Abstract
In Baiu season intense rainstorms occur frequently in western Japan along the Baiu front. On 22-23 July 1983, an intense rainfall event continued more than ten hours in the western part of the Chugoku district and the maximum 1-day precipitation amount reached 300 mm.
We made a forecast experiment using limited area models with grid sizes of 63.5 km and 25.4 km and evaluated the effect of increased grid resolution and representation of orography in the models on this intense rainfallevent.
The two models predicted less amouts of precipitation than the observation. The locations of maximum precipitation tend to move eastward in this models, while it stayed almost at the same position in the observation.
The features of sea level pressure, wind and water vapor do not differ significantly between the 63.5 km and 25.4 km models. However, there are large differences in the intensities of upward motion and positive vorticity in the Baiu frontal zone between the two models. They are much stronger due to the more active condensation heating in the 25.4 km model. This fact results in some improvement of the intensity and horizontal distribution of precipitation.
The inclusion of a steep orography in the 25.4 km model show a tendency that the location of maximum precipitation become stationary and close to that of the observation and its amount increased.
