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Observations of the winds in tropical cyclones are still limited. We propose a new method for deriving the tangential winds in tropical cyclones, which employs a spectral analysis of high‐frequency cloud imaging by latest‐generation geostationary meteorological satellites such as Himawari‐8. The method was applied to the visible images of boundary layer clouds in the eye of Typhoon Lan （2017） over an 8.5‐hr period. The low‐level tangential winds over the central two thirds of the eye in radius were close to a rigid body rotation and increased with time. On its outside was a region with striating clouds rotating at much higher angular velocities, which may have been supergradient. Asymmetric motions were visualized as the deviation from the inner rotation, and the vorticity of some mesovortices were quantified. These asymmetric motions are suggested to transport angular momentum to accelerate the inner rotation. Plain Language Abstract Observations of the winds in tropical cyclones （TCs） are still limited. The latest‐generation geostationary meteorological satellites such as Himawari‐8 capture TCs‘ cloud motions that were previously unobservable. We propose a method for deriving the tangential winds in TCs using a spectral analysis of high‐frequency cloud imaging by these satellites. The proposed method was applied to the visible images of lower clouds in the eye of Typhoon Lan （2017） over an 8.5‐hr period of daytime observations. The low‐level tangential winds over the central two thirds of the eye in radius were close to a rigid body rotation （rotational motion which has no deforming component）, and its speed was increased with time. On its outside was a region with striating clouds rotating at much higher angular velocities. Asymmetric motions were visualized as the deviation from the inner rigid body rotation, and the vorticity of some mesovortices （small scale rotational features found in the TCs） were quantified. These asymmetric motions are suggested to transport angular momentum to accelerate the inner rotation. This study proves the usefulness of geostationary satellites to diagnose and study wind structures of TCs.
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