Monthly Discussion on
Seasonal Climate Outlooks (No. 126)
(20 August 2024)
Tokyo Climate Center (TCC)
Japan Meteorological Agency (JMA)1

Outline
1. Summary and Discussion<Slide 3>

2. Latest State of the Climate System (Jul. 2024)<Slides 4 – 14>

3. Three-month Predictions (Sep. 2024 – Nov. 2024)<Slides 15 – 22>

Explanatory Notes<Slides 23 – 27>

Notes:• The present monthly discussion is intended to assist National Meteorological andHydrological Services (NMHSs) in WMO RA II (Asia) in interpreting WMC Tokyo’s
seasonal prediction products. It does not constitute an official forecast for any nation.
Seasonal outlooks for individual countries should be obtained from the relevant NMHS.
• Seasonal predictions are based on a JMA’s Seasonal Ensemble Prediction System (EPS),
which is based on the coupled atmosphere-ocean general circulation model (CGCM).
• JMA provides three-month prediction products around the 20th of every month withwarm-season (Jun. – Aug.) prediction products in February, March and April, and withcold-season (Dec. – Feb.) prediction products in September and October.
• Unless otherwise noted, the base period for the normal is 1991 – 2020.

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1. Summary and Discussion
ENSO• ENSO-neutral conditions persisted in July.
• It is more likely that La Niña conditions will develop by boreal winter (60%) than ENSOneutral conditions will continue (40%).

Prediction for September-October-November 2024 (SON 2024)• In the 200-hPa velocity potential field, large-scale divergence anomalies are predicted fromthe Indian Ocean to the Maritime Continent, while large-scale convergence anomalies arepredicted over the Pacific.

• In the 850-hPa stream function field, cyclonic and anti-cyclonic circulation anomalies
straddling the equator are predicted over the Indian Ocean and the western Pacific, respectively.
• A high probability of above-normal precipitation is predicted from near South Asia toSoutheast Asia. A high probability of below-normal precipitation is predicted over the western
Indian Ocean, the eastern Middle East, and the western equatorial Pacific.
• A high probability of above-normal temperatures is predicted over a wide area from theIndian Ocean to the Pacific. A high probability of below-normal temperatures is predicted overparts of South Asia and the western equatorial Pacific.

32. Latest State of the Climate System

July 20244

<July 2024> Extreme Climate Events<Monthly Report on Global Extreme Climate Events>
https://www.data.jma.go.jp/tcc/tcc/products/climate/monthly/index.html

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<July 2024> Temperature• Monthly mean temperatures were extremely high from Japan to Indonesia, in southern Central Siberia,
from western South Asia to around the Persian Gulf, from the southern Arabian Peninsula to western
Northern Africa via Europe, in western North America, and from the southeastern USA to northern SouthAmerica.

Normalized anomaly of monthly mean temperature<World Climate Chart (Monthly)> https://www.data.jma.go.jp/tcc/tcc/products/climate/climfig/?tm=monthly

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<July 2024> Precipitation• Monthly precipitation amounts were extremely high from southern Central Siberia to eastern Mongolia,
in and around southern Central Asia, from the northern Indochina Peninsula to central India, in Turkey,
from the Midwest to southeastern USA, and in southern Mexico.
• Monthly precipitation amounts were extremely low from Western Russia to southern Europe and innorthern Mexico.

Monthly precipitation ratio<World Climate Chart (Monthly)> https://www.data.jma.go.jp/tcc/tcc/products/climate/climfig/?tm=monthly

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<July 2024> Sea Surface Temperature (SST)• In the equatorial Pacific, remarkably positive SST anomalies were observed in the western part andnegative SST anomalies were observed in the eastern part.
• In the North Pacific, remarkably positive SST anomalies were observed from the western part of thetropics to the mid-latitudes and in the eastern part of the tropics.

• In the Indian Ocean, remarkably positive SST anomalies were observed around Madagascar and from thecentral to eastern parts of the tropics.

Monthly mean SST anomaly (˚C)<Monthly mean SST anomalies (Global)> https://www.data.jma.go.jp/tcc/tcc/products/elnino/ocean/sst-ano-global_tcc.html

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<July 2024> ENSO Monitoring Indices• ENSO-neutral conditions persisted inJuly.
• The NINO.3 SST was near normal witha deviation of -0.1ºC in July.

• The Southern Oscillation Index (SOI)
value was -0.9.
• The area-averaged SST in the tropicalwestern Pacific (NINO.WEST) region
was above normal.

• The area-averaged SST in the tropicalIndian Ocean (IOBW) region wasabove normal.

