As spring approaches in Japan, the country's weather forecasters face one of their biggest missions of the year: predicting exactly when the famed cherry blossoms will bloom Photo: AFP/File
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The art and science of Japan's cherry blossom forecasting

17 Comments
By Natsuko Fukue

As spring approaches in Japan, the country's weather forecasters face one of their biggest missions of the year: predicting exactly when the famed cherry blossoms will bloom.

Japan's sakura or cherry blossom season is feverishly anticipated by locals and visitors alike. Many tourists plan their entire trips around the blooms, and Japanese flock to parks in their millions to enjoy the seasonal spectacle.

"People pay more attention to the cherry blossom season than any other flower in Japan," Ryo Dojo, an official of the statistics unit at the Japan Meteorological Agency, told AFP.

The most basic element of predicting when the delicate pink and white petals will begin to unfurl is a large data set of temperatures. That's because the flowers will come earlier if temperatures rise quickly in spring, Dojo said.

Conversely, if temperatures in the autumn and winter period are higher than usual, the blooms can end up being delayed. Extreme weather can affect the trees too, with unusual patterns in 2018 prompting some blossoms to appear in October, well before the usual season.

In general, blooms begin as early as March in southern Kyushu and appear as late as May in northernmost Hokkaido.

In a bid to improve its forecasts, some outfits have started crowdsourcing data, including Weathernews, a firm in Chiba near Tokyo. It relies on photos of buds sent in regularly by 10,000 citizens across the country who are registered on the company's website and app.

"Cherry blossom forecasting is impossible for us without this system," spokeswoman Miku Toma said.

The company launched what they call the "sakura project" in 2004, signing up members who choose their own cherry tree and send pictures of its buds to the firm at regular intervals.

"We realized we could see the details of how buds grow thanks to the pictures sent to us," Toma said. "So we decided to incorporate the project to help predict blossoms."

Just observing the bud can give surprisingly accurate information about how far the flower is from full bloom. A sakura bud still a month from blossoming will be small and firm, but after 10 days, the tip turns slightly yellow-green, and then a darker green part emerges.

When the tip of the bud turns a faint pink, it's just a week until bloom-time.

Thanks to the project, Weathernews has accumulated data from two million reports on cherry flower buds in the past 15 years, which it uses to increase the accuracy of its forecasting. It also incorporates weather data collected from its own observation devices across Japan -- 13,000 locations in total, 10 times more than the official weather agency has.

Weathernews employees also call around 700 parks regularly to check the growth of cherry flower buds. The company and other forecasters also employ mathematical models and algorithms.

Otenki Japan, a forecaster run by a subsidiary of precision-equipment manufacturer Shimadzu, even began using artificial intelligence to predict cherry blossoms in 2018.

The forecasts are not only for flower fans, but reflect the fact that sakura season is big business in Japan. Cherry blossoms symbolize the fragility of life in Japanese culture as full blooms only last about a week before the petals start falling off trees.

And in that period and the preceding weeks, shops will pack their shelves with sakura themed merchandise. Pink and white blossoms seem to decorate everything from beer cans to sakura-flavored chips and flower-themed candy. The season is traditionally celebrated with hanami, or viewing parties, in cherry blossom hotspots, with picnics organized beneath the trees.

The season is also considered one of change, as it marks the start of the new business year, with many university graduates starting their first full-time jobs and older colleagues shifting to new positions.

Japan's Meteorological Agency stopped forecasting cherry blossoms in 2010, after more than five decades, saying other organizations were now making predictions with sufficient accuracy. The agency does, however, still declare the official start of cherry blossom season by monitoring 58 so-called barometer trees.

The trees are at locations across the country, and the precise locations are considered a closely-guarded secret. One of them in Tokyo, however, is known to be at the Yasukuni Shrine.

From the beginning of March, inspectors visit the barometer trees once a day, with the trips increasing to twice daily as blossoming nears, Dojo said.

"We check flowers with our own eyes. And we announce the blossoming if five or six flowers appear," he added.

© 2019 AFP

©2019 GPlusMedia Inc.


17 Comments
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Do any other countries have cherry blossoms?

0 ( +4 / -4 )

@Chip Star - USA has them because gifted from Japan many many years ago.

5 ( +6 / -1 )

Don't' get me wrong, I think they are beautiful and I understand the cultural implications, but me thinks it's much ado about nothing.

1 ( +10 / -9 )

THIS is what it's really all about:

*And in that period and the preceding weeks, shops will pack their shelves with sakura themed merchandise. Pink and white blossoms seem to decorate everything from beer cans to sakura-flavored chips and flower-themed candy.** The season is traditionally celebrated with hanami, or viewing parties, in cherry blossom hotspots, with picnics organized beneath the trees.*

Cherry blossoms are beautiful, but over-hyped/marketed heavily; they probably sell well, because the tree thrives all over Japan. I do enjoy the temperate weather, and beer, though.

