Sea surface temperatures of central and eastern equatorial Pacific continued to cool in the past month or so. Climate models around the world forecast the cooling trend to persist this winter, indicating that La Niña may start to develop. However, the La Niña event is expected to be weak. Statistical analyses suggest that during La Niña, winter temperatures in Hong Kong tend to be generally lower than those during the ENSO-neutral state. On the other hand, under the influence of global warming and local urbanization, winter temperatures in Hong Kong reveal a significant long-term rising trend. Climate models around the world forecast southern China to have normal to above-normal temperature for this winter. Taking all available information into consideration, the overall winter temperature in Hong Kong is expected to be near normal.
The impact of La Niña on Hong Kong winter rainfall is not significant. The majority of climate models forecast that rainfall over southern China is likely to be normal to below normal for this winter.
Although the overall winter temperature in Hong Kong is expected to be near normal, day-to-day fluctuations in weather
and temperature could still be quite large with occasional cold weather or even very cold weather. Reference should therefore
be made to the latest assessment provided by the local weather forecast and 9-day weather forecast issued by the Observatory.
(Cold weather refers to temperature falling to 12 ºC or below. On average, there are 17 cold days per year. Very cold weather
refers to temperature falling to 7 ºC or below. On average, there are six very cold days for every ten years.)
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 spring 2017 (March to May 2017) will be available around 1st March 2017.
Seasonal forecast charts provided by G-RCM and major climate centres: