What are the ingredients for severe weather?

 Many things need to come together in order to form severe weather. The week ahead will feature several combinations of ingredients that will fuel severe storm potential. The main ingredients for severe weather include moisture, instability, lift, and wind shear.

Moisture is a primary ingredient for severe weather as clouds and rain don't form in drier air. One way to simply measure moisture is the dew point. When dew point temperatures rising well into the 50s and even 60s, that allows for sufficient low-level moisture for strong storms. This works to develop a broad "warm sector" where storm development may be possible.

That moisture also works in tandem to develop instability. That is a measure of storm energy, or how quickly or easily air will rise. When you have very warm and moist air at the surface, it rises quickly through cooler air above it, forming clouds and eventually thunderstorms. Extreme levels of instability can produce explosive thunderstorm development when a little cumulus cloud evolves into a towering cumulonimbus cloud in a short time.

But you also need something to kick off the storms. Air at the surface sometimes needs a little boost to get it moving in the right direction. Lobes of "vorticity" or atmospheric forcing can work to give the air bubbles a push to begin the lifting process. Sometimes this can be a cold front or warm front, forcing air upward as it encounters the temperature difference along that front.

Then once you get storms to develop, you need wind shear to keep them going. Without shear, storms rain themselves out, choking out the updraft with rain-cooled air. Shear works to tilt that updraft and allow rain to fall away from the base of the storm itself. Shear can be a difference in wind speed or direction with height. Both speed and directional shear can work to develop rotating updrafts, which can then form mesocyclones and eventually tornadoes. Strong shear in the lowest levels typically enhances tornado potential.

Each severe weather event has its own combination of moisture, instability, lift, and shear. Sometimes when one ingredient is lacking, the others can make up the difference. But all severe weather events have some levels of each of these ingredients. Keep an eye out for these terms as meteorologists discuss upcoming potentials for severe storms!