East Asia and Western Pacific METEOROLOGY AND CLIMATE

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near the northern tip of Taiwan. Wind hodograph in Fig.8 illustrates wind change
with height at different time over Pan-Chiao station. The pre-frontal low level jet
and warm advection was very obvious. Behind the surface front, low level wind
shifted to the north- easterly and backed with height. This indicates cool and dry
air advection prevailed in the low level.
5. RADAR ANALYSIS
Fig. 9 shows the reflectivity field observed by the Kaoshuing radar from 0000
LST to 1500 LST June 25 with one hour interval. These Figs are the CV maps
showing the horizontal distribution of the maximum reflectivity in the vertical
column. Following the southward movement of the surface front, convection was
observed along the coast of mainland China during the evening hours of June 24,
the convective activity moved into the strait afterward. At 0000 LST June 25,
a line echo associated with the frontal system developed into a strong convective
rainband in the northern part of the Taiwan Strait and slowly moved southward.
At 0100 LST June 25, this line rainband transformed into a wave-like pattern(Fig.lO).
At the tip of the wave-shape echo, the radial velocity field showed
convergence centers and rotation signatures (lebelled by CON in Fig. 10). The
analysis of the vertical cross section indicated that this area was also in association
with stronger convection. In addition to the convergence zone, we also noted
that there was a divergence signature appearing in the rear of this MCS rainband.
We think it was the result from the rear downdraft motion aloft. The coupling
between southwesterly inflow updraft and this rear downdraft was probably responsible
for the organization of this strong convection.
The convective activity associated with the slowly moving rainbaad continued
as it approached the coast , Stratiform precipitations were noted ahead of and
behind of the system. From the analysis of the reflectivity field and radial velocity
field of TOGA radar during the period of 0700 to 1000 LST, a long-lived cell (>
30 dBz) with 40km long and 20km wide (cell L) was observed right in front of
the strong wind shear line (Pig. 11). Although this cell had changed its shape and
intensity, it did not dissipate completely over four hours. Due to the slow motion
of this cell, the accumulated rainfall was very high near Taidhung area. Taichung
reported nearly 175mm of rain by 2100 LST, and the TOG A radar site was flooded
and nearly ceased operation of the radar.