Skew

Bulletin #17B recommends using the weighted skew value, G
W
, to determine frequency factor values in Equation 4-2.
To calculate weighted skew, use this equation, and follow the steps provided in Bulletin #17B:
Equation 4-6.
Where:
  • G
    W
    = weighted skew value
  • InlineEquation39= regional skew from Figure 4-4
  • G
     = station skew from Equation 4-5
  • InlineEquation410= mean square error of InlineEquation39 for Texas, is = 0.123 (RMSE = 0.35) (Judd et al. 1996), which replaces the value of 0.302 (RMSE = 0.55) presented in Bulletin #17B.
  • MSE
    G
     = mean square error of G. MSE
    G
     is a function of G and period of record
Generalized skew coefficients for Texas (Judd 1996) () (click in image to see full-size image)
Figure 4-4. Generalized skew coefficients for Texas (Judd 1996) (
 InlineEquation39
)
Equation 4-7.
Where N is the record of length and
  • A
     = -0.33 + 0.08 |
    G
    | for |
    G
    | ≤ 0.90
  • A
     = -0.52 + 0.30 |
    G
    | for |
    G
    | > 0.90
And
  • B
     = 0.94 - 0.26 |
    G
    | for |
    G
    | ≤ 1.50
  • B
     = 0.55 for |
    G
    | > 1.50