LCQ3: Countering cold spells
Following is a question by the Hon Andrew Leung and a reply by the Secretary for Commerce and Economic Development, Mr Gregory So, in the Legislative Council today (March 2):
In late January this year, Hong Kong experienced the coldest spell in 59 years. Some meteorologists have warned that global extreme weathers will occur more and more frequently. On January 17, the Hong Kong Observatory (HKO) forecast a minimum temperature of 10 degrees Celsius seven days later (i.e. on January 24), and thereafter adjusted the forecast minimum temperatures downward every day until it made a forecast on January 23 that the minimum temperature on the following day would be 6 degrees Celsius. However, the actual minimum temperature on January 24 was 3.1 degrees Celsius, representing a forecast error of nearly 3 degrees, which was far more than the average error of 1 to 2 degrees in the past year. On the other hand, it has been reported that some foreign weather forecasters had predicted eight days before January 24 that the temperature in Hong Kong on January 24 would fall to zero to 4 degrees Celsius, making a forecast error smaller than that of HKO. Moreover, on January 25, the Education Bureau (EDB) made a last-minute announcement that classes of all kindergartens, schools for children with physical disability, schools for children with intellectual disability and primary schools would be suspended on that day due to the persistently intense cold spell. In this connection, will the Government inform this Council:
(1) whether it has assessed if the weather gauging equipment of HKO and the weather information it releases to the public are inferior to those of its overseas counterparts; if it has assessed, of the outcome; whether HKO has plans to procure more advanced equipment, and whether it will, by making reference to the practices of the United Kingdom and Australia, release weather information on "apparent temperature" to the public; if HKO will, when it will start doing so; if not, of the reasons for that;
(2) given that while sleet (i.e. "雨夾雪" in Chinese, meaning rain and snow mixed) was reported in Hong Kong on January 24, and HKO called this phenomenon "雨夾小冰丸" (i.e. rain with small ice pellets) in Chinese that morning and subsequently changed it to "雨夾小冰粒", why HKO used Chinese terms such as "雨夾小冰丸" and "雨夾小冰粒" instead of "雨夾雪" as appeared on the "Cool Met Stuff" page of its web site; and
(3) given that heating systems have not been installed in most schools currently, whether EDB will consider issuing guidelines on class suspension arrangements in severely cold weather to enable students, parents and school authorities to make advance preparation?
My reply to the three parts of the question is as follows:
(1) Weather centres around the world primarily make use of computer models to prepare weather forecasts. In addition to making use of its own self-operated computer model which is developed for specific application in Hong Kong, the Hong Kong Observatory (Observatory) also makes reference to computer models that are reputed globally for their good performance, including those of the European Centre for Medium-Range Weather Forecasts, Japan Meteorological Agency and United States National Oceanic and Atmospheric Administration. The Observatory would take into account the past performance of such models, their forecast locations, actual observations, etc. in preparing consolidated forecasts. This approach is consistent with that adopted by other major cities and advanced areas. In the past year, the average error of temperature forecasts made by the Observatory using the said approach is approximately 1 degree Celsius, the performance being on par with top standards in the world.
The main meteorological facilities of the Observatory comprises meteorological radars, a meteorological satellite reception system, a lightning location network, etc.. Such facilities are adequate for meeting the present needs of the Observatory in relation to the provision of weather forecast services. The Observatory will keep abreast of developments and consider acquiring more advanced meteorological facilities suitable for use in Hong Kong in a timely manner, so as to enhance the department's ability in carrying out weather monitoring, forecasts and warnings.
The Observatory has drawn experience from the cold weather event in January, with a view to enhancing its forecasting techniques to meet the challenges of more extreme weather conditions brought by climate change. The Observatory will continue to exchange experiences with meteorological organisations around the world on matters such as weather monitoring, forecasts and warnings.
In future and when necessary, the Observatory will include more specific contents and wording in its Cold Weather Warnings, such as wind chill effect, slippery icy roads, etc. to better explain the actual impact of very cold weather to the public. The Observatory will also provide more detailed information on regional temperatures. Starting from early March, the Observatory will release the temperatures at Tai Mo Shan and Tate's Cairn, so as to provide the public with more timely information on temperatures. Furthermore, the Observatory will strengthen public education and communication to enable the public to better understand and prepare for the impact of climate change and extreme weather.
(2) "Sleet" is the English equivalent for both "雨夾冰粒" (rain with ice pellets) and "雨夾雪" (rain with snow). As a relatively generic weather term, "sleet" does not have any standard international definition. Instead, its meaning varies in different places. For instance, "sleet" refers to the precipitation of "rain with snow" in Britain and Australia, but it means "rain with ice pellets" in the United States.
The difference between "rain with ice pellets" and "rain with snow" lies in the form of the solid precipitation, that is whether it is in the form of ice pellets or snow. An ice pellet is a relatively hard and translucent granule, which bounces on hitting the ground. Snow has a soft and fluffy structure and falls gently onto the ground. Based on local weather observations and the images provided by members of the public, "rain with ice pellets" instead of "rain with snow" had appeared in Hong Kong on January 24. Records showed that Macau also reported "rain with ice pellets" instead of "snow" or "rain with snow" on the same day. After taking into account public reactions and to avoid misunderstanding, the Observatory eventually used the term "rain with ice pellets" to describe the weather on January 24, having considered that the reference to "冰粒" (ice pellets) would be more easily understood by the public as it is closer to our everyday language.
The Observatory uses the more generic term "sleet" on its website and relevant "Cool Met Stuff" video to summarise two types of mixed phenomena, namely rain with snow and rain with ice pellets. In future, the Observatory will make clear the different characteristics of various weather phenomena in its public education material to help the public better understand these classifications.
(3) The Education Bureau (EDB) and the Observatory have in place a notification mechanism in respect of inclement weather conditions, including Tropical Cyclone Warning Signal No. 3 or above, red/black rainstorm warning, and other unusual weather conditions. The EDB has also informed schools of arrangements to be taken in the event of inclement weather conditions such as tropical cyclones and heavy persistent rains via circulars.
If there are potential threats to the safety of students under inclement weather conditions, the EDB will maintain close contact with the Observatory, and inform schools of the contingency measures to be taken, such as territory-wide or district-based class suspension, as soon as possible and as necessary. Such measures have long been effective. To prepare for possible emergency situations including inclement weather conditions in certain districts, individual schools have drawn up school-based contingency plans in the light of their specific circumstances, so as to facilitate necessary and special arrangements such as class suspension.
Taking this opportunity, the EDB would like to clarify that the decision to suspend classes for certain schools on January 25, as announced on the previous day, was made with students' safety and health as the top concern. The decision has taken into account a host of factors, including the very cold weather, strong wind, freezing rain and icing on high ground brought by a rare intense cold surge influencing Hong Kong at that time, as well as the ability of students to take care of themselves. Hence, the decision was made with students' best interest as the prime consideration, and was not taken solely on the grounds of exceptionally cold weather.
Ends/Wednesday, March 2, 2016