Study the table below, which shows average monthly wind speed data for a coastal meteorological station in an upland ecosystem.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Average monthly wind speed (knots) | 16 | 18 | 15 | 12 | 11 | 9 | 9 | 10 | 12 | 15 | 15 | 17 |
State the mode for the wind speed data.