New Hurricane Insights

© 2005 Door & Access Systems Publish Date: Fall 2005 Author: Al Mitchell Page 52

New Hurricane Insights By Al Mitchell, Director of Research, Wayne-Dalton Corporation

On Sunday, July 10, 2005, Hurricane Dennis ripped through the Pensacola area. The region had cleaned up only about 70 percent of the damage from Ivan, the storm that hit in September 2004.

The Differences of Dennis Dennis stormed ashore just after noon, whereas Ivan struck around midnight. This daytime storm gave me a better opportunity to visually witness the storm’s fury. After what I observed in Dennis, I was glad I didn’t see most of Ivan.

The wind speeds near the center of the storm (130 mph) were about the same for both storms - a Category 3 hurricane just before landfall. However, Dennis was a smaller storm in coverage area and moved almost three times as fast as Ivan. The eye of Dennis came ashore about 30 miles east of Pensacola, whereas the eye of Ivan came ashore about 20 miles west of the city.

The conditions experienced were remarkably different. Since Dennis was smaller and had a faster forward motion, we were under hurricane force winds for less than an hour. In contrast, because of Ivan’s larger size and slower forward movement, that level of winds existed in the area for 10 to 12 hours. Thus, Dennis caused significant damage, but along a relatively narrow path.

New Observations A radio report said that residents just east of the eye would experience the wind speed of the eye wall (120 mph) plus the forward speed of the storm (20 mph). This would result in wind speeds of 140 mph (equivalent to Category 4 winds) against their structures. Conversely, 20 miles away, the people at the west eye wall would see 100 mph (equivalent to Category 2) winds.

During the height of the storm, I observed a very unusual “white-out” condition. I have seen “white-out” conditions in snowstorms, but never in a hurricane. I saw rain driven sideways by the wind, creating large vapor trails around the corners and over the tops of buildings. I couldn’t see our pool, only 25 feet from the house.

My Garage Door Commentary Concerning garage doors, here are some personal observations I gained from Hurricane Dennis.

· Doors that survived previous storms may not survive the next one. None of our inland test doors failed during Ivan, but six of our test doors failed during Dennis.

Reviewing our test data, all of these doors exhibited minor signs of stress and fatigue after Ivan, but all remained securely in place and were operable. However, these minor signs of stress and fatigue, such as slight creasing in the raised panel areas and slight twisting of the end stiles or roller carrier hinges, are indications that the door may not resist an additional wind event. In this case, they did not.

The doors that did not show signs of fatigue and stress after Ivan survived Dennis and remained operable. However, we have decided to replace a few of these doors that now show signs of stress and fatigue.

· Manufacturers should consider offering comprehensive damage assessment guidance for dealers and installers. Our industry’s customers need good information on whether their doors, and in some cases their structures, can survive the next storm.

· Similarly, I suggest that dealers do courtesy inspections of their installations and make recommendations to homeowners if it appears their doors will not weather another storm. The Technical Data Sheets DASMA is working on in this regard have taken on added significance.

· Test the effects of water infiltration. Manufacturers may need to examine the effects of wind-driven rain on door products sold in hurricane-prone areas. Perhaps we need product ratings on this matter.

To conclude, we here in the Pensacola area have decided not to be selfish. Therefore, over the next several years, we would like to share the storms with people outside of Florida. We have had enough here for a while.