Increasing tropical cyclone intensity and potential intensity in the subtropical Atlantic around Bermuda from an ocean heat content perspective 1955- 2019
- 1University of Southampton, National Oceanography Centre, Southampton, United Kingdom of Great Britain – England, Scotland, Wales (s.hallam@noc.soton.ac.uk)
- 2Irish Climate Analysis and Research Units, Maynooth University, County Kildare, Ireland
- 3National Oceanography Centre, European Way, Southampton, SO14 3ZH
- 4Bermuda Institute of Ocean Sciences, 17 Biological Station, St. George’s GE 01, Bermuda
- 5Bermuda Weather Service, Bermuda Airport Authority, St. George’s DD03, Bermuda
- 6Met Office, Fitzroy Road, Exeter, EX1 3PB
Here we investigate tropical cyclone (TC) activity and intensity within a 100km radius of Bermuda between 1955 and 2019. Our results show a more easterly genesis over time and significant increasing trends in tropical cyclone intensity (maximum wind speed (Vmax)) with a decadal Vmax median value increase of 30kts from 33 to 63kts, together with significant increasing August, September, October (ASO) sea surface temperature (SST) of 1.1°C (0.17 °C per decade) and ocean temperature between 0.5–0.7°C (0.08-0.1°C per decade) in the depth range 0-300m. The strongest correlation is found between TC intensity and ocean temperature averaged through the top 50m ocean layer (T50m) r=0.37 (p<0.01).
We show how tropical cyclone potential intensity estimates are closer to actual intensity by using T50m opposed to SST using the Bermuda Atlantic Timeseries Hydrostation S dataset. We modify the widely used sea surface temperature potential intensity index by using T50m to provide a closer estimate of the observed minimum sea level pressure (MSLP), and associated Vmax than by using SST, creating a T50m potential intensity (T50m_PI) index. The average MSLP difference is reduced by 12mb and proportional to the SST/ T50m temperature difference. We also suggest the index could be used over a wider area of the subtropical/tropical Atlantic where there is a shallow mixed layer depth. Finally, we outline the TC wind-pressure relationship observed for the subtropical Atlantic around Bermuda, explaining 77% of the variance, which may prove useful for future prediction.
(Environmental Research Letters, 2020, in revision)
How to cite: Hallam, S., Guishard, M., Josey, S., Hyder, P., and Hirschi, J.: Increasing tropical cyclone intensity and potential intensity in the subtropical Atlantic around Bermuda from an ocean heat content perspective 1955- 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7803, https://doi.org/10.5194/egusphere-egu21-7803, 2021.
