On the Dependency of Atlantic Hurricane and European Windstorm Hazards

Abstract

The Atlantic hurricane season and the European windstorm season are found to be negatively correlated in a seasonal forecast model. The probability of extremes occurring in both seasons is compared to the probability of extremes in each season being independent of one another. An above average Atlantic hurricane season is followed by an above average European windstorm season less often than if they were independent, consistent across three intensity measures. The El Niño–Southern Oscillation is found to be in the positive (negative) phase when hurricane activity is suppressed (enhanced) and European windstorm activity is enhanced (suppressed). A clear extratropical response in the seasonal forecast model to El Niño/La Niña provides a probable pathway for the observed correlation between the extreme event seasons. This result has important predictability implications for both the actuarial and seasonal forecasting communities.