History-WX · The Missing Link

The Descent

How the split reaches the ground: the column is the wind circling the pole, 500 to 1 hPa — cyan where the westerlies hold, red where they reverse. The bright ring tracks the sinking reversal, the glowing core the descending warmth. Below: temperature at 850 hPa — the air-mass level. After Jan 25 the column fades out and the surface takes over: watch the cold pour into North America. Jan 3 – Feb 20, 2021, ERA5. Keys: D draw · 1/2/3 color · C clear.

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– u 60°N · 10 hPa — below 0 = major warming

Time–height · u 60°N (the descent)

Reading the scene

Wind around the pole (u 60°N)

Sinking reversal front

Warm anomaly core

T 850 hPa anomaly (ground)

−16 K0+16 K

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Jan 5 · The split Jan 25 · Down to the surface Mid-Feb · The outbreak