STORM-EX: Towards bridging the transition gap in statistical synthetic storm modelling

Post-tropical cyclones are a subset of tropical cyclones that have undergone extratropical transition, a process by which they lose tropical characteristics and take on those of extratropical cyclones. These cyclones can then impact areas outside typical tropical cyclone extent with high winds and copious amounts of precipitation. Due to their relative rarity (in the North Atlantic approximately 50% of the ~14 tropical systems that form annually undergo extratropical transition) the data on these storms is relatively scarce.

Our aim is to build a model capable of generating a global dataset of transitioning storms so their risks can be calculated despite the paucity of data. This model will be built as an extension of STORM (Synthetic Tropical cyclOne generRation Model) which has had success in generating synthetic tropical cyclone tracks and pressure profiles. We will model the jet stream, the transition of the storm, different extratropical transition pathways, storm position and windspeed, and finally storm lysis. This involves several challenges, as statistical models cannot capture all the complex interactions that take place during extratropical transition. The parameters of interest will be identified through literature and model refinement. Data will be drawn from model simulations and data produced in literature. Initial work has shown that the model can generate cyclone tracks and reproduce basic interactions with the jet stream.