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THE BAROMETER
- What falls as it rises and rises as it falls?
- The answer is, of course, the barometer because pressure decreases as altitude increases and so the barometer will fall as you climb a mountain or go up in a balloon!
- With a series of high pressure systems sweeping across the continent, as is usual during the winter months, one’s thoughts turn to the aneroid barometer found in many homes on the Range where the day often begins by the ritual tapping of the barometer to see which way the needle jumps!
- Although barometers should be adjusted for height above sea level by turning a small screw at the back, it does make sense to adjust for Mean Sea level instead so that it is easier to read weather maps on TV or newspapers.
- Always bear in mind it is more important to know what the barometer is doing rather than what the needle is showing.
- Early home barometers were very helpful by including a little blue and red disc to show whether the barometric pressure was rising or falling. This avoided the need for ritual ‘tapping’!
- If your barometer is a more recent model the face will show the units in hectopascals, the unit of pressure measurement accepted around the world. However, should the markings be in inches then multiplying by 33.85 will bring inches to hectopascals (hPa).
- The face may also show such words as Stormy, Rain, Change, Fair, Very Dry as a guide to current or future weather, but in fact has little practical application other than being decorative.
- Atmospheric pressure changes are irregular and knowledge of them is very important in the study of winds and weather patterns in forecasting weather.
- Barometers used to predict weather should be read in conjunction with outside air temperature and relative humidity. The following guide lines are used by some weather watchers.
- Barometer steady, humidity increase, temperature falls = Chance of rain
- Barometer steady, humidity decreases, temperature rises = Fine
- Barometer rises, humidity increases, temperature steady = Showers.
- Barometer quick rise/fall, humidity increases, temperature plunges = Thunderstorms.
- Barometer falling, high humidity, temperature rising = Heavy rain.
- Barometer rising, humidity falls, temperature rising = Wind change, fine.
- Barometer falling, humidity high, temperature plunging = Weather deteriorating rapidly.
- Finally, watch the Weather Bureau’s synoptic maps and compare your location’s barometric pressure with the isobars shown.
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