On Monday, a large low-pressure system covered almost all of the United States. By this, I mean the circulation of air around the low was unusually large.
At the center of all this, the barometric pressure at Hector Airport reached 28.79”, or 975.4 millibars. This breaks the November record of 28.86” set November 15, 1930. The all-time record of 28.54” set March 15, 1920, remains.
Weather has been unusually warm over North America this fall and equally unusually cold over much of Europe and Asia. Extremely strong high pressure (31.33”, or 1061 millibars) has been measured recently in Siberia. The record low pressure was, of course, at the center of a large winter storm system, but it was not unusually strong or terribly windy because there was no accompanying high pressure in North America to produce a pressure change.
In western South Dakota there was considerably more wind due to proximity to a region of high pressure in the Rockies.
