1) You can often predict the short-term weather with clouds by simply looking upwind.
2) Air pressure, wind and wind direction, whether it's humid or warm or cool does not indicate severe weather.
3) There's no such cloud as a 'cululonimbus' cloud.
Otherwise ... meteorologists ask three basic questions when making a forecast.
1) What's going on? (observation)
In other words, what is the present weather?
Is it sunny?
Is it raining?
Is it windy?
Observations include surface conditions ... such as temperature ... wind direction / speed ... dew point ... and barometric pressure and from remote sensing platforms such as rawindsondes ... satellites .. and radars.
2) Why is the current weather occurring? (analysis)
In other words, why is it sunny?
Why is it raining?
Why is it windy?
Meteorologists analyze observations --- first at the large 'big picture' scale ... then progress to smaller and smaller scales -- looking for familiar patterns or signatures ... such as fronts ... clouds ... radar imagery ... and their movements responsible for producing the current weather.
3) How is the current weather likely to change (forecast)
In other words, will sunny conditions continue or change?
How long will the rain continue?
When will the wind subside?
The forecast expresses the meteorologist's expectation of how the present weather will evolve over time on time scales from a few hours up to two weeks. Forecasters use a combination of output from numerical weather prediction models ... statistics ... climatology... and professional experience.
Category-shifting Ron the idiot Troll still afoot.
Copy'n paste-free Meteorologist.