Seasonal Forecast for Summer 2020
(June to August 2020)
Assessment (as of 28 May 2020):
- Sea surface temperatures of the equatorial Pacific on the whole were above normal since November 2019, albeit with relatively small anomalies. As the warmer-than-normal sea surface temperatures persisted for six months, an El Niño event was established. Based on the latest oceanic observations as well as forecasts by a number of climate models around the world, sea surface temperatures of the equatorial Pacific are expected to cool in the next couple of months, transitioning gradually to ENSO-neutral conditions. In other words, the El Niño event will be short-lived and weak. Based on statistical analysis, the chance for normal to above-normal summer rainfall in Hong Kong is slightly higher during ENSO-neutral conditions.
- Under the influence of global warming and local urbanization, summer 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 summer.
- The majority of climate models around the world forecast normal to above-normal rainfall over southern China this summer due to anomalous southerlies which favour moisture transport. Taking the above information and the development trend of sea surface temperatures of the equatorial Pacific into consideration, the chance for normal to above-normal rainfall in Hong Kong this summer is expected to be slightly 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 autumn 2020 (September to November 2020) will be available around 1st September 2020.
Seasonal forecast charts provided by G-RCM and major climate centres: