April 2006

No. 4
Contents
El Niño Outlook (April 2006 - October 2006)

1

JMA’s seasonal numerical ensemble prediction for 2006 summer

2

Summary of Asian winter monsoon 2005/2006

3

Stratospheric major warming event in January 2006

5

TCC’s research and development activity

5

El Niño Outlook (April 2006 - October 2006)
The NINO.3 SST is likely to be close to normal during thelatter half of spring and this summer, and be around normal until mid-autumn in 2006. The current La Niña event islikely to dissipate during the prediction period.
In March 2006, negative SST anomalies were
widely found in the central and eastern equatorial Pacific (Figure 1). The SST deviation from the sliding
30-year mean SST averaged over the NINO.3 region
was -0.8°C for March 2006, and its five-month runningmean values have consecutively exceeded -0.5°C from
October in 2005 to January in 2006. In the subsurface
ocean temperature, positive-in-west and negative-ineast pattern, as have been found since January, were
found during March (Figure 2). The convective activities over the western equatorial Pacific were above
normal, and at the lower level of troposphere, easterly
wind anomalies continued over the central and westernequatorial Pacific during March (Figure 3). Current
atmospheric and oceanic conditions in the equatorial
Pacific are consistent with those during La Niña events.
In accordance with the eastward movements of thenegative subsurface temperature anomalies in the eastern equatorial Pacific, it is likely that warm waters in
the western equatorial Pacific start to migrate eastward.
On the other hand, easterly wind anomalies were predominant around the dateline during late March, andFigure 2 Depth-longitude cross sections oftemperatures (upper) and anomalies (lower)
along the equator in the Pacific Ocean for
March 2006
Base period for normal is 1987-2005.

Tokyo Climate Center

those lead to the considerations that it is unlikely to result in the
rapid increase of the SST anomalies in the central and easternparts.
The JMA's El Niño forecast model predicts that the NINO.3
SST will be close to normal during spring and summer, and be
above normal afterwards (Figure 4). Taking into consideration,
however, that the model tends to be biased toward positive in thelatter half of prediction period
under such conditions thatwarm waters are accumulated
in the western equatorial Pacific, it is expected that the
NINO.3 SST will be slightly
lower than the model prediction.
Judging from all theabove, NINO.3 SST is likely
to be close to normal during
the latter half of spring andthis summer, and be aroundnormal until mid-autumn in2006. The current La Niña
event is likely to dissipate Figure 1 Time-longitude cross section of SST anomalies along theduring the prediction period.
equator in the Pacific Ocean for(Yoshinori Oikawa, March 2006
Climate Prediction Division) Base period for normal is 1971-2000.

Figure 3 Zonal wind anomalies at
850 hPa along the equator for March
2006.
Base period for normal is 1979-1993.

1

Figure 4 SST deviation outlook for the
NINO.3 region by JMA’s El Niño forecast model
The red line with closed circles shows theobserved SST deviation, and the yellow
boxes show the predicted SST deviation
for the next seven months. Each box denotes the range of 70 % confidence.

