How do meteorologists forecast weather?

Sometimes with difficulty. :-).

http://en.wikipedia.org/wiki/Weather_forecasting

they use radars from the satelites

Meteorologists forecast weather by analyzing various atmospheric and environmental factors using a combination of scientific instruments, computer models, and historical weather data. Here's a step-by-step process they typically follow:

1. Collecting Data: Meteorologists gather data from various sources, including weather stations, satellites, weather balloons, radar systems, and buoys. These sources provide information on temperature, humidity, air pressure, wind speed and direction, precipitation, and more.

2. Analyzing Patterns: Meteorologists study weather patterns to identify trends and anomalies. They examine large-scale atmospheric systems like high and low-pressure systems, fronts, and jet streams. They also monitor smaller-scale phenomena like local wind patterns and cloud formations.

3. Using Computer Models: Meteorologists input the collected data into computer models that simulate the behavior of the atmosphere. These models use complex mathematical equations to predict how the atmosphere will evolve over time. The models consider factors such as air pressure, temperature gradients, moisture content, and the Earth's rotation.

4. Observing Historical Data: Meteorologists compare current weather patterns with historical data to recognize similar conditions that led to specific weather events in the past. This helps in making predictions based on past outcomes under similar circumstances.

5. Fine-tuning Forecasts: Based on the computer model output and historical analysis, meteorologists fine-tune their predictions. They consider the strengths and weaknesses of different models, compare multiple scenarios, and update their forecasts accordingly.

6. Communicating Forecasts: Meteorologists share their forecasts with the public, using various media platforms, such as television, radio, online reports, and mobile applications. They provide information about expected weather conditions, potential hazards, and the duration of the forecasted events.

It is important to note that weather forecasting is an ongoing process, and meteorologists continuously monitor and update their forecasts as new data becomes available. This allows for real-time adjustments and improvements to increase the accuracy of the predictions.