Disaster Risk Reduction

Early warning information on
extreme events
Yoshiji Yokote, Director, Climate Prediction Division, Global Environment and Marine Department,
Japan Meteorological Agency

As recognized by the High-Level Taskforce on the Global
Framework for Climate Services (GFCS), people aroundthe world are affected by climatic conditions. This isparticularly the case with extreme weather and climate events,
which represent fundamental risks to climate-sensitive sectors.
In this regard, early warning of extreme events, including
periods of very high or very low temperatures, should be positioned as an important element in climate risk management. InJapan, there is demand for such information with a higher levelof user-friendliness in the agricultural sector to complement thedevelopment of effective measures against extreme
temperatures. Other sectors, including those ofhealth and energy, also require such information
due to the high risk of heatstroke and possible
power shortages caused by the increased use of air
conditioners in hot summer conditions.
The Japan Meteorological Agency (JMA) has a long
history of providing climate information, including
climate monitoring, seasonal forecasts, El Niño moni-

An EWIEW map issued on 30 July 2010. EWIEW is in effect in the red and blue areas (with a 30 per cent or more probability of very high or low seven-day
mean temperatures respectively). The box on the right shows text information issued for the Tohoku region (originally in Japanese)
Source: JMA[ 151 ]

Disaster Risk Reduction

toring and outlooks, and climate change projections. Until recently,
however, no climate information was supplied to specifically urge
the implementation of appropriate measures against high temperatures and other extreme events. Based on the increased skill of
seasonal forecasts and the above-mentioned social demand, JMA
therefore commenced the operational provision of Early Warning
Information on Extreme Weather (EWIEW) in March 2008 withthe aim of contributing to meteorological risk management inclimate-sensitive sectors. EWIEW is a probabilistic forecast highlighting the possibility of extreme events (such as very high or lowtemperatures) from one to two weeks ahead, and is issued to 11
regions in Japan.
EWIEW is provided in a number of ways. JMA makes theinformation widely available on its website1 in map, table andtext format indicating current nationwide issuance, and its local
offices issue EWIEW in text form within their areas of responsibility. In addition to information for use by the general public
on the website, EWIEW is also sent directly to national andlocal governmental organizations, media providers and private
weather-related companies so that they can broadcast the warnings themselves and/or prepare and issue information tailored tousers’ needs. For example, local governments may send messages
to farmers urging them to take measures against potential damage
from high temperatures.
Scientific basis
JMA operates the Ensemble Prediction System (EPS) for one-monthforecasts, using the Atmospheric Global Circulation Model, which
provides one-month numerical prediction data on temperature andother conditions. EWIEW is based on predicted data for regionalscale seven-day mean temperatures (T7d) in individual regions foreach day during periods of 5-14 days ahead. When a high probability(30 per cent or more) of a very high or very low regional-scale T7d
anomaly is predicted for one or more regions of Japan, JMA issues
EWIEW including:• Estimates of predicted temperatures meeting the criteria for
EWIEW issuance• The relevant duration, region and a brief message on the possible
social impacts of such high/low temperatures• The predicted probability of the expected condition occurring• Details of expected general weather conditions considered likely
to induce extreme climate situations.
Criteria for announcing the probability of very high or low
temperatures in EWIEW are calculated for each region using
JMA’s historical records of regionally averaged observed T7dvalues covering the 30-year period from 1981 to 2010. The criteria for very high and very low are the 90th and 10th percentiles

Probability of predicted seven-day mean temperature anomaly forfive categories for 4-10 August 2010, issued on 30 July for theTohoku region (originally in Japanese)of these historical records, respectively. On Tuesdays
and Fridays, JMA predicts whether temperatures willreach these criteria for each region and issues EWIEW
accordingly. If an expected criterion is not met, theagency issues information to notify of a change in its
outlook and reports on the progress of temperature
conditions since the latest EWIEW.
JMA roughly estimated the skill of EWIEW based on
3,600 cases for all regions in Japan from March 2008
(when EWIEW was first issued) to January 2011. For
the categories of very high and low temperatures, thehit ratios (that is, the number of occurrences of thepredicted phenomenon against the number of EWIEW
issuances) were 62 per cent and 57 per cent respectively.
While there is certainly room for improvement in theserates, the information is well received and appreciatedby various user sectors.
In addition to the four elements of EWIEW listed
above, JMA also provides detailed probabilistic prediction products for individual regions through the same
website independently of EWIEW issuance. These products show the scientific basis of EWIEW and provide
users with information on probabilities within the rangeof their own threshold values. The products are:• Daily tables of predicted T7d anomaly probabilities
in five categories (very high, high, normal, low, andvery low)
• Time sequences of these probabilities• Cumulative probability functions (CPFs) andprobability density functions (PDFs) of predicted
T7d anomalies.
These data are provided not only for the 11
EWIEW regions but also for 152 stations where
JMA performed observations from 1981 to 2010.
The information is calculated using both numericalprediction data from EPS and regression coefficients
estimated from hindcast experiments (re-forecasts)
conducted using the same EPS for the 30-year period
1981-2010. The skill levels of these products wereevaluated using hindcast experiment data and were
found to be satisfactory in terms of probabilistic
prediction metrics such as Brier skill scores. CPF
and PDF graphs are considered to have high potential
for possible future customized use of the scientificbasics used to produce EWIEW. For example, JMA
regularly provides the energy (electric power supply)
sector with information on the most likely predicted
T7d value together with more tailored information
covering the period one week ahead, which can be
estimated from its graph-form representation. Using
this newly available data, operators in the sector can
now estimate electric power demand for the coming
two weeks more efficiently and reasonably.
Use of EWIEW
EWIEW is expected to be used in a variety of fields
in addition to its current main user sectors of agriculture and health. In one notable case, the information

