WetBulb Globe Temperature: Why it is a concern for the Air Force Marathon

Have you ever heard of the term WetBulb Globe Temperature? Likely not, but it’s serious business at Wright-Patterson Air Force Base, and again this year, it could force marathon organizers to call the race quits if WBGT reaches a certain level Saturday.

>>Air Force Marathon: Thousands of runners expected from across U.S.

Storm Center 7 Meteorologist Jesse Maag explains what it means.

“Oftentimes on hot days, meteorologists will talk about the heat index, or the ‘feels like temperature.’ Air Force meteorologists have another method of measuring heat and they go to pretty great depths to calculate it,” Maag said.

Last year, the Air Force Marathon released a statement about how the heat could affect the race:

"Safety of the runners and our volunteers is of paramount importance so we have protocols in place for a variety of contingencies including adverse weather conditions. We have color-coded advisories based on wet bulb globe temperature, which is the standard across the industry and accounts for temperature, humidity, wind and other factors. We have a fully trained weather office that is constantly watching weather and advising leadership. ... If the WBGT approaches the barrier for black conditions (>82 F) then we would begin reviewing procedures and potentially implement an orderly cancellation with runners taking shelter at first aid and water stations until buses arrive to bring them back to the finish line."

>>Traffic: What to expect marathon morning

Maag explained the heat index accounts for both the temperature and relative humidity, disregarding other atmospheric factors.

The wet bulb globe temperature, or WBGT, used by the Air Force, takes into account not only the air temperature and relative humidity, but also the wind speed, sun angle and cloud cover.

By using more variables, the Air Force expects to have a more accurate representation of the way the air feels on a hot day.

The scale is slightly more complicated for the WBGT than the heat index, however. It doesn’t measure how the air feels like the heat index. For example, a calculated WBGT over 82 degrees is considered extremely dangerous.

That is the temperature at which the Air Force Marathon organizers would stop the race, according to an alert sent to participants Friday.

So what will the WBGT and forecast be on Saturday for the 2019 Air Force Marathon?

Storm Center 7 Meteorologist Kirstie Zontini said the sunrise will be at 7:23 a.m. with early morning temperatures in the upper 60s.

By midday, temperatures will be in the low 80s. The WetBulb Globe temperature at noon will be in the low to mid-70s.

This is in a range where race officials would advise runners to slow down but it isn’t high enough that they would stop the race.

Early afternoon temperatures will keep climbing into the upper 80s. The WetBulb Globe temperature at noon will be in the upper 70s.

This is in a range where race officials would advise runners slow down and watch for any course changes, but it also isn’t high enough that they would stop the race.

Some slightly muggy conditions will be expected as well towards midday but skies are expected to be sunny with some scattered clouds.

Comments on this article