AFWA Gust Calculator

The maximum convective downdraft is computed in 2 ways:

V1 = 13 * sqrt(T1)
V2 = V + (13 * sqrt[(T1+T2)/2])

Enter values for the following variables, then click Calculate.

T1: To determine T1, first answer the following questions:
Is there an inversion?
Yes
No

Is the top of the inversion more than 200 hPa above the surface?
Yes
No
1. Descend dry adiabatically from the 850-hPa temperature to the surface. The temperature at this point is TMAX.
2. From this surface temperature, proceed up moist adiabatically to 600 hPa.
3. Subtract the 600-hPa dry bulb temperature from this valued to get T1.
4. Enter T1: (°C)
1. Proceed up a moist adiabat from the surface to 600 hPa. Note the temperature.
2. Subtract the 600-hPa dry bulb temperature from this value to get T1.
4. Enter T1: (°C)

TMAX = max t = (°C)
T2 = mixing ratio at melting level = (°C)
V = mean wind speed (kt) in the lowest 5,000 feet = (kt)

V1 = = maximum wind gust (knots)
V2 = = maximum wind gust (knots)