The TSR (Tropical Storm Risk) extended range forecast for North Atlantic hurricane activity in 2023 anticipates a season with activity below the 1991-2020 30-year norm level. The forecast spans the period from 1st June to 30th November 2023 and employs data through to the end of November 2022.
TSR uses the forecast August-September sea surface temperatures in the Atlantic Main Development Region (10º-20ºN, 60º-20ºW) and the forecast July-September Caribbean trade wind anomaly over the region 7.5º-17.5ºN, 100º-30ºW as predictors.
The latter uses forecast August-September Niño 3.4 sea surface temperatures which we predict to be warmer than average leading to increased vertical wind shear and a modest suppressing effect on Atlantic hurricane activity.
In addition, of the two years since 1950 where three consecutive La Niña conditions occurred during summer and autumn (1954-1956 and 1998-2000), the following Atlantic hurricane season was near or below average.
Large uncertainties remain in whether ENSO neutral or El Niño conditions will be present next summer however it is extremely unlikely a fourth consecutive La Niña event will be present. We express the forecast uncertainty in terms of probability of exceedance for Accumulated Cyclone Energy (ACE) and for hurricane numbers.
Seasonal outlooks for North Atlantic hurricane activity contribute to the anticipation of risk for insurance companies, other weather-sensitive businesses, and local and national governments. However, the uncertainty associated with such forecasts is often unclear.
This reduces their benefit and contributes to the perception of forecast ‘busts’. The robust assessment of risk requires a full and clear probabilistic quantification of forecast uncertainty with the forecast issued in terms of probability of exceedance (PoE).
In this way the chance of each hurricane number/activity outcome occurring is clear for the benefit of users.
Going forward TSR is including robust forecast probability of exceedance (PoE) information based on the recommendation and methodology described in Saunders et al. (2020).
Download the extended range forecast report here – https://www.eurotempest.ltd/wp-content/uploads/TSRATLForecastDecember2023.pdf
For more information on TSR, visit – https://www.tropicalstormrisk.com/