Flight level winds to Surface winds

[Tarmo Tanilsoo]

Hello.

When I have read reconnaissance reports from different storms, I have always noticed a remark "Maximum flight level wind 75 kt" etc. Wondering, how to convert flight level winds to surface wind? Does it depend from height of the plane?

Best wishes,

 

[cdcollura]

Good day, Tarmo, this is Chris Collura...

In hurricane recon flights, a common correction is 90% from the standard 5,000 to 10,000 foot flight level winds. This is as in MOST cases (where there is good boundary layer mixing, convection, etc).

In other words, a 75 knot flight level wind woudl correlate to (90 %) of that which is 75 x .90 = 67.5 knots.

Also, to convert KNOTS to MPH, multiply knots by 1.15. In the above example, 67.5 knots (x 1.15) gives a surface wind of about 77.6 MPH.

Chris C - KG4PJN

 

[B Ozanne]

Does anyone know why you can use the same formula for different flight levels? I know this is a common practice, but I don't know the reasoning behind it.

Tarmo, welcome. First stormtrack member from Estonia. Very cool.