Wednesday, July 6, 2016

Big Typhoon Threatens Taiwan

Powerful Typhoon Nepartak could prove
to be one of the worst such storms to hit
Taiwan in many years.  
A nasty typhoon is heading toward Taiwan, and if it makes landfall there, it could be more destructive than most.

The typhoon, named Nepartak, will probably slam into Taiwan's east coast late Thursday or early Friday.

(Typhoons are hurricanes in the eastern Pacific. They are exactly that - hurricanes - but they're called typhoons in that part of the world.)

Nepartak is a Category 5 storm, the strongest and most dangerous of typhoons.

It looks like it might have reached peak intensity earlier today, and has weakened just a tiny bit. Sustained winds at last report were 172 mph, which is pretty scary. 

The current slight weakening doesn't mean that trend will continue.  

Strong typhoons and hurricanes sometimes go through what is known as an eyewall replacement cycle.  When this happens, the extremely intense thunderstorms around the storms' eye break down, and reform either closer of further away from the center of the storm.

This would make the eye either bigger or smaller than before. Once the eyewall replacement cycle is complete, a typhoon or hurricane has the potential to strengthen again.

Nepartak might indeed re-strengthen before it reaches Taiwan. It's over very warm water, which tends to feed typhoons and help make them stronger. Upper level winds over and near the typhoon are light.

Lighter upper level winds encourage typhoons and hurricanes to maintain themselves or get stronger, while more powerful winds high in the atmosphere tend to weaken these storms.

Moreover, as the Washington Post's Capital Weather Gang notes, Nepartak is what is known as an annular storm, which is kind of rare.

Usually, typhoons and hurricanes have spiral bands of sbowers and thunderstorms radiating out fro the center. Annular storms just have a dense circle of intense storms around the eye with no spiral bands.

Flooding in eastern China recently turned this
escalator into a waterfall. In addition to the destruction
Typhoon Nepartak is expected to cause in Taiwan,
it will also worsen eastern Chinese flooding.
Image from the South China Morning Post.  
Annular storms tend to weaken much more slowly than regular typhoons or hurricanes, so Taiwan can't count on any kind of miracle collapse of the storm.

Taiwan is fairly used to typhoons as they often get them, but if this one makes landfall in Taiwan as a Category 5, things could get particularly nasty.

On top of the obvious problems with the winds and storm surges along the coast, up to three feet of rain might fall on parts of Taiwan with Nepartak.

As you an imagine, that would cause incredible flash floods and landslides as the storm hits the hilly, mountainous island.

Nepartak is ending a record long stretch without a tropical storm in the part of the Pacific Ocean where it's traveling now. It had been 199 days between typhoons there.

Too bad such a nasty one is breaking the storm-free streak.

Another big problem with Nepartak is it's pushing more moisture into flood ravaged eastern China. 

Floods there have claimed at least 110 lives in the past couple weeks and has damaged or destroyed thousands of buildings. Heavy rain associated with Nepartak is only going to make matters worse in China.

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