Post-storm Wind Analysis of Hurricane Wilma by HRD

[Tampa Bay Hurricane]

I have one question. The 1935 hurricane and Charley 2004 were similar in terms of size, wind radii, and rapid intensification, so why did Charley produce a much lower surge than the 1935 TC? The "damming" effect of the railroad embankment (mentioned by Recurve in an older post) likely contributed to the height of the 1935 surge, but that TC arrived from the deeper offshore waters of the Atlantic. That should reduce surges on the east coast of FL, unlike the shallower Gulf Coast shelf, which induces higher surges.

Does anyone think the higher Gulf Coast surges may apply only to tropical cyclones with large wind fields, while greater storm surges are produced by smaller, intense hurricanes (i.e. Andrew and 1935) on the Atlantic side? In other words, Katrina-sized hurricanes would produce larger surges on the Gulf side than a Katrina-sized TC on the Atlantic side, but a rapidly intensifying, compact TC would induce a higher surge on the east coast of FL than a similar storm on the Gulf side. Note that the largest storm surges on the east coast of Florida have resulted from small, extremely intense monsters (16.9 feet at Cutler Ridge in Andrew and 18 feet at Long Key in 1935), while the highest surges on the Gulf Coast have been from larger storms such as Katrina, Ivan, et al.

Does that make sense?

Noting that, could the Labor day storm have had a larger windfield of cat 1 winds that made
the surge?
If not then the small area of lower pressure allowed massive rise of deep ocean
water due to steep pressure falls, which is not as easily obtained if the hurricane
field is spread out, meaning larger storms make less atlantic surge.

I call this a small mountain of water effect with steep pressure
falls over a small area over deep water that causes the water
to "mountain" up to a higher surge over deeper atlantic waters.

[Recurve]

I am by no means any kind of expert on surge or any aspect of storms, but I've read everything I can about 1935. I experienced Andrew's surge in Coconut Grove and Wilma's surge in Key Largo, as well as seeing the effects of Rita and Georges in the Keys, Ivan in the panhandle and a few other storms.

the accounts of the Labor Day Hurricane surge seem very complicated and somewhat mystifying. The Long Key Fishing Camp manager (and weather bureau reporting observer, J.E. Duane) said the camp was first inundated by surge from the bayside, and after the eye passed, a wall of water rushed in from the oceanside of Long Key. I guess this is consistent with an offshore flow on the left side of the storm as it approached, which blew water from Florida Bay over the island, and also would have blown water out from the oceanside coast. The terrific surge from the oceanside after passage of the eye seems like it could have been more of a "rebound" surge -- water rushing back in from the ocean once the strong northerly winds had passed, rather than a surge driven before the wind.

The AOML page has this information:

"The wind lulled briefly between 8 and 9 p.m. at Alligator Reef [oceanside off Islamorada], with direction shifting sharply from northeast to southeast; this point was just at the northern edge of the calm center. A calm of 40 minutes' duration was experienced on Lower Matecumbe Key; and, as reported above, there was 55 minutes' respite at Long Key fishing camp, but the wind changes at the latter point indicate that the geometric center passed slightly to northward. It is somewhat difficult to reconcile these reports with the general storm path. The rate of progression over this section of the track was about 10 miles per hour, however, and from this it is estimated that the calm center was perhaps eight miles in diameter. "

I have never been able to figure out how an 8-mile eye produced calm at Lower Matecumbe and at the South end of Long Key. I'll have to recheck the distance using a chart, but it doesn't seem both could have been in the eye. Had the eyewall expanded or an EWC taken place?

As to Wilma, the very large windfield and the funnel configuration of upper Florida bay seems to have produced an unexpectedly large surge, on the order of 8-10 feet (rough guess) along Key Largo.

The questions earlier about small vs. large and oceanside vs. west coast of florida are very interesting. Andrew's surge in south Dade was of course from Biscayne Bay rather than true open ocean. Was Charlie's surge damped at all by the ten thousand islands? I wonder if there's an accurate surge measurement for Andrew on Elliott Key. I would not want to have been in Stiltsville that night.

[MiamiensisWx]

I think Recurve's post answers my question. If Andrew and the 1935 hurricane struck another portion of eastern FL that did NOT involve a shallow bay, their surges would've likely been much lower and similar to Charley's minimal surge (due to small wind radii) on the west FL coast. In all likelihood, the relationship between size and surge (larger wind field equals larger surge) applies equally to the Atlantic coast of Florida as it does on the Gulf Coast. An outer concentric eyewall can also contribute to larger surges, as seen on the shallow Gulf shelf waters.

