Assessment (as of 30 August 2017):
- Sea surface temperature over the central equatorial Pacific cooled in the past month, becoming near-normal by mid-August. According to forecasts by a number of climate models around the world, the sea surface temperatures of the central and eastern equatorial Pacific are likely to remain normal for the rest of the year.
- Under the influence of global warming and local urbanization, autumn temperatures in Hong Kong exhibit a significant long-term rising trend. Climate models around the world also forecast normal to above-normal temperature over southern China this autumn.
- Climate models around the world generally forecast that the rainfall over southern China this autumn would be normal to below normal. The chance for normal to below-normal autumn rainfall in Hong Kong in 2017 is expected to be higher.
- Climate prediction centres around the world generate seasonal forecasts, employing a variety of methods including
dynamical models, statistical methods, expert judgment and combinations of them. Predictions from different centres do
not always agree and large discrepancies can occur at times. The Observatory adopts an ensemble approach to formulate
its seasonal forecast for Hong Kong, taking into consideration available products from major climate prediction centres
and the Global-Regional Climate Model (G-RCM) operated in house. Thus,
the resulting forecast issued by the Observatory may be different from the forecast given by G-RCM.
- The Observatory gratefully acknowledges the Tokyo Climate Center of the Japan Meteorological Agency and the National
Centers for Environmental Prediction of National Oceanic and Atmospheric Administration, USA for providing dynamical
prediction model forecast and hindcast data to support the formulation of seasonal forecast for Hong Kong.
- Forecast for December 2017 to February 2018 will be available around 1st December 2017.
Seasonal forecast charts provided by G-RCM and major climate centres: