Remembering May 20, 2013

David Andra, lead meteorologist for the National Weather Service in Norman, says he expected a busy afternoon weatherwise on May 20. Photo by Brent Fuchs.
David Andra, lead meteorologist for the National Weather Service in Norman, says he expected a busy afternoon weather-wise on May 20. Photo by Brent Fuchs.

Tornado Emergency

David Andra remembers the first “big one.”

Moments before the May 3, 1999, Bridge Creek-Moore tornado, Andra, now lead meteorologist for the National Weather Service office in Norman, issued the first official tornado emergency. The urgency of this warning – a desperate plea to the populace – predicated a potentially devastating weather event. Until May 20, 2013, the term hadn’t been used in Oklahoma for about a decade.

“The phrase ‘tornado emergency’ is used to drive home the point that we’re likely dealing with a tornado of exceptional size and strength,” Andra says. “A tornado of this type poses an especially deadly threat, especially when thousands of homes, schools and businesses lie in its path.”

For many Oklahomans, the day started off much like any other day. For Andra and his crew at the National Weather Service, however, the morning began with a meeting to coordinate plans for what they expected to be a dangerously busy afternoon for severe weather in central and southern Oklahoma.

“Warm, humid days in the Oklahoma spring are often ripe for tornadoes,” Andra says. “On this day, the dry line, a boundary where storms often develop, was nearby. The change in wind with increasing height in the atmosphere was favorable for any storms that developed to rotate …We also felt that storms would develop sooner than often happens in May, and this brought an extra concern for schools and parents.

“After storms developed, we were carefully scrutinizing Doppler radar information throughout the depth of the growing storms, looking for signs (that) they were organizing into rotating storms,” Andra continues. “Unfortunately, that happened swiftly.”

The afternoon unfolded as the NWS predicted – quickly and brutally. For most Oklahomans, the rapid speed of severe weather development is usually not surprising. But even for those who were carefully watching the weather May 20, the rate at which the storms grew was shocking.

As the system intensified, both NWS staff and viewers at home watched with familiar dread as a prominent hook echo developed on the radar. Andra says that as signs began to point at circulation near the ground, field observers confirmed their worst fears: A potentially catastrophic strike was aimed at the south Oklahoma City metro area.

At 3:01 p.m., Andra issued a tornado emergency.