No.4 | April 2006

JMA’s seasonal numerical ensemble prediction for 2006 summer
In 2006 summer, slightly active Asian monsoon except for the western North Pacific region is predicted by JMA’s seasonal numerical ensemble prediction system, but it is noted that the skill of Asian monsoon prediction is not so high that the results should be interpretedwith caution.
1. Introduction
In this report, JMA’s seasonal numerical ensemble prediction
for 2006 summer (JJA), which was used for one of prognostic
tools for the JMA’s operational warm season outlook issued on
25th April 2006, is introduced. The prediction consists of 31 ensemble members of which initial date is 17th April 2006. Details
on the prediction system and verification maps based on 21-year
hindcasts are available at http://okdk.kishou.go.jp/products/model/
index.html.
The two-tiered method is adopted in the prediction system. So,
firstly predicted SST anomalies are explained in the report, andsecondly predicted circulation fields in the tropics and sub-tropics
are described associated with the predicted SST anomalies. Finally, predicted circulation fields in the middle and high latitudes
in the Northern Hemisphere are described.
2. SST anomalies (Figure 5)
During 2006 summer, the SST anomalies are predicted to beslightly above normal except the following areas: the equatorial
eastern Pacific, the southern Indian Ocean, and the Antarctic
Ocean, where they are predicted to be slightly below normal. As
mentioned in the previous article in this issue, it is likely that thecurrent La Niña event lapse during the latter half of the spring andthe summer, but La-Niña-like conditions persist in the predicted
SST anomalies in JJA.
3. Circulation fields in the tropics and sub-tropics (Figure 6)
As expected from the predicted SST anomalies, below normal
precipitation is predicted in the equatorial eastern Pacific andabove normal precipitation is predicted in the Maritime continentand the tropical Indian Ocean. Although predicted precipitation
amount is, on the whole, slightly above normal in the Asian monsoon region, that is slightly below normal in the western North
Pacific monsoon region. Consistent with the precipitation pattern,
the upper tropospheric velocity potential anomalies are negative(more divergent) over the Indian Ocean and positive (more convergent) over the tropical Pacific, and also, anomalous large scale
divergence flow is predicted near Central America and over thetropical North Atlantic.
Corresponding to these anomalous divergent flows, characteristic rotational flow anomalies are predicted such as 1) northwestward extension of the Tibetan High in the upper troposphere,2) westward extension of the North Pacific Subtropical High in thelower troposphere.
Though positive precipitation anomalies are seen over the maritime continent and over the tropical Indian Ocean, the forecastingskills for the precipitation are generally so low in those areas thatthe results and corresponding predicted circulation anomalies
should be interpreted with caution.
4. Circulation fields in the middle and high latitudes (Figure 7,
Figure 8, Figure 9)
The ensemble prediction says that the summer mean 500-hPa
height anomalies will be above normal over most parts of theNorthern Hemisphere, except for the arctic region and the highlatitudes such as northern Europe and northwestern part of North
America. This predicted large scale anomaly pattern is similar in
most parts to the one of the leading modes of the low frequency

Tokyo Climate Center

2

Figure 5 Predicted SST anomalies for 2006 JJA

(a)

(b)

(c)

(d)

Figure 6 Predicted atmospheric fields for 2006 JJA(Ensemble mean of 31 members)(a) Precipitation (contour) and anomaly (shading). Contour
interval is 2 mm/day,(b) Velocity potential at 200 hPa (contour) and anomaly(shading). Contour interval is 2×106 m2/s,(c) Stream function at 200 hPa (contour) and anomaly(shading). Contour interval is 16×106 m2/s,(d) Stream function at 850 hPa (contour) and anomaly(shading). Contour interval is 5×106 m2/s.

No.4 | April 2006

tudes (130°E-150°E, 50°N-60°N), is also positively biased.
This suggests that the Okhotsk high will be more active thannormal .
(Shuhei Maeda, Climate Prediction Division)

variability of the atmosphere in the Northern Hemisphere:
EOF2 of 500hPa height anomalies in JJA which could becalled the Arctic Oscillation (AO) in summer. The probabilistic distribution of EOF2 score predicted by each member ispositively biased, and the ensemble average of predicted
EOF2 scores is about 0.8: positive phase of the AO is predicted with high probability. The probabilistic distributionof the Okhotsk high index, which is defined by area averaged 500hPa height anomalies in the East Asian high lati-

Figure 8 Histogram of predicted (2006 JJA) EOF2 scores (left)defined by the second EOF of 500 hPa height anomalies in the
Northern Hemisphere (right)
Figure 7 Predicted 500 hPa height in the Northern Hemisphere for 2006 JJA(a) Ensemble mean (solid contours; interval is 60 m) and anomaly(dashed contours; interval is 30 m). Negative anomalies areshaded.
(b) Ensemble mean (solid contours; interval is 60 m) and the probabilities of anomalies predicted to be above{+0.42×standard deviation} or below {–0.42×standard deviation}.
Areas where probabilities exceed 50 % arehatched. Areas above {+0.42×standard deviation} are crosshatched, and areas below {-0.42×standard deviation} are single
hatched.

