Spatio-Temporal Variability of the North Atlantic Subtropical High and Tropical Cyclones: Results From NOAA-CIRES-DOE Twentieth Century Reanalysis v3 (20CRv3) and HURDAT2

The North Atlantic Subtropical High (NASH) has one of the largest influences on the path of tropical cyclones (TCs) in the northern Atlantic Ocean (NA). This semi-permanent anticyclone forms one pole of the large-scale circulation prevalent over the Atlantic basin, with its opposing pole being the sub-polar low further to the north. This study seeks to quantify anomalous pressure fields indicative of the NASH, to identify patterns in TC activity in the NA basin, and to relate the two over time and space.

TC activity is derived from observed data incorporated in the HURDAT2 dataset. A NASH climatology is created using NOAA 20^th Century Reanalysis v3 (20CRv3) data. Initial results show a relationship between the Ortegren Bermuda High Index (BHI) and tropical cyclone density, especially Cabo Verde-type TCs. In addition, the BHI shows a persistent negative trend between 1851 and 2014.

An extension of this work will be made using the HiResMIP component of CMIP6. A climatology of the NASH and future TC tracks will be obtained out to 2100 to investigate the variability and change of these phenomena not only in the past and present, but also the future.