07-05-2025
2 Hour Lead Time For Tornadoes Is Possible But Do We Want It?
302085 01: The Funnel Of A Tornado Touches Down May 12, 1997 In Miami, Fl. Five People Were Injured ... More And Approximately Twenty Thousand Residents Lost Power When The Storm Struck Downtown Miami. (Photo By) Getty Images
We are in the peak of the U.S. severe weather season, and tornadic storms have been particularly prevalent this season. During my tenure in the meteorological field, one of the 'holy grail' research challenges has been to improve tornado warning lead times. A NOAA research program has demonstrated that we may be able to give up to two hours of advance warning of a tornado. Here's how it is possible as well as some thoughts on whether we want it.
Two Hours of Lead Time Is Now Possible
Of course, we want to give as much lead time as possibly for tornadoes, but it is complicated. Tornadoes can be life-altering events that affect families, businesses, and communities for years. I will explore, however, some of the caveats with additional lead time a bit later, but let's explore the Warn-on-Forecast System developed by NOAA's National Severe Storms Laboratory.
The NOAA Warn on Forecast System has evolved from years of research. NOAA NSSL
According to a NOAA website, the system, '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.' In March, a long-track, strong tornado hit Carter County, Missouri. This storm caused significant damage as the tornado tracked along the ground for more than 50 miles. According to NOAA, '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.' People had nearly two hours of lead time before the EF-3 tornado touched down in the county at 9:51 pm.
Even prior to that issuance, the NWS issued a Special Weather Statement at 8:34 pm that, 'A significant and long-track tornado was likely in the area.' This was all based on the WoFS output. According to NOAA, forecasters spoke highly of the coordinated guidance provided by the NSSL scientists as the event unfolded.
Timeline of warnings and tornado activity in Carter County, Missouri (March, 2025). NOAA NSSL
What is WoFS
According to the NOAA webpage, NSSL developed the system. They noted that it is, 'A rapidly updating, high-resolution computer model designed to predict the probability and location of severe weather like tornadoes.' That night the system predicted two hours in advance that supercell storms would cross Carter County. As a meteorologist myself, we often see guidance in the model that suggests tornadic storms. However, what strikes me is the confidence forecasters had to 'act' on the information so early. Given the path of destruction with this tornado, those early phone calls and Special Weather Statements likely saved lives.
Are There Down Sides Of Too Much Lead Time?
NOAA reported that in this example, 'The two-hour lead time given by the NWS Paducah Weather Forecast Office was invaluable…. 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.' However, some studies have found mixed messages when it comes to lead time. A 2008 study published in the scientific journal Weather and Forecasting found that up to 15 minutes lead time led to a reduction in fatalities, but beyond that time threshold, there was an increase in fatalities compared to the absence of a warning.
JOPLIN, MO - MAY 24: Damage is seen one day after a tornado tore through Joplin killing at least ... More 122 people on May 24, 2011 in Joplin, Missouri. The tornado that ripped through the town of about 50,000 people May 22, is being called the deadliest single tornado in the U.S. in 60 years. (Photo by) Getty Images
In 1999, legendary severe weather expert Chuck Doswell wrote in Weatherzine , 'It's hard to imagine any real need for warnings with lead times longer than 32 minutes! In fact, it's possible that longer lead times would be less effective because they might not convey a strong enough sense of urgency.' The first tornado of the day, according to studies tends to have the lowest lead time, and it increases for subsequent tornadoes. Average lead time is around 13 to 15 minutes. In a 2002 study of schools and assisted living facilities, the response to the question, 'What is the ideal lead time?' ranged from a median of 15 minutes (schools) to 30 minutes (assisted living). A 2011 study found that the public ideally wanted about 34 minutes of lead time, which is less than the one to two hours now possible with the WoFS system.
Why It All Matters
That 2011 study suggested that too much lead time may lead to a reduced sense of urgency. I can see scenarios in which people said, 'Oh, I still have time to pick up groceries or the dry cleaning.' There is complexity and nuance to this discussion. There are likely many factors including the type of population, time of day, perceived vulnerability, and so forth. NOAA made the point that, 'Outdoor events, hospitals, schools, and people with no access to a tornado shelter need much more time to evacuate or find safe shelter.'
Overall, the Missouri story is important because WoFS did not appear overnight. It evolved from years of research, development, and evaluation. Steven Thur is NOAA's Assistant Administrator for Research. In a social media post on LinkedIn accompanying the NOAA press release, he said, 'This new system will save lives. In 2024, NOAA: National Oceanic & Atmospheric Administration confirmed 1,796 tornados, the 2nd highest total since record-keeping began in 1950. Those storms killed 54 individuals across 17 states. So far in 2025, there have already been 35 fatalities across 16 states.'
Henryville Elementary School staff greet returning students Wednesday, March 21, as they disembark ... More from school buses at temporary classrooms the school district is renting from Graceland Baptist Church in New Albany, Ind. Wednesday was the kindergarten through sixth grade students' first day back at school since a tornado heavily damaged Henryville, Ind.'s three-school campus. That March 2 storm was part of a wave of tornadoes that killed 13 Indiana residents. (AP Photo/Rick Callahan) Copyright 2012 AP. All rights reserved.
