Impact of North Atlantic Jet Stream on the Seasonality of Hurricane Translation Speed changes

Abstract:

Tropical cyclone (TC) translation speed (TCTS) can affect the duration of TC-related disasters, which is critical to coastal areas. Based on HURDAT2 and NCEP/NCAR Reanalysis 1datasets, the climatological changes of TCTS and their relationship to the changes of mid-latitude jet stream and storm migration are discussed here for storms near the North Atlantic coast during 1948-2019. The variability of TCTS shows substantial seasonality. Significant accelerations of TCTS are found in June and October, while prominent slowdown of TCTS is found in August. We suggest the seasonality in TCTS can be largely explained by the seasonality of changes in both mid-latitude jet stream and storm migration. The increase of TCTS in June and October is related to the strengthened ambient steering wind caused by the equatorward displacement of the jet stream and poleward migration of storm locations, while the decrease of TCTS in August may be caused by the weakened jet speed and equatorward migrated storms. In September, however, the slowdown effects of poleward displacement and weakening of jet stream on TCTS are largely compensated by the poleward migration of storm locations, therefore, no significant change in TCTS is observed.

We emphasis that it is necessary to take a seasonality view in discussing the climatological change of storm motion. Changes in TCTS differ substantially with month, they are even opposite in sign in some months (e. g. August and October). However, previous studies mainly take the year-mean view during their exploration on TCTS trends, which could largely obscure the actual features in the variations of storm motion and bring in large uncertainties. Similarly, although the poleward migration of storm location in recent decades is proposed, we find that that the changes of storm locations show prominent seasonality. Our findings may deepen the understanding of the climatological changes of TCTS, which may help the projection of hurricane behaviors under the changing climate.