The Positive North Atlantic Oscillation with downstream blocking and Middle East snowstorms: Impacts of the North Atlantic Jet

Here, the North Atlantic conditions are examined that determine the EB tilting direction, defined as being perpendicular to the dipole anomaly orientation. Using daily reanalysis data, the NAO+ events are classified into strong (SJN) and weak (WJN) North Atlantic jet types.

A composite analysis shows that the EB is generally stronger and located more westward and southward during SJN events than during WJN events. During SJN events, the NAO+ and EB dipoles exhibit NE-SW tilting, which leads to strong cold advection and large negative temperature anomalies over the Middle East and southeastern Europe. In contrast, northwest-southeast (NW-SE) tilting without strong negative temperature anomalies over the Middle East is seen during WJN events.