Singapore Met Service developing more accurate rainfall model

Monica Kotwani Channel NewsAsia 23 Jun 14;

SINGAPORE: The Meteorological Service Singapore is working on a modelling system that could forecast more accurate information of heavy rainfall across the island. This means being able to predict where it could rain, and how much rainfall that area could experience.

The Met Service said such a model could be developed within the next year or two, and give authorities a longer lead time than the current 20 to 30 minutes, to react to potential flooding or other situations.

At the Changi Meteorological Station, which is located near Changi Airport, observers take readings of rainfall, runway visibility, wind speed, temperature and the amount of sunlight hours Singapore receives.

A day-shift typically sees about two staff and one supervisor working about 10 hours, while the night shift goes on for about 14 hours.

The observers code the data and disseminate it to the Met Service's headquarters, located within the airport terminal. The data is collated with other information and then passed on to incoming aircraft, as well as the relevant authorities.

The data is also used to make weather forecasts -- ranging from three hours to three days.

However, experts said even with current technological advances, being in the tropics has its challenges.

Dr Chris Gordon, director of Centre for Climate Research at the Met Service, said: "A lot of the rainfall which is a particular aspect of the weather for Singapore is being produced by thunderstorms.

"Thunderstorms have some particular characteristics -- not only do they produce a lot of rain, but they also appear and disappear relatively quickly compared to other types of weather systems in different parts of the world.

"One of the challenges here is how do you forecast such a system that's going to arrive, do its thing, and then disappear in a very short period of time? The other aspect of it is that they're in a very small scale."

Dr Gordon said the Met Service is looking at adapting the existing United Kingdom unified modelling system by plugging in local and satellite data into the model.

By adapting it, the model can give a finer scale resolution of forecasting thunderstorms.

The Met Service also looks at various satellite data to detect haze and hotspots, but this may be hampered by passing clouds and the lack of real time information as some satellites pass through only twice a day.

The Met Service expects better pictures and updates from next year when a new breed of satellites are activated.

The Met Service is also preparing for emerging hazards that could have an impact on Singapore.

One area it is studying is space weather -- where solar flares may cause a disturbance to the Earth's magnetosphere. Such magnetic storms could affect communications, power and satellites.

Dr Felicia Shaw, the deputy director of the Met Service's Hazard, Risk and Impact Assessment Unit, said: "Even though magnetic storms are thought to impact high latitudes more, understanding the impact on the world is going to benefit Singapore because it could potentially impact us.

"We have many sensors for weather, but we may now need new ones for emerging hazards and also expertise because to analyse, to interpret the information, requires a certain intellectual capability."

- CNA/ac

System to raise weather forecast accuracy in the works
SIAU MING EN Today Online 24 Jun 14;

SINGAPORE — The Meteorological Service Singapore (MSS) is developing a modelling system that will provide more accurate predictions on where and when heavy rainfall will hit areas in Singapore, eventually providing a longer lead time for various parties to react.

The Singv Model, adapted from the Met Office’s unified modelling system in the United Kingdom, plans to narrow the scope of weather data supplied by global met services and incorporate local weather data to provide a more accurate forecast.

Speaking to reporters yesterday on the sidelines of a media tour of facilities at Changi Airport that are used to observe, monitor and forecast the weather, MSS director-general Wong Chin Ling noted that, while the model is not entirely new, it is one that had not really been tried in the tropics.

“We hope the model is actually able to better predict convective-scale — (or) small-scale — localised thunderstorms that are common in Singapore all year round. These are the kind of weather systems we encounter,” she said.

With more accurate forecasts, Dr Chris Gordon, Director for the Centre for Climate Research Singapore, noted that it would also help in contingency planning for floods here, for instance.

Ms Wong added that national water agency PUB would benefit from the longer lead times the forecasts could provide.

The current lead time is between 20 and 30 minutes, and the MSS hopes to eventually improve it to a few hours with the model.

At present, global forecasts can be produced at 12-hour intervals and at coarser spatial resolutions of about 25km — that is, providing weather data, such as temperature, humidity and wind conditions, for every 25km.

The model aims to provide weather data for every 1.5km on the island.

This could mean that, instead of forecasting rainfall over central parts of Singapore, the model could further pin-point it to an area such as Toa Payoh, said Ms Wong.

Likewise, Dr Gordon noted that a 12-hour forecast might miss out thunderstorms that come and go in a few hours.

Thus, to produce more regular forecasts, local weather data — from weather radar and automatic weather stations, for instance — will be included in the model.

Dr Gordon added that the model is expected to produce useful forecasts in the next one to two years, as the team continues to build on its ability to assimilate data.

'Wild weather' not from climate change
Lim Yi Han My Paper AsiaOne 24 Jun 14;

SINGAPORE - If you think that global warming is behind the erratic weather patterns here, such as the recent heavy rainfall or dry spell, you may be wrong.

This is because climate change here due to global warming may only be seen a century from now, said Chris Gordon, director of Centre for Climate Research Singapore, which is part of the National Environment Agency's (NEA's) Meteorological Service yesterday.

Global warming is caused by the release of greenhouse gases from human activity. Experts like Dr Gordon say they "cannot definitively answer" what could be the culprit for intense weather patterns such as the heavy rainfall, which led to recent flash floods that have wreaked havoc in parts of Singapore, which included shutting down the Ayer Rajah Expressway last September.

"So it is true that in this region, climate change will also project increasing extreme rainfall, but that is in 100 years' time."

In fact, the current weather changes could be "just a natural variation of the climate", he pointed out, adding that urbanisation may also be a cause, which is the case for other major cities in the region as well.

"(This is because) the actual change in the surface characteristics of the island can affect the convective thunderstorms that we've been having," noted Dr Gordon.

Apart from the intense rainfall, February was Singapore's driest month in nearly 150 years, and the windiest in three decades, according to the NEA.

Going forward, there is "no reason to expect" that Singapore will see more of such conditions but, at the same time, there are also limitations in the current climate models.

But as Singapore is in the Tropics, it makes it more difficult to accurately predict the weather.

This is because tropical weather systems have unique features such as thunderstorms caused by convections, a process where hot moist air rises and forms clouds.

Currently, the accuracy rate of the three-hour forecast is about 90 per cent.

The lead time for a heavy rainfall prediction is about 30 minutes at best, but this could also be improved to more than an hour.

Wong Chin Ling, director-general of the Meteorological Service, said: "The challenge for us... is that there is always this demand for information about where exactly is heavy rainfall going to fall, and how much is this.

"These are very difficult questions for us to address but we are looking into a very high-resolution model and making use of latest technology to help us provide a more reliable forecast of heavy rainfall."