How Meteorologists Determine the Presence of Severe Weather

Severe weather can take on a number of forms, ranging from large hail to gusty winds to tornadic activity. While laypeople throw around the term of "severe weather" to indicate a variety of impacts, meteorologists use specific criteria to define these risks. Here is what you need to know what forecasters mean when they use the term.

What Constitutes Severe Weather

Now that severe weather season is ramping up, it is important to understand how meteorologists define the specific impacts associated with stormy conditions. Any type of weather event that presents a danger to life and property is considered to be severe. Potential hazards unleashed by Mother Nature include lightning strikes, high winds, tornadoes, hurricanes, flash flooding, freezing rain, sleet, and hail.

The National Weather Service (NWS) is the agency in charge of issuing alerts that detail potential risks. At the most basic level, these alerts generally come in the form of watches or warnings. A watch is issued when the necessary atmospheric conditions are present to support the development of meaningful impacts. Meanwhile, a warning is used when the threat is imminent.

For instance, the NWS will issue a flash flood warning when heavy rainfall is already. happening. Likewise, powerful winds can trigger a high wind warning.

Criteria Used to Designate a Severe Thunderstorm

The NWS uses a defined set of criteria to designate the presence of a severe thunderstorm. Only one of the three possible criteria points needs to be met for a storm to be deemed a severe event.

The first criterion that will mark a thunderstorm as severe is hail that is a quarter-size or larger. This equates to a measurement of about 1 inch in diameter. Meteorologists use this size as it is generally when you can expect the hail to cause damage. Hail that measures over an inch in diameter is likely to cause damage to roof shingles and vehicles.