Figure 9 Histogram of predicted(2006 JJA) Okhotsk high indicesdefined by area averaged 500 hPa
height anomalies in the East
Asian high latitudes (130E-150E,
50N-60N)

Ve r i f i c a t i o n re s u l t s a n d p ro b a b i l i s t i c p re d i c t i o n p ro d u c t s o f
t h e n ew J M A ’ s s e a s o n a l E n s e m bl e P re d i c t i o n S y s t e m
As introduced in the TCC News No.3, JMA’s seasonal
Ensemble Prediction System (EPS) was upgraded in March
2006. In advance of the upgrade, 21-year hindcast (19832003) of the new system was carried out in order to checkthe forecasting skills of the new system and to provide therelevant information for postprocessing the EPS outputs,
including correction of model bias. The verification resultsof the hindcast and the probabilistic prediction products us-

ing the MOS technique (see the TCC News No.2) are now
available on the TCC web site. The verification was conducted along the WMO Standard Verification System forLong-Range Forecast (SVSLRF). Besides, registered users
can download the GPV of the hindcast. Please visit ourverification page and check the skills before using our prediction products.
(Shuhei Maeda, Climate Prediction Division)

Summary of Asian Winter Monsoon 2005/2006
In the former half of the season, the winter monsoon was
predominant and cold surges frequently occurred over East Asia,
which led to severe damage, especially over 100 fatalities due toheavy snowfalls in Japan.

such as airplanes and trains.
(2) Landslide in the Philippines (February)
On 17 February, a large-scale landslide occurred in Leyte
Island, the Philippines. It was reported that more than 1000
persons died and missed. Up until several days before thelandslide, about 500 mm of precipitation was observed infive days (Figure 10). It is considered that this heavy rain
was caused by the sustained active convection due to theconfluence of strong trade wind and cold surge from theEurasia continent and to geographical features (Figure 11).
(3) Drought in southern China
Since last autumn, southern China has experienced dry
condition. In February, the shortages of drinking water forover 300,000 people in Beihai were reported. In Beihai,

1. Extreme Climate Events(1) Cold wave and heavy snow in East Asia (December)
In December, extremely low temperatures were observed
from southern Central Siberia to Japan due to persistentcold-air flow from the Arctic. Record-breaking heavy
snowfalls were also observed in the Japan Sea Side of Japan.
In Japan, more than 80 persons died during December, thetotal number of the deaths reached 150 due to the heavy
snowfalls in this winter. In northeastern China and Korea, it
was also reported that heavy snow disrupted transportation

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No.4 | April 2006

the Bay of Bengal to the Philippine Sea (Figure 14).
Maeda (2005) suggested that these features were caused by
predominant negative phase of the AO (Arctic Oscillation)and enhanced by the stationary Rossby wave train trappedin the Asian jet. It was suggested that there might be someinteraction between the tropics and extra-tropics, but itneeds further examination (http://okdk.kishou.go.jp/news/
topics_20060127.html). In the latter half of the season,
both Siberian High and Aleutian Low became weak(Figure 13). As a result cold surges didn’t frequently takeplace in eastern Asia south of western Japan (Figure 14).
(1: Ayako Takeuchi and 2: Yayoi Harada,
Climate Prediction Division)

precipitation amounts from October 2005 to February 2006
were about 80 mm, which is about one thirds compared to thenormal. Over 30 mm out of the five-month total precipitation, 80 mm, fell in the last three days of February.

2. Atmospheric circulation
The features of atmospheric circulation and surface climate were very different between in the former and in thelatter half of Asian winter monsoon season during 2005-2006(Figure 12, Figure 13 and Figure 14). In the former of theseason, northeastern Asian winter monsoon pattern was
highly dominant, that is to say, both Siberian High and Aleutian Low were very strong (Figure 13). Cold surges frequently occurred, and reached over the South China Sea andthe Philippine Sea. Convection was remarkably active from

Figure 10 Total precipitation for 8-12 Feb. 2006 around the
Leyte island
The numbers in the upper left of the circles denote precipitation(unit: mm). The circles show observatories. There is no observatory
on St. Bernard, where a landslide occurred.

Figure 11 OLR anomalies and 850hPa winds averaged for
8-12 Feb. 2006
The shades show OLR anomalies and the arrows show 850 hPa
winds. The blue (red) shades denote areas where the convective activities were stronger (weaker) than normal.

Figure 12 Surface temperature anomalies in
the former (left panel) and latter (right panel)
half of 2005/6 Asian winter monsoon season.
Original data are the daily temperature of
SYNOP reports. The periods for average in left
and right panels are 1 Dec. 2005 – 15 Jan. 2006
and 16 Jan. 2006 – 28 Feb. 2006, respectively.

