JMA Seasonal Prediction of South Asian Climate for

JMA Seasonal Prediction of South Asian Climate for OND 2017 Takuya Komori Tokyo Climate Center (TCC) Japan Meteorological Agency (JMA) 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Contents • Outline of JMA Seasonal Ensemble Prediction System • Current oceanic condition • JMA’s seasonal numerical ensemble prediction • Probabilistic Forecast • Summary 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Contents • Outline of JMA Seasonal Ensemble Prediction System • Current oceanic condition • JMA’s seasonal numerical ensemble prediction • Probabilistic Forecast • Summary 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Specification of Seasonal EPS Model JMA/MRI-CGCM 2 Resolution [Atmosphere] H: TL 159 (~110 km), V: L 60 (up to 0. 1 h. Pa) [Ocean] H: 1. 0ºlon. , 0. 3– 0. 5ºlat. (with Tri-polar grid), V: L 52+BBL Forecast range 7 months Initial conditions [Atmosphere] JRA-55 (JMA Climate Data Assimilation System) [Ocean] MOVE/MRI. COM-G 2 (Ocean Data Assimilation) [Land] JRA-55 land analysis Boundary conditions SST: Predicted, Sea ice: Sea-ice model Ensemble method Combination of Breeding of Growing Modes (BGM) and Lagged Average Forecast (LAF) Ensemble size 51 (13 BGMs & 4 initial days with 5 -day LAF) Freq. of model product creation Once a month (around 20 th of every month) In this presentation, • Initial month: Sep 2017 • Forecast period: OND 2017 • Baseline: 1981 -2010 average 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Prediction Skill for El Niño forecast Hindcast experiments for 30 years (1981 – 2010) NINO. 3 150 W-90 W, 5 S-5 N 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Prediction Skill of JMA Seasonal EPS Bias-corrected Anomaly Correlation for OND (Initial month: September) Hindcast experiments for 30 years (1981 – 2010) SST Precipitation 2 m Temperature Relatively low prediction skill should be considered in South Asia 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Prediction Skill of JMA Seasonal EPS Area-averaged precipitation for OND (Initial month: September) Hindcast experiments for 30 years (1981 – 2010) South Asia Precipitation Anomaly [mm/day] 30 N South Asia 20 N 10 N 60 E [mm/day] South Asia CI 2 r=0. 30 CI 2 DL 90 E 115 E 140 E r=0. 75 170 E 170 W DL forecast ANALYSIS [mm/day] ANALYSIS 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11) 5 N 5 S ANALYSIS r=0. 73

Contents • Outline of JMA Seasonal Ensemble Prediction System • Current oceanic condition • JMA’s seasonal numerical ensemble prediction • Probabilistic Forecast • Summary 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Monthly Mean SST Anomalies (Aug 2017) • Pacific – SSTs are above normal in the western equatorial Pacific, but below normal in the central and eastern equatorial Pacific. • Indian Ocean – SSTs are above normal in the southwestern Indian Ocean, but below normal in the southeastern Indian Ocean. Namely, it’s a positive IOD like distribution. 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

SST Indices SST indices are defined as deviations from the climatological mean based on a sliding 30 -year period, removing long-term trend. August 2017 NINO. 3 -0. 2 o. C NINO. WEST +0. 81 o. C IOBW +0. 11 o. C 2006 2017 El Niño Neutral La Niña 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Contents • Outline of JMA Seasonal Ensemble Prediction System • Current oceanic condition • JMA’s seasonal numerical ensemble prediction • Probabilistic Forecast • Summary 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

SST and OHC for ONDJF 2017 -2018 Initial date: 8 th Sep 2017 Ensemble mean Time-longitude cross section along the EQ (September-March) SST anomalies Indian Ocean Pacific Ocean Heat Content anomalies Atlantic Indian Ocean [o. C] Pacific Atlantic [o. C] SSTs for ONDJF 2017 • For subsurface water, a cold Kelvin wave is predicted to move eastward from the boreal autumn to winter. • It is likely that La Niña like SST conditions will persist from the boreal autumn to winter. anomaly [o. C] • A positive IOD like OHC condition is predicted to end around December in the Indian Ocean. 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Predicted area-averaged SSTs for ONDJF 2017 Initial date: 8 th Sep 2017 IOBW ONDJF NINO. WEST ONDJF NINO. 3 ONDJF Red dots indicate observed values, and yellow boxes indicate predictions. Each box denotes the range where the value will be included with the probability of 70%. • IOBW is predicted to be near normal. • NINO. WEST is predicted to be near or above normal. • NINO. 3 is predicted to be near or below normal. Prediction Skill for ONDJF (Anomaly Correlation, 1981 -2010 hindcast) IOBW ACC=0. 87 NINO. WEST ACC=0. 70 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11) NINO. 3 ACC=0. 88

