Wind shear values can be generally determined with a basic calculation. The value is derived from a change in wind speed over a change in altitude of thousands of feet. The formula used is:
(windspeed at Altitude A - windspeed at altitude B) / ((Altitude A - Altitude B)/1000) = wind shear value.
So for example:
At FL380, the winds are 86 kts, and at FL400, 96 kts. The difference is 10 kts. The difference in altitude is 2000. 10/2 = 5 Shear Value.
(96-86) / ((40,000 - 38,000) / 1000) = 5
For a more accurate indication of turbulence along the route and altitudes of flight, consult ForeFlight's turbulence report (obtained with a Sentry Plus), Dispatch Custom Navlog Builder, the vertical cross-section chart provided in the briefing, and in-app turbulence map layers as more modern and reliable indicators. Along with the turbulence icons in the custom Navlog, all of these are modern alternatives to basic calculations for shear values.
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