NINO.3

SOININO.WEST

IOBWMonthly values (thin lines) and five-month running means (thick lines). The shading indicates El Niño (red) and La Niña (blue) events.
< El Niño Monitoring and Outlook> https://www.data.jma.go.jp/tcc/tcc/products/elnino/elmonout.html

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<July 2024> Convective activity in the Tropics• Convective activity was enhanced from the North Indian Ocean to the western equatorial Pacific,
indicating active Asian summer monsoon circulation, and suppressed to the east of the Philippines andfrom the tropical eastern North Pacific to South America.

Monthly mean
OLR anomalies
Shading: OLR anomalies (W/m2)

Monthly mean
Velocity potential,
Divergent wind vector, andVelocity potential anomalies
at 200-hPa
Contour: velocity potential (106m2/s)
Vector: divergent wind vector (m/s)
Shading: velocity potential anomalies (106m2/s)“D” and “C” indicate the centers of large-scale
divergence and convergence anomalies,
respectively.
<Monthly Mean Figures> https://www.data.jma.go.jp/tcc/tcc/products/clisys/figures/db_hist_mon_tcc.html<Animation Maps (Global Area)> https://www.data.jma.go.jp/tcc/tcc/products/clisys/anim/anim_tp.html

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<July 2024> Equatorial Intraseasonal Oscillation• The active phase of equatorial intraseasonal oscillation was unclear.

Time-longitude cross section of seven-day running mean
velocity potential anomalies at 200-hPa (5˚S – 5˚N)

MJO diagram<MJO> https://www.data.jma.go.jp/tcc/tcc/products/clisys/mjo/moni_mjo.html

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<July 2024> Upper-level Circulation• In the upper troposphere, anti-cyclonic circulation anomalies were seen from northern Africa to western
East Asia and a wavy anomaly pattern was seen to the north of them, with cyclonic circulation anomalies inCentral Asia and anti-cyclonic circulation anomalies over Japan. Cyclonic circulation anomalies were also
seen from the south of Alaska to the tropical western North Pacific, indicating the enhanced Mid-Pacifictrough.

Monthly mean
Stream function andits anomalies at 200-hPa
Contour: stream function (106m2/s)
Shading: stream function anomalies (106m2/s )“H” and “L” indicate the centers of anti-cyclonicand cyclonic circulations, respectively.

Monthly mean
Velocity potential,
Divergent wind vector, andVelocity potential anomalies
at 200-hPa
Contour: velocity potential (106m2/s)
Vector: divergent wind vector (m/s)
Shading: velocity potential anomalies (106m2/s)“D” and “C” indicate the centers of large-scale
divergence and convergence anomalies,
respectively.
<Monthly Mean Figures> https://www.data.jma.go.jp/tcc/tcc/products/clisys/figures/db_hist_mon_tcc.html<Animation Maps (Global Area)> https://www.data.jma.go.jp/tcc/tcc/products/clisys/anim/anim_tp.html

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<July 2024> Low-level Circulation• In the lower troposphere, extremely anti-cyclonic circulation anomalies were seen to the south of Japan.
• In the sea level pressure field in the tropics, negative anomalies were seen from Africa to the Indian Ocean, andpositive anomalies were seen from the south of Japan to the central North Pacific, indicating enhanced westward
expansion of the North Pacific Subtropical High.

Monthly mean
Stream function andits anomalies at 850-hPa
Contour: stream function (106m2/s)
Shading: stream function anomalies (106m2/s)“H” and “L” indicate the centers of anti-cyclonicand cyclonic circulations, respectively.

Monthly mean
Sea level pressure anomalies
andSurface wind vector anomalies
Contour&shading: sea level pressure anomalies(hPa)
Vector: surface wind vector anomalies (m/s)“H” and “L” indicate the centers of anti-cyclonicand cyclonic anomalies, respectively.
<Monthly Mean Figures> https://www.data.jma.go.jp/tcc/tcc/products/clisys/figures/db_hist_mon_tcc.html<Animation Maps (Global Area)> https://www.data.jma.go.jp/tcc/tcc/products/clisys/anim/anim_tp.html

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<July 2024> Northern Hemisphere Circulation• In the 500-hPa height field, a polar vortex shifted toward the western hemisphere. Negative anomalies were seen near Central
Asia. Significantly positive anomalies were seen over the sea south of Japan.
• In the sea level pressure field, negative anomalies were seen near Greenland in association with the shifted polar vortex. Negative
anomalies were seen from a wide area of Eurasia to northern Japan and positive anomalies were seen from the sea south of Japanto a wide area of the North Pacific, indicating the westward extension of the North Pacific subtropical high and the intensified
East Asian summer monsoon. The subtropical high over the North Atlantic extended northwestward.
• Temperatures at 850-hPa were above normal over a wide area with significantly positive anomalies over southeastern Europe, theeastern Eurasia and near Japan in the mid-latitudes.

