity was generally insensitive to the lateral boundary forcing.…”

“…While tropical variability has been considered as the primary modulator of Atlantic TC activity (e.g., Gray, 1984Gray, , 1990Vimont & Kossin, 2007), there is substantial interest in the potential impact of extratropical atmospheric variability on TC activity, especially the TC tracks and landfall locations (e.g., Ballenzweig, 1959;Elsner, 2003;Murakami et al, 2016). Recent studies highlighted a strong negative correlation between measures of TC activity and equatorward propagating Rossby waves on the seasonal scale (Papin, 2017;Zhang et al, 2017;Zhang & Wang, 2019), although these extratropical waves may also facilitate TC development near the U.S. coast (Bentley et al, 2016;Davis & Bosart, 2004;Galarneau et al, 2015). Recent studies highlighted a strong negative correlation between measures of TC activity and equatorward propagating Rossby waves on the seasonal scale (Papin, 2017;Zhang et al, 2017;Zhang & Wang, 2019), although these extratropical waves may also facilitate TC development near the U.S. coast (Bentley et al, 2016;Davis & Bosart, 2004;Galarneau et al, 2015).…”