Prospects for predicting the type and timing of the surface response after stratospheric events

Extreme events in the stratosphere, so-called sudden stratospheric warming (SSW) events, can have a significant impact on surface weather. However, only about two thirds of SSW events have a surface impact, and the expected response is not always observed at the same time lag after the stratospheric event. In order to achieve skillful long-range predictions it will be necessary to understand the reasons for the presence or absence of a response, and to successfully predict the timing of the surface impact.
This contribution investigates several potential long-range predictors for the tropospheric response: the persistence of the lower stratospheric temperature signal, anomalous eddy driving in the east Pacific, as well as the North Atlantic weather regime present at the onset of the stratospheric event. All of these are found to help determine the type and timing of the tropospheric surface impact, and a strong potential for long-range predictability of several weeks based on these predictors is found over Europe.