Megastorm Patricia inflicts little damage on Mexican coast "Nature was good to us"

...."We were fortunate as to where it made landfall. It was not a densely populated area," said Dennis Feltgen, a meteorologist and spokesman for the U.S. National Hurricane Center. "You and I would be having a very different conversation if this went over the top of Puerto Vallarta."

He said the lack of fatalities was probably the result of the storm's narrow footprint. Category 5 winds extended 15 miles out on either side of the eye, and hurricane-force winds extended for 35 miles from the center of the storm.

On Saturday, Patricia's maximum sustained winds had dropped to 30 mph (45 kph), according to the hurricane center. The storm's remnants were expected to feed into existing rain hitting southern Texas.....

....The mountains in the area quickly weakened the storm, and the coastal landscape did not offer the large area of shallow water necessary for a storm surge that could have become a devastating wall of water.

The storm was also moving fast enough at landfall — about 20 mph (35 kph) — that its heavy rains "did not stay in place long enough to generate the kinds of devastating floods we've seen in the past from Mexican hurricanes," said Jeff Masters, director of meteorology at Weather Underground.

Mexico's transport secretary, Gerardo Ruiz Esparza, put it another way: "Nature was good to us."

Force is not the same as power. Area does not equal volume. Temperature does not equal heat content. To say it was the strongest storm on record, and be accurate for damage assessment, the force had to be factored by volume. Basically you cannot assess strength or power without relating it to volume or size of eye. The more apes get involved, the more mistakes are made.

In my several decades of casual storm-watching, I had always understood that a tight, well-defined eye was indicative of an intense hurricane. The eye just fell apart about a hundred miles offshore, more rapidly than I recall ever seeing, even after landfall. It intensified very quickly and deteriorated very quickly. An odd storm, imho. The mountains there have been mentioned as being the cause, but it hadn’t even made landfall. Certain Caribbean islands are mountainous, and hurricanes are weakened typically when crossing them, but I don’t recall one with this sort of barometric pressure and windspeed being basically broken up and degraded into a tropical depression.

Thanks for pointing that out. My size of eye comment should have been about the size of hurricane force winds fields. Got lazy fingers. Cat 5 only extended out 15 miles. Small storm. Fastest wind speed, but not strongest storm. Pee Wee Herman can hit you pretty fast, but a slow punch from Rhonda Rousey will deck ya.

Well recognized that force isn’t the same as power, but the force of the wind is proportional to the square of the wind velocity, so with respect to structures and the effects of their environment, I’d fully expect wind velocities of sustained winds and 3 sec gusts to exert a specific force on those structures.

If sustained winds are over 160 mph, especially when measured with gusts upwards of 245 mph, I’d expect to see far greater devastation than could be protected from plywood and nails/screws as fasteners or uplift from most structural designs.

Caribbean Basin WFCM for 150mph, Wind Exp C, Seismic Design Cat D, allows for about 420plf uplift, 370 plf lateral loading and 230 plf in shear. In order to implement those loads, one needs 2 courses of 8 common nails on all sheathing to sill and floor plates at 4”oc and field nailing no greater than 6” oc. (Many cases 3”oc at edges). Get any more fasteners and you have problems with stitching failures. Any fewer fasteners, and the sheathing won’t remain attached to the structure at those loads. These are for bldgs no greater than 16’ wide and 24’ long.

While some codes might provide safety factors from 1.25 to 4, doubling the wind velocity will quadruple the wind forces.

I would fully expect a large percentage of structures in the path of such a storm, especially the first 1500-3000 ft from the shoreline, to have been removed entirely from their foundations, and possibly including their foundations.

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