Just how ferocious was the Labor Day hurricane? (analysis)

[JetMaxx]

Most of us have heard the stories....about a small but ferocious hurricane that struck the Middle Keys and SW Coast of Florida on Labor Day of 1935...taking more than 500 lives. Many of you also know it was a category 5 hurricane; and along with Andrew and Camille, are the only hurricanes of record to strike the U.S. at cat-5 intensity.

Here's a few facts you may not have heard, and an analysis of just how strong the Labor Day hurricane really was....and why so few people in the core survived:

To begin with, the Labor Day hurricane was very intense. As it slowly crossed from the Bahamas toward the southern tip of Florida, the hurricane crossed over the very warm Gulf Stream (30-31°C)....and was peaking in intensity as it struck the Middle Keys late on September 2nd.

A confirmed barometric pressure of 26.40" (894 mb) was measured on Lower Matecumbe Key, and after extensive analysis was conducted on the barometer (pressure chamber testing)...both at WBO Miami and NWS in Washington DC, it was determined the pressure was even lower....26.35" (892.3 mb). Another barometer at nearby Long Key measured 26.98" (913.7 mb) before the observer J.E. Duane was knocked unconscious as his home was obliterated (he miraculously survived).

Supporting the 892-894 mb central pressure was a confirmed storm surge around 20' feet. In 1960, hurricane Donna (930 mb) produced a 13' foot storm surge in the same area....which gives an estimate of 20' in a 895 mb hurricane. High water marks (including wind waves) were measured as high as 30' above sea level).

Now that we've determined this was a category 5 hurricane with estimated 892.3 mb pressure and 20' storm surge....how do we analyze the wind speed that occurred? First, we know from firsthand accounts that the destruction was beyond description....beyond anything any of the surveyors and rescuers had ever seen. It has since been compared to the aftermath of an airliner disaster....or a violent tornado. True, most of those that perished that tragic night drowned in the tremendous storm surge that innundated the Middle Keys....but there were numerous reports of dismembered bodies, and survivors that lost arms and legs from flying debris and being blown into objects.

There were several confirmed reports in the core area of
"sandblasted" dead bodies being found....men that lashed themselves and their families to trees to try and storm surge that were literally sandblasted to death; skeletons were found hanging in trees wearing leather belts and shoes (ALL skin and clothing gone!). It is a gruesome event that has never been observed in another hurricane aftermath in the western hemisphere (not even Camille and Gilbert).

What kind of wind speeds are we talking about? The Labor Day hurricane was even smaller in size than 1992's hurricane Andrew....it was tiny. Hurricane force winds only extended across the Keys from Tavernier to Key Vaca...a 40 mile swath (or about 20 miles in all directions). A normal sized hurricane with a central pressure
of 892 mb would be expected to have sustained winds of 185-190 mph, with gusts over 210...but as we saw with hurricane Andrew (and to a lesser extent Camille)....small hurricanes sometimes have higher winds because of the extremely tight pressure gradient near the eye.

Andrew had estimated sustained winds near 175 mph at it's peak (153 kts), based on 10,000 flight level winds east of Eleuthera of 197 mph (170 kts). This occurred with a central pressure of 922 mb/ 27.23". A normal rule of thumb is a 5 kt increase in sustained wind speed for every 6 mb drop in pressure that occurs in a deepening hurricane....

Here's an example:

922 mb = 153 kt (176 mph)
916 mb = 158 kt (182 mph)
910 mb = 163 kt (187 mph)
904 mb = 168 kt (193 mph)
898 mb = 173 kt (199 mph)
892 mb = 178 kt (205 mph)
(in other words, 892-894 mb = 200-205 mph sustained winds)

We also have micro-monster hurricane Iris from a couple years ago to compare. Estimated sustained winds were 125-130 kt (145-150 mph) even though the central pressure was in the 950 mb range (normally associated with a 110 kt hurricane). Extrapolate from 950 mb down to 892 mb and you find estimated sustained surface winds in the Labor Day hurricane were likely 173-178 kts (200-205 mph). We have two reliable estimates from recent small but violent hurricanes that suggest sustained wind speeds in the Middle Florida Keys were at or in excess of 200 mph (175 kts)

So we theorize sustained winds were around 200 mph over those two Keys...or similar to a strong F3 tornado; but there were much stronger wind gusts. At landfall near Homestead AFB, Florida....Andrew is estimated to have had sustained winds of 165-170 mph (145 kts), with gusts in the 200-205 mph range (borderline F3-F4 tornado range).

