National Hurricane Center
What Makes Storm Surge expecialy Dangerous. Something that often comes up when we talk about tropical systems is the storm surge its effects on coastal regions. It is one of the deadliest aspects of all tropical systems including hurricanes, typhoon and cyclones. But what makes this storm effect dangerous? Well first what haft to explain what causes storm surge. As a tropical system develops its vast wind field begins to expand, with that it starts to push the water around the system. As it nears coastlines this though water is pushed on shore with sometimes catostrphic force. To show this just watch a lake or a pond on a windy day, you will see that the waves on the downwind side of the body of water is higher, this is what we call fetch, and with the case of a typhoon that spans thousands of miles the fetch is often very large. Another factor playing in to storm surge is low air pressure, something that effects us everyday yet we take little time to think about it is the air pressure that pushes down on us due to earth rich atmosphere. In the center of a typhoon though the pressure is often much lower that it is on an average day, thus letting the water to expand under the less force of the air and in return cuasing a bubble or dome of water under the tropical system. These factors combined often result in sudden and dangerous increases in water levels near tropical coastlines where this phenomena occurs. The worst conditions of storm surge also often take place in areas with a shallow slop or gradient leading up the coastlines. The gentle slope of the US Gulf Coast is a prime example of this. This slope gives the water time to build up with little friction to slow it down. Closer to home in Manila Bay storm surge often occurs due to the shallow slope of the bay leading up the coastal metro areas. On the other hand storm surge is not so bad along coastal areas of Taiwan as the steep continental slope migrates the devasting surges seen in other places of the world. Wherever you are though if a typhoon or equivalent system heads your way do stay away from low lying coastal areas. Water levels could also rise quickly in the matter of moments. Thus becoming not only dangerous, but very deadly.