Title: Subseasonal Prediction of the Stratospheric Polar Vortex: Skill, Uncertainty, and their Dynamical Origins
Abstract:
Wintertime variability of the stratospheric polar vortex (SPV) is strongly influenced by upward-propagating planetary waves, which break in the stratosphere and deposit momentum, thereby weakening the vortex. Because SPV variability can affect surface weather, it provides a potential source of predictability on subseasonal timescales. In this talk, I first assess how skilfully SPV variability is predicted by the ECMWF subseasonal prediction system. I then show how uncertainty in SPV predictions depends on the SPV state at forecast initialization. Finally, I use the 2018 sudden stratospheric warming as a case study to show how large forecast uncertainty can originate from known teleconnection pathways — propagating from the tropical troposphere, into the extratropics, and ultimately into the stratosphere.
