How a weather warning is generated
——See the whole process of early warning from the landing of typhoon "Siamba"
In the past few days, under the influence of typhoon "Siamba", tornadoes frequently visited many places in Guangdong.
At about 15:30 on July 4, a medium-level tornado occurred near Yundonghai Street, Sanshui District, Foshan City, resulting in broken branches and damage to the factory shed.
On the same day, the Foshan Meteorological Observatory issued a tornado warning an hour in advance, gaining valuable time for local disaster prevention and personnel evacuation.
How is the "life-saving" weather warning delivered to us?
Recently, the reporter came to the relevant units of the China Meteorological Administration to explore the scientific and technological support behind the first line of defense for meteorological disaster prevention and mitigation.
A steady stream of first-hand observational data is delivered to numerical models in time
In recent years, extreme and disastrous weather such as short-term heavy rainfall and tornadoes has occurred frequently around the world, causing serious damage to the safety of people's lives and properties.
Based on radar and satellite data analysis, it is an important technical support for my country's forecast business.
Back in the afternoon of June 26, a tropical disturbance seized the "space" left on the tropical ocean surface after the subtropical high extended westward and lifted northward, and began to develop and grow.
A few days later, it grew into the first typhoon "Siamba" to land in my country this year, and after making landfall, it headed northward, bringing abundant rain.
At that time, looking at the rudimentary, slightly broken and asymmetrical spiral shape on the satellite cloud map, it was difficult to predict its prospects.
However, seasoned forecasters have given it full attention.
Because its location - the ocean to the east of the Philippine Islands, is an important source of typhoons that affect our country.
Relying on satellite cloud images, forecasters can intuitively understand the general trend of the weather system, but accurate forecasting work must be based on precise observation data.
my country has the world's largest comprehensive meteorological observation system, with more than 70,000 automatic weather stations, 236 radars, more than 120 sounding stations, and 7 in-orbit Fengyun meteorological satellites, which together form an integrated ground-air-sky observation network. , which can not only capture the weather dynamics in the first time, but also accurately measure the minute-level or even second-level precise data behind the wind and cloud movements.
Abstracting a concrete typhoon into data such as air pressure, temperature, wind direction, and wind speed is very important for modern weather forecasting.
For hundreds of years, meteorologists have summarized the laws of atmospheric motion into a set of equations.
Today, supercomputers are used to obtain approximate numerical solutions to these systems of equations—that is, numerical prediction.
Since its birth, numerical forecasting has been developed for more than half a century, and the accuracy and timeliness have been improved qualitatively. It is also known as one of the greatest scientific and technological achievements in the 20th century. It can effectively predict the weather changes in the next seven days or so. , and progress at a rate of 1 day extension every 10 years.
Looking back at typhoon "Siamba", its various data are continuously gathered from various observation instruments to the meteorological big data cloud platform, and experienced transmission, quality control, aggregation, analysis... Observational data is passed to the numerical model, and it is expected that it will calculate results as close to reality as possible.
Numerical models give forecasts, but forecasters can't sit back and relax
"'Siba' will move north-westward at a speed of 10 kilometers to 15 kilometers per hour... From July 2 to 3, it will make landfall along the coast from the east of Hainan Island to the west of Guangdong, and the landing intensity will be tropical storm or severe tropical storm. Storm level." On June 30, "Siamba" was upgraded to a tropical storm and officially named.
This is the forecast conclusion of the Central Meteorological Observatory on that day.
Behind the simple words, not only the operation of numerical models, but also the hard work of forecasters.
In fact, what numerical forecasting is best at is being able to forecast the general development of the weather system many days in advance, such as the general trend of typhoons and the imminent occurrence of large-scale rainfall.
However, it is impossible to predict the exact path of the typhoon and how much rainfall will fall in a certain place.
This requires forecasters to revise forecast conclusions as close to reality as possible.
During the forecasting process of "Siamba", forecasters from the Central Meteorological Observatory, Guangdong, Guangxi, Hainan, Hong Kong, Macao and other places analyzed various data, studied various data, compared the right and wrong of various subjective and objective forecasts in the past, and also Often get together to discuss research, and ultimately come to forecast conclusions.
