The Atlantic Hurricane season and the European Windstorm season are
found to be co-related 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 NiÃ±o 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 extra-tropical response in
the seasonal forecast model to El NiÃ±o/La NiÃ±a provides a probable
pathway for the observed co-relation between the extreme event seasons.
This result has important predictability implications for both the
actuarial and seasonal forecasting communities.