Seasonal Forecast for Autumn 2020
(September to November 2020)
Assessment (as of 31 August 2020):
- In the past month or so, sea surface temperatures of the central and eastern equatorial Pacific remained normal to below normal. 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 cool gradually in the next few months, indicating that La Niña may start to develop. Based on statistical analysis, La Niña has no significant impact on autumn rainfall in Hong Kong.
- Under the influence of global warming and local urbanization, autumn temperatures in Hong Kong exhibit a significant long-term rising trend. The chance for normal to above-normal temperature is generally higher. Climate models around the world forecast normal to above-normal temperatures over southern China this autumn.
- The majority of climate models around the world forecast that there will be more moisture transport to the south China coast this autumn and rainfall over the region will be above normal. Hence, the chance for normal to above-normal rainfall in Hong Kong this autumn is expected to be relatively 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 winter 2020/21 (December 2020 to February 2021) will be available around 1st December 2020.
Seasonal forecast charts provided by G-RCM and major climate centres: