29 August 2005– Hurricane Katrina makes landfall as a Category 3 hurricane near Buras-Triumph, Louisiana. Death totals in coastal areas of Louisiana, Mississippi, and Alabama are lower than expected, for two reasons. One, Katrina came ashore as a Category (Cat) 3 storm with sustained winds of 125 miles and hour, not a Cat 5 with 175 mph winds.* Two, the local Weather Forecast Office of the National Weather Service issued this bulletin the day before. When a weather bulletin contains words such as “devastating,” “most powerful,” and “will make human suffering incredible by modern standards,” it’s advisable for those in the path of said storm to get the blazes away from the damned thing.
I remember Katrina because I was, indeed, getting the blazes away from said storm– in the form of going to Lakeland for an engineer’s seminar. One of the other groups was from Pensacola, and they were getting reports that even that far away, the storm was doing some decent damage. Even before the news began covering it, everyone at the conference (all of us civil and structural engineers) knew that New Orleans would flood. We also knew that N’Awlins was going to suffer great loss of life, due to the lack of evacuations. (The highest estimate was around 5% of the population– 15,000 or more.)
We all shook our heads– didn’t these people understand what was coming for them? I had Opal pass right over my head in ’95– along with close hits from Georges in ’98, Allison in ’01, and Frances and Ivan in ’04. Heck, Cindy in ’04 went into almost the same area…
(H/T Linoge for reminding me… like the news coverage hasn’t…)
* Doing the math, a 125 MPH wind produces 40 (125^2 * .00256) pounds a square foot of pressure, but a 175 MPH wind creates 78.4 (175^2 * .00256) PSF. (What’s sad is that I had to look this up– I used to have to know these calculations by heart.) At some point below 175 MPH, the wind would have turned the low-pitched roofs on the coat into wings, and ripped them from the buildings. Notice that in footage and photos from hurricane zones, the roofs that survive have a moderate pitch– usually around 45 degrees. This allows the wind to blow over them, but not so quickly as to produce lift… like a spoiler on an aircraft’s wing. Sorry, I worked as a structural engineer, this is fascinating to me….