Source: JMA[ 152 ]

Disaster Risk Reduction

the use of EWIEW in other sectors, and operators
in various fields are expected to use the probabilistic prediction products provided on the JMA website
in their climate risk reduction activities. An exampleof this may be the use of the information in creatingplans for sales of commodities, which are sensitive toclimate conditions. CPFs and PDFs are expected tosupport next-generation forecasting that will advise
users of the probability of temperatures moving above
or below their self-set threshold values.
JMA is currently working to address four major challenges regarding EWIEW:

Cumulative probability function (CPF) and probability density function(PDF) of predicted T7d anomalies for 4-10 August 2010, issued on 30
July for Tokyo. The horizontal axis shows the T7d anomaly. The blue andgreen lines show the CPF and PDF for the prediction, while the yellowand pink lines show those for the occurrence of climatology values. Users
can change the critical value (the light-blue line) on the website to see

Dissemination of EWIEW and strengthening of related
interpretive activities
EWIEW is not yet widely known in Japan. As manypotential users may be able to make good use ofsuch information in their decision-making activities,
JMA is seeking and exploring further opportunities
for dialogue with such users in order to interpret thecharacteristics and usage of EWIEW. The provisionof briefings to broadcasting-organization meteorologists and members of the press is also important. Such
activities are expected to support the dissemination ofEWIEW in Japan.

the cumulative probability applicable to the area shaded in light blue
(originally in Japanese)
Source: JMA

led local agricultural organizations in Japan’s northern Tohoku
region to provide local farmers with guidance in relation to an
extremely high-temperature event in April 2008. The Sendai
District Meteorological Observatory responsible for the Tohoku
region issued successive EWIEW on high local temperatures on 8,11, 15, 22 and 25 April 2008, advising attention to farm productmanagement. In response to the EWIEW issued on 8 April, theAomori Prefectural Government in Tohoku issued special information for agricultural production on 11 April calling for frequentventilation in greenhouses to avoid poor germination of rice crops,
vegetables, flowers and ornamental plants due to soaring temperatures. The prefectural governments of Akita, Miyagi and Yamagata
in Tohoku also called for similar measures against predicted hightemperatures. Farmers use such special information to implement
appropriate field-crop management techniques as necessary.
EWIEW is also efficiently used in the health sector. When very
high temperatures are predicted and EWIEW is issued, relevant
local governments inform the public of the increased potential riskof heatstroke as well as efficient countermeasures to be taken. As
heatstroke can be prevented by appropriate behaviour, such caution
is considered highly effective and important. Schoolteachers also
use EWIEW to give appropriate guidance to pupils.
Future issues
In the last four years since JMA started providing EWIEW operationally, a number of governmental agricultural organizations inJapan have leveraged the information in their activities to provide
farmers with agricultural technical guidance. JMA also promotes[ 153 ]

Addition of more meteorological elements to EWIEW
To complement the temperature information alreadyprovided, JMA is currently considering the additionof other meteorological elements as targets of prediction. In terms of prediction skill and the impact ofsuch information on society, JMA plans to add dataon expected snowfall for the Sea of Japan side of thecountry in winter.
Improvement of prediction techniques
To support better prediction of extreme events withgreater accuracy, there is a need to develop and improveprediction tools and techniques such as the numericalatmospheric model and ensemble prediction techniques, application methods including calibration ofnumerical prediction results based on hindcast experiments, and approaches to downscaling.
Provision of seamless weather/climate information
to users
Seamless information on weather and the climate will
help users to prepare and take countermeasures using
EWIEW in combination with analysis of current climate
conditions and weekly forecasts.
In response to these challenges, JMA engages in
activities in collaboration with research organizations on the user side with the aim of producing
user-friendly climate information that supports decision-making. One such activity is a pilot project topromote the use of climate information in the agricultural sector in collaboration with Japan’s National
Agriculture and Food Research Organization Tohoku
Agricultural Research Center.