Bill Read's Blog: Area of low pressure in the Gulf
The area of low pressure in the Gulf of Mexico south of New Orleans normally would be cause of concern for those of us on the upper Texas coast. Pressures are relatively low and there is a clearly a closed circulation -- weather speak for winds turning in a counter clockwise direction surrounding the lowest pressure. The ocean temperature in the Gulf is at its hottest level of the season, more than enough heat content to support a hurricane. This low has been drifting south and southwest the past two days away from land, usually another warning sign.
So why am I not concerned? Well, this visible satellite image gives us clues on the environment surrounding the low. First, all the thunderstorms are displaced south of the surface center. What this tells us is that there is significant northerly wind shear, where winds aloft are moving the tall thunderstorms away from the center. This shear is forecast to continue to be a factor today and increase tomorrow. Second, the absence of any tall clouds across the northern Gulf in this picture is a hint that the air is dry and stable. I usually use a different satellite image, called water vapor, to diagnose the dry and moist areas in the areas of suspect storms. Dry and stable air will inhibit this system’s ability to develop into a tropical storm.
The cold front that will move through our area Saturday will quickly absorb this low pressure and move it quickly east and northeast toward Florida. NHC gives this system only a 20 percent chance of becoming a depression or tropical storm today or tomorrow.
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