“Hurricane” Hal Needham is a storm surge scientist who specializes in data-driven storm surge analysis. He is the founder and president of Marine Weather and Climate.
Super Typhoon Meranti is barreling through the Pacific and will threaten China with a major storm surge event on Wednesday night.
In the pre-dawn hours local time Wednesday, Meranti approached the southern tip of Taiwan as a Super Typhoon with maximum sustained winds near 190 mph. This would place the storm well above the threshold for a Category 5 hurricane in the Atlantic or Eastern North Pacific basins.
Fortunately for Taiwan, Meranti’s center of circulation is forecast to track south of the island. Nonetheless, the powerful storm will inflict damage from extraordinary waves, wind and heavy rain/mudslides.
The real concern for coastal flooding will come Wednesday night, as Meranti approaches China’s coast as a Super Typhoon, with winds equivalent to a Category 4 hurricane. The Joint Typhoon Warning Center predicts Meranti’s maximum sustained winds will be 132 mph around midnight tomorrow local time, as the storm is centered just off the coast of China.
Meranti’s storm surge potential will be a great concern in places like Xiamen, China. In 1983, Super Typhoon #4 took a similar track to Meranti and generated a 5.87-foot (1.79m) storm surge in Xiamen. The 1983 typhoon was weaker than Meranti, however, approaching the coastline with 92 mph winds.
Of course, typhoon size is a factor in storm surge height as well. If Meranti’s size remains comparable or larger than the 1983 typhoon, and the winds remain stronger, the surge potential will be greater than in 1983 and could exceed 10 feet in portions of coastal China. The country observes a storm surge of this height around once every three years with 15 surges exceeding 10 feet observed in the 50-year period from 1949 to 1998.
Although such storm surge heights may not sound extreme by global comparison, the impacts of a coastal flood like this could be severe given the dense coastal population in China. Even two decades ago, the 3.3 feet coastal plain in China contained 73 million people, enabling low-magnitude surges to have major impacts.
Typhoon Fred in 1994 provided an excellent example of severe coastal flooding impacts in China from a moderate storm surge level. Even though the highest storm surge level only reached 8.8, this typhoon destroyed 323 miles of seawalls, inundated 189 towns and flooded more than 22 million people.
This should cause coastal residents to take precautions and prepare for a widespread storm surge from Meranti.
Coastal populations should also consider Meranti’s timing when considering evacuation. Meranti’s greatest surge potential will come around the time of landfall, which will be after midnight on Wednesday night. It is always harder for people to discern a flood situation during the dark of night, so it is wise for coastal residents to either evacuate or prepare for storm surge during the daylight hours on Wednesday.
This originally appeared on Hurricane Hal’s Storm Surge Blog.