Dennis Back to Category 4

The recon aircraft sent back a central pressure of 941 mb just before 10 pm tonight. On the Saffir Simpson scale, that pressure would make Dennis a category 4 storm. The winds are not really up to cat 4 strength yet but they will do so shortly I think.

The difference between a cat 3 storm and a cat 4 storm hitting a coast line is quite dramatic. If it stays this strong or god forbid gets stronger, then the Alabama Gulf coast will be hit very hard. Likely worse than Ivan which weakened a bit as it hit land.
Something to remember that the force of the wind is not linear. When the wind speed doubles the force goes up by 4 not 2. That is why the increase in wind speed with a category 4 storm is so much more dangerous.
The storm surge will also be higher. Perhaps over 9 feet. The storm surge is a wall of water that will accompany the hurricane at and to the right of the eye. The low pressure in the storm and the winds actually will make the ocean level about 9 feet higher near the center of the storm.

The storm surge will hit the gulf coast very quickly. Not like a wave but the water will suddenly rise several feet in a matter of minutes. In hurricane past, the storm surge was the main killer in hurricanes, not the winds. Because of warnings and evacuations of susceptible areas, that is no longer true in most first world countries.

We will be doing extensive updates every 30 minutes starting at 6 am Sunday. Even if we do not get damage, We realize that many people have homes, friends and relatives on the coast.

Later,
Dan