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Earth from Orbit: Wildfires Spawn Severe Weather

July 29, 2021

Wildfires continue to rage in the western U.S. Some of the most intense fires have generated their own weather, with thunderstorms, lightning, and even a confirmed tornado. 

As a fire burns, it generates a large amount of heat, which causes air and moisture to rise, along with smoke and ash. When it reaches the upper atmosphere, it often cools and condenses to form what are known as pyrocumulus or “fire clouds” over the blaze. Some of the moisture is already present in the atmosphere, while some of it also evaporates from burning plants fueling the fire below. If the fire is large enough, the intense heating can generate a smoke-infused thunderstorm, or pyrocumulonimbus cloud, also known as pyroCb.

PyroCb clouds can produce lightning, which can set off even more fires. They also generate stronger winds, which fan the fire, making it hotter and helping it spread. In some cases, the air may rise so fast that it creates a tornado.

Several active fires in the U.S. have recently formed pyroCb clouds and generated severe weather. The Bootleg Fire burning in southern Oregon is currently the largest active fire in the U.S. It continues to grow and exhibit extreme fire behavior. PyroCb have generated thunderstorms, lightning strikes, and at least one confirmed tornado. On July 24, 2021, the National Weather Service in Medford, Oregon, confirmed the Bootleg Fire spawned a rare tornado on the eastern edge of the fire on July 18. 

California has also been hit hard by a series of big wildfires this summer, outpacing last year’s fire season. The Dixie and Tamarack fires have exhibited extreme fire behavior and spawned severe weather. The Dixie Fire grew so volatile on July 20 that it generated a pyroCb  that produced lightning. The storms generated by the fire exacerbated fire conditions, which hampered firefighting efforts. Meanwhile, the Tamarack fire near the California-Nevada border has grown with such force that it also generated its own weather. 

As of July 28, 2021, there are 81 large active fires in 12 states, destroying more than 1.6 million acres of land. More than 21,000 wildland firefighters and support personnel are assigned to incidents across the country. Extreme fire behavior is being fueled by severe drought and record heat. When wildfires also spawn severe weather, dangerous conditions become even worse. 

NOAA satellites are our eyes in the sky, detecting and monitoring wildfires as well as severe weather created by the most intense fires. GOES-16 (GOES East) and GOES-17 (GOES West) keep constant watch over the same area, monitoring fire conditions in real time. They detect the heat signature from fires, pinpointing where and how intense each fire hot spot is. They also alert us to the presence of dangerous pyroCb clouds and monitor ensuing severe weather conditions. The Joint Polar Satellite System’s NOAA-20 and Suomi-NPP satellites also capture high-resolution images of these kinds of clouds and monitor the weather conditions that produce them.