Seasonal outlook of the East Asian Summer in 2015

1. Seasonal outlook of the East Asian Summer in 2015 Motoaki Takekawa Tokyo Climate Center Japan Meteorological Agency 11th FOCRAII

2. Oceanic conditions in April 2015 SST anomalies # The distribution of SST anomalies shows an El Nino like condition. # Positive anomalies are dominant in sub-surface sea temperature along the equatorial central and eastern Pacific Sub-surface sea temperature anomalies in the equatorial Pacific 11th FOCRAII

3. Inter-seasonal evolution of oceanic conditions Time-Longitude cross section along the equator SST zonal wind stress Ocean Heat Content # Strong westerly bursts excited warm Kelvin waves with large amplitude. # Kelvin waves have reached the west coast of South America.

4. Predicted oceanic conditions in JJA (1) SST anomalies # El Niño conditions will redevelop. # Prediction skill is pretty good. Prediction accuracy ( verification result by the 30-year hindcast ) 95% significant Anomaly correlation coefficients 11th FOCRAII

5. Predicted sub-tropical circulation in JJA (1) Suppressed convection anomalies Active convection anomalies Precipitation and anomalies # Distribution of precipitation shows characteristics of El Niño events. # Prediction skill is good. Prediction accuracy ( verification result by the 30-year hindcast ) 95% significant Anomaly correlation coefficients 11th FOCRAII

6. Predicted sub-tropical circulation in JJA (2) 200hPa velocity potential and anomalies Large scale divergence anomalies # Anomaly pattern of 200hPa velocity potential shows characteristics of El Niño events. Large scale convergence anomalies Precipitation and anomalies 11th FOCRAII

7. Predicted sub-tropical circulation in JJA (2) 200hPa stream function and anomalies # Anomaly pattern of stream function shows typical patterns which were observed when El Niño events occurred. Cyclonic circulation anomalies El Nino composite : 200hPa stream function anomalies Wave train 11th FOCRAII

8. Predicted sub-tropical circulation in JJA (2) 200hPa stream function and anomalies # The CGCM has significant skill in not only the Rossby response, but also zonal north-south shift of sub-tropical jet. Prediction accuracy ( verification result by the 30-year hindcast ) 95% significant Anomaly correlation coefficients 10th FOCRAII

9. Predicted sub-tropical circulation in JJA (3) El Nino composite: 850hPa stream function anomalies # Anomaly pattern of stream function shows typical patterns which were observed when El Niño events occurred. 850hPa stream function and anomalies Cyclonic circulation anomalies Anti cyclonic circulation anomalies 11th FOCRAII

10. Interannual variation of summer mean temperature Temperature ranks during recent 10years (2005-2014) Tropospheric thickness temperature # Hot summer has been dominant in Japan recently. # warming tendency is seen in tropospheric thickness temperature . 11th FOCRAII

11. Predicted sub-tropical circulation in JJA (4) Tropospheric thickness temperature(JJA 200-850hPