In addition to observing wind speed, wind direction, temperature, air pressure, and humidity meteorologists observe ...

In addition to observing wind speed, wind direction, temperature, air pressure, and humidity meteorologists observe Radar, Meteorology and Clouds.

Explanation:

Meteorologists are people who specialize in understanding the atmosphere and by using their knowledge they make predictions about the weather forecast.

Radar is one of the tools used by meteorologists to analyze and make predictions about the weather.

By observing the clouds, the meteorologists inspect the chances for rain to occur. Meteorologists clearly know that all kinds of clouds cannot produce rain and they know how to differentiate the rain-producing clouds from the ones which cannot produce rain.