The process flow of the proposed hybrid paradigm for sub-seasonal forecasts of continental scale cold air outbreaks in mid-latitudes.

We calculate stratospheric mass transport into the polar region from forecast outputs of the US NOAA NCEP's operational CFSv2 model and use it as our forecasts for the strength of the atmospheric mass circulation, which is called ST60N index. The anomalous strengthening of it is indicative of the high probability of occurrence of cold air outbreaks in mid-latitudes.

Because cold air outbreak events are accompanied with development of low and high pressure system and frontal circulations, our forecasts of cold air outbreaks are also indicative of snow, frozen rain, high wind, icy/freezing and other winter storm related hazards besides a large area of below-normal cold temperatures.