In meteorology the Ellrod index is a technique for forecasting
clear-air turbulence
In meteorology, clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues, such as clouds, and is caused when bodies of air moving at widely different speeds meet.
The atmospheric region most suscept ...
(CAT). It is calculated based on the product of horizontal deformation and vertical
wind shear
Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizont ...
derived from numerical model forecast winds aloft.
The deformation predictors are calculated using following information.
* ''Shearing deformation'':
:
.
* ''Stretching deformation'':
:
.
Where ''u'' and ''v'' are horizontal components of the wind.
* ''Total deformation'' equals to:
:
.
* ''Convergence'':
:
* ''Vertical wind shear'':
:
And the resulting index is given by:
:
To correspond to clear-air turbulence
pilot report
A pilot report or PIREP is a report of actual flight or ground conditions encountered by an aircraft. Reports commonly include information about atmospheric conditions (like temperature, icing, turbulence) or airport conditions (like runway con ...
s the following table can be used:
See also
*
Aviation Weather Center
The Aviation Weather Center (AWC) provides weather information and forecasts for air flights over United States territory and at certain altitudes for global traffic. It works with customers, such as commercial airlines, and international partners ...
External links
Aviation Weather Center Ellrod Forecast
Meteorological indices
Turbulence
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