Spring 2009

No. 16
Contents
El Niño Outlook (April – October 2009)

1

JMA’s Seasonal Numerical Ensemble Prediction for Summer 20092

Warm Season Outlook for Summer 2009 in Japan

4

Summary of Asian Winter Monsoon 2008/2009 - Extremely high temperatures in Asia

4

Unusual Major Stratospheric Sudden Warming Event from January to February 2009

6

Experimental Introduction of ITACS

6Tokyo Climate Conference - Better Climate Information for a Safe and Sustainable Society

7

El Niño Outlook (April – October 2009)
The NINO.3 SST is likely to become closer to normal inspring, and is expected to be near normal during summer. It
is likely that the current La Niña conditions will end in spring.
In March 2009, the SST deviation from the sliding 30year mean SST averaged over the NINO.3 region was -0.6°
C. The five-month running mean value of NINO.3 SST
deviations for January was -0.5°C. In March, SSTs wereremarkably below normal in the eastern equatorial Pacific,

while negative SST anomalies in the central part were
weaker than in February. Negative SST anomalies in theeastern part strengthened temporarily in early March before
gradually weakening again (Figures 1 and 3a). While positive subsurface temperature anomalies persisted in the western equatorial Pacific, negative anomalies in the central andeastern parts were weaker than in February (Figures 2 and3b). La Niña conditions have persisted, but have been following a weakening trend.

(a)

(a)

(b)

(b)

Figure 1 Monthly mean (a) sea surface temperatures (SSTs)and (b) SST anomalies in the Pacific and Indian Ocean sectors in March 2009
The contour intervals are 1˚C in (a) and 0.5˚C in (b). The baseperiod for the normal is 1971 – 2000.

Figure 2 Monthly mean depth-longitude cross sections of(a) temperatures and (b) temperature anomalies in theequatorial Pacific for March 2009
The contour intervals are 1˚C in (a) and 0.5˚C in (b). The baseperiod for the normal is 1979 – 2004.

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No. 16 | Spring 2009

It is possible that warm waters in the western equatorial
Pacific will propagate eastward and that the area of negative SST anomalies will contract in the months ahead.
JMA's El Niño prediction model predicts that the
NINO.3 SST will be near normal during the prediction period (Figure 4).

(a)

In consideration of the above factors, the NINO.3 SST
is likely to become closer to normal in spring and to be nearnormal during summer. It is likely that the current La Niña
conditions will end in spring.
(Ichiro Ishikawa, Climate Prediction Division)(b)

Figure 3 Time-longitude cross section of (a) SST and (b) ocean heat
content (OHC) anomalies along the equator in the Pacific Ocean
OHC is defined here as the vertical average temperature to a depth of 300
m. The base periods for the normal are 1971 – 2000 for (a) and 1979 –2004 for (b).

Figure 4 SST deviation outlook for NINO.3 as predicted by the El Niño prediction modelThis figure shows a time series of monthly SST deviations
for NINO.3 (5˚N – 5˚S, 150˚W – 90˚W). The thick linewith closed circles shows the observed SST deviation
values, and the boxes show the values predicted for the
next six months by the El Niño prediction model. Eachbox denotes the range into which SST deviation is expected to fall with a probability of 70%.

JMA’s Seasonal Numerical Ensemble Prediction for Summer 2009
In summer 2009, convection is predicted to be active in
the Asian monsoon region in general and inactive in the central part of the equatorial Pacific and the equatorial Atlantic.
In the Asian monsoon region, convection is expected to berelatively inactive to the east of the Philippines, which may
induce a weak northwestward extension of the North PacificHigh. However, these results should be interpreted with caution due to the insufficient reliability of data on the detailed
distribution of precipitation in the Asian monsoon region.

normal in the western part. The El Niño monitoring index
of the NINO.3 region, which is the deviation from the sliding 30-year mean SST averaged over the area, was -0.6°C,
and La Niña conditions have continued since winter2008/2009. According to the El Niño outlook, La Niña
conditions will end this spring and near-normal conditions
will persist this summer.
The SST anomalies used in JMA’s seasonal numericalensemble prediction system are shown in Figure 5. SSTs
are expected to be near normal from the central to easternparts of the equatorial Pacific, reflecting the termination of
the La Niña conditions. Above-normal SSTs are expected
widely in other regions.

