Dvorak technique

The Dvorak technique ( developed in 1974 by Vernon Dvorak ) is a commonly used system in order to determine the intensity of tropical cyclones, subjectively, using satellite imagery and infrared images.

Details about the technology

The Dvorak technique exploits the fact that developing hurricanes same intensity have the most similar properties, and that the appearance of these hurricanes usually characteristically changed with increasing intensity. The structure of a tropical cyclone is analyzed every 24 hours to see if the cyclone has strengthened, weakened, or maintain its intensity. There are several templates of typical storm structures that enable the core and rain band structure of the storm are compared in order to draw conclusions on the intensity can. If one eye is identified on infrared images of the storm, can also be closed on the intensity by differences in temperature of the warm eye and the surrounding cloud structure. (This applies, the warmer the eye and the colder the cloud top of the eyewall are, the stronger the hurricane. ) Upon completion of the analysis for each system, a so-called T- number and a CI number (Current Intensity, " current intensity " ) set. The T numbers range from 1 ( lowest intensity ) to 8 (highest intensity). For most storms T numbers are identical to the CI numbers, except for the rapidly weakening systems where the CI number is higher than the T - number.

Structure types

A distinction is made between different structures that can be observed during a storm, and allow the upper and lower bound of the intensity.

  • Curved rain band structure ( T1.0 - T4.5 )
  • Scherungsstruktur ( T1.5 - T3.5 )
  • Central Dense Overcast (CDO ) ( T2.5 - T5.0 )
  • Eye initial stage ( T4.0 - T4.5 )
  • Eye structure ( T4.5 - T8.0 )

If the structure has been discovered, then by analysis of the found features are closed ( eg, length and curvature of the rain bands) to a T number.

Use

The Dvorak technique is in the Atlantic with stronger systems usually used for other observations ( reconnaissance flights, QuikSCAT data, ship and buoy observations) only for comparison scale. Only for storms in the eastern Atlantic, in which reconnaissance flights would be burdensome because of the large distance to the base, the Dvorak technique is specifically used to determine the storm intensity. The Dvorak technique, however, sets storms in all other developing regions, the main basis for determining the storm intensity dar. ( reconnaissance flights are only in the Atlantic and eastern Pacific performed)

Wind speed Knot (unit) Eye (cyclone) Hurricane Wilma National Oceanic and Atmospheric Administration
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