By Mark Dorsten —
The NHC report has multiple references to wave action and the most notable, on page 9 of 72 is erroneous. Additional information on wave height is included on page 50 of 72.
The Report references a YouTube video: https://www.youtube.com/watch?v=igsz7cqg-Zk&t=26612s
Page 9 is excerpted in italics
SOUTHWESTERN FLORIDA
Maximum inundation levels of 10 to 15 ft AGL occurred on Fort Myers Beach and Estero Island. A USGS water level sensor measured a wave-filtered water level of 12.70 ft above MHHW at Fort Myers Beach Pier (Fig. 8, Fig. 10), which was the highest water level measurement from this network. Nearby, a remote camera mounted by stormchaser Max Olson captured the evolution of the storm surge event on Fort Myers Beach. The camera was located less than 0.5 miles to the east on Estero Blvd relative to the USGS water level sensor. A timeline of images taken from this video footage is shown in Figure 11: (a) The onset of storm surge inundating the streets, (b) rapidly moving water carrying large floating debris, (c) a home in the view of the camera floating off its foundation with large waves crashing over it, (d) waves splashing over the camera, mounted approximately 12 ft above the road, and (e) receding waters revealing a barren landscape approximately 6.5 hours after the first image. Figure 10 shows the USGS hydrograph and the photo timeline overlaid to help relate the sensor measurements to on-the-ground impacts. These observations provide a glimpse of the life-threatening and destructive power of the storm surge and waves that occurred throughout the area.
The collapse referenced in the Report occurred at 4:18:30 in the video.
Aaron Harris P.E. disagrees with the NHC narrative with the following points:
- The threshold at the bottom of the front door was visible. This means the flood waters didn’t enter the house.
- At the height of the surge, the wind-driven waves would have crossed Denora Blvd which would not provide sufficient fetch. In other words, the waves would have been blocked by the buildings on the other side of Donora Blvd.
- At the time of the collapse of the house in the video, the trees are bending, the electric lines are shaking, and wind can be heard in the soundtrack.
- At 4:18:39, after a series of strong gusts, the roof breaks up and the top of the wall leans backward, away from the force of the wind. The building then twists from the force of the wind as it breaks apart.
- Only after the wind breaks the roof and walls from the floor does the surge have the necessary uplift force to carry away the remains of the structure.
- The wind destroyed the structure approximately 1-hour before the maximum surge height.
On page 50 the Report includes a graph of the maximum surge versus the maximum wave height above MHHW (Mean High Water Level). The timing of this event is after 1:30 PM but well before 2:00 PM. The maximum surge and wave height is approximately 1-hour later.
Figure 10 lists an Unfiltered water level of 15.3 feet and a filtered water level of 12.7 feet. Based on this we can infer a wave height of 2.6 feet.
This seems to match photographs and eyewitness accounts of the wave heights. The Max Olsen video doesn’t document wave heights above 2.5 feet. The following photograph was taken by a security camera video overlooking the swimming pool at a condominium complex south of the USGS measuring station. Notice the waves out from the beach but not in the pool area.
We believe this is due to the shallow water extending out from the beach. Waves break in shallow water. Since the water becomes shallow miles out from Fort Myers Beach, the waves broke multiple times before reaching shore.
The eyewitness accounts of imbedded tornados should not be discounted. These coupled with damage rotated out of the wind direction indicate the 15-tornados documented in the HNC report is probably far below what actually occurred.