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Note: HRES and Ensemble Control Forecast are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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• over land, is dependent upon the surface vegetation (See Table9.3-1).
• over sea, the drag on the low-level air flow is modelled using the Charnock parameter.  This includes an aerodynamical roughness length that is a function of the 10m wind speed, but limited to a maximum value of that associated with 10m winds of 40m/s.  Read more information about coupling between the atmosphere and ocean waves in waves near tropical storms.

Also considered is a representation of drag from small scale orography.  Flow around steep orographic features gives temporary, variable and quickly fading atmospheric waves that lead to drag - Turbulent Orographic Form Drag (TOFD).

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• See the impact of Cycle 47R3 on representation of wind gusts.
• Read more on parameterisation of convective gusts (page 15).
• Read about EFI parameters for forecasting severe convection (which contains informative case studies, where there are references to gusts associated with active convective systems).
• Watch a comprehensive lecture on Model Physics: Concepts, Practice and Products (36sec delay in start, winds and gusts discussed from 31min15sec to 36min40sec).
• Read a 2015 paper on extra-tropical Cyclones and the strong wind phenomena that are associated

(FUG Associated associated with Cy50r1)