Monthly meangeopotential heightand its anomalies at 500-hPa

Monthly mean
temperatureand its anomalies at 850-hPa

Monthly meansea level pressure
and its anomalies

Contour: geopotential height (m)Shading: geopotential height anomalies (m)Contour: temperature (˚C)
Shading: temperature anomalies (˚C)

Contour: sea level pressure (hPa)Shading: sea level pressure anomalies (hPa)<Monthly Mean Figures> https://www.data.jma.go.jp/tcc/tcc/products/clisys/figures/db_hist_mon_tcc.html

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3. Three-month Predictions

September – October – November 2024
(SON 2024)(Initial date for the Seasonal EPS: 8 August 2024)

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<SON 2024> Sea Surface Temperature (SST)• ENSO-neutral conditions persisted in July.
• It is more likely that La Niña conditions will develop by boreal winter (60%) than ENSO-neutralconditions will continue (40%).
• The NINO.WEST SST likely to be above or near normal until boreal winter.
• The IOBW SST is likely to come close to normal in boreal autumn and remain near normal in boreal winter.

Three month mean
Sea surface temperature (SST)ENSO forecast probabilities

Contour: SST (˚C); Shading: SST anomalies.

(a) IOBW

Outlook of the SST deviation(c) NINO.3(b) NINO.WEST

(b)

(c)

(a)

Verification based on hindcast(See “Explanatory Notes (2)”https://www.data.jma.go.jp/tcc/tcc/products/model/hindcast/CPS3/index.html
for the definition of the SST indices.)
https://www.data.jma.go.jp/tcc/tcc/products/model/hindcast/CPS3/shisu/shisu.html

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<SON 2024> Global Circulation• In the 200-hPa velocity potential field, large-scale divergence anomalies are predicted from the Indian
Ocean to the Maritime Continent, while large-scale convergence anomalies are predicted over the Pacific.
• In the 200-hPa stream function field, anti-cyclonic circulation anomalies straddling the equator arepredicted over the Indian Ocean, corresponding to the northward-shifted subtropical jet over southernEurasia. Cyclonic circulation anomalies straddling the equator are predicted from the western to central
Pacific. These circulation anomalies are associated with the upper-level large-scale divergence andconvergence anomalies.

Three month mean
200-hPa velocity potential
Contour: 200-hPa velocity potential (106 m2/s)
Shading: 200-hPa velocity potential anomalies (106 m2/s)

Three month mean
200-hPa stream function
Contour: 200-hPa stream function (106 m2/s)
Shading: 200-hPa stream function anomalies (106 m2/s)

Verification based on hindcast
https://www.data.jma.go.jp/tcc/tcc/products/model/hindcast/CPS3/index.html

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<SON 2024> Asian Circulation• In the 850-hPa stream function field, cyclonic and anti-cyclonic
circulation anomalies straddling the equator are predicted overthe Indian Ocean and the western Pacific, respectively, inassociation with the following anomalous precipitation.
• In the sea level pressure field, negative anomalies are predictedfrom the Indian Ocean to the Maritime Continent. Positive
anomalies are predicted over the subtropical western NorthPacific, indicating the enhanced southwestward extension of
the subtropical high over the North Pacific.
• Above-normal precipitation is predicted from the central Indian
Ocean to Southeast Asia, and below-normal precipitation ispredicted over the western equatorial Pacific.

(a)

[m/s]

(b)

Three month mean(a) 850-hPa stream function anomalies
and wind vector anomalies
Contour&Shading: 850-hPa stream function anomalies (106 m2/s)
Vector: wind vector anomalies (m/s)(c)(b) sea level pressure and its anomalies
Contour: sea level pressure (hPa)Shading: sea level pressure anomalies (hPa)(c) precipitation and its anomalies
Coutour: precipitation (mm/day)Shading: precipitation anomalies (mm/day)
Verification based on hindcast https://www.data.jma.go.jp/tcc/tcc/products/model/hindcast/CPS3/index.html

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<SON 2024> Northern Hemisphere circulation• In the 500-hPa height field, positive anomalies are predicted over a wide area in the Northern Hemispherewith significantly positive anomalies near the Arctic Ocean and the mid-latitudes.
• In the 850-hPa temperature field, positive anomalies are predicted over a wide area in the Northern
Hemisphere, except near northwestern North America.
• In the sea level pressure field, positive anomalies are predicted to the southwest of Alaska, and negative
anomalies are predicted from southern Eurasia to near Japan.

