| Month | Cubic Equation | R2 |
| Jan | 0.689 + 0.0017 G − 5.764 × 10−08 G2 − 3.357 × 10−12 G3 | 0.971 |
| Feb | 2.489 + 0.0007 G + 3.124 × 10−07 G2 − 2.658 × 10−11 G3 | 0.952 |
| Mar | 17.324 − 0.008 G + 2.429 × 10−06 G2 − 2.117 × 10−10 G3 | 0.951 |
| Apr | −11.905 + 0.0103 G − 1.862 × 10−06 G2 + 1.132 × 10−10 G3 | 0.984 |
| May | 9.046 − 0.0013 G + 4.712 × 10−07 G2 − 1.304 × 10−11 G3 | 0.965 |
| Jun | 522.308 − 0.315 G + 4.329 × 10−05 G2 − 1.821 × 10−9 G3 | 0.971 |
| Jul | 243.453 + 0.1123 G − 1.487 × 10−05 G2 + 7.321 × 10−10 G3 | 0.959 |
| Aug | −249.824 + 0.134 G − 2.233 × 10−05 G2 + 9.652 × 10−10 G3 | 0.987 |
| Sep | 26.255 − 0.0336 G + 6.328 × 10−06 G2 − 5.120 × 10−10 G3 | 0.958 |
| Oct | 127.854 − 0.0832 G + 1.490 × 10−05 G2 − 1.004 × 10−9 G3 | 0.961 |
| Nov | 4.865 − 0.003 G + 3.174 × 10−07 G2 + 2.224 × 10−11 G3 | 0.955 |
| Dec | −30.432 + 0.042 G−1.012 × 10−05 G2 + 2.234 × 10−09 G3 | 0.968 |