Moreover, with the continuous changes of the weather system, this forecast conclusion should be updated in a timely manner.
The forecast conclusion is based on science, and the transformation from forecast to early warning also has to go through a rigorous process.
Data remains the core criterion for this process.
According to the "National Meteorological Disaster Emergency Plan", the forecast value obtained through research and judgment is compared with the standard threshold value of the early warning level set in advance through research. When the conditions are met, the corresponding type and level of meteorological warning will be issued.
Zhang Tao, chief forecaster of the National Meteorological Center, told reporters that the early warning of the Central Meteorological Observatory is an early warning in the form of a forecast. For example, when a thunderstorm is forecast, it is simulated through an algorithm, which is a simulation of the future. It's just an approximation. It's a normal thing to have errors, but how to overcome the problem under the constraints is the mission of the forecaster.
The core task of forecasters is to improve the accuracy and refinement of weather forecasting.
Whether the "last mile" is smooth is related to the effectiveness of disaster prevention
Every piece of early warning information "released" has to take a "must go through", that is, the national early warning information release system.
As a part of the national emergency command platform system, the national emergency early warning information release system has established a national, provincial, municipal and county-level early warning information release center. It can be targeted and sent to the disaster prevention responsible person in the affected area within 1 minute.
At 10:00 on June 30, the Central Meteorological Observatory issued a blue typhoon warning, pointing out the area affected by "Siamba".
Although the warning was issued, the work of the meteorological department was far from over.
"We are like doctors. Forecasting the weather is like seeing a doctor on duty. Weather conditions such as wind, rain, thunder and fog are like different diseases faced by doctors in different departments." Zhang Tao introduced that on the one hand, forecasts and warnings need to be updated at any time; on the other hand, the Central Meteorological Observatory The early warning issued has a large scope and wide coverage, mainly based on the impact of the typhoon on the whole country, and focuses on reminding all relevant departments to make emergency preparations.
From "release" to delivery to affected people, the time for people to take disaster prevention and avoidance measures is often only a few hours or even dozens of minutes.
In this limited and precious time, whether the "last mile" of weather warning information goes smoothly is directly related to the effectiveness of disaster prevention and mitigation.
If Typhoon "Siamba" makes landfall, the personnel of the Typhoon and Ocean Forecast Center will make live analysis, situation forecast, coastal area forecast, offshore area forecast, distant sea area forecast, maritime bulletin, and marine weather bulletin based on various locally monitored data. , marine weather warning and other products, and released through websites, television, radio and other media.
The seemingly trivial work is extremely important, testing the ability of grassroots meteorologists to grasp the weather according to local conditions.
During the impact of "Siamba", under the wings of the typhoon, which has an impact range of thousands of kilometers, there are also hidden tornadoes with an active area of only a few kilometers, from appearing to disappearing for tens of minutes to hours.
They are scattered in Guangzhou, Foshan, Chaozhou, Shantou and many other places.
It is a problem worldwide to make accurate and timely forecasts and warnings for these destructive "little men".
The meteorological department made an attempt - at 14:30 on July 4, the Foshan Meteorological Observatory issued a special warning for tornadoes down to the town street: "It is expected that there may be tornadoes in the southwest of Sanshui, Yundonghai, and Leping within two hours, please immediately Organizing defenses, especially owners of buildings with poor factory roofs and wind resistance, should organize evacuation as soon as possible.” This move bought valuable time for tornado response.
From observing the movement of large-scale weather systems such as subtropical highs, to capturing the generation and disappearance of extremely small-scale weather systems such as tornadoes, the birth of an early warning is inseparable from the accumulation of science and technology, the accumulation of experience, the close linkage of comprehensive observation systems, and the "important tool of the country" in numerical forecasting. "Put in.
In Zhang Tao's view, it is still necessary to reach every subtle corner of the service, and it is even more necessary to face the reality that it is impossible to predict 100% accurately, and still devote 100% of the courage and enthusiasm to the heart.
(Our reporter Cui Xingyi, our correspondent Liu Zhao)