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Wind direction and barometer tendency

Table relating wind direction to change in atmospheric pressure.

Ideally, these 'rules' should be used with other 'evidence'; for example, noting how the character of the sky changes over time, whether the wind is veering or backing, how fast (or otherwise) the pressure is changing. Neither does it (always) discuss the differences between on the coast, the coastal plains, or someway inland - these will make a difference in many situations. This table covers non of these points and therefore should be used with much caution.


 N  Mainly dry but cold weather. Night frosts.  Cold & dry except near east coasts.  First autumn frost is not far away; dry, sunny cold weather in the southwest.  Snow showers decreasing, followed by hard frost.
 NE  Cold, cloudy weather, with sunshine on western coasts.  Cool & cloudy in the southeast but fine & sunny in west & northwest.  A fine spell except near east coast.  A spell of severe weather in the north and Midlands.
 E  As NE, but more likely to persist.  Fine spell, breaking down later with rain from the south.  As NE  Cold or very cold, dry weather with serious risk of snow to follow.
 SE  A fine dry spell, relatively mild.  Two or three days of hot weather; thunder later.  'Indian Summer' weather.  As E, especially serious in late Winters. Persistent fog inland.
 S  A short warm spell.  A short, very warm spell.  As S, but less likely to persist.  Thick and persistent fog inland.
 SW  Good growing & sowing weather. Mild & mainly dry.  A warm spell with little rain, except on western coasts & hills, where drizzle likely.  Coastal & hill fogs in the west, but fine & mild inland.  Short spell of mild, cloudy weather, much hill fog.
 W  As SW  As SW  Temporary fine, mild spell.  As SW.
 NW  Showers decreasing. Short cool, dry spell.  As in spring, but cold (for summer).  Temporary cool spell with scattered showers.  Showers of sleet or hail, decreasing in frequency.



 N  Snow/sleet showers, possibly thunder.  Cold thundery weather with hail.  Showers followed by night frosts.  Snow or snow showers, heavy on hills.
 NE  Rain in eastern areas, remaining dry in the west.  As in spring  Little immediate change.  Snow in eastern areas but not heavy.
 E  As NE  As NE  As NE  Thaw, possibly preceded by snow.
 SE  Rain approaching southwestern areas.  Thunderstorms.  Rain in the south, possibly heavy locally.  Heavy snow in the southeast.
 S  Rain imminent.  Rain & possibly thunder.  Rain imminent, probably heavy and prolonged.  As autumn. Very mild.
 SW  Rain imminent.  Rain imminent.  Rain & gales.  As autumn. Mild.
 W  Rain or showers.  As in spring.  Rain or showers. Mild weather continuing.  As autumn.
 NW  Showers & colder weather with hail and thunder.  As in spring.  Showery weather; risk of hail or thunder: cool.  Heavy showers of sleet or snow; risk of hail & thunder.

From: 'Experiments in Meteorology'

Some other rules based on observation of the barometer - published in Rinne, J., Koistinen, J., & Saltikoff, E. : Suomalainen sääkirja - etanasta El Niñoon. (In Finnish) Otava, Keuruu 2001. ISBN 951-9435-93-X
(With thanks to Elena Saltikoff for passing this on . . .)

Very basic barometer forecast rules

(NB ... assumes the unit is working properly!)

Look at the change in 3 hours.
If the pressure is descending, there is a low pressure coming.
If it's ascending (or rising), the low is passing or a high pressure is coming.
When the pressure is changing rapidly (> 6 hPa/3 hours), it's windy (or potentially windy).

More detailed:
Sinking (falling) slowly (0.5 - 3 hPa in 3h): low is weak, dying or moving slowly. You might get some rain but typically no high winds.
Sinking (falling) moderately (3-6 hPa/3h): rapid movement or deepening low. Moderate winds and rain in warm front. The low is passing you fast so day after tomorrow will typically be fine.
Sinking (falling) 6-12 hPa/3h: Storm.

And rise is connected to gradually drier weather.

[ N.B.
hPa (hectopascal) are the same thing as mbar (millibars), and in older publications and on older barometers, you may see the abbreviation 'mb', also meaning millibar. Typically the values (at sea level) will be within a range 50 hPa either side of 1000, but allow for some extremes at either end. An older barometer might have mmHg (i.e. millimetres of mercury, with numbers near 760) or even inHg (inches of mercury). ]