Precipitation and 200 h. Pa Velocity Potential for OND 2017 Initial date: 8 th Sep 2017 Ensemble mean Precipitation Velocity potential at 200 h. Pa D Anomaly (shaded) [mm/day] • Positive anomalies (Heavy rainfall) are predicted over the Philippines and South China Seas in association with warm SST conditions. • Negative anomalies (Light rainfall) are predicted over the equatorial central Pacific Ocean in association with La Niña like conditions. C Anomaly (shaded) [106 m 2/s] • Negative (Divergence) anomalies are predicted over the Philippines in association with the heavy rainfall around the Philippines. Over the western Indian Ocean, the forecast uncertainty is relatively large. • Positive (Convergence) anomalies are predicted over the equatorial Pacific Ocean in association with La Niña like conditions. 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Precipitation over South Asia for OND 2017 Initial date: 8 th Sep 2017 Anomaly (shaded) Ensemble mean [mm/day] • Precipitation is predicted to be near or above normal in South Asia. 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Temperature over South Asia for OND 2017 Initial date: 8 th Sep 2017 Anomaly (shaded) Ensemble mean [o. C] • Temperature is predicted to be slightly above normal in most part of South Asia. 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Histograms of Area-averaged Precipitation Anomalies for OND 2017 Initial date: 8 th Sep 2017 51 ensemble members RAIN (South Asia) 60 E-90 E, 10 N-30 N Dry Wet Near or above normal RAIN (DL) 170 E-170 W, 5 S-5 N RAIN (CI 2 Region) 115 E-140 E, 10 N-20 N Dry Wet Above normal Wet Dry Below normal (Large ensemble spread) (Small ensemble spread) La Niña Prediction Skill (Anomaly Correlation, 1981 -2010 hindcast) ACC=0. 30 ACC=0. 75 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11) ACC=0. 73

Predicted Dipole Mode Index (DMI) for ONDJF 2017 Initial date: 8 th Sep 2017 51 ensemble members DMI = SST(50 -70 E, 10 S-10 N) - SST(90 -110 E, 10 S-0) OND • DMI is predicted to be neutral or slightly positive. DJF • DMI is predicted to be neutral. Low prediction Skill Prediction Skill for OND and DJF (Anomaly Correlation, 1981 -2010 hindcast) OND ACC=0. 75 DJF ACC=0. 17 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Contents • Outline of JMA Seasonal Ensemble Prediction System • Current oceanic condition • JMA’s seasonal numerical ensemble prediction • Probabilistic Forecast • Summary 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Probability (%) of Most Likely Category for OND 2017 Initial date: 8 th Sep 2017 Temperature • • • Probability (%) of Most Likely Category Precipitation Most likely category for temperature : – above normal in most part of South Asia. Most likely category for precipitation : – near or above normal in most part of South Asia. Relatively low prediction skill should be considered. 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11) Model Output Statistics (MOS) technique based on the 30 years hindcast is used. Masked grids denote insufficient prediction skill (ROC area score < 0. 5).

EUROSIP Forecast for OND 2017 Initial Month: Sep 2017 1991 -2010 baseline • A most likely category of temperature is above normal in South Asia. • • A most likely category of precipitation is near or above normal in South Asia. La Niña like conditions are predicted. JMA joined a member of EUROSIP public products since March 2017. Copyright © European Centre for Medium-Range Weather Forecasts EUROSIP public products are referenceable in the following website. http: //www. ecmwf. int/en/forecasts/documentation-and-support/long-range/seasonal-forecastdocumentation/eurosip-user-guide/multi-model 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Summary JMA Seasonal Ensemble Prediction System predicts as follows: (Outlook for Oceanic conditions) • It is likely that La Niña like SST conditions will persist through boreal winter. • It is likely that the Indian Ocean SST (IOBW) will be near normal until boreal winter (Outlook for Temperature in South Asia) • Above normal in most part of South Asia. (Outlook for Precipitation in South Asia) • Area-averaged precipitation of South Asia is expected to be near or above normal from October to December 2017. 　More plots are available at: http: //ds. data. jma. go. jp/tcc/products/model/index. html 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Backup Slides 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

EUROSIP Forecast for OND 2017 Initial Month: Sep 2017 1991 -2010 baseline • A most likely category of MSLP is below normal in South Asia. • • A most likely category of SST is near or above normal in South Asia. La Niña like conditions are predicted. JMA joined a member of EUROSIP public products since March 2017. Copyright © European Centre for Medium-Range Weather Forecasts EUROSIP public products are referenceable in the following website. http: //www. ecmwf. int/en/forecasts/documentation-and-support/long-range/seasonal-forecastdocumentation/eurosip-user-guide/multi-model 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

850 h. Pa wind and SLP for OND 2017 Initial date: 8 Sep 2017 • Ensemble mean 850 h. Pa wind anomaly SLP Cyclonic circulation anomalies extending over the 10 N-20 N latitudinal band from Africa to the Philippine Sea are predicted. • Negative anomalies extending over the Arabian Sea, South Asia, the South China Sea and the Sea south of Japan are widely predicted. left: 850 -h. Pa stream function (106 m 2/s) and wind vector anomalies (m/s); right: sea level pressure (h. Pa) 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)

Prediction Skill for Seasonal forecast Hindcast experiments for 30 years (1981 – 2010) 2 m Temperature Precipitation (Northern Hemisphere) (Tropics) 11 th Session of the South Asian Climate Outlook Forum (SASCOF-11)