The primary reason meteorologists observe differences in air pressure when predicting weather is due to: (a) The sun heats different places at different rates.
Why does this occur
The sun unevenly heats the Earth's surface, causing variations in temperature across regions. Warmer air is less dense and tends to rise, creating areas of lower pressure.
Conversely, cooler air is denser and sinks, leading to areas of higher pressure. These temperature differences create pressure gradients, influencing wind patterns and weather systems.
Hence the differences in pressures are observed given that The sun heats different places at different rates.