Obviously with Hurricane Ida coming it’s all over the news. They’re saying storm surges could be several feet. I understand if it breaks a dam or a levy how the water can get that high. But how can a Hurricane bring so much water inland?
In: Earth Science
Wind blowing unobstructed over the surface of the ocean will drag water along with it, just like how wind on a lake will whip up waves. The high winds of a hurricane push a volume of water with it making the sea level higher under the hurricane. As it comes ashore the water has nowhere to go but inland. That’s what storm surge is.
There is also the condition that the biometric pressure is so low with in the storm that it raises the sea level – that much energy is mind boggling
Check out *Isaac’s Storm* by Erik Larson for a fascinating explanation of how super storms form, woven into a narrative about the destruction of Galveston, Texas in 1900
Three main factors:
1. **Wind.** The last report I saw showed Ida at 121 mph wind gusts. That level of wind speed will literally push the water of the ocean inland.
2. **Atmospheric Pressure.** Hurricanes–like any storm–are examples of low-pressure systems, though hurricanes have more dramatic drops in pressure than a normal thunderstorm. The last report I saw showed the pressure in Ida at 933 mb (or 27.55 inHg if your used to inches of mercury; anything below 29.8 is considered low). Normal atmospheric pressure is 1,013 mb. That means the pressure is 80 mb below normal. 80 mb = 1.16 psi, so every square inch of water effectively has 1.16 less pounds of air pushing down on it, which allows the water level to rise.
3. **Rain.** Hurricanes have rain, which adds to the water.
A storm surge is basically when wind blows the ocean up onto the land.
If you put some water on a plate and blow on it, you’ll be able to get it to go at least partway up the rim of the plate on the side you’re blowing towards. That’s basically what the hurricane is doing, except on a continental scale.
Hurricanes also produce large amounts of rain (which is water they evaporated from the ocean while they were over it), which isn’t technically part of the storm surge but definitely does contribute to flooding.
Stick a straw into a glass of water. Blow straight across the top of the straw. If you do it correctly it will create a low pressure area and draw the water up the straw. Same thing is happening with the low pressure atmospheric pressure and wind velocity of the hurricane.
So hurricanes are low pressure systems, like really low pressure cause they’re so big. Think of a bowling ball on a trampoline, the ball will push the trampoline down, now imagine that trampoline was water and air and the bowling ball is the hurricane. The hurricane It’s going to displace A LOT of air and A LOT of water.
Storm surge is the wind pushing water up the shore like a snow plow or bulldozer. You can recreate this effect by blowing on a near full glass of water. You will see the side opposite of the wind rising.
1) Winds are literally pushing the ocean onto the land. This is the storm surge and what causes a lot of the initial damages.
2) There is a massive amount of rain in the storm. This leads to flooding further inland as more rain falls than the existing drainage system can handle, as well as makes flooding down stream worse as they are already flooded from the storm surge.
The atmosphere presses down on everything, we constantly have high and low pressure areas, weather casters talk about all the time. Think of a water bed, if you press down the area around rises a little. a hurricane is an enourmous low pressure system, so the water rises as much as if you took a toilet plunger to pull up on that section of water bed. and then you have wind pushing waves higher, the timing of the tides…and a couple FEET of rain water.
Latest Answers