Monday, September 28, 2015

Super Typhoon Dujuan Slams Taiwan

Super Typhoon Dujuan slammed into eastern Taiwan today as a category-4 typhoon, with maximum sustained winds of approximately 225 KPH / 140 MPH (Met Office 2015). Dujuan made landfall slightly after 0900UTC or 1900 local time.

Dejuan's impressive size and structure was evident in this visible satellite image taken as the sun rose on Monday morning.
Source: @DanLindsey77

Radar and satellite loops depicted a large, powerful typhoon, which dumped tremendous rainfall on this mountainous island. As with other islands in the region, mudslides will be a major threat as heavy rains try to run off the steep terrain.

Most impacts from this storm appear to be from intense winds and heavy rain so far. Storm surge levels on Taiwan tend to be suppressed because the bathymetry, or offshore water depth, is deep, which does not allow water to pile up as efficiently. Also, Taiwan does not have as many defined bays and inlets as the Philippines, so water does not get funneled or trapped as efficiently.

Dujuan generated large waves on Taiwan's east coast
Source: @EarthUncutTV

Although typhoons tend to generate modest storm surge levels on Taiwan, wave heights along the coast are often tremendous. This occurs because waves “feel the bottom” of the ocean and break their energy when they reach shallow coastal waters. On islands with deep bathymetry (and usually high mountains), like Taiwan and Hawaii, most of this wave energy remains intact until the waves are striking the shore.

Dejuan generated massive waves that slammed into sea walls on Taiwan's east coast

Typhoon Doug in 1994 provides a good example of a super typhoon that generated moderate surge levels but massive waves on Taiwan. Doug produced a maximum storm surge of 1.5 – 3.0 m (5 – 10 ft) near Lungtung Harbor, but wave heights reached 20 m (66 ft) (Wang et al. 2005).

Typhoon Doug (1994) track and intensity. 


 Met Office, 2015: See

Wang, Y.H., I.H. Lee, D.P. Wang, 2005: Typhoon induced extreme coastal surge: A case study at northeast Taiwan in 1994, Journal of Coastal Research, 21, 548-552.

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