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 ]