Three-dimensional structure of misocyclone associated with thunderstorm observed by Ku-band FM-Chirp fast scanning radar

Severe weather, such as heavy rainfall, flash flood and gusts associated with thunderstorms in an urban area of dense population may cause serious damages to social activity. A filed campaign called Tokyo Metropolitan Area Convective Study for Extreme Weather Resilient Cities (TOMACS) aims to understand the processes and mechanisms of severe weather, using dense meteorological observation networks in Tokyo Metropolitan Area.

During the TOMACS field campaign, a misocyclone associated with thunderstorm occurred in Tokyo Metropolitan area was observed from close range by a Ku-band FM-Chirp fast scanning radar (Ku-band radar) on 6 May 2012. The Ku-band radar with high spatial and temporal resolution (volume scan updates every 1min) and dense network of twelve Automated Weather Stations (AWS) provided a unique dataset to analyze detailed three dimensional structure of the misocyclone and its parent storm.

The major features of the misocyclone and its parent storm are as follows. 1) Surface wind and pressure variations observed by AWS clearly show a cyclonic vortex passage, which means the misocyclone passed at near the surface. 2) The misocyclone was first detected up to 2.5 km AGL. It rapidly developed and propagated upward to 3.5 km AGL (more than one third of the depth of the parent storm) within 2 minutes. 3) An interesting evolution of hook echo was observed. As the misocyclone developed vertically, pattern of radar reflectivity changed from hook shape to spiral shape with weak-echo hole (eye).