Abstract
An extremely sharp pressure dip accompanied with a mesoscale disturbance was observed in the northwestern quadrant of Typhoon 8124 (Gay) passing off the coast of the Boso peninsula. The amount of pressure drop was so large that the minimum pressure value associated with the disturbance (967.4mb) was almost comparable to the central pressure of this typhoon (965mb). The steering velocity and the lifetime of the disturbance was estimated to be a little faster than the typhoon movement and more than five hours respectively. The structure was analyzed based on the data from dense network of surface meteorological observations and a doppler radar installed in MRI, and it was shown that the surface wind field and the cloudiness distribution had internal gravity wave characteristics. The disturbance was accompanied with a rainband system, and the surface pressure dropjump phenomena seems to be closely related to the finer structure of systematic convective activity with the east-west wavelength of 90km embedded in the rainband.
