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Weather forecasting is a difficult task, but using basic readings we can get a better understanding of what is happening and what is likely to happen.

(The following is not a full technical reference, it's only my interpretation.*)
 


There are two types of readings used on our site:

Weather Readings:

Air Pressure
Temperature
Humidity
Wind Speed and Direction
Rain Fall

Calculated Readings:

Dew Point
Wind Chill
Cloud Base

 

Lacrosse WS2350 Weather Station
Used To Collect Our Weather Data

Weather Readings:

Air pressure: (Barometer) is a very useful element to weather forecasting. 
We all know when we look at the barometer for a high pressure in the summer and dread the low pressure coming in the winter!
The change in air pressure is a trend that is useful in weather prediction.  If the trend is a rise in pressure then generally the weather will be improving, whereas a fall in pressure shows a worsening outlook.
The gauge used shows the actual reading along with the high and low point for the day, plus the pressure trend is indicated with an arrow.
Air pressure is also a part of the calculation of dew point (precipitation). 

 

 
Temperature: This is the air temperature recorded in the shade. The temperature we feel is obvious when we are standing out doors but it is affected by sunlight and wind.
This gauge shows the present reading and the high and low for the day plus a trend arrow. 
Temperature is also a part of the calculations of dew point and wind chill.


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Humidity: This shows the moisture content of the air and is recorded in a percentage of what the air is capable of holding. This is a strange element to the weather and it can be misleading.  We know the feeling in summer when the humidity is high (hot & sticky).  Unfortunately the high moisture content fools us in regard to the true temperature, and our skin is unable to cool us down by sweating due to the moisture in the air, which makes us feel hotter.

When the humidity is combined with pressure and temperature you can work out the dew point or likelihood of precipitation (rain, snow etc.).

The gauge shows the humidity percentage and has a trend arrow.

 

 

Wind speed & direction: There are several elements to these readings and the first is the direction of the wind.  Every location has a good and bad wind direction.  Wind for us can have a down side when it comes from the North in both summer and winter, whereas the South Westerly  is a good wind in the summer but is wet in the winter.  The other element is speed, which can be felt as a gentle breeze in the summer or a full gale in the winter.  The gust of the wind can be the damaging event. 

There are two gauges to view - one is the wind direction showing both the now and average, which is relative to the compass or in degrees from zero (North) through 180o (South) and back to 360o (North again). 

The other gauge shows the average speed and the gust wind speed. This is another base element to weather calculations (wind chill).  Wind speed is an indication of the change of pressure caught between the isobars we see on the TV forecasts.  The closer together they are the more windy it gets.

 

 


Rainfall: Keeping a record of rainfall amounts is a useful tool in determining certain trends. The rise and fall along with other elements can be used as an indication of weather events coming or going.  Rainfall or the lack of it could be a useful tool for planning farming work etc. For example fishing or canoeing is no good if the river is low or in flood.

There are several gauges showing the daily, monthly and annual rain fall.

 

 

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Calculated Readings:

Dew Point: This calculation is the point at which the air releases its water (precipitation), this shows as dew, fog, rain or when freezing, frost or snow. This reading is calculated with a formula such as below:

A well-known approximation used to calculate the dew point Td given the relative humidity RH and the actual temperature T of air is:

 
where
 
where the temperatures are in degrees Celsius and "ln" refers to the natural logarithm.
The constants are:
a = 17.271
b = 237.7 C

(via wikpedia)

Thankfully this is calculated for you!


Our gauge shows a calculated temperature at which precipitation could occur.

 

Wind ChillThis was first used in the Antarctic before the Second World War, and then used during the war for battle planning.

This is how cold it actual feels in relation to the temperature and wind.  The cooling effect on your body can vary greatly.  On a calm day when it's cold, just walking creates a cooler feel to the air, but when the wind picks up the cooling effect is greater.

There is a formula and table for the wind chill calculation but we have a gauge to show this. 

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Cloud Base: This is a guide to what altitude clouds may form.
It is estimated from surface measurements of air temperature and humidity.

Don't confuse this with cloud height, which is the distance from cloud base to cloud top.

 

Other Dials and Graphs

There are several other gauges and graphs that we use to record the weather and its trends.  These can be found on the weather trends page.

A simple graph can show the pattern of the weather quite dramatically.

On this graph you can see on day 1 a drop on the barometer and an increase in wind speed.  This also corresponds with a rise in rainfall and a
plateau in temperature.

What actually happened that day was a blustery morning with a very windy period including driving rain.  The high wind gust was 32.9 mph and we lost our electricity for a short time. 

Not the best of days to hill walk!

If you follow the graph you can see the pattern the weather followed.  A rise and fall in the barometer reading and two periods of high winds, along with a rise in rainfall and a lower temperature reading.

Also you can see the wind is predominantly from the South to West.

 

 

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There are similar gauges on the weather trends page - they show a range of readings in one place.

 


These gauges show the same readings in a different layout:

1/  Current wind speed
2/  Wind direction
3/  Average wind speed
4/  The amount of temperature depression
5/  Outdoor temperature
6/  Outdoor humidity
7/   Barometer readings
8/  Wind chill temperature
9/   Rainfall
10/ Dew point
11/ Cloud base

 

 

All the images used on this page are under copyright to Weather Display & Weather Display Live
 and have been reproduced by kind permission.

*Never plan important events on the readings from this site or from the Internet*

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Martin Toon 2009