A new webpage on "Backward Trajectory map" (http://www.weather.gov.hk/wxinfo/trajectory/trajectory_e.shtml) was launched on the Observatory's website commencing 18 November 2008.

The map on the webpage shows the backward trajectory of the air mass reaching Hong Kong for the past 72 hours. The webpage may be useful for the public in tracing the origin of air mass reaching Hong Kong under different weather patterns.