Part 1. What are Long-Term Forecasts? JWA’s Proprietary “2-Year Long-Term Weather Forecast” and Its Business Applications

2025.06.30

Weather-related risks are increasing globally.
In Japan, the highly volatile weather patterns shaped by the country’s unique topography make the use of accurate weather forecasts essential for successfully conducting businesses. In particular, long-term forecasts play a vital role in business planning and strategic decision-making.

This article explains the proprietary extended long-term weather forecasting technology developed by Japan Weather Association (JWA), and Part 2 introduces its applications.
Part 2. What are Long-Term Forecasts? JWA’s Proprietary “2-Year Long-Term Weather Forecast” and Its Business Applications

Key Points of This Article

• Due to its unique topographical features, Japan experiences extremely volatile weather, making the use of weather forecasts essential for business in the Japanese market.
• In particular, long-term weather forecasts are necessary for production and procurement strategies, annual business planning, and medium- to long-term risk management.
• Japan Weather Association was the first in the weather industry to develop a proprietary extended long-term weather forecast (2-year long-term weather forecast.)
• This 2-year long-term weather forecast provides not only trend information but also quantitative data, making it applicable to concrete strategic planning.

1. Introduction: Weather Forecast Periods and their Business Applications

Climate change and extreme weather are increasing weather-related risks worldwide.

Japan in particular, is situated on the eastern edge of the Eurasian continent, and due to its unique topography, it experiences extremely volatile weather patterns. As a result, the use of weather forecasts is indispensable for business planning, executing, and risk management in the Japanese market.
For characteristics of Japanese weather: Why Is Japan’s Weather So Difficult to Forecast? ―How the Four Seasons and Topography Create Weather Complexity and Affect Businesses―

Weather forecasts have different characteristics depending on the forecast period. The table below summarizes typical forecast periods, forecast targets, and examples of business applications.

As the forecast period extends, it becomes increasingly challenging to provide detailed predictions. Forecasts therefore tend to shift from quantitative figures to more qualitative trends.

2. What Are Long-Term Forecasts? — General Long-Term Forecasts and Business Applications

In general, long-term weather forecasts exceeding one month tend to be less accurate and typically provide broad-area statistical probabilities as qualitative data.

While probability forecasts can help identify early signs of risk, they often fall short of offering the level of detail needed for confident, informed business decision-making. Moreover, since long-term forecasts differ significantly from the short- and medium-term forecasts people are familiar with, businesses may struggle to apply them effectively.

That said, in areas such as business planning, production and procurement strategies, new product development, and long-term risk management, accurate forecasts of future conditions can lead to increased sales and reduced costs.

For “highly accurate future forecasting” in business, high-accuracy long-term weather forecasts are vital. Part 2 highlights its applications in business.

3. JWA’s Extended Long-Term Forecast: “2-Year Long-Term Weather Forecast”

With the guidance and collaboration from Professor Hiroaki Ueda of the University of Tsukuba, JWA has developed the first “2-Year Long-Term Weather Forecast” technology in Japan’s weather industry.

The “2-Year Long-Term Weather Forecast” has three key features that address the challenges of conventional long-term forecasts.

3-1. A Proprietary Forecasting Method with Longer Lead Times and Improved Accuracy Compared to Conventional Long-Term Forecasts

With the guidance and collaboration of Professor Hiroaki Ueda of the University of Tsukuba, Japan Weather Association has spent four years developing a new machine learning-based seasonal forecasting method for Japan that includes indicators such as convective activity and sea surface temperatures in tropical and subtropical regions that are highly correlated with Japan’s weather.

As a result, it is now possible to forecast unusual weather conditions that were previously considered difficult to predict—such as extremely warm temperatures during cold seasons or record-breaking summer heat—more than a year in advance.

Forecast accuracy has also improved significantly. Compared to the conventional method, which offers forecasts up to six months ahead, this new approach has reduced the forecast error at the six-month lead time by up to 40%.

3-2. Quantitative forecasts available by month and region, including weather elements beyond temperature

The “2-Year Long-Term Weather Forecast” provides specific forecast values on a regular basis. These forecasts can be incorporated into existing systems and tools.

In addition to nationwide averages, forecasts are available at individual regional levels, supporting production and procurement planning tailored to specific areas.
Furthermore, while conventional long-term forecasts generally focused only on temperature, the two-year long-term weather forecast provides quantitative forecasts of multiple weather elements beyond temperature. It also includes forecasts of the number of approaching typhoons and the timing of the end of the rainy season well in advance.

In addition to standard weather elements, information such as the start and end of the rainy season and typhoon activity enables planning that reflects key summer trends in Japan.

3-3. Information provided through data and reports

In addition to providing quantitative data, JWA also offers services and consulting that include seasonal insights and other qualitative information.

Rather than just delivering the data, JWA also assists in how to apply it and respond to questions and concerns. Forecasts can be customized by region and indicators.

This “2-Year Long-Term Weather Forecast” is already being utilized in industries such as energy and apparel.
Specific business use cases are introduced in Part 2.

4. Conclusion: More Accurate Long-Term Forecasts Enhance Business Value

Weather is one of the few areas where future conditions can be predicted using physical models. This predictive capability is highly valuable for businesses, as weather impacts a wide range of industries.

In Japan, where weather patterns are highly volatile, high-accuracy long-term forecasts are essential for both preparedness and the effective utilization of weather information.
The Japan Weather Association’s “2-Year Long-Term Weather Forecast” helps transform an uncertain future into one that is strategically manageable and plan-ready.

If you are interested in the “2-Year Long-Term Weather Forecast” or JWA’s advanced forecasting and consulting services, please contact us via [Contact Us].