NASA Research Team Captures Rare Pileus Cloud Over Wildfire

• A research team under NASA’s INSPYRE campaign successfully observed a rare pileus (cap) cloud forming atop a pyrocumulus cloud during the Sand Creek fire in Montana.
• Pileus clouds are indicators of vigorous convection and typically form when a rapidly rising updraft displaces a moist layer of air above it.
• The observation provides unique, high-resolution data on how surface wildfire dynamics interact with atmospheric convective processes.

Observation and Methodology

• Date: August 11, 2026, at 5:40 p.m. local time.
• Instruments: The MASTER (MODIS/ASTER Airborne Simulator) mounted on a NASA ER-2 high-altitude research aircraft.
• Data collection: MASTER utilized 50 spectral bands to capture both the active surface fire behavior via shortwave-infrared and the structural characteristics of the convective plume.
• Mechanism: The rapidly rising pyrocumulus acted as an artificial mountain, forcing a horizontal layer of moist air upward until the water vapor condensed into the ephemeral cap.

Scientific Context

• Pileus clouds are transient, usually lasting only a few minutes, making this specific observation highly valuable to the science team.
• While commonly seen in severe thunderstorms or following volcanic eruptions, they are rarely documented in such detail in association with wildfire plumes.
• This data is central to the INSPYRE project’s goal of mapping the chain reaction from surface heat to plume development and cloud formation.