Assessment (as of 30 August 2019):
- In the past month or so, the cooling trend of the central and eastern equatorial Pacific continued. Overall speaking, sea surface temperatures of the region returned to normal in July 2019, indicating that the El Niño had come to an end. Based on the latest oceanic observations as well as forecasts by a number of climate models around the world, sea surface temperatures of the central and eastern equatorial Pacific are expected to remain normal this autumn (September-November).
- 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 temperatures over southern China this autumn.
- Climate models around the world generally forecast that there will be less moisture transport to the south China coast this autumn and less rainfall over the region. The forecasts by climate models are consistent with the forecasts given by other objective statistical methods. Hence, normal to below-normal rainfall in Hong Kong is expected this autumn.
- 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 winter 2019 (December 2019 to February 2020) will be available around 1st December 2019.
Seasonal forecast charts provided by G-RCM and major climate centres: