WE bare all of ups aware of the importance to our future weather of the little clock like dial in the hall. As they used to say:
When the wind backs and the weather glass falls,
Then be on guard against gales and squalls
As early as 1698, the German physicist, Gottfried Wilhelm Leizniz, had proposed the idea of "a little closed bellows that would be compressed and dilate by itself, as the weight of the air increases and diminishes".
Unfortunately, it was impossible in the late 17th century to manufacture a bellows that remained both flexible and airtight for any length of time and the technical realisation of the concept had to wait until 1843 when a Frenchman, Lucien Vidie, produced the first satisfactory instrument of this kind.
Nowadays, the aneroid barometer is commonplace but can it really tell what the weather has in store for us?
The effectiveness of the domestic barometer as an indicator of the future weather is severely limited. Accurate forecasts are difficult enough for a meteorologist with up to the minute reports of temperature, pressure, humidity and wind over a large area of the globe.
The barometer, on the other hand, merely measures the atmospheric pressure at a single point, so it is asking a lot of the instrument to expect consistently accurate predictions based on this information alone. But this said, the behaviour of the barometer does offer some clues to the future.
Perhaps the most important thing is that the pressure tendency whether pressure is rising or falling is more important than how high or low it is. Generally, high pressure is indeed associated with quiet, settled weather, and low values often bring changeable and windy conditions. But there are many exceptions to this rule.
You will get more guidance from the instrument if you also note the direction of movement of the needle, having used the static pointer to mark a previous reading of some hours earlier.
Rising pressure usually means an improvement in the weather, but meteorologists say "rapid rise, rapid fall" a surge in pressure seldom lasts long and is soon followed by a sharp drop which heralds the approach of the next depression. A slow steady rise, on the other hand, often means that an anti cyclone is becoming established over the area, which may result in a spell of calm and sunny weather.
In the case of falling pressure, however, the faster it drops, the worse the likely consequences. The rapid pressure fall last Thursday turned out to be the precursor of the storms experienced that night.