Regarding the 1935 hurricane's eye diameter, maps reveal that the distance between Layton, FL (center of Long Key) and the northern end of Lower Matecumbe Key is ~7.54 miles. The center of the eye crossed Craig Key (between Long Key and southern end of Lower Matecumbe), and the 892 mb corrected reading was recorded on this spoil island. Overall, an 8-mile center could've certainly covered most of Long Key and Lower Matecumbe Key, especially given its exact landfall coordinates. It is quite likely that the center fits the 8-10 mile range at landfall on the Florida Keys. It seems probable that the TC was reaching its maximum intensity over the islands, as it began to weaken after exiting the Keys. The cyclone was similar to Charley in terms of size and rapid pre-shore intensification, so sustained winds were probably +150 kt at landfall. The RMW was also quite diminutive. Recent reanalyses suggest that the storm may have attained maximum sustained winds of 185 mph (160 kt) as it crossed the Florida Keys.

On a final note, I would not be surprised if the TC featured a classic "moat" signature (small inner core and initial stages of an outer concentric eyewall) as it struck the Keys. An ERC may have commenced after it left the islands.

Classic "moat" signature with powerful (150 mph) Charley as it struck Charlotte Harbor and Cayo Costa:

http://www.nhc.noaa.gov/prelims/2004charley4.jpg

[Derek Ortt]

which side did the 18 foot surge come from in the 1935 hurricane. I would suspect it came from Florida Bay (Andrew's surge was 17 feet in Biscayne Bay, but calculations show only about 10 feet had it hit Key Biscayne... the surge at Key Biscayne was in the 4 feet range from Andrew)

The deep water, shallow water vs size... I have never heard of that before and does not really fit with the equations

To further demonstrate this point, the surge of the 1926 Miami hurricane was not responsible for the large death toll. Much of that was due to people attempting to evacuate Miami Beach during the eye of the storm

[Ed Mahmoud]

OT, but I've just started reading an account of the muck farmers of Lake Okechobee and the 1928 hurricane.


Well into the book, and no hurricane yet.

[MiamiensisWx]

which side did the 18 foot surge come from in the 1935 hurricane. I would suspect it came from Florida Bay (Andrew's surge was 17 feet in Biscayne Bay, but calculations show only about 10 feet had it hit Key Biscayne... the surge at Key Biscayne was in the 4 feet range from Andrew)

The deep water, shallow water vs size... I have never heard of that before and does not really fit with the equations

To further demonstrate this point, the surge of the 1926 Miami hurricane was not responsible for the large death toll. Much of that was due to people attempting to evacuate Miami Beach during the eye of the storm

The majority of the surge likely originated from Florida Bay, though I would refer to Recurve's post for information on the surge. It does make sense, since it is more consistent with our present knowledge.

[Category 5]

which side did the 18 foot surge come from in the 1935 hurricane. I would suspect it came from Florida Bay (Andrew's surge was 17 feet in Biscayne Bay, but calculations show only about 10 feet had it hit Key Biscayne... the surge at Key Biscayne was in the 4 feet range from Andrew)

It would depend on where you were.

[Category 5]

The deep water, shallow water vs size... I have never heard of that before and does not really fit with the equations

That probably comes from the East Coast of Florida not being very surge prone (the water is deeper there) as compared the the NGOM (where the water is shallow)

Some of it has some sense to it, think of a Tsunami, which rises when it reaches shallower water.

[wxman57]

I ran a SLOSH MOM (Maximum Of Maximum) surge for a Cat 5 striking the keys. Notice that for a hurricane approaching from an easterly direction, the max possible surge is about 10-11 feet. This is due to the deeper water east of the Keys. However, to the west and northwest side of the Keys, the max possible surge is much higher:

[Category 5]

An area like Everglades city would be in big trouble.

[Recurve]

Thanks Wxman for that model graphic.

For those interested, quote from article posted at AOML on the Labor Day surge:
http://www.aoml.noaa.gov/hrd/Storm_pages/labor_day/labor_article.html

Over a distance of about 30 miles, from the settlement of Tavenier (about 25°01' N., 80°32' W.) to Vaca Keys, the destruction of buildings, roads, viaducts, and bridges was practically complete. Much of this damage was caused by the overwhelming depth and strong washing flow of the storm tide that piled up on the Keys under the driving power of the storm. The tracks of the Florida East Coast Railroad were completely destroyed where they crossed between islands and were shifted bodily off their roadbed over long stretches on the Keys. An 11-car train, sent to Lower Matecumbe Key in an effort to rescue inhabitants, was washed from the tracks and only the locomotive withstood the force of wind and tide.

