How did hurricanes get defined as 74+ MPH windstorms?

[HurricaneBelle]

A Google search didn't really help in this department. I'm trying to get at how hurricanes were defined as storms with 74+ MPH winds, as opposed to, say, 50, 60, 70, 80 or some other number. When were hurricanes first defined as such with relation to the 74 MPH cutoff, and who came up with the definition?

I've seen references to the Saffir-Simpson scale, but that wasn't developed until 1971, and we had hurricanes well before then. I've also seen reference to the Beaufort Scale, where level 12 and above is a hurricane, but if that was used, who defined level 12 and above as a hurricane?

Anyone know?

[Hurricanehink]

That's a very good question. I always assumed that's the wind speed at which most storms develop an eye.

[HURAKAN]

Not sure of the right answer but the Beaufort Scale to measure winds goes up to 12 or 65+ knotsand 12 is defined as hurricane force

[Cyclenall]

You know I was just thinking this a couple days ago, I never knew the answer to this. The same goes for who and why was TD strength pinned at 25 knots (is this correct?) and then just 5-10 knots more and it becomes a TS (where did the term originate?).

[somethingfunny]

This is completely anecdotal, non-scientific and just personal experience, but right around 74mph it's no longer easy for a person to stand upright.

74mph seems like an odd number but it's just the closest conversion to 65 knots which is a nice even number.

[psyclone]

65 knots is the threshold so it just converts weird. same thing for gales (ts force) 35 knots = 39mph...again, another strange number.

[Florida1118]

According to Bryan Norcross's book, 'The Hurricane Almenac', Hurricane is made at 74mph or 65kts based on the Beaufort Scale. So it would appear thats why

[Chacor]

Just for the record, hurricane force is 64 kt, although for all intents and purposes, because the NHC (and other global agencies) round off to five, it's 65 kt.

[BigA]

I think it's a fascinating coincidence that 65kt or 74 mph seems to be about the wind speed in which tropical cyclones develop an eyewall and eye, the two most distinctive features of a hurricane, when the origin of the wind speed criterion was completely unrelated.