Hong Kong Observatory Launches Seasonal Climate Forecasts

The Hong Kong Observatory will start issuing seasonal forecasts in early March 2006. Mr. K. H. Yeung, Assistant Director of the Hong Kong Observatory, and Dr. John Roads, Director of the Experimental Climate Prediction Centre (ECPC) of the University of California at San Diego, jointly briefed the media on the seasonal forecasts this (7 February 2006) afternoon.

Dr. Roads is a pioneer in short range climate forecasting. He obtained his Ph.D. from the Massachusetts Institute of Technology, studying under Professor Edward Lorenz who is one of the founders of chaos theory. Dr. Roads has authored or co-authored over 100 scientific publications.

Mr. Yeung said that seasonal forecasts refer to forecasts of the average weather in the coming month, year, or season. For instance, a forecast can be for a warmer than average summer, or a colder than average winter. These forecasts are useful for planning activities which are influenced by the weather or the climate. For example, they can be used to assess the demand for soft drinks in the summer or for warm clothing in the winter, and to adjust the production or inventory levels accordingly. The Chicago Mercantile exchange in the United States even offers weather futures.

He said that the seasonal forecasts to be issued would be on the average temperature and the total rainfall in the coming three months, and would be issued in March, June, September and December via the Observatory's website. These forecasts will be expressed in terms of "above normal", "near normal" and "below normal" temperature or rainfall. The primary tool for producing the forecasts is a regional climate model adapted from ECPC. Model-generated forecast maps will also be displayed on the HKO website. Outputs of climate models from other climate centres will be taken into consideration in the formulation of the seasonal forecasts.

Mr. Yeung explained that climate models are not too different from the numerical weather prediction models. In both cases, computers are used to simulate future weather changes. With the present state of technology, the accuracy of climate models is not yet as good as that of numerical weather prediction models. That is why the Observatory is only issuing the seasonal forecasts on an experimental basis, before doing so as part of the regular forecasting service later on when the technology has gained more maturity. This is the practice adopted by other climate centres.

Dr. Roads said that currently most centres use global climate models to produce seasonal forecasts. ECPC is one of the few centres to have developed regional climate models. He explained that while global models can cover a larger area, their resolution is relatively low. On the other hand, regional models cover smaller areas, but have higher resolution. Hong Kong is located in an area of complex terrain. It is appropriate that the Observatory has selected to use a regional model for its seasonal forecasts.

Dr. Roads added that he is very happy that the Hong Kong Observatory has adapted ECPC's regional model. He expects that more and more centres will be utilizing this model or this type of model to produce seasonal forecasts.

Mr. Yeung pointed out that proper use of seasonally forecasts requires experience. He encouraged those in weather-sensitive businesses as well as the community at large to try to make use of the seasonal forecasts, gaining experience in the process so that they can use them more effectively in the future.

The web addresses for the Observatory's seasonal forecasts are http://www.weather.gov.hk/tc/en/wxinfo/season/season.htm (Chinese), and http://www.weather.gov.hk/en/wxinfo/season/season.htm (English).

Assistant Director of the Hong Kong Observatory Mr. Yeung Kai-hing and Director of the Experimental Climate Prediction Centre, University of California at San Diego Dr. John Roads elaborating on the Hong Kong seasonal climate forecasts.