STORM2K

I just finished watching a couple of movies on storm chasers and viewed some amazing tornados. My question is can you tell by looking at a tornado what F class it is because no one in the movie mentioned how powerful the tornados were. Is it determined by damage estimates?

You can't tell the T or F rating just by looking at it. You either need a ground survey afterwards, or doppler on wheels estimates. If you have DOW estimates there will be a site investigation done as well I would expect.

Sure you can if it flatens a brink building or a steal inforced one then its a f5.

P.K. wrote:You can't tell the T or F rating just by looking at it. You either need a ground survey afterwards, or doppler on wheels estimates. If you have DOW estimates there will be a site investigation done as well I would expect.

One of the tornados was surrounded by about twenty storm chasers with equipment. Could they have doppler in the vans?

They are rather expensive so its only really for research purposes within universities etc. They look like this. I don't know how many there are in the USA, we don't have any in the UK though.

Matt, you really need to get a closer look at damaged structures than watching from a safe (If there is one with a TN that strong) distance.

Cookiely wrote:I just finished watching a couple of movies on storm chasers and viewed some amazing tornados. My question is can you tell by looking at a tornado what F class it is because no one in the movie mentioned how powerful the tornados were. Is it determined by damage estimates?

No and yes.

Howard Bluestein and his student chasers deploy a much smaller Doppler for use at close ranges. Some chasers have adapted marine radars for their use, however they have run afoul of the Federal Communications Commission since they did not get the required licenses to operate and did not provide the required technical data to the FGG including RF energy exposure risk assessments.

Steve

Most estimates of a tornadoes palcement on the Fujita scale are done by post event investigation of the debri and damage fields. As a general rule of thumb though the larger the base, or wider the damage path the stronger the system.

NFLDART wrote:Most estimates of a tornadoes palcement on the Fujita scale are done by post event investigation of the debri and damage fields. As a general rule of thumb though the larger the base, or wider the damage path the stronger the system.

No . . . that's a very bad rule. Generally, wider tornadoes will be stronger, but not all strong tornadoes will be wide. Following that could get you badly hurt or killed.

Matt-hurricanewatcher wrote:Sure you can if it flatens a brink building or a steal inforced one then its a f5.

what if that building isnt properly secured to the ground? What if that building was old or improperly built? see, there is alot of variables that go into it...

According to the latest requirements, a building that isn't properly secured to the ground can never receive an F5 rating.

WindRunner wrote:

NFLDART wrote:Most estimates of a tornadoes palcement on the Fujita scale are done by post event investigation of the debri and damage fields. As a general rule of thumb though the larger the base, or wider the damage path the stronger the system.

No . . . that's a very bad rule. Generally, wider tornadoes will be stronger, but not all strong tornadoes will be wide. Following that could get you badly hurt or killed.

Correct, it is dangerous to try to estimate strength from the width.

Have a look at http://www.nssl.noaa.gov/users/brooks/public_html/papers/lengthwidth.pdf although I've only read through parts of it quickly after finding it earlier.

I've noticed that I can guess about how powerful it is within one F scale...I'm not always right, but it's not extremely hard to tell.

There is a possible way to visually measure wind speeds in a tornado. This formula was published by Tim Marshall.

V = 3.28 x D / 2 x T x 0.682

However below is a very simplified, approximated version of it:

V = D / T

V = Velocity in MPH
D = Diameter in feet
T = Time for 1/2 revolution in seconds

For example, if the tornado is 1300ft wide (1/4 mile) and a piece of debris along the funnel's edge takes 10 seconds to go from one side to the other, the wind speed is about 130 mph.