Tropical Cyclone Activity and Extratropical Rossby Wave Breaking: A See-Saw Relationship in the Atlantic Basin

This study explores the relation between Atlantic TC activity and extratropical Rossby wave breaking (RWB). With an objective algorithm, we identified RWB events in the hurricane seasons of 1979-2013. On the synoptic scale, these events significantly perturb the local environment, including the distribution of wind shear and moisture. On the seasonal scale, the variability in the occurrence of RWB is in concert with the regional climate variability. In seasons with more (less) frequent RWB occurrences, the tropical Atlantic is dominated by strong (weak) wind shear and dry (wet) atmosphere. The relation contributes to the strong negative correlation between the frequency of RWB and Atlantic TC activity. The negative correlation holds for various measures of TC activity, and the statistical significance is comparable to that of the correlation between tropical Atlantic SST and TC activity. The strong correlation is mainly contributed by RWB events over the West Atlantic, where both RWB and TCs occur frequently. In this region, the periods of active (inactive) RWB correspond to the periods with strong (weak) wind shear and inactive (active) TC activity on both the seasonal and intraseasonal scales. Taken together, this study highlights the tropics-extratropics connection and the overall negative impacts of RWB on Atlantic TC activity, and the findings may have important implications for the subseasonal to seasonal prediction of TC activity.