Figure 13 Sea level pressure and anomalies
in the former (left panel) and latter (rightpanel) half of 2005/6 Asian winter monsoon
season.
The contours show historical values and theshades show anomalies. The periods for average are the same as in Figure 12.

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No.4 | April 2006

Figure 14 Wind at 850 hPa and OLR
anomalies in the former (left panel)and latter (right panel) half of 2005/6
Asian winter monsoon season.
The stream lines show historical winds
and the shades show OLR anomalies.
The periods for average are the same as
in Figure 12.

S t ra t o s p h e r i c m a j o r w a r m i n g eve n t i n Ja n u a r y 2 0 0 6
A remarkable sudden warming event took place in January 2006. The
event was identified as “Major warming”. Since the warming occurred,
the state that the temperature was above normal had persisted until the
middle of February.
Climate Prediction Division, JMA, has routinely monitored thestratospheric circulation, focusing on Stratospheric Sudden Warming(SSW) events, and issued a STRATALERT report everyday during
the occurrence of a SSW (http://okdk.kishou.go.jp/products/clisys/index.html#STRAT).
Figure 15 shows time sequence of 30hPa temperature over the
North Pole. The warming started in the beginning of January 2006
(identified as “Minor”). Before the temperature returned to its normal, an additional warming event occurred in the end of the month(identified as “Major”). The temperature reached to -30 ℃, 40 ℃
higher than its normal. At that time, meridional temperature gradientin the zonal mean field was reversed, and corresponding to it, easterly winds appeared north of 60°N. Such a strong warming event israre in January and has occurred the first time since 1995. Thoseconditions had persisted until the middle of February. At the time ofthe occurring of the major warming, developed ridge over central
Siberia was remarkable at 30 hPa. It was analyzed that vertical andhorizontal energy propagation of planetary-scale waves from thetroposphere to the stratosphere played an important role in the major

warming.
The details of the analysis are available at http://
okdk.kishou.go.jp/news/topics_20060425.html(Masashi Ujiie, Climate Prediction Division)

Figure 15 Time sequence of temperature (℃) at 30hPa over the North Pole in 2005/2006
Black line shows the temperature from September
2005 to April 2006. Gray line shows its climatology.

T C C ’ s R e s e a rc h a n d D eve l o p m e n t A c t iv i t y-Development of a Downscaled Probabilistic One-month ForecastAs TCC’s research and development activity, TCC started conducting a three-year research project in 2004, in cooperation
with the FUJITSU FIP Corporation, on the development of detailed
probabilistic one-month forecasts in Southeast Asia which are
expected to be incorporated into decision-making processes in avariety of socio-economic sectors.

mendations: 1) to construct a longer-term and higherquality surface climate database in the Southeast Asian
region; 2) to improve the statistical downscaling technique,especially for precipitation forecasts; and 3) to search thebest use of the point-wise probabilistic forecasts and its
applications through communication and cooperation withthe producers and users of climate prediction informationin the Southeast Asian countries.
(1) Construction of a surface climate database
A longer-term and higher-quality surface climate database of daily maximum/mean/minimum temperature anddaily precipitation compared with the existing climate dataset was successfully constructed for the Southeast Asia
region. The number of the observatories, where we could
estimate the daily normal, was over 200 for temperatureand 300 for precipitation about three times as many as theexisting one. These new daily surface climate data arequite useful not only for developing and verifying thepoint-wise probabilistic forecast, but also for monitoring
and assessing the abnormal climate condition in Southeast
Asia operationally at JMA on a daily basis.

1. Purpose of this research
The main three objectives of this research project are as
follows:
1) development of the technique deriving appropriate probabilistic forecasts from JMA’s one-month Ensemble Prediction System (EPS) products;2) development of the statistical downscaling technique forobservation-point forecasts in Southeast Asia from global
prediction model outputs; and
3) research on effective ways to use detailed probabilistic
forecast based on the techniques developed in the above 1)
and 2) in socio-economic activities.
2. Achievements in 2005
In the second year of this project, 2005, three research
objectives were set in accordance with the first year’s recom-

