# How to read the barometer?



## tact

My watch kept showing me values like 1006 to 1013hpa.What can I infer from it?:think:What does it mean?What is the barometric pressure when it is going to rain?:-sThanks in advance!


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## ridinfool

Yeah........ what he said!

:-s


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## cal..45

tact said:


> My watch kept showing me values like 1006 to 1013hpa.What can I infer from it?:think:What does it mean?What is the barometric pressure when it is going to rain?:-sThanks in advance!


there is no way to tell what the pressure is when it is going to rain. there are however a few "rules of thumb" which are easy to remember and which should give you a hint about weather forecast.

*1.* your altitude. the air pressure at sea level (0 meters) is presumed to be normal at 1013 millibar (mb or hpa). one millibar is equal to about 8.3 meters. now let us asume your altitude is 100 meters above sea level then the airpressure would be 1001 (when it is normal). anything above 1001mb would indicate that it is going to be nice weather (or already is), anything below 1001 vice versa - in theory.

*2.* the strenght of barometric drifts. lets assume your barometer rises in about 3 hours two millibar and it drops in the next three hours four millibar it will most probably mean nothing at all. airpressure rises and falls all day long and as long as there are no serious drops or gains, not much will happen to the weather. of course there can always travel a small cloud nearby which pours some rain but no barometer will ever show that because a cloud is not a low.

about one and a half week ago, my barometer dropped within 48 hours from 1027millibar (which was exceptional high) to 970 millibar (which was exceptional low). now, with a drop of 57millibars in two days, you can bet your ass, that it is going to be one ****ty weather and i tell you, it was ;-) (almost a full day of rain and snow with temperatures only slightly above 0° celsius).

the key to read a barometer succesfully, is experience. if you start to get interested in weather forecast, you will have to learn how to read barometric drifts. it will take you some time but eventually you will get a feeling for it. remember: weather is *WAY* to unpredictable, to make a real rocket science out of it. but with practice and patience you should nonetheless learn enough about it, to bring your forecasts to a satisfiying level, at least 75% or so.

of course the goal to all this is a reliable and proven instrument. it is imperative to have...

- thermo compensation
- drift compensation (alti lock) 
- absolute pressure and sea level pressure

...to make halfway precise forecast.

if one or more of these three points are not implemented, forecasting will be more a wild guessing game than anything else. unfortunately almost each and every casio ABC watch is lacking those points, which puts the competitors literally lightyears ahead.

cheers


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## zapiao

If a barometer rises, good weather is coming, if goes down, the weather will deteorate - in theory because not always happens that way:-!


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## Catch22

The way I learned to read the baro graph on my abc's was to watch the weather and see what the graph was showing. So to start with let the weather tell you what the baro graph means and not the other way round.

Holger's description above of course, as always, is a very good explination, but you will have other factors other then the weather that will affect the graph. Travelling in a car, being in an air conditioned building (temp and pressure) and possibly your own calibration of the equipment you are using.

Hope this helps.


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## Konrad

tact said:


> My watch kept showing me values like 1006 to 1013hpa.What can I infer from it?:think:What does it mean?What is the barometric pressure when it is going to rain?:-sThanks in advance!


I copied this from an educational web site:
"Decreasing air pressure often indicates the approach of a low pressure area, which often brings clouds and precipitation. Increasing air pressure often means that a high pressure area is approaching, bringing with it clearing or fair weather."

For local barometric observation any basic wristwatch with a barometer will suffice. Weather forecasting can quickly become very scientific and/or technical, see the links below.

I also recommend www.wunderground.com so you can check if there is a local station near you to cross-check your wrist watch observations.

Konrad.

http://www.weathergraphics.com/fcstbook/

http://www.weathergraphics.com/dl/

http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KNVMINDE7


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## dbluefish

As a boater I enjoyed and often needed the ability to at least guesstimate changing weather. It would not do to be out on the water and be surprised. So clouds helped (mackeral sky usually meant changing weather for the worse), and the sunset(red sky at night, sailors delight; red sky in the morning, sailors take warning)was a hint of things to come. In the same light and with a huge BLOCK of salt, I have been monitoring my barometric pressure on my Citizen Aerochron. If it moves up and stays up or rises, good day on the water and good day to take my bike out for a ride. If it drops and seems to keep dropping throughout the day, bad weather is probable. Hell all this is fun in any case and weather is a crap shoot. Especially here in FL as the barometer can be rising, and i am out on m y bike, and that one stinking cloud, soaks my sorry butt. lol

JMHO

paul


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## bagou01

I'm starting to gain interest in this to know if i should go out with my daughter in the park or not, but i can't manage to understand one thing : the timing of those guesstimates.
Does a rising graph mean the weather will improve in the minutes, hours, in the afternoon (given i take the reading in the morning)....
I know it's not accurate at all but despite this, should the interpretation be in a matter of hours or more immediate?
thanks a lot


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## dwalby

bagou01 said:


> I'm starting to gain interest in this to know if i should go out with my daughter in the park or not, but i can't manage to understand one thing : the timing of those guesstimates.
> Does a rising graph mean the weather will improve in the minutes, hours, in the afternoon (given i take the reading in the morning)....
> I know it's not accurate at all but despite this, should the interpretation be in a matter of hours or more immediate?
> thanks a lot


The barometer could start dropping days before the storm, hours before the storm, but rarely minutes before a storm. That's probably irrelevant to your question anyway. You're better off looking out the window to make the decision about going to the park.

Probably the best way to describe the relationship is a storm will typically occur while the barometer is falling, or has recently fallen. But, a falling barometer doesn't necessarily indicate that a storm will be approaching, a lot depends on how much and how fast its dropping.

stormy weather is usually associated with low pressure, and clear weather with high pressure, but just about anything is possible and varies a lot depending on your location. Its possible to have lower than average pressure with clear weather, and higher than average pressure with stormy weather.


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## Rocket1991

Meteorology 101 – Stormstalker


Posts about Meteorology 101 written by Shawn




stormstalker.wordpress.com


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