A salute to Vernon!

American meteorologist Vernon Dvorak, a photo from a presentation by the National Hurricane Center

Imagine a well-developed hurricane way out in the Atlantic. We need to know just how powerful its winds are, but it is too far way to send in a hurricane hunter. We would need a way to estimate the storm’s wind strength and just how strong it’s becoming. Here’s an example of Hurricane Isabel back in 2003, way out there, between the African coast and the Caribbean:

Water Vapor satellite courtesy of NOAA

Here is the teletype message of the storm estimating its intensity based on the Dvorak technique, which I have highlighted.

Dvorak intensity scale used to estimate winds with Isabel

Hurricane Isabel would go on to reach Category 5 status, eventually weakening to 105 mph winds as it struck North Carolina.

So just what is the Dvorak technique estimating intensity? National Hurricane Center Meteorologist Vernon Dvorak developed this procedure in 1973 using cloud patterns of developing tropical storms to estimate just how strong they are. Based on the cloud pattern, a T (or inTensity number) was assigned. Sounds simple, but this took years of research using as many satellite pictures as he could get a hold of! Remember, in the 1960s and 1970s, you had to sort through a lot of files and photos! Not much Google help in those days! The first guide looks pretty rudimentary:

courtesy NOAA

I blogged last April about new improvements that have been made to this scale which you can read about right here. In addition, Vernon Dvorak created an intensity scale of just how strong the winds of a tropical system are or will be based on the barometric pressure. The lower the pressure, the stronger the winds. In fact, last night on KPRC 2 at 10 p.m., I noted that the developing Caribbean system is estimated by the American Model to reach 150 mph winds in the Gulf of Mexico. How did I know that? Look at the current forecast of 927 millibars a week from today:

courtesy Tropicaltidbits.com

The Dvorak intensity scale gives me an estimate which I’ve highlighted below:

Dvorak intensity scale

You can see that 921 mb creates a 161 mph wind speed while 935 mb creates a 145 mph wind speed, so at 927 mb I estimated 150 mph -- that is invaluable information, obviously.

Vernon Dvorak died yesterday. He was 100 years old! So this blog salutes his hard work, brilliant mind, and dedication to the science of meteorology. Thank you, sir! You’ll be remembered forever.


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About the Authors:

KPRC 2's chief meteorologist with four decades of experience forecasting Houston's weather.