ALL ABOUT WEATHER

INFORMATION ABOUT WEATHER

The state of the atmosphere with respect to wind, temperature, cloudiness, moisture, pressure, etc.  




                    


HOW TO FORECAST WEATHER

How to predict weather from nature:
When you are on your wilderness trip, some basic knowledge about how to predict weather will help you to take appropriate action for not getting into trouble and risk your safety.


Air pressure

Changing weather means changing air pressure. Decreasing air pressure 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 a fine and clear day. A barometer measures air pressure and is a well-known instrument to predict weather.

There are also nature signs of changing air pressure that can be used to forecast weather. For example, on a fine and clear day, the smoke from the campfire rises steadily. If it starts swirling and descending, the air pressure decreases and bad weather will be expected. 

Clouds

An ability to accurately read cloud formations is important when you want to understand how to predict weather. Clouds are classified into different types, according to height and shape. Not all clouds bring rain, some are signs of fine weather.

During a fine day (1), the clouds are white, the higher the finer. Storm clouds (2) are generally black, low, and massed in large clusters. If wet weather is approaching (3), the cloud will form a grayish veil. This means it is time to take shelter.

Red Sky

A red sky at either dusk or dawn is one of the most beautiful natural signs you can use to predict the weather. At dusk, a red sky indicates that the next day will probably be a dry and fine day. This is due to the sun shining through dust particles being pushed ahead of a high pressure system bringing in dry air. A red sky at dawn often means that an approaching low ressure system is bringing in a lot of moisture in the air. This is a fair indication that a storm is approaching.

WEATHER FORECAST
Weather forecasting is the application of science and technology to predict the state of the atmosphere for a given location. Human beings have attempted to predict the weather informally for millennia, and formally since the nineteenth century. Weather forecasts are made by collecting quantitative data about the current state of the atmosphere on a given place and using scientific understanding of atmospheric processes to project how the atmosphere will evolve on that place.

Cloud Cover

Each circle represents a weather station. The circle at each station is empty if skies are clear. The circle is white if it’s cloudy. A line within the circle or a half-filled circle means "partly cloudy."

Wind and Wind Direction
The little arrows attached to each weather station point in the direction the wind is blowing from. The more barbs at the end of each arrow, and the longer they are, the harder the wind is blowing. Each long barb is 10 knots (about 11.5 miles per hour or 18 kilometers per hour). Each short barb is half that amount. A barb that looks like a triangle is blowing at 50 knots (about 58 mph or 80 kph).

Air Temperature The number to the upper left of each station is the air temperature in degrees F (for U.S. maps) or degrees C (for other countries).
Dew Point
The number to the lower left of each station is the dew point temperature in degrees F (for U.S. maps) or degrees C (for other countries). The dew point is a measure of moisture; it shows how much you'd have to cool the air to get a relative humidity of 100 percent. The higher the dew point, the more water vapor there is for producing rain or snow.

Barometric Pressure

The number to the upper right of each station is the barometric pressure. Since the pressure goes down with altitude, this reading has been adjusted to show the pressure as if the station were at sea level. The typical sea-level pressure is a little bit more than 1000 millibars. (The number is in kilopascals (kPa), which is the same as millibars).

The number has been compressed to fit the map by lopping off the first one or two digits (which are always a "10" or a "9") and omitting the decimal point before the last digit. For example, the code "085" would mean 1008.5 millibars, while 954 would be 995.4 millibars.

Put it all together!

See if you can find any lines that go around centers of high and low pressure. They are called isobars; they connect stations with equal barometric pressure, so you can see where the highs and lows are. The wind usually follows the isobars, with a slight trend in the direction of the low pressure area.

Look at the wind direction around your forecast city. Is the air blowing from colder areas toward your city, or is warmer air moving in?

Will clouds or precipitation be coming, and if so, a lot or a little?

Will there be rain, sleet, or snow?

2. Study the satellite images

Satellite images show the amount of cloud cover. Clouds can act like a blanket helping to keep night warmer if the sky is clear. But clouds during the daytime can block the sun and keep temperatures cooler.

What does the image show? Is there much cloud cover? Do you think it will increase or decrease, based on what you have learned from the weather maps?

3. Study actual weather forecasts for your city