Tropical Cyclone - It's the generic term for a non-frontal large scale low-pressure system over tropical or sub-tropical waters. These systems have organized convection (i.e. thunderstorm activity) as well as a definite cyclonic surface wind circulation. When the cyclonic winds become sustained at 40 mph they are called tropical storms. They become hurricanes when sustained winds reach 74 mph or greater.

Brontophobia - This phobia is defined as the irrational fear of thunder. For those who suffer, it creates high anxiety even though the thunder may pose no real threat to them.

Rain Gauge - An instrument used to measure the amount of rainfall that occurs over a specific site. A standard rain gauge can measure up to 8 inches. The first known device that was used for measuring rainfall was invented in Korea in 1441.

Derecho - A widespread and usually fast-moving complex of thunderstorms that produce damaging straight-line winds. These systems are long lived, as the swath of wind damage associated with them extends for hundreds of miles. Wind gusts can range from 60 to over 100 mph in a derecho.

Equinox - Time of year when day and night are nearly equal in length. The equinoxes signal a transitional time of year. In the northern hemisphere, the autumnal equinox is the transition season that leads up to winter. Conversely, the vernal equinox is the transition season of spring that leads to summer. On the equator, the sun can be seen directly overhead at noon on the day of an equinox.

Polar Vortex - The polar vortex is an area of low pressure that coincides with the pool of arctic air that encircles the North or South Pole. Each fall, the polar vortex begins to form due to decreasing daylight near the poles. By mid-winter it becomes more influential to the weather patterns in the mid-latitudes.

Tropopause - Zone of the atmosphere that marks the transition between the troposphere below and the stratosphere above. The tropopause is the top of the troposphere. 75 percent of the mass of the atmosphere is located below the tropopause. The height of the tropopause varies between 4 to 12 miles.