1. Introduction
This report outlines JMA’s seasonal numerical ensemble
prediction for summer 2009 (June – August, JJA), which
was used as a prognostic tool in the Agency’s operational
warm-season issued on 23 April 2009. The prediction consists of 51 ensemble members with an initial date of 17
April 2009, and employs a two-tier method: first, global
SSTs are predicted using a combination of persistentanomalies, climatology and forecast using JMA’s El Niño
prediction model (an atmosphere-ocean coupled model),and the specific SSTs are then fed into an atmosphericmodel. Details of the prediction system and verification
maps based on 22-year hindcast experiments (1984 – 2005)
are available at http://ds.data.jma.go.jp/tcc/tcc/products/
model/index.html. Section 2 below presents the global SST
anomalies predicted, followed in Section 3 by a descriptionof the predicted circulation fields in the tropics and subtropics associated with these anomalies. Finally, the predicted circulation fields in the middle and high latitudes of
the Northern Hemisphere are explained in Section 4.

3. Circulation fields in the tropics and sub-tropics(Figure 6)
Above-normal precipitation is generally predicted for
the Asian monsoon region, and below-normal precipitation
is predicted in the central part of the equatorial Pacific andthe equatorial Atlantic. In the Asian monsoon region, remarkably above-normal precipitation is predicted around

2. SST anomalies
In March 2009, SSTs in the equatorial Pacific were below normal from the central to the eastern parts and above

Tokyo Climate Center

Figure 5 Predicted SST anomalies for JJA 20092

No. 16 | Spring 2009

the Bay of Bengal and New Guinea Island, while relatively
light precipitation is expected to the east of the Philippines.
However, it is possible that the heavy precipitation predicted around New Guinea Island may be overestimated.
Upper tropospheric velocity potential anomalies are expected to be negative (i.e. more divergent) from the Bay of
Bengal to the Maritime Continent, and positive (i.e. moreconvergent) around the central part of the equatorial Pacificand the equatorial Atlantic, reflecting the precipitation
anomaly patterns in the tropics.
In the upper troposphere, anti-cyclonic circulation
anomalies are predicted in the southern part of the EurasianContinent. Cyclonic anomalies are expected on the Northern Hemisphere side of the tropical Pacific and from East
Asia to the east of Japan. In the lower troposphere, cyclonic anomalies are predicted from the Arabian Sea toSoutheast Asia and from East Asia to the east of Japan, andanti-cyclonic anomalies are predicted in the east of the Philippines. These features imply that the Tibetan High isstronger than normal, especially in the western part, andthat the northwestward extension (to East Asia) of theNorth Pacific High is weaker. However, this may becaused by subdued convective activity in the east of thePhilippines and excessively heavy precipitation around
New Guinea Island.
4. Circulation fields in the middle and high latitudes of
the Northern Hemisphere (Figure 7)
Predicted 500-hPa height anomalies are generally positive in the mid-latitudes, while negative anomalies are expected to the east of Japan. Negative anomalies of sea levelpressure are predicted in the North Pacific region. However, these results should be interpreted with caution due tothe insufficient reliability of the extension of the North Pacific High.
(Masayuki Hirai, Climate Prediction Division)

(a)

(c)

(b)

(d)

Figure 6 Predicted atmospheric fields in the tropics and sub-tropics for JJA 2009 (ensemble mean of 51 members)(a) Precipitation (contours) and anomaly (shaded). The contour interval is 2 mm/day.
(b) Velocity potential at 200 hPa (contours) and anomaly (shaded). The contour interval is 2 x 106 m2/s.
(c) Stream function at 200 hPa (contours) and anomaly (shaded). The contour interval is 16 x 106 m2/s.
(d) Stream function at 850 hPa (contours) and anomaly (shaded). The contour interval is 5 x 106 m2/s.

