Chinook Winds

In 1892, E.B. Garriott wrote for the fledgling U.S. Weather Bureau, Following a period of intense cold the Chinook wind is a welcome visitor in the Northwest. The icy clutch of winter is loosened. The earth throws off its winding sheet of snow. Humanity ventures forth to inhale the balmy, spring-like air. Animate nature rejoices.

Key Takeaways:

• Chinook winds are powerful, warm foehn winds occurring in the Rocky Mountains, known for rapidly raising temperatures by 30-40 degrees, typically between November and March, particularly in regions like the Livingston Box.
• These winds result from strong cross-mountain airflow driven by pressure differences, causing compressional heating on the lee side and often amplified by complex flow dynamics (subcritical-supercritical flow) that create intense downslope winds.
• Chinooks pose significant aviation hazards due to severe turbulence, wind shear, hydraulic jumps, and rotors, affecting all flight levels immediately downwind of the mountains and extending for miles.
• Accurately forecasting chinook severity is challenging, as surface reports can be misleading and numerical models struggle with fine-scale details, requiring pilots to have a conceptual understanding of the associated wave patterns and turbulence zones.

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