Anyone got any tips for the MET stuff?
Warm air flowing over a body of water absorbs moisture
Warm air rises, cold air sinks. Rising air cools due to the pressure drop, sinking air heats due to the pressure increase.
Rising air eventually condenses, when temp = dewpoint
Air flows from areas of high pressure to areas of low pressure, and is influenced by "oreographic" features such as mountains.
Air flowing from A to B gets a swing to the left due to the Coriolis effect. (To the right if on the Southern hemisphere.)
Water freezes when it gets below 0C, except when it's very pure, in which case it can exist in supercooled liquid form well below 0C, until it is confronted with an "impurity" like any part of an aircraft, and then freezes instantaneously.
The Met office tries to log and predict all this and communicates this to you in the form of METARs, TAFs, SIGMETs, VOLMET and the F215/216/415/416 forms.
For aircraft performance predictions the ISO has defined something called the "standard atmosphere", which is a theoretical model only with certain properties, but which you'll never encounter in real life.
Everything else can be logically derived from the above.