Posted on 05/08/2007 6:04:05 PM PDT by xcamel
FUJITA SCALE | DERIVED EF SCALE | OPERATIONAL EF SCALE |
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F Number | Fastest 1/4-mile (mph) | 3 Second Gust (mph) | EF Number | 3 Second Gust (mph) | EF Number | 3 Second Gust (mph) | |
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0 | 40-72 | 45-78 | 0 | 65-85 | 0 | 65-85 | |
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1 | 73-112 | 79-117 | 1 | 86-109 | 1 | 86-110 | |
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2 | 113-157 | 118-161 | 2 | 110-137 | 2 | 111-135 | |
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3 | 158-207 | 162-209 | 3 | 138-167 | 3 | 136-165 | |
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4 | 208-260 | 210-261 | 4 | 168-199 | 4 | 166-200 | |
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5 | 261-318 | 262-317 | 5 | 200-234 | 5 | Over 200 | |
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*** IMPORTANT NOTE ABOUT ENHANCED F-SCALE WINDS: The Enhanced F-scale still is a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to the 28 indicators listed below. These estimates vary with height and exposure. Important: The 3 second gust is not the same wind as in standard surface observations. Standard measurements are taken by weather stations in open exposures, using a directly measured, "one minute mile" speed.
NUMBER (Details Linked) | DAMAGE INDICATOR | ABBREVIATION |
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1 | Small barns, farm outbuildings | SBO |
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2 | One- or two-family residences | FR12 |
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3 | Single-wide mobile home (MHSW) | MHSW |
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4 | Double-wide mobile home | MHDW |
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5 | Apt, condo, townhouse (3 stories or less) | ACT |
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6 | Motel | M |
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7 | Masonry apt. or motel | MAM |
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8 | Small retail bldg. (fast food) | SRB |
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9 | Small professional (doctor office, branch bank) | SPB |
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10 | Strip mall | SM |
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11 | Large shopping mall | LSM |
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12 | Large, isolated ("big box") retail bldg. | LIRB |
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13 | Automobile showroom | ASR |
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14 | Automotive service building | ASB |
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15 | School - 1-story elementary (interior or exterior halls) | ES |
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16 | School - jr. or sr. high school | JHSH |
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17 | Low-rise (1-4 story) bldg. | LRB |
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18 | Mid-rise (5-20 story) bldg. | MRB |
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19 | High-rise (over 20 stories) | HRB |
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20 | Institutional bldg. (hospital, govt. or university) | IB |
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21 | Metal building system | MBS |
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22 | Service station canopy | SSC |
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23 | Warehouse (tilt-up walls or heavy timber) | WHB |
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24 | Transmission line tower | TLT |
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25 | Free-standing tower | FST |
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26 | Free standing pole (light, flag, luminary) | FSP |
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27 | Tree - hardwood | TH |
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28 | Tree - softwood | TS |
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A 95 page PDF file explaining the development and makeup of the Enhanced F-scale now is available, both here at SPC and from the Texas Tech server.
I doubt Dr. Fujita would be very happy with this "new scale"
Who knows, he said his old scale was not perfect and it needed improvements.
Clear as mud to me:’)
Why would he be unhappy with it? He agreed his scale was flawed.
His comment about “flawed” had to do with under reporting strength/damage ratios, and it was a huge political (politically correct) fight to get number approaching 300 mph even discussed openly. He knew higher was not only possible, but likely. The technology to accurately measure 10 second bursts (not 3 second like was agreed to) didn’t exist at the time. It does now, and he was dead on right... they (NOAA) are underreporting on purpose.
Well if it’s any consolation peak shear force winds were as high as 240 knots according to radar for the Greensburg Tornado.
OK then a reply would be to that is, “Which is worse if you are driving a SUV getting hit by a yugo doing 100mph or getting hit by a semi doing 75 mph?”
Let me correct this:
OK then a reply would be to that is, “Which is worse if you are driving a SUV getting hit by a yugo and it is going 100mph or getting hit by a semi going 75 mph?”
“Yes”
:-)
It’s not the wind alone that does that, it’s the pressure differences inside of the cyclone that can, for lack of a better word, soften the telephone pole.
I guess my point I am trying to make is that the size+speed is more important than just speed alone.
it all comes down to mass in motion — basic physics.
Having worked in the structural engineering field for a few years, I can see the corrolation between the different levels of intensity of a tornadic event and the structures it “could” effect, depending on that force acting on the structure...
But...
To me its all destructive, and dependent upon a few other factors in how a structure “might” fail...And it all happens so fast it is just impossible to design effectively enough to counter all the variables you could possibly compile into the design...
You can do your best, and there are guidelines and industry standards...But you can only do so much...
I would say that its important to go as far as you can with what you have available, but always look for ways to encourage people to prepare for the worst, and create plans and shelter you can get to very quickly that anyone can take advantage of to protect lives...
Anyone who has looked at the devastation in that town, if you notice how many (below ground) shelters beside those destroyed homes in those pictures, showed the doors open, know that those shelters saved lives, and that is the best thing yet out of this whole ordeal...
5.56mm
Those look like APB’s (Anthony Power Beams) coming across the top of those internal wall frames out from theat center room (shelter)...
I saw that pic yesterday, but it didn’t register till you mentioned it...
If they had more incentive to make “internal” armored rooms that would either be “no cost” or give a substantial insurance break to homes built in areas like this would really save a lot of lives if you ask me...
I’m having one built into our new home this time...No breaks for us, except peace of mind, and the skill to make use of it when the need arises...
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