Weather forecasts

Meteorology is the science that studies weather conditions. Weather and climate are not the same thing.

Time is when we talk about the weather conditions that happen at any given time. Climate deals with the most frequently occurring atmospheric conditions in a given region.

Factors interfere with weather forecasting

Some factors may interfere with the weather forecast: clouds, air masses, cold and hot fronts, temperature, air humidity and atmospheric pressure.

Clouds: are formed by water droplets produced from the evaporation of rivers, lakes, oceans, etc. There are four types of clouds according to air movement: strata, cumulus, cirrus and nimbus.

Strata are gray clouds like fog. It forms in overlapping layers (one over the other). Your presence in the sky can be synonymous with rain.

Cumulus are white flake clouds. Your presence indicates good weather.

Cirros are wide, white clouds formed by thin ice crystals. Indicates good weather.

Nimbos are dark gray clouds and indicate bad weather.

Air masses: These are large blocks of air that extend horizontally for a few thousand kilometers and vertically for a few hundred meters or kilometers.

They can last several days or even weeks. They originate in the polar (cold) and tropical (warm) regions. The air masses do not stand still, they follow a definite trajectory, but they may be stationary in a certain region for some time.

When they move, they will carry ahead the air that is on their way. That's why the clashes between the air masses happen. And the meeting of these two masses with different temperatures is called front, which can be cold or hot.

Measuring devices

According to the speed of the winds, it is possible to tell when an air mass will arrive at a certain place. To measure this velocity we use a anemometer. In this device, there is a device that records how many rotations are given in a given time, indicating the wind speed.

To know the wind direction, a device called windsock. The windsock is in the shape of an open bag at both ends, the fixed end being larger than the loose one. The incoming air flow aligns the windsock according to the wind direction.

To measure the temperature, we use the thermometer, which is an instrument that can be used to measure our body temperature as well as to measure water, air, or anything else. Generally, thermometers are made of a liquid metal that expands when the temperature, mercury, of the chemical formula Hg increases.

Air humidity (amount of water vapor in the atmosphere) is also an important factor in weather forecasting. The wetter the air, the more chance of rain. The instrument that measures air humidity is the hygrometer.

To measure the amount of rainfall in a given location, use the pluviometer. It consists of a funnel and a graduated glass cylinder.

Atmospheric pressure depends on air humidity. Dry air is heavier than humid. So the drier the air, the higher the atmospheric pressure. If the pressure decreases, the humidity increases, so it is likely to rain in this place. To measure atmospheric pressure a barometer, which may be aneroid or mercury.

The aneroid barometer has a closed cylindrical metal chamber where the air is thin. This camera has a movable lid that is rigidly attached to a pointer. If the pressure changes, the cap moves. Then the pointer also moves. Next to the pointer is a graduated scale that allows the measurement of the atmospheric pressure value.

The mercury barometer measures the pressure according to the height of the column containing this metal in a glass tube.

How to forecast the weather

There are meteorological services that are responsible for collecting weather data. In Brazil, an agency is responsible for this collection that comes from the weather stations of each state, artificial satellites that rotate around planet Earth and also from other countries. Through this information, meteorologists make their weather forecasts.

Weather satellites around the earth are able to take photographs of the air masses and clouds in the atmosphere. They also record the speed of the winds and their direction. This data is sent to the weather station.