Ever feel like you have the weight of the world on your shoulders? The atmosphere weighed a bit extra in the United Kingdom on Sunday beneath the strongest high-pressure system observed there since 1926. The measured value of 1051.2 millibars, set in South Uist, Scotland, also set a record for the month of March and will go down in the books as one of the United Kingdom’s highest air pressure readings ever recorded during any month.
Air pressure is a measure of how much air is sitting on top of us. If there’s more air, the mass atop us is heavier — and the downward pressure greater. But if there’s less air overhead or the air is rising, the air pressure is lower. The presence of high- and low-pressure systems is what drives much of our weather.
What the record means
What Sunday’s record actually means is that the air over the United Kingdom was sinking and weighing a little more.
Ordinary sea-level air pressure equates to about 14.7 pounds per square inch. (We don’t “feel” like we’re carrying that much weight, because we have been since Day One. It’s just like how a goldfish doesn’t notice how much the water above it weighs.) But in Scotland on Sunday, the amount of air overhead weighed about 15.2 pounds per square inch.
That’s a difference of only 3 or 4 percent, but for some it may be noticeable — especially for those with joint issues or arthritis. For most folks, though, there should have been no discernible difference.
More records could be possible
The United Kingdom also experienced anomalously high air pressure in January, when Wales recorded the United Kingdom’s highest air pressure in more than 60 years. The reading of 1050.5 millibars was well above the sea level mean of 1015 millibars. In general, high-pressure values are associated with fair weather, while low-pressure areas tend to bring inclement conditions.
But Sunday’s record narrowly inched out the January reading. South Uist recorded a 1051.2 millibar air pressure reading. The record is 1053.6 millibars, set in Aberdeen on Jan. 31, 1902.
Seasons play a role
At higher latitudes, you’re more likely to set air pressure records during the cold months. That’s because heavy, cold Arctic high-pressure systems are able to spill farther south out of the Arctic Circle. During the dead of winter, they can bring a bitter chill and crystal-clear skies.
During the summer months, the air is usually too warm, and therefore not dense enough, to pile up an air pressure that hefty.
In the wintertime, a baroclinic zone inches closer to the mid-latitudes. That’s a fancy way of saying the temperature can vary steeply over short distances in the winter — between mild air to the south and frigid air banked in the north. Such temperature contrasts give rise to strong storms, the centers of which can occasionally bring record low air pressure.
During the summer, the fluctuations in air pressure are much more modulated. While hurricanes do feature dramatically lower air pressures than mid-latitude cyclones, they’re considerably smaller. Outside a hurricane’s eye, air pressure levels off quickly.
More air pressure records could be set in Canada later this week. All-time air pressure records for northern Nunavut are between 1060 and 1064 millibars. The American GFS model projects a developing high-pressure system that may approach 1065 millibars there later this week.