● More rain than expected, no rain but heavy rain warning

On August 6, the Meteorological Administration predicted that 50 to 100 mm of rain would fall in Gwangju from August 7 to August 8. However, in fact, during August 7-8, a lot of rain of 516mm poured in Gwangju, and flood damage continued.

On August 4th, the Meteorological Administration issued a heavy rain warning in Seoul all day. Heavy rain alarms are issued when 3 hours of precipitation is 90mm or more or 12 hours of precipitation is expected to be 180mm or more. In other words, when heavy rain is expected within 12 hours, a heavy rain warning should be issued. From this year on, the Meteorological Administration has divided the heavy rain warning zone in Seoul into four areas: △west north, northeast, southwest, and southeast. On August 4th, a heavy rain warning was issued in the northwestern part of Seoul. However, the rain that fell on the official observatory of the Meteorological Administration in Jongno, the northwestern region of Seoul, was 3.9mm. As a result, the heavy rain alarm in the northwestern part of Seoul was issued incorrectly.

Even if the forecast is not correct, it should have delivered the weather conditions as close to the actual situation to the citizens as possible using the heavy rain warning.

Weather forecasts clearly have scientific limitations. By the way, have we reached that scientific limit? Let's compare it to Japan, where the weather is the closest to us.

● Rain forecast accuracy, 66% for Korea and 73% for Japan

The weather forecast accuracy is 92.7% in 2019. Many people think that it is higher than expected, but this figure includes sunny weather forecasts. Forecast accuracy, including sunny days, is advantageous in countries with more sunny days. In a dry country with only 30 days of rain a year, forecast accuracy will be over 90% even if the weather authorities forecast the weather as'clear' throughout the year.

So what we need to look at is'non-forecast accuracy'. Let's take a look at the probability of detection of rainfall, which indicates the accuracy of the rain forecast. To get the POD, you need to calculate the number of days it rained, that is, the day when the rain forecast was correct, and the day when the rain forecast was not performed. The calculation method of POD proposed by the World Meteorological Organization (WMO) is as follows.

POD = (Rain Forecast Right) ÷ (Rain Forecast Right + Rain Forecast No Rain

) Looking at Korea's last three years' rain forecast accuracy (POD) value, it is an average of 66%. It means that the rainy weather is set 2 out of 3 times. This figure is probably close to the accuracy of the forecast you're experiencing. It showed an increase of 62% in 2017, 66% in 2018, and 70% in 2019 for 3 years.

Japan is using the term capture rate. Japan's capture rate, POD, or Japan's non-forecast accuracy has averaged 73% over the last three years.

Weather forecasts are said to have scientific limitations, but Japan's non-forecast accuracy is 7% higher than that of Korea. It is said that the forecasting ability of the Korea Meteorological Agency is still insufficient.
● Increased forecast accuracy? Meteorological Agency reliability is rather reduced

The challenge facing the Meteorological Agency is not just forecast accuracy. The problem is reliability. The Meteorological Administration conducts a survey on the level of satisfaction of the people in the meteorological service every year to investigate the public's trust in the Meteorological Administration. The general public's confidence in the Meteorological Agency has declined over the past three years to 70.8 points in 2017, 70.3 points in 2018, and 69.3 points in 2019.

There are parts that I don't understand. As mentioned earlier, the accuracy of precipitation forecasts by the Meteorological Administration has steadily increased from 2017 to 2019. There is a paradoxical situation in which the accuracy of precipitation forecasts increases, but the reliability of the meteorological agency decreases.

In fact, in the process of reporting the forecast accuracy of the Japan Meteorological Agency, I think I know the answer to some extent. The problem of the Korea Meteorological Administration is poor information disclosure and one-way communication.

● Japan reveals the number of incorrect forecasts and reasons in detail When

I entered the website of the Japan Meteorological Agency, I could clearly feel the difference in the amount of information. Our Meteorological Agency only discloses the accuracy of the forecast, one number per month.

Shall we look at the Japan Meteorological Agency website? Accuracy statistics have been analyzed for all forecasts such as forecast accuracy, probability of matching sunny days, probability of matching rainy days, probability of missed forecast, accuracy of 24-hour forecast, accuracy of 3-day forecast, accuracy of 1-week forecast, etc. It.

It is not possible to know the accuracy of the forecast in Korea at any point in time. Moreover, Japan was not only disclosing the accuracy of forecasts for each region in detail. In the case of Okinawa, the forecast accuracy is slightly lower than the average, but it was explained one by one what makes forecasting difficult for the region.


In Korea, the accuracy of the forecast in Seoul, the accuracy of Jeju Island, and the accuracy of Gangwon-do will all be different, but Korea only discloses one national average. I'm going to go to Tokyo in a week, but I think how well the weather forecast in Tokyo after a week was good, how well the forecast in Okinawa two days after, on average, and the Japanese people were getting this information.

Precipitation forecast accuracy is published by most meteorological agencies around the world. This is because the World Meteorological Organization WMO recommends disclosure of forecast accuracy. The person who accepts the information needs to know the accuracy of the information so that they can use it more efficiently and wisely.

However, the Meteorological Agency, whose forecast accuracy is lower than that of the neighboring country, lacks explanation. In particular, the public's credibility does not rise as only one-sided, principled answers are repeated about the past weather. Just because the weather is notified every hour does not mean good communication. In order to communicate with the people, you need to provide detailed information that the people will understand. If the people suffered discomfort due to a bad forecast, the reason should also be revealed in detail.

However, the Meteorological Agency said that whenever disbelief about forecasts erupts, "because of climate change", "summer is volatile", "weather forecasts have scientific limitations", "our forecast accuracy is very high in the international community. It is urgent to avoid controversy by saying, "There are more areas with forecasts."

It seems that the Meteorological Agency needs to analyze itself, starting from whether it is unilateral communication with unkind explanations, why the people's trust is declining backwards even though the forecast accuracy is increasing, and what other countries are taking.