Comparing the Predictability of Arctic and Atlantic Basin Cyclones Using Ensemble-Based Sensitivity Analysis of MPAS Forecasts

Arctic cyclone (ACs) are ubiquitous features during the boreal summer that can be long-lived systems associated with prolonged strong winds, leading to very rapid sea ice loss events. Accurate sea ice predictions may require accurate predictions of cyclone-related wind speed and direction, which critically depends on cyclone track and intensity. Nevertheless, there is a relatively small number of studies that focus on summer AC predictability, aside from the record-breaking Great Arctic Cyclones of August 2012 and 2016. Therefore, the goal of this study is to assess the processes that limit AC position and intensity predictability for particular cases and compare them to Atlantic basin cyclones. The processes that limited the predictability of these systems will be investigated using Model for Prediction Across Scales (MPAS) ensembles forecasts, with 60 km horizontal resolution over most of the globe and higher resolution refinement to 15 km over the region on interest. The MPAS forecasts will be used as input into the ensemble-based sensitivity technique to evaluate hypotheses on the relative contribution of uncertainty in the lower tropospheric baroclinicity and precipitable water and upper tropospheric troughs to the predictability of cyclone track and intensity. Preliminary results from an August 2013 AC demonstrate that AC position is sensitive to the tropopause-based polar vortex pattern, including the development of an upstream short-wave trough early in the forecast and downstream Tropopause Polar Vortex later in the forecast. Conversely, a January 2013 Atlantic basin cyclone demonstrate that Atlantic basin cyclone position is sensitive to the interaction of multiple short-wave troughs at early lead times. Further, both storms demonstrate that intensity is sensitive to warmer low-level temperatures and moisture near the cyclone. An additional June 2020 AC and January 2014 Atlantic basin cyclone will provide further validation of the above processes and results.