The Warn-on-Forecast System, a revolutionary new forecasting tool being developed by NOAA’s National Severe Storms Laboratory, seeks to equip forecasters with critical information between watches and warnings to allow them to offer longer lead times in the face of severe weather and tornadoes.

A long-track, strong tornado struck Carter County, Missouri, on March 14. The tornado, classified as an EF-3 by the National Weather Service (NWS) was on the ground for more than 50 miles, leaving a path of destruction in its wake. The community is still recovering from the harrowing storms; however, thanks to the coordinated efforts of National Weather Service (NWS) forecasters, NSSL scientists and local emergency personnel, the public had a roughly two-hour safety messaging lead time. 

The emergency manager immediately shared information from the 7:40 p.m. phone call with other safety officials and on social media, he sounded the sirens well before any warnings were issued, and ultimately credits the advanced messaging, derived from WoFS, as having saved lives.

NSSL’s experimental Warn-on-Forecast System (WoFS) was running on March 14 to assist with the anticipated tornado outbreak. Emboldened in part by the confidence of the WoFS output, NWS forecasters at the Paducah Weather Forecast Office placed calls to four counties, including to Carter County emergency officials at 7:40 p.m., more than two hours before the EF-3 tornado entered the county at 9:51 p.m. 

The office followed up with a Special Weather Statement—an official product that is disseminated to all NWS partners and the public—at 8:34 p.m. Both actions advised first responders, emergency managers and broadcasters that a significant and long-track tornado was likely in the area. With a culture of trust and cooperation long fostered between these vital groups, the impact of the direct phone call and Special Weather Statement was profound.

“Our EM’s [emergency managers] over the past couple of days have repeatedly told us how much help those direct phone calls were. Hats off to your [NSSL] team. This guidance [WoFS] is valuable,” said Chris Noles, the Acting Meteorologist-in-Charge at NWS Paducah. 

Noles also points out that real-time insights on WoFS forecasts from NSSL experts who helped design the system are, “instrumental in directing us toward certain forecast parameters…before the tornado.” NSSL scientists shared these insights in real-time collaboration chat rooms during the outbreak.

Both emergency managers and broadcast partners picked up on the unusual tone and confidence the NWS expressed that night. According to Noles, one broadcast meteorologist in the Paducah market told him the Special Weather Statement “rattled me.” 

Carter County is a mostly rural area with often poor cell phone coverage, and sits at the edge of various television markets, meaning it is difficult to convey a coordinated, timely weather message there. The emergency manager immediately shared information from the 7:40 p.m. phone call with other safety officials and on social media, he sounded the sirens well before any warnings were issued, and ultimately credits the advanced messaging, derived from WoFS, as having saved lives.

WoFS’ Role: Providing Critical Forecast Confidence

Developed by NSSL, WoFS is a rapidly updating, high-resolution computer model designed to predict the probability and location of severe weather like tornadoes. On the night of March 14, WoFS predicted well-developed, strongly rotating storms would traverse Carter County with more than two hours of forecast lead time. That strong signal from WoFS gave forecasters further confirmation of a scenario they knew was possible, and the confidence to take action via the early phone call and Special Weather Statement.

Noles says, “[WoFS] outputs at 00z [7:00 p.m.] at least gave us the notion…to call those four counties we cover out there to tell them we were very concerned that long track tornadoes would occur in their area.”

Time Is Safety

While additional lead time for destructive storms like this is a benefit to everyone, there are those for whom this type of information is invaluable and potentially lifesaving. For some, seeking shelter from a tornado or severe storm is as simple as getting into a storm shelter at their home. For many others, it’s not so easy. Outdoor events, hospitals, schools, and people with no access to a tornado shelter need much more time to evacuate or find safe shelter. 

The two-hour lead time given by the NWS Paducah Weather Forecast Office was invaluable. After sharing the advanced messaging with county emergency personnel and social media pages, the Carter County emergency manager reported the number of people checked into a designated shelter in Van Buren rose from four to 125 well before the tornado arrived. Knowing those people personally, he feels that many would not have left their vulnerable homes to seek shelter except for the very early messaging.

Ultimately the goal of Warn-on-Forecast is to bridge the information gap between NWS watches and warnings. By equipping forecasters with additional information about the probability for and potential location of severe weather, Warn-on-Forecast can help them create longer lead times for safety messaging for flooding, severe weather and tornadoes; changing the scale from mere minutes to potentially hours. 

Armed with that kind of lead time, even vulnerable populations or institutions are better able to seek shelter and make decisions to protect themselves and those in their charge.