2 ( +6 / -4 )

I remember well when JMA stopped forecasting as private agencies (in the article) were more on top of it through hteir extensive data collecting system. At first they resisted because they were The Authorative Agency.

And in my neck o the woods, only recently local NHK has stopped (I think) officially announcing the start of the cherry season based on when an historical tree comes into blossom.

It got to the point over the last decade or so, where many citizens were already flocking to see the first blossoms at many sites - ahh the connectivity of the internet - but NHK hadn't announced, it so it was still "Not Sakura Season".

Many quietly chuckled over that for a long time.

1 ( +2 / -1 )

Do any other countries have cherry blossoms?

Yes of course! Some nice locations:

Vancouver, British Columbia in the Queen Elizabeth Park.

Macon, Georgia.

Bonn, Germany, Alstadt Cherry Festival.

Jerte Valley, Spain.

St. Louis, Missouri near the Gateway Arch.

Sceaux, Hauts-de-Seine, France. Paris has also its fair share of cherry trees.

Vilnius, Lithuania.

Jinhae, Changwon, South Korea, Jinhae Gunhangje festival.

London England, Kew Gardens.

Brooklyn, New-York, Botanic Garden.

Edinburgh, Scotland, The Meadows park.

Curitiba, Brazil, Botanical Garden.

Seattle Washington, University of Washington,

Shanghai, China, Shanghai Campus festival.

Teipei, Taiwan, Yangmingshan National Park.

San Francisco, California, Northern California Cherry Blossom Festival.

Stockholm, Sweden, The King's Garden.

Boston, Massachusetts, Charles River Esplanade.

Washington, D.C., National Cherry Blossom Festival.

Etc, etc....

6 ( +8 / -2 )

Cherry blossoms are beautiful, but over-hyped/marketed heavily

They are latched onto by marketers, but sakura have a longer history than that too.

Any amateur student of Zen can tell you the sakura symbolizes the impermanence or fleeting nature of beauty and life.

0 ( +1 / -1 )

And in the fullness of time, after the blossoms and bees, presumably you get the fruit, cherries galore one would assume, so are there not many many products made of the cherries filling the shelves and exported around the World ?

-1 ( +0 / -1 )

Will G - they are "Ornamental Cherries" ie non-fruiting varieties.

The fruiting varieties are called Sakuranbo and are quite common, but nothing like the extensive plantings of Sakura.

While Sakura in full blossom is very nice, the real spring event I wait for, is the new, fresh vivid green that carpets the once dull dreary monotones of a deciduous winter.

2 ( +3 / -1 )

in the fullness of time, after the blossoms and bees, presumably you get the fruit, cherries galore one would assume

One would assume, wouldn't one? Apparently though (I've been told) the cherry trees that produce the prettiest blossoms don't actually produce very much fruit, or very tasty fruit. Hence the lack of cherries filling the shelves, and the high price of the few little jewels that do make it to the shops.

Sakura-based foods tend to make use of the petals and leaves (eg sakura-mochi), not the fruit.

-1 ( +0 / -1 )

It's a shame the flowers bloom so short and are so weak. One rain shower and everything is gone. But I love hanami and everything around it.

0 ( +2 / -2 )

Don't they just use growing degree days or corn heat units to forecast the blossoms? Really easy to pull CHU off of all the weather stations and have a computer auto-update the forecast throughout the day.

-1 ( +0 / -1 )

but me thinks it's much ado about nothing.

I can understand it may add a bit of color and brighten up the dreary landscape of city dwellers, but when you live in the country and have trees all around you all the time its just another day in the season of things.

0 ( +1 / -1 )

The art and science of Japan's cherry blossom forecasting

Right, now please explain why so many places throughout Japan had a burst of cherry blossoms opening last year at the end of October and early November?

Guess your "AI" needs more intelligence!

-2 ( +0 / -2 )

And in the fullness of time, after the blossoms and bees, presumably you get the fruit, cherries galore one would assume, so are there not many many products made of the cherries filling the shelves and exported around the World ?

Different type of cherry tree altogether produces cherries. These don't.

1 ( +3 / -2 )

Do any other countries have cherry blossoms? yes they do, and in the UK we have them as well, but not in the abundance like they have in Japan, we have one or two here and there mainly in peoples back gardens or one on the front, which does not have the visual impact unlike Japan. I am sure there is a small group in the local park as well.

0 ( +0 / -0 )

Look out the window, don’t watch NHK weather news. My plum tree is in 30 % blossom today.

-1 ( +0 / -1 )

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