Bob Johns is an American meteorologist specializing in severe convective storms and tornado

Tornado

A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone, although the word cyclone is used in meteorology in a wider...

es. Johns spent his career in forecasting and forecaster training. Now retired, he is working on a project reanalyzing the Tri-State Tornado

Tri-State Tornado

The Tri-State Tornado of Wednesday, March 18, 1925, was the deadliest tornado in U.S. history. With 695 confirmed fatalities, the tornado killed more than twice as many as the second deadliest, the 1840 Great Natchez Tornado...

. He furthered forecasting techniques and developed the modern conceptualization of the derecho

Derecho

A derecho is a widespread and long-lived, violent convectively induced straight-line windstorm that is associated with a fast-moving band of severe thunderstorms in the form of a squall line usually taking the form of a bow echo...

 following landmark work on “northwest flow” severe weather patterns. Johns also introduced the enhanced wording "particularly dangerous situation

Particularly dangerous situation

A particularly dangerous situation is a type of enhanced wording first used by the National Weather Service's Storm Prediction Center in Norman, Oklahoma on certain severe weather watches...

" (PDS) to tornado watch

Tornado watch

A tornado watch is issued when conditions are right for a tornado to form. Since any thunderstorm capable of producing a tornado is defined as severe, a tornado watch is also automatically a severe thunderstorm watch...

es for the 2 April 1982 tornado outbreak

Tornado outbreak

While there is no single agreed upon definition, generally at least 6-10 tornadoes produced by the same synoptic scale weather system is considered a tornado outbreak. The tornadoes usually occur within the same day, or continue into the early morning hours of the succeeding day, and within the...

.

External links

• Listing of formal publications (Storm Prediction Center
  Storm Prediction Center
  The Storm Prediction Center , located in Norman, Oklahoma, is tasked with forecasting the risk of severe thunderstorms and tornadoes in the contiguous United States. The agency issues convective outlooks, mesoscale discussions, and watches as a part of this process...
  
  )