Alex – not my “best neighbor” when we lived in Cincinnati, but the storm brewing in the Gulf of Mexico. When we think of hurricanes, we think of high winds blowing things off the map. We think of big swirling masses of air wiping out entire villages or even cities. We think mass wind destruction.

We think wrong.

According to The Weather Channel, more people die of water in a hurricane than die from the wind damage. Part of the water problem is the storm surge. The big swirling mass of wind puts pressure on a large surface area of water, pushing it ahead of the storm. Storm surge waters can combine with high tides to create more havoc, but the surges themselves are problematic.

Even worse is the amount of rain associated with a hurricane. This rain can travel farther inland as well, unlike the storm surge. This rain can cause major flooding both along the coastal region hit, and also inland as the storm moves toward its final dissolution.

In June 2001, the tropical storm, Allison, moved toward Houston and did $5 million in damage – and it was just the remnants of the storm dropping all the absorbed moisture.

So what causes some storms to be rainier? It isn’t the intensity of the winds, but rather the speed of the storm’s movement over water. Rainfall is inversely proportional to speed. This makes eminent sense. The slower the storm moves, the more time it has to pick up moisture. Once it slows down to 10 mph or less, it really picks up the water.

Graphic demonstrating rainfall and wind speed

So what is Alex doing? According to The Weather Channel:

First, Alex’s forward motion is expected to be slow. The farther north the storm moves, the slower it is expected to go. No matter what the track, Alex is seen to be moving slowly both over water and over land.

“Alex has a long fetch of deep moisture” is the next point. Since I had no idea what the term “fetch” meant in this instance, I looked up the definition. It is the distance upstream of the measurement site (eye of the storm, I assume in this instance). This second graphic is illustrative, showing even more bands of storm issue to the east and north of the center, which makes for lots of moisture upload.

Path of Tropical Storm Alex

Lastly, there are previous fronts to contend with – in the picture, that would be the red and blue line holding back the quick dispersal of Alex. Usually these fronts die out over the Tennessee Valley and Southern Plains, but in a trifecta move toward a perfect storm, this isn’t happening right now. Instead the front is making a “wind shift” line which would be a target area for the formation of rain and thunderstorms.

This doesn’t even talk about the oil floating around in the Gulf at this time, nor to the recovery efforts and how this and later storms will affect those.

But I thought it was interesting and had no idea why some hurricanes were so rainy and others – not so much. The reason I love writing (and reading) is the opportunity to learn.

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