Since the Windshear and Turbulence Warning System (WTWS) commenced operation at the Hong Kong International Airport (HKIA), automatic alerts of low-level windshear (sustained headwind change of 15 knots or above) are provided to cover up to 3 nautical miles from touch-down or take-off for both arrival and departure corridors.
During recent meetings of the Windshear and High-Impact Weather (WHIX) Panel, it has been pointed out that, once a departing aircraft reaches an altitude of 1000 feet or above, effect of significant windshear and turbulence on the aircraft would be minimal. Subsequent studies by the Observatory also confirmed that the removal of departure-corridor WTWS alerts beyond 2 nautical miles (corresponding to an altitude around 1000 feet) would bring minimal impact on the performance of the windshear and turbulence warning service at HKIA.
The revised alerting criteria will be operationally implemented starting from 1 January 2015. In summary, following the revision, windshear alerts (WSA) and all turbulence alerts from WTWS will no longer cover "3 MF" for any departure corridor (including 07LD, 07RD, 25LD and 25RD). This change will not affect windshear and turbulence alerts for arrival corridors (07LA, 07RA, 25LA and 25RA), i.e., up to 3 nautical miles from touch down. Microburst alerts (MBA), considering its significance, will also continue to cover up to 3 nautical miles of all corridors.
Please stay tuned to latest announcements through NOTAM, the Windshear Booklet and Aeronautical Information Publication.