(a)

(b)

Figure 7 Predicted atmospheric fields in the middle and high latitudes of the Northern Hemisphere for JJA 2009 (ensemble mean of 51 members)(a) 500 hPa height (contours) and anomaly (shaded). The contour interval is 60 m.
(b) Sea level pressure (contours) and anomaly (shaded). The contour interval is 4 hPa.

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No. 16 | Spring 2009

Warm Season Outlook for Summer 2009 in JapanFor 2009 summer in Japan, mean temperatures are likely
to be above normal or near normal in most regions. The
warm season and rainy season (Baiu) precipitation amounts
have no significant features for all regions.

the TCC website at http://ds.data.jma.go.jp/tcc/tcc/
products/japan/outlooks/outlook2t.html.
2. Outlook backgroundLong-term upward trends are clear in summer (June –August) mean temperatures nationwide. The zonal mean
tropospheric temperature calculated from thickness averaged over the mid-latitudes of the Northern Hemisphere(30 – 50°N) also tends to be above normal.
Positive anomalies in 500-hPa height and 850-hPa temperature are predicted over the Asia-Pacific area. Considering that these positive anomalies will cover the AsiaPacific area, the summer mean temperature base is expected to be higher than normal. Convective activity is
predicted to be positive over the Bay of Bengal and New
Guinea Island, and negative near the Philippines. On average, convective activity will be positive over Asianmonsoon areas. Negative convective activity near
the Philippines may lead to weaker-than-normal
strength in the North Pacific High around Japan.
However, as described in the previous article, theprediction skill for convective activity over Asianmonsoon areas is not sufficient, and SSTAs in thewestern Pacific have been positive in recent years.
Convective activity near the Philippines is therefore
expected to be higher than the prediction, and thestrength of the North Pacific High around Japan is
expected to be near normal. On the other hand,
positive sea-level pressure anomalies are predictedaround the Sea of Okhotsk, suggesting the possibility of the Okhotsk High appearing and bringing cool
air to the region around northern Japan.

1. Outlook summary
JMA issued an outlook for the coming summer overJapan in February, and updated it in March and April.
Mean temperatures are expected to be above normal witha 50% probability in western Japan and Okinawa/Amami,
and near normal or above normal with a 40% probability
each in eastern Japan (Figure 8). For all regions, the precipitation amount outlook for the warm season and rainyseason (Baiu) has no significant features. Probabilistic
forecasts of mean temperatures and precipitation amounts
for the whole summer, as well as precipitation amounts in
the Baiu season for each region of Japan, are available on(Noriaki Watanabe, Climate Prediction Division)
Figure 8 Probabilistic Forecast of Seasonal Mean Temperatures forsummer (June – August 2009)

Summary of Asian Winter Monsoon 2008/2009- Extremely high temperatures in Asia
Surface climate conditions
In winter 2008/2009, most Asian countries experienced
higher-than-normal temperatures (Figure 9).
Figure 10 shows extreme climate events from December 2008 to February 2009. Extremely high temperatures
were observed around the Indian subcontinent in December
and January. Furthermore, extremely high temperatures
were observed not only around the Indian subcontinent but
also in other Asian countries in February. The former was
thought to be caused by a meander in the Asian subtropicaljet around the Indian subcontinent, while the latter is attributed to a significant northward shift in the westerly
jet from its normal position (see the next section).
Meanwhile, extremely low temperatures were observed
around the Indochina Peninsula in January, and extremely
heavy precipitation was observed around the South China
Sea in January and February.

Figure 9 Seasonal temperature anomalies for winter(December – February) 2008/2009
Anomalies are deviations from the normal (i.e., the 1971 – 2000
average). The contour interval is 1°C.

