A Climatology of the Extratropical Flow Response to Recurving Atlantic Tropical Cyclones

Previous case studies have noted a significant extratropical flow response to recurving Atlantic tropical cyclones (TCs), which is often linked to extreme weather events downstream. This study examines the modification of Rossby waves on the extratropical tropical jet in response to recurving Atlantic TCs from a climatological perspective. Changes in amplitude and location of Rossby waves are identified using a wavelet decomposition technique on isentropic potential vorticity. The climatology demonstrates that recurving Atlantic TC events are capable of modifying the amplitude of the extratropical flow. A subset of events were associated with a period of Rossby wave de-amplification followed by a period of amplification several days later. The characteristics of the TC were not significantly associated with the resulting extratropical flow modification-- a result consistent with previous Western North Pacific climatologies. The nature of the extratropical flow response is most strongly tied to the phasing of the recurving TC with the nearest trough at the time of recurvature, although the phasing cannot explain all of the variance in the results. Additionally, this study demonstrates the effect of recurving Atlantic TCs on downstream predictability. Using ensemble forecasts from the European Centre for Medium-Range Weather Forecasts, case studies reveal that a period of rapid downstream error growth occurs near the time of TC recurvature. Ongoing research is addressing the climatology of these low-predictability events as well as the dynamical and physical mechanisms responsible for the error growth.