If the sustained winds in the Labor Day hurricane were 200-205 mph, it's also likely peak gusts in the NE eyewall reached 225-230 mph...or possibly even stronger. This is the equivelent of a F4 tornado...and explains the aftermath of sandblasted and dismembered bodies.

Is my analysis foolproof? No it isn't....but the NHC in 1988 (Dr Bob Case) estimated sustained winds in the Labor Day hurricane were 175-180 kts (200-205 mph) in a letter he sent me; and structural engineers on the scene after the 1935 hurricane estimated sustained winds between 150-200 mph, with gusts reaching 200-250 mph....using analysis techniques and equipment primitive by todays standards.

By any yardstick, the Labor Day Hurricane of September 1935 was the most intense hurricane to ever strike the United States....and a repeat today would IMO be catastrophic; especially along the lower Southwest Coast of Florida....which was almost barren in 1935, but experienced wind gusts well in excess of 100 mph (estimated at 130-150 mph at both Marco Island and Boca Grande). Those barrier islands from Marco Island north to Lido and Longboat Key are now very heavily populated, with billions upon billions of dollars in property value in harms way.

PW

[drezee]

Interesting points

[Toni - 574]

Thanks JettMaxx for that eye opening info. My family talks about the 1935 hurricane as a comparision of majors that has hit Florida, but did not have all of those grusome details. Even though it is hard to think about something so sad, at the same time it makes you so aware of what could happen again some day! Again, thanks for the info.

[Colin]

Wow! :o Thanks for all that information there, Perry!

[Southernmost Weather]

Yes, thanks for posting that topic. And if you would like to read further about the Labor Day Hurricane, follow this link. It will provide you with photos of the devastation and some first-person accounts.

http://www.keyshistory.org/shelf1935hurr.html

[Stormsfury]

Once again, JetMaxx delivers another very insightful and outstanding post.

Thanks for the link, Southernmost Weather

[JetMaxx]

Thanks for the kind words folks

Someone emailed me this morning wondering if the Labor Day hurricane affected the Tampa Bay area? YES....in downtown Tampa, sustained winds reached 80-85 mph with peak gusts estimated near 100 mph.

IMO it's likely the barrier islands of Pasco, Pinellas, and Manatee counties experienced sustained winds of over 100+ mph...and possibly major hurricane conditions (over 110 mph sustained...gusting over 125 mph).

The hurricane's estimated intensity of 90 kts at it's second landfall NW of Cedar Key is IMO incorrect. At the time (1935) there were no weather stations anywhere near the area where the hurricane made landfall...and the coastal area between Perry to Cedar Key was very sparsely populated (still is today). Given this was a small hurricane in diameter, I honestly believe it was much stronger than the category-2 ranking assigned to it by NHC.

Even though it missed Cedar Key by 30-40 miles, storm tides there were reported by locals as the highest observed since the major hurricane of September 1896....lending credence to my theory that the Labor Day hurricane was still a major hurricane at the second landfall point near Cross City, Florida (there were also reports of winds over hurricane force and considerable property damage at Lake City, Florida and Valdosta, Georgia...both well inland).

[Stormsfury]

IMO, it's also hard to imagine a CAT 5 storm unwinding as fast as it did also, however, it did move slowly ... only then as it moved northward that it picked up speed ...

One thing also to note, again was the small size of the 1935 Labor Day hurricane and small circulations can rapidly change ... however, as JetMaxx posted, there were reports of hurricane force winds in inland GA ... it did begin to pick up forward speed as well and likely in that time beforehand, the hurricane probably went through an eyewall replacement cycle and expanded in its core ... it's also interesting to note, that the best track never weakened it below 65 mph (55kts) across it's entire journey over land (on its second landfall which took a full 36-48 hrs to cross) ... another red flag that the Labor Day storm was stronger during its second landfall across the Florida Panhandle. Best Track also brings #2 to hurricane status right after exiting the coast again.


http://weather.unisys.com/hurricane/atl ... /track.dat

[Stephanie]

Interesting history of the Labor Day hurricane Perry!

[vbhoutex]

That is simply freaky to read!!! I had seen the reports of the bodies stripped of skin, etc. but had somehow forgotten about it. Now comes the thought of it happening again-today-A MORE THAN FRIGHTENING SCENARIO ANYWHERE ON THE COASTS OF THE US!!! IT WOULD BE WAY PAST A CATASTROPHE IF ONE LIKE THAT HIT ANYWHERE ALONG THE US COAST!!! IT WOULD BE UNIMAGINABLE!! As always Perry and SF are providing us with great information and educational interest!! THANKS GUYS!!!