East Asia and Western Pacific METEOROLOGY AND CLIMATE

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one meter. Most of the water level gauges are located within a harbor or on
bridge pier in a river system. In the first case, the computed water levels are
usually higher than the harbor water level due to damping effects of the
harbor mouth. In the second case, the computed surge level is usually lower
than those observed in a river due to the effects of flood stage. These factors
have to be considered during the model adjustment stage.
Fig. 4 shows the distribution of water level induced by a typical typhoon
toward 300°T at 5.1 m/s with a central pressure of 965 mb. The maximum
positive surge (157 cm) is located near the Tansui River entrance while the
maximum negative surge (-70 cm) is located near Keelung. With the model,
we have made 1300 simulations using typhoons of various strengths and
directions passing through Taiwan. For each coastal area, surge heights are
being analyzed for engineering design and planning purposes. For example,
near Taipei, severe surge heights are ranked and tabulated on top of Fig. 5.
The lower diagram in Fig. 5 shows the storm track index map with
probability roses for typhoon's movements within each 1° by 1° square
according to past data.
In the south-western part of Taiwan, the elevation of many coastal ares
are very low. During the high tide conditions, even a small typhoon passing
through the Phillipines may cause floodings near the SW coast. The writers
believe that those areas are located off deep waters of relatively low latitude.
The large Rossby radius of deformation (700-900 km) when combined with
the coast-trapped waves made the problem worse.
In our prediction operation, improvements are needed in four major areas,
namely, better typhoon track forecast (e.g., see Tsay 1982), higher coastal
resolution, more verification/adjusment, and a better wind field model.
ACKNOWLEDGMENTS
The execution of this study would not have been possible without the
help of many colleagues. They are: Drs. S. Y. Chen, L. H. Chang, -L. H.
Fong,C. Y'Kwqh, C. K, Li, T, C. Li, F. C. Liu, W, M. Liu, from the Central
Weather Bureau; Messrs. Y. C. Hwang, W, Lin, N. H. Ma, from the Science