FOG BLOG U.S. WEATHER LOG: STRONG WINDS CREATE DUST STORMS IN SOUTH DAKOTA!

A derecho hit South Dakota on Thursday — but what does that mean? And what is a haboob? The National Weather Service tweeted that Thursday's storm "will be classified as a derecho," but what is a derecho?

The term derecho (duh-RAY'-choh) was coined in 1888, according to the National Oceanic and Atmospheric Administration. The word is Spanish for "direct" or "straight." The term was used for a short time during the late 19th century, but it disappeared from use for nearly 100 years, when meteorologists starting using the term in the mid-1980s.

The national Storm Prediction Center determines whether a storm is officially a derecho.

The structure of a derecho-producing storm looks distinctive in radar and satellite imagery, Ken Pryor, a research meteorologist at the Center for Satellite Applications and Research at NOAA told the Des Moines Register in 2013. "The systems are very large and have signatures that are very extreme," he told the Register. "You get large areas of very cold cloud tops that you typically wouldn't see with an ordinary thunderstorm complex. The storms take on a comma or a bow shape that's very distinctive." Derechos can pack lethal gusts in excess of 100 mph — hurricane strength — across a front stretching for many miles, and last for hours. Storms that have sustained winds of at least 58 mph and leave a path of damage at least 250 miles long qualify as derechos, according to the National Weather Service.

The storms that hit South Dakota had wind speeds that exceeded 100 mph. A haboob is a wall of dust that is pushed out along the ground from a thunderstorm downdraft at high speeds, according to NOAA. Haboobs can occur anywhere in the United States, NOAA reports, but they are most common in the Southwest.

The term haboob, which was first used in 1897, is most commonly associated with the infamous dust storms in Sudan. However, in 1971, a group of scientists witnessed an Arizona dust storm so huge that they proposed calling it a haboob, the Arizona Republic reports.