Ellrod index

In meteorology Ellrod index is a technique for forecasting clear-air turbulence. It is calculated based on the product of horizontal deformation and vertical wind shear derived from numerical model forecast winds aloft.The deformation predictors are calculated using following information.
* "Shearing deformation":: $DSH=frac\{dv\}\{dx\}\; +\; frac\{du\}\{dy\}$.
* "Stretching deformation": : $DST\; =\; frac\{du\}\{dx\}\; -\; frac\{dv\}\{dy\}$. Where "u' and "v" are horizontal components of the wind.
* "Total deformation" equals to:: $DEF\; =\; sqrt\{DSH^2\; +\; DST^2\}$.
* "Convergence":: $CVG\; =\; -(frac\{du\}\{dx\}\; +\; frac\{dv\}\{dy\})$
* "Vertical wind shear":: $VWS\; =\; frac\{Delta\; V\}\{Delta\; Z\}$ And the resulting index is given by:: $EI\; =\; VWS\; imes\; (DEF\; +\; CVG)$

To correspond to clear-air turbulence pilot reports the following table can be used:

* [http://aviationweather.gov/exp/ellrod/info.php?mdl=NAM Aviation Weather Center Help ]
* [http://aviationweather.gov/exp/ellrod/nam/ Aviation Weather Center EI display ]