(Takafumi Umeda, Climate Prediction Division)

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No. 16 | Spring 2009

December 2008

February 2009

January 2009

Figure 10 Extreme climate events from December 2008 to February 2009

Conditions of convective activity and atmospheric circulation
The winter monsoon in Southeast Asia was stronger
than normal, and convective activity was enhanced aroundthe South China Sea and the Philippines (Figure 11). Coldsurges periodically affected Southeast Asia except in February, bringing extremely low temperatures to the Indochina
Peninsula in January. These features were consistent with
La Niña conditions.
Meanwhile, the winter monsoon in East Asia was
weaker than normal because of a surface pressure anomaly
pattern in which both the Siberian high and the Aleutian
low were weaker than normal (Figure 12). These conditions were dominant in February, when the westerly jet
shifted significantly northward from its normal position(Figure 13) and the polar vortex was located in eastern Siberia (Figure 14). Moreover, the subtropical jet meandered,and the phase of a ridge stayed over the Indian subcontinent
in December and January (Figure 15), bringing extraordinarily high temperatures to India.

Figure 13 Latitude-time cross section of 250-hPa zonal
wind speeds (shaded) and their normals (contours) averaged from 60˚E to 150˚E
The data here are seven-day running-mean values, with eachdate indicating the start of the seven-day period .

(Norihisa Fujikawa, Climate Prediction Division)

L
L

L

L

H

Figure 14 Monthly mean 500-hPa height (contours) andtheir anomalies (shaded) in February 2009

Figure 11 Seasonal mean OLR anomalies (shaded)
and 925-hPa stream function anomalies (contours)

H
L

Figure 15 Time-longitude cross section of 200-hPa stream
function anomalies averaged from 15˚N to 30˚N
The data here are seven-day running-mean values, with eachdate indicating the start of the seven-day period.

Figure 12 Seasonal mean SLP (contours) and theiranomalies (shaded)

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No. 16 | Spring 2009

Unusual Major Stratospheric Sudden Warming Event from January to
February 2009
An unusual major stratospheric sudden warming event
took place from January to February 2009. The propagationof the planetary wave of zonal wave number 2 during winter2008/09 was the strongest seen in the past 30 winters.

Then, zonal winds reversed from westerlies to easterlies in
mid-latitudes, and easterlies expanded from 50°N to theNorth Pole. The polar vortex split clearly into two in late
January (Figure 17), and the reversed zonal wind direction
was observed throughout the stratosphere to the north of
60ºN in early February. Accordingly, this event was identified as a major SSW in line with WMO’s classification.
A poleward increase in temperature was clearly observed to
the north of 60ºN. Consequently, the reverse of zonal mean
zonal winds continued until the end of February 2009.
More details on this major SSW event are available on the
TCC website at http://ds.data.jma.go.jp/tcc/tcc/news/
press_20090528.pdf.

The Climate Prediction Division (CPD) of JMA routinely monitors stratospheric circulation, focusing on
Stratospheric Sudden Warming (SSW) events. STRATALERT reports are issued via WMO’s Global Telecommunication System every day during periods of SSW.
The 30-hPa temperature in the polar region was around-83˚C at the beginning of January, before a rapid increase in
air temperature reaching above -35˚C was observed in midJanuary (Figure 16). The CPD began to issue STRATALERT reports for a minor SSW on 19 January 2009.

(Yayoi Harada, Climate Prediction Division)

Figure 16 Time series of temperatures at 30-hPa
level over the North Pole in winter 2008/2009
The black line shows temperatures for winter 2008/2009.
The gray line shows the climatological mean.

Figure 17 10-hPa Geopotential height (contours) anddeviations from its zonal mean (shaded) for 22 – 26
January 2009
The contour interval is 240 m.

