Storms...What is the big deal???

Due to recent weather events, Irene, I have decided to take a different turn for this post.


Needless to say the recent hurricane has been a topic of lots of conversation this weekend and I realized many people don't understand what the "big deal was". We all know that weather predicting is not an exact science and sometimes we tend to be skeptical of just how much damage these storms can cause. As a country, or world for that matter, we have not been keeping track of weather for very long.... in the grand scheme of things. Technology has sure helped weather forecasters to be able to predict times, directions and magnitudes of storms, but they still can not predict damage and they will never be able to...why you ask? I am going to try to explain that ...to the best of my ability!

I have heard several newscasters trying to prepare everyone for this recent 100 year storm. Well what is a 100 year storm??   Well it is literally a storm that happens once every 100 years. How do we know it is a 100 year storm?  Well....it is a guess at best!! Our weather records are barely 100 years in the making so it is thought that this storm will only happen once every 100 years.

Why do we categorize these storms in this way? Storms are rated by years, for instance 25, 50, 100 and 500 year storms.  Now a 25 year storm is suppose to happen every 25 years a 50 year storm every 50 years and so on and so on. Our weather records are pretty good for the last 25 and 50 years but when it gets to 100 years it is sketchy at best!! ( We have no idea if there has ever been a 500 year storm!!)

This rating system is VERY IMPORTANT!!!  It is used to determine many things from how to build, where to build and what to build.

One of this biggest concerns with Irene was the amount of rain and water that was going to by forced onto land and how fast that said water will go away.   This is called the "peak run-off rate". There is a rather complicated formula that is used to determine this. The mathematics are not all that hard but the factors that go into the formula can be difficult to figure out. This formula takes into account the soil type, where in the US you are located, the slope of the land and how much rain is received in an hour.

This formula is very important and used to determine how to build levees, dams, retaining walls and yes even buildings!  We can also determine with this formula how much erosion will take place from the run-off of water.

Now lets all think back to science class when we use to pour water into cylinders filled with different materials like gravel, pebbles and sand...I hope you all did this !!! The cylinders with the gravel filled with water faster, the pebbles a little slower and the sand the slowest....why is this important??? Because this is just like different types of soil...they all have different rates of absorption. So it can be determined how fast the rain and water will be absorbed in different landscapes. Please keep in mind that concrete and blacktop can not absorb water...it just runs off to the lowest level of the landscape.

There have been more examples of storms that hit the east coast in the North Carolina region so it kind of easier to more accurately predicted how the storm will affect that region. BUT, in New york City there has not been many of these types of storms.

SO what is the big deal? Why were there so many warnings and evacuations?

Now we have to think back to history class.....what did our landscape and population look like 100 years ago? VERY different than what it is today!!!  There were no high rises buildings, subways, tunnels or mile after mile of concrete!! The population density was also MUCH lower!!

To put it bluntly....there is/was absolutely no way for anyone to predict how a storm like this would affect these cities along the northern Atlantic coast....it has never happened in recent history!  Since this storm was weakened as it "stood" over the the North Carolina area the affects on the areas as the storm moved north was much less than expected!

However......the amount of rain still falling in the area is a problem! There has already been a lot of rain in the region for the month which has saturated the ground. So the rain that is now falling has no where to go. So now the biggest risk of this storm is the flooding that is following it. This is when the peak run-off rates come into play again. Most structures are built to withstand 100 year storms.  But let me reiterate....100 years ago the landscape looked much different than it does today!! This storm is basically a test for some of the man made dams and levees in the area....let's hope they pass the test!


What is the bottom line???   LISTEN to the storm warnings!!! Weather forecasters and safety officials are doing their best to keep everyone safe.  There is no way to precisely predict the affects of these large storms. The only way we can know for sure what is going to happen is to see what happens when the storms go through different areas. Then we can compare the storms and more accurately predict what will happen the next time. Unfortunately we will not know the worst case until it happens!

Remember that old saying " if we do not learn from history we are doomed to repeat it"?  It was not so long ago we had to learn the hard way from Katrina....let's not let that happen again!!!

If you were or are in the path of this storm let me know how it has affected you and the area you live in....and please, please stay safe!!!