The disposition of debris and nature of the erosion of the railroad embankments clearly indicate that the destructive tide flowed with an intense effect over the Keys from southwest to northwest, in the direction of advance of the storm center.

As is usually the case, the destructive effects extended considerably farther to the right than to the left of the path of the center. Had there been no accompanying tide, the damage undoubtedly would have been severe but by no means so complete as that resulting from tidal inundation. The track and crossties of the railroad were in one stretch washed off a concrete viaduct 30 feet above ordinary water level, but wave action superimposed on the tide no doubt play a part in this destruction. Reports agreed in the description of the great rapidity with which the rise of the sea came in from the southern side of the Keys as a "wall of water" or a "high wave."

from J.E. Duane's report

6 p.m.---Barometer 28.04; still falling. Heavy rains. Wind still N., hurricane force and increasing. Water rising on north side of island.
6:45 p.m.---Barometer 27.90. Wind backing to NW., increasing; plenty of flying timbers and heavy timber, too---seemed it made no difference as to weight and size. A beam 6 by 8 inches, about 18 feet long, was blown from north side of camp, about 300 yards, through observer's house, wrecking it and nearly striking 3 persons. Water 3 feet deep from top of railroad grade, or about 16 feet.
7 p.m.---We were now located in main lodge building of camp; flying timbers had begun to wreck this lodge, and it was shaking on every blast. Water had now reached level of railway on north side of camp. (Ed. Note---This was water rapidly piled up from the shallow expanse of Florida Bay, under the drive of northerly hurricane winds.)
9 p.m.---No signs of storm letting up. Barometer still falling very fast.
9:20 p.m.---Barometer 27.22 inches; wind abated. We now heard other noises than the wind and knew center of storm was over us. We now head for the last and only cottage that I think can or will stand the blow due to arrive shortly. All hands, 20 in number, gather in this cottage. During this lull the sky is clear to northward, stars shining brightly and a very light breeze continued; no flat calm. About the middle of the lull, which lasted a timed 55 minutes, the sea began to lift up, it seemed, and rise very fast; this from ocean side of camp. I put my flashlight out on sea and could see walls of water which seemed many feet high. I had to race fast to regain entrance of cottage, but water caught me waist deep, although writer was only about 60 feet from doorway of cottage. Water lifted cottage from its foundations, and it floated.
10:10 p.m.---Barometer now 27.02 inches; wind beginning to blow from SSW.
10:15 p.m.--The first blast from SSW., full force. House now breaking up---wind seemed stronger than any time during the storm. I glanced at the barometer which read 26.98 inches, dropped it in water and was blown outside into sea; got hung up in broken fronds of coconut tree and hung on for dear life. I was then struck by some object and knocked unconscious.

Several things strike me: The big surge from the oceanside coming in the lull in the eye (on Long Key, to the left edge of the eye). The first flooding on Long Key was from the bayside and reached at least 16 feet. To the right of the eye, the train that was derailed was washed toward the bayside (on Upper Matecumbe Key). And the railroad ties being washed off the viaduct "30 feet" above normal water level -- but that being on top of the viaduct, it seems possible there was a seawall effect, the surge smashing into the viaduct and shooting upward much higher than even the waves and surge would have been where it could flow over land.

[Derek Ortt]

one thing about the oceanside... the deep water which protects the area from surge, makes it vulnerable to very high waves

[MGC]

Sounds like a typical surge of a Cat-5. I talked with several people in Hancock County that were foolish enough to stay for Katrina. All of them said the surge came up quickly in three big waves in short order. Within minutes the water rose over 10 feet well inland. A girlfriend of mine rode out Katrina in her home that didn't flood during Camille. The house is located on a 20 foot bluff on Bayou Delisle, a tributary of the Wolf River. She also said the water rose quickly and they all had to scramble into the attic. I was on the phone with her while she was in the attic asking where the hurricane was. The phone went dead shortly after I told her. There had to have been some impressive wave action during the 35 hurricane. The Keys are not that high anyway but I suspect the majority of the surge came from Florida Bay.....MGC