Three month meangeopotential heightand its anomalies at 500-hPa

Three month mean
temperatureand its anomalies at 850-hPa

Three month meansea level pressure (SLP)
and its anomalies

Contour: geopotential height (m)Shading: geopotential height anomalies (m)Contour: temperature (˚C)
Shading: temperature anomalies (˚C)

Contour: sea level pressure (hPa)Shading: sea level pressure anomalies (hPa)

Verification based on hindcast https://www.data.jma.go.jp/tcc/tcc/products/model/hindcast/CPS3/index.html

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<SON 2024> Thickness Temperature• Thickness temperature in the Northern Hemisphere mid-latitudes in July 2024 was record high for July.
• The thickness temperature is predicted to remain above normal, corresponding to the predicted positive
anomalies of 500-hPa height and 850-hPa temperature over a wide area in the Northern Hemisphere.

Inter-annual variability of monthly mean
thickness temperature anomalies in the
Northern Hemisphere mid-latitudes (30oNto 50oN) in July from 1947 to 2024

Monthly time series of thickness
temperature anomalies in the NorthernHemisphere mid-latitudes (30oN to 50oN)

Verification based on hindcast https://www.data.jma.go.jp/tcc/tcc/products/model/hindcast/CPS3/index.html

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<SON 2024> Probability Forecasts (precipitation)• A high probability of above-normal precipitation is predicted from near South Asia to Southeast Asia.
• A high probability of below-normal precipitation is predicted over the western Indian Ocean, the eastern
Middle East, and the western equatorial Pacific.

Verification based on hindcast
https://www.data.jma.go.jp/tcc/tcc/products/model/probfcst/3-mon/hind/html/skill_score_reg.html
https://www.data.jma.go.jp/tcc/tcc/products/model/probfcst/3-mon/hind/html/skill_2d_3-mon.html

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<SON 2024> Probability Forecasts (temperature)• A high probability of above-normal temperatures is predicted over a wide area from the Indian Ocean tothe Pacific.
• A high probability of below-normal temperatures is predicted over parts of South Asia and the westernequatorial Pacific.

Verification based on hindcast
https://www.data.jma.go.jp/tcc/tcc/products/model/probfcst/3-mon/hind/html/skill_score_reg.html
https://www.data.jma.go.jp/tcc/tcc/products/model/probfcst/3-mon/hind/html/skill_2d_3-mon.html

22Explanatory Notes (1)Latest state of the climate system• Extreme climate events and surface climate conditions are based on CLIMAT messages.
For details, see https://www.data.jma.go.jp/tcc/tcc/products/climate/index.html• SST products are based on MGDSST and COBE-SST2 data.
For details, see
MGDSST https://www.data.jma.go.jp/goos/data/rrtdb/jma-pro/mgd_sst_glb_D.html
COBE-SST2 https://www.data.jma.go.jp/tcc/tcc/products/elnino/cobesst2_doc.html• Atmospheric circulation products are based on JRA-3Q data:
https://jra.kishou.go.jp/JRA-3Q/index_en.html
For details, see https://www.data.jma.go.jp/tcc/tcc/products/clisys/index.html• The base period for the normal is 1991 – 2020.

Three-month predictions and warm/cold season predictions• Products are generated using JMA’s seasonal EPS which is based on the CGCM.
For details, see https://www.data.jma.go.jp/tcc/tcc/products/model/index.html• Unless otherwise noted, atmospheric circulation prediction products are based on theensemble mean, and anomalies are deviations from the 1991 – 2020 average for hindcasts.

Contact: tcc@met.kishou.go.jp

23Explanatory Notes (2)SST monitoring indices (NINO.3, NINO.WEST and IOBW)• The SST baseline for NINO.3 region (5˚S – 5˚N, 150˚W – 90˚W) is defined as a monthly

average over a sliding 30-year period (e.g., 1994 – 2023 for 2024). The thresholds ofabove the baseline, near the baseline, and below the baseline categories are +0.5 and -0.5.
• The SST baselines for the NINO.WEST region (Eq. – 15˚N, 130˚E – 150˚E) and theIOBW region (20˚S – 20˚N, 40˚E – 100˚E) are defined as linear extrapolations with respect
to a sliding 30-year period in order to remove the effects of significant long-term warmingtrends observed in these regions. The thresholds of above the baseline, near the baseline,
and below the baseline categories are +0.15 and -0.15.
•These SST indices are derived from MGDSST datasets after June 2015 and those ofCOBE-SST2 before this.

Contact: tcc@met.kishou.go.jp

24Names of world regions

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WMO Regional Association regions

Reference: WMO General Regulations

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TCC website

https://www.data.jma.go.jp/tcc/tcc/index.html

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