Changes in weather patterns influencing future tropical cyclone risk in the Caribbean

Abstract:

It is relatively well understood that tropical cyclones (TC) will intensify as sea surface temperatures (SST) warm. Also, more severe impacts from TCs are expected as the amount of precipitation brought by TCs increases with the water holding capacity of the atmosphere and storm surges become more damaging with rising sea levels. It is however less certain, how the overall frequency of TCs might change.

TC formation mainly depends on the state of the atmosphere. Favourable conditions for TC formation are low vertical wind shear, moist air in the mid troposphere and the presence of perturbations. While most global circulation models struggle in producing reasonable tropical storms, their representation of the before mentioned variables is substantially better. We therefore aim at analysing the occurrence of favourable weather conditions for TC formation and intensification in a large ensemble of climate simulations that also includes low resolution models that do not adequately represent TCs.

We use self-organizing maps to define a set of daily weather patterns using the ERA5 reanalysis and assess the associated TC risk for each weather pattern by analysing observed TC tracks for days of each pattern. We further check whether the association between certain weather patterns and TC risk holds in different climate states by analysing the occurrence of TCs in each weather pattern in a few high-resolution models in warmer future scenarios.

By analysing the occurrence of favourable conditions for TC formation and intensification we are not restricted to the few TC resolving climate models. Thereby we get an indirect, but more comprehensive projection of how the future tropical cyclone potential might change.