Fire and water are opposites, but when it comes to weather, they are interconnected. Large wildfires can generate their own weather systems. Weather travels through vertical columns in a convective process, but fire and weather are almost cyclical in nature as they create and destroy one another.
Wildland fire communities partner with the National Oceanic and Atmospheric Administration (NOAA) to stay informed of weather trends. NOAA issues a fire-weather forecast twice daily and spot forecasts for controlled burns and active fires. Fire resources move around the state based on NOAA’s meteorology team’s calculations.
Lucas Boyer from NOAA’s Grand Junction office says, ”We had some dry lightning in our forecast yesterday, so they were discussing moving tankers around to where they would be able to squash a lightning-started fire.” Dry lightning is the occurrence of a lightning storm where the precipitation evaporates before wetting the ground. Colorado and much of the West has been in a sustained drought for years making dry fuels such as dead trees more prolific.
The two prime mechanisms for predicting critical fire weather are relative humidity and wind. Colorado has experienced record winds this year and long stretches of low relative humidity (less than 15%). Dry lighting combined with low humidity, drought and high winds can create a volatile and flammable environment.
All weather systems are generated by vertical movement in the atmosphere. Large fires have a lot of thermal dynamic energy, pushing extreme heat rapidly upward into the cooler atmosphere. This convection process develops pyrocumulonimbus clouds that can transform into thunderstorms and lightning. These firestorm events are a very localized phenomenon because the dynamic vertical heat energy slows in the radius of the cooler atmosphere surrounding the blaze.
Boyer gives an example, “If you’ve ever stood around a campfire, you will see leaves moving in trees above it. However, if you look at the trees behind you, their leaves will hardly be moving at all.”
Traditional thunderstorms are not as stagnant as firestorms. Boyer explains, “The atmosphere is like a river, it’s a fluid and it’s always moving, and there are these waves of energy that the frontal boundaries move along…”
The upper-level winds steer the atmosphere in a specific direction, making it possible to see a storm approaching on the horizon. Boyer says, “When a thunderstorm collapses and all of its mass drops to the surface, you get these gusty outflow winds and those will contribute to fire growth as well.” At higher elevations, the storm is much closer to the land’s surface, contributing to the probability of lightning strikes. Cloud to ground strikes are common, but there are also plenty of thunderstorms where the lightning stays within the cloud or goes from cloud to cloud.
There are 27 different categories of clouds. Boyer explains how they form: ”When you move a parcel of air at the surface, say you take a really warm parcel of air from a fire, and it’s going to rise into the atmosphere, and it’s going to move into a cooler atmosphere, as the atmosphere cools, you will get condensation. At some point, there will be enough moisture for that parcel to cool and release condensation and create a cloud.” Once the column of atmosphere saturates, it transforms from cloud to rain, falling to the surface with gravity’s pull. Boyer says hail follows a similar process, “Giant hailstones are moving up and down through the column in the thunderstorm collecting ice through each pass, making vertical laps.”
Boyer says counting the seconds between thunder and lightning to determine storm distance is not a myth. The seconds being relative to the miles of distance from the storm is primarily accurate based on the speed of sound. The inconsistency in electrical current and static charge can also interfere with lightning being linear. Boyer believes the extreme heat and distance of a lightning bolt might add to the optical illusion of it being jagged.
Understanding weather and fire behavior is key to preventing and containing wildfires. For instance, the cooling atmosphere at night often causes an inversion and wildfires tend to “sit down” and smolder, giving fire crews time to recuperate. As the day heats up into the afternoon and the winds start blowing, the fire behavior will become more active and can start to rage again. The particulates of matter the fire has consumed transform into embers that float down to the earth once they migrate away from the fire’s vertical force and can ignite dry fuels.
Meteorologists are scientists, but they still view information through different lenses. Sometimes, the science is subject to more Socratic methods involving debate and discussion. While the forecast process has certainly improved, meteorologists will unlikely be able to predict the weather to within a span of minutes. People are probably far off from controlling the weather, so we need to learn how to live with it in this warming climate. Thankfully, meteorologists and firefighters have teamed up to keep us safe in the Arid West.
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