Hydrographic data acquired in the Taiwan Strait during the past decade sugg
est that, in winter, a zonal oceanic front develops over the Chang-yuen Rid
ge implying that the northward moving Kuroshio branch current cannot persis
tently hug the west coast of Taiwan as it flows toward the East China Sea a
s previous suggested. A three dimensional numerical model is used to study
the dynamic process leading to the hydrographic pattern observed in the Tai
wan Strait in winter. Model results show that the warm Kuroshio branch wate
r in the Peng-hu Channel is blocked and then is forced to deflect westward
as it impinges on the southern flank of the ridge, On the other hand, the m
onsoon-driven southward flowing cold China coastal water spreads southeastw
ard into the northern Taiwan Strait when it passes around the Dal-tan Islan
d. The cold water bulge occupies the upper layer of the area north of the r
idge in time as winter progresses. The overall flow behavior in the strait
in winter favors the formation of the oceanic front over the ridge between
the two water masses.