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No.4 | April 2006

(2) Improvement of the statistical downscaling technique
The statistical relationships were examined for themonthly mean precipitation at each month and observatory.
It was found that the effect of the orographical predictor wasquite different from place to place and season to season. Fourclassifications seemed possible: 1) where the JRA-25 precipitations reproduce the observed precipitation well without any
calibrations, such as the eastern part of the Philippines in wintertime, 2) where the JRA-25 precipitations correlates wellwith the observed precipitation and the orographic effect is
not so important, such as the western part of the Malay Peninsula in wintertime, 3) where the orographic predictor significantly improves the estimation, such as the western part ofThailand, and 4) where the orographic effect is not enough to
reproduce the observed variability of precipitation, such as
the inland area of Indochina Peninsula in summertime. Figure 16 shows some of the results. The relationships were
examined for the weekly precipitation of each month, too, andalmost the same results came out, though the orographicaleffect seemed a little smaller than the monthly cases. This
research gave us valuable information on the characteristicsof the JRA-25 precipitation in the tropics, too.
(3) Research on the possible field for climate forecast application
TCC visited Thai Meteorological Department (TMD) and
Malaysia Meteorological Service (MMS) in March 2006. It

was quite informative for us to visit and talk with the direct
users of TCC’s products. TCC and both TMD and MMS
could understand the each other’s current status of climate
related services and agreed to promote the cooperative andcollaborative relationships to develop advanced climate
information applications. It was identified that agricultureis the top priority field for advancing climate applicationand the detailed and precise forecast of precipitation are
primarily required. It was recognized that we would promote direct communication with the end-users of our climate information.

3. Plans on research in 2006
In the last year of this project, 2006, three research
objectives were set in accordance with the second year’s
recommendations: 1) to develop and evaluate the MOStype statistical downscaling technique, especially for precipitation forecasts in the Southeast Asia region using the
20-year hindcast data; 2) to develop and evaluate the pointwise probabilistic forecast using the 20-year hindcast data;and 3) to provide the above prototype products to TMD
and MMS for evaluation of their practical utility for thedevelopment of tailored information for specific users.
The details of this research are described in http://
okdk.kishou.go.jp/about/
TCC_research_and_development_2006.pdf(Shingo Yamada, Climate Prediction Division)

Figure 16 Time series of monthly mean precipitation (mm/day)Left and right panels show Catbalogan, the Philippines, in January and Hpa-an, Myanmar, in June, respectively. In both panels, solid anddot black lines show precipitation of observation and of JRA-25, respectively. In left panel, blue line indicates the precipitation estimatedfrom single regression on JRA-25 precipitation. In right panel, red and blue lines indicate the precipitation estimated from single regression on JRA-25 precipitation and from multiple one on JRA-25 precipitation and wind multiplied by the slop of terrain, respectively.

T C C h av i n g a n n o u n c e d i t s i m p l e m e n t a t i o n p l a n o f t h e R C C
functions in WMO RA II
TCC is preparing for playing an integral part of the Regional
Climate Center (RCC) Network of WMO Regional Association(RA) II and has announced its implementation plan (http://
okdk.kishou.go.jp/about/implementation_plan_2006.pdf)
of
RCC functions including current status and future plan of climate-related services in JMA.
It was decided in the 13th Session of WMO RA II, held in
Hong-Kong during 7-15 December 2004, that the RCC Network
consists of multiple multifunctional centers and has five key
functions: that is, operation, coordination, data services, training
and capacity building, and research and development functions.
According to the Designation Procedures for RCC Network in
RA II, the RCC Network is planned to start its operation on a
Any comments or inquiries on this newsletter and/or
the TCC website would be much appreciated. Please email to the following address:
tcc@climar.kishou.go.jp(Chief Editor: Shingo Yamada)Tokyo Climate Centerpilot basis in May 2006.
TCC has been conducting a variety of activities forassisting NMHSs in the Asia-Pacific region in climaterelated services since when it was established, April
2002. TCC is willing to further execute its tasks and
RCC functions, especially through collaborative researchand development activities (see the previous article),which aim to advance the utilities of climate informationand prediction in various socio-economic sectors for
mitigating climate-related disasters and adopting climate
variability and change.
(Shingo Yamada, Climate Prediction Division)

Tokyo Climate Center (TCC), Climate Prediction Division, JMA
Address: 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan
TCC website: http://okdk.kishou.go.jp/index.html

6No.4 | April 2006