When the North Gets a Chill: The Stratosphere's Role in US Winter Woes

The US has been experiencing serious cold snaps lately, even as winters warm up overall. Scientists have uncovered interesting connections to the stratosphere, the layer of the atmosphere above where planes fly.

Key Patterns Identified

1. Displaced Upper-Level Vortex Over Western Canada

   • Brings harsh winter conditions to the northwestern US.

2. Weakened Upper-Level Vortex Shifting Toward the North Atlantic

   • Leads to severe winter weather in the central and eastern US.

Common Traits

• Stretched lower-level vortex
• Stratospheric wave reflection

Shift in Winter Weather Events

• Since 2015, severe winter weather events have been moving northwestward across the US.
• This shift coincides with:
• A rise in the frequency of the westward-focused pattern.
• A change in the El Niño-Southern Oscillation phases.

Driving Factors

• A complex mix of stratospheric shifts and ocean patterns.
• Understanding these connections can improve winter weather predictions and better prepare for extreme cold events.