Weather blog: Hurricane Harvey, the inner workings of a storm
If there’s one thing that’s been on everyone’s minds, it’s safe to say that would be Hurricane Harvey. Harvey hit the Texas coast Friday night as a Category 4 hurricane with winds of 140 mph. When Harvey hit, the massive storm caused immediate and catastrophic destruction to the Texas coast. Since then the storm has weakened into a tropical storm with winds of 40 mph, but a new and potentially more dangerous threat has emerged. Now we’re talking about torrential rain coming in increments of feet verse inches.
The question becomes why. Why is Texas and most notably Houston getting so much rain? First, let’s talk about hurricanes and how they form. There are a few key ingredients required for hurricanes to form and sustain themselves. Hurricanes actually form along the west coast of Africa and simply start as a cluster of thunderstorms. Once they get over the Atlantic, they begin to feed off the warm waters that provide moisture and energy. For that to happen though, the Atlantic must be at least 80 degrees. As air rises into the storm, it is forced out at the top creating the eye of the hurricane. Given the area of low pressure at the surface and the Coriolis Effect, the storm rotates counterclockwise as it moves across the Atlantic. So let's recap so far hurricanes need warm water, and a lack of land. When hurricanes go over land, they tend to fall apart. There’s one more key ingredient, and that would be high pressure aloft. Essentially, we need a lack of wind shear. If there’s strong wind shear then the winds can almost slice through the storm taking it elsewhere. A lack of wind shear allows the storm to grow and develop especially in altitude.
In the case of Harvey, the storm continued to intensify until it became a Category 4 storm before making landfall and weakening to a tropical storm. This is where Harvey gets interesting. Sitting just along the coast and moving less than 5 mph it can still feed off the warm Gulf waters. This allows the feeder bands to sustain themselves and continue to rotate around the area of low pressure that resulted from the initial development. As long as the storm is not moving or moving very slowly and feeds off the energy provided by the Gulf of Mexico, we’ll continue to see further rain and thunderstorm development.
Harvey is actually forecast to move back out into the Gulf before once again making landfall as a tropical storm later this week. This means the Texas coast and even portions of Louisiana will continue to get more rain only increasing the already catastrophic flooding.