Experimental Introduction of ITACSJMA has developed a useful web-based tool for climate
diagnosis referred to as ITACS, which stands for Interactive
Tool for Analysis of Climate System. ITACS will enable
users not only to monitor current climate status but also to
analyze the complicated system that lies behind climaticconditions. An experimental version of ITACS will bemade available on the TCC website, which is intended foruse by National Meteorological and Hydrological Services
and related research institutes. For more details, including
application, please see http://jra.kishou.go.jp/itacs-info/tcc/
conditions.html.
The information available on ITACS includes climatological data such as JRA/JCDAS*1 as well as data on
ocean analysis, sea surface temperatures and monthly world
climate data from surface stations. The first three types areproduced by JMA. World climate data from surface stations are obtained from CLIMAT messages that JMA re-

Tokyo Climate Center

ceives via the GTS line, and OLR data are provided courtesy of NOAA. All available historical data archived by
JMA are used in ITACS, and daily data is updated a few
days after observation.
Figure 18 shows the main page of the ITACS tool. The
main procedure to create a chart of the user’s choice is verystraightforward, and involves simply choosing or setting
parameters for the chart or statistical analysis and clicking
the Submit button. Simple charts will be displayed within a
few seconds, and the results of statistical analysis will appear within a few minutes. Some graphical parameters for
GrADS can also be customized on this page. As shown in
Figure 19, regular plane charts as well as vertical cross sections, time cross sections, time series representations andanimations can be displayed with a number of ITACS axis
options. As an example chart, Figure 20 shows the distribution of correlation coefficients between SST and OLR.

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No. 16 | Spring 2009

In this way, it has become possible to statistically analyze
data using various methods such as correlation analysis,
regression analysis, composite analysis and significant testing without the need for troublesome computer programming.
*1 JMA and the Central Research Institute of ElectricPower Industry (CRIEPI) conducted a 26-year reanalysis
project referred to as JRA-25. Following the completion of
JRA-25, JMA also operates a real-time climatic assimilation system known as JCDAS. For details, please see
http://jra.kishou.go.jp/JRA-25/index_en.html.
(Shingo Ushida, Climate Prediction Division)

Figure 18 Top page of ITACS

Figure 20 Map showing the correlation between SST valuesin August around the Philippines (10˚N, 110˚E – 20˚N,
150˚E) and OLR in September

Figure 19 Time-longitude cross section of 200-hPa velocity potential (10˚S – 10˚N)

Tokyo Climate Conference - Better Climate Information for a Safe andSustainable Society
JMA will hold the Tokyo Climate Conference: Better Climate Draft Agenda
Information for a Safe and Sustainable Society in Tokyo, Japan, Monday, 6 July 2009
from 6 to 8 July 2009.
- Opening ceremony- Keynote speeches
This Conference will bring together representatives both
- Regional climate information: RCC and RCOF
from users and providers of climate information and ser- Best practices of climate information utilization invices as well as prominent scientists and experts on climatesocio-economic sectors
related matters. The Conference aims at identifying actions- International cooperation for enhancement of climate
and methods to develop an effective framework involving
services
users and providers to create user-oriented products andpromote their utilization, with a focus on the Asia-Pacific
Tuesday, 7 July 2009
region. The results of the Conference are expected to con- Working group discussion
tribute, as inputs from the region, to World Climate Confer- Summary of working group outcomesence-3 to be held in Geneva, Switzerland, from 31 August- Draft of Conference Statement
to 4 September 2009. In order to raise social awareness ofclimate information usage, an open symposium is schedWednesday, 8 July 2009
uled for the final day.
- Open symposium- Approval of Conference Statement(Kumi Hayashi, Tokyo Climate Center)
Any comments or inquiries on this newsletter and/or the Tokyo Climate Center (TCC), Climate Prediction Division, JMA
TCC website would be much appreciated. Please e-mail Address: 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan
to: tcc@climar.kishou.go.jp
TCC website: http://ds.data.jma.go.jp/tcc/tcc/index.html(Chief Editor: Kumi Hayashi)Tokyo Climate Center

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No. 16 | Spring 2009