Fascinated by how thunderstorms develop? Ever wondered what the "key" ingredients are for severe storms?
For the atmosphere to produce thunderstorm activity, four major ingredients are required. Here is a handy little acronym to remember: S.L.I.M.
S is for Shear: Winds that change in speed and direction in the atmosphere at different heights.
L stands for Lift. A frontal boundary or trough system. Basically, two masses of air that collide and cause the air to lift. A perfect example is what we call a dryline. Dry west to south-westerly winds meeting a more moist east to north-easterly flow, and where these two collide the air is forced to rise.
I for Instability. Where a parcel of air is warmer that it's surrounding air and rises under its own buoyancy. Sounds complicated? If I was to boil a pot of water and put the lid on, then once boiled, remove the lid and watch how rapidly the steam rises towards the ceiling. That air is hotter than the surrounding air, therefore allowing it to lift.
Moisture. Last but not least, potentially the most important ingredient for thunderstorm development. The drier the air (measured by the dew point), the less chance of thunderstorm development.
When you put all these ingredients together, the recipe becomes ripe for thunderstorm development. That is when mother nature puts on a truly amazing show!
S.L.I.M: Shear, Lift, Instability, Moisture, GFS charts