The recipe for storms, how we forecast potential downpours

SOUTH BEND, Ind.-- Summertime is prime time for storms in Michiana and across the Midwest—some of which are strong or severe. Summer conditions provide all of the right ingredients for storms. The main ingredients are humidity, instability, lift, and wind shear.

Humidity - moisture in the atmosphere that makes the air more buoyant, meaning it's easier to lift.

Instability - warm air near the surface quickly rises into cooler air aloft. Warm air and upward motion fuels storms, continuing development.

Lift - mechanism needed to get the air moving upward. One common trigger is a cold front, which forces warm, moist air to rise as it moves in.

Wind Shear - changes in wind speed and/or direction at different heights. It contributes to the formation of updrafts and downdrafts, which help organize and strengthen storms.

Once all these factors are at work together, thunderstorms are the results. Some storms produce downpours that lead to flash flooding.

Meteorologists use a forecasting tool called Precipitable Water, aka PWAT, that estimates potential rainfall by measuring the amount of moisture, or humidity, in the atmosphere. The higher the PWAT value, the greater the potential for heavy rain when storms form.

It is worth noting that all the rain that fell on July 19th, accumulated in just minutes as the storm passed, mainly effecting LaPorte and St. Joseph IN Counties. Flash flooding quickly became a concern as some areas reported 6–8 inches of standing water on roads and in parking lots.

When humidity is high and storm conditions are right, flash flooding is a real risk. As we round out the last month of summer, we should continue to be aware of storms and prepare for them.