*This is a work in progress, more info coming soon.
There are three conditions necessary for deep convection:
1.) A deep, conditionally unstable environmental lapse rate
2.) Deep boundary-layer moisture
3.) Low-level convergence (or lifting) sufficient to “release” the instability
Convection feeds on the potential energy inherent in the temperature in the moisture stratification, and this potential energy is known affectionately by the meteorological community as CAPE (Convective Available Potential Energy) and is in J/kg.
It is defined as the integral from the LFC (level of free convection) to the EL (equilibrium level) of F/(rho)’dz. F is the upward buoyancy force per unit volume on the rising air parcel due to the temperature difference between the parcel and its environment, rho’ is the density of the parcel, and dz indicates that we are taking the integral with respect to height. We do some weird derivation stuff, and we find out that the integral is essentially the area on the skew-T plot from the LFC to EL and pounded by the temperature sounding on the left and the moist adiabat on the right. CAPE values of 0-1000 are considered marginal for convection, but when values get above 4000, look out.
*When it comes to wind, storms generally move at the average direction and speed of all the horizontal wind vectors in their component of the atmosphere. But it’s not just horizontal wind profiles that drive storms… vertical ones have a huge impact as well.
Written by Charlie Phillips – charlie.weathertogether.net. Last updated 12/1/2017