What is a heat index? We define terminology commonly used by the National Weather Service

Ever wondered what a gustnado or tropical funnel cloud is? If so, look no further than the National Weather Service.

The NWS has been issuing forecasts and recording the weather for over 150 years. Created in 1870, the government agency has over 100 offices across the country, including one in Fort Worth.

Weather terminology is more than just rain or snow. Here’s what a few of NWS’ most common terms mean:

• Cap- A layer of warm air aloft that essentially prevents the air at the surface from lifting. It keeps the cooler air from rising thus suppressing thunderstorms.

• Dewpoint- The temperature at which the air must be cooled for water vapor to condense, thus forming dew.

• Gustnado- A whirlwind that forms near a thunderstorm’s outflow boundaries. While not classified as a tornado since they do not connect to any rotation to the cloud base, a Gustnado is more of a thunderstorm wind event.

• Heat index- What the temperature feels like to the human body when combined with humidity and air temperature.

• Fujita scale- A scale used to measure tornado intensity by analyzing wind speeds.

• Jet stream- Strong winds that are concentrated in a narrow stream in the atmosphere, also known as high-altitude winds.

• NOAA- The National Oceanic and Atmospheric Administration. The NWS is an agency within NOAA.

• Scattered showers- Rain showers covering 25% to 54% of an area.

• Tropical funnel cloud- Spin in the atmosphere that starts near the ground and twists up into clouds much like a tornado. While its not classified as a tornado, wind speeds do get up to 40 to 70 mph.

• Tornado warning- A tornado has been spotted nearby and people need to take cover immediately.

• Tornado watch- A tornado is possible in the area.