Polar Vortex Dynamics

Stratospheric circumpolar wind belt that contains Arctic air. Cross-section from pole to equator showing temperature and wind structure across pressure levels.

Vortex State

Stratosphere 10 hPa

Polar Temp−78°C

Mid-lat Temp−42°C

Jet Speed85 m/s

AO Index+2.3

What's Happening

Strong polar vortex. Cold air confined near pole. Zonal westerly winds at 80–90 m/s. Stable stratospheric conditions. AO positive phase.

Downward Coupling

Stratospheric signals take 2–6 weeks to propagate down to the troposphere. SSW events are the #1 subseasonal forecast opportunity — they predict cold air outbreaks 2–4 weeks out.

Sudden Stratospheric Warming (SSW): When planetary Rossby waves propagate up from the troposphere and deposit westward momentum in the stratosphere, they can decelerate or reverse the polar night jet in just 5–7 days. The Arctic stratosphere warms by 30–50°C. This disrupts the tropospheric jet stream 2–8 weeks later, increasing cold air outbreaks. On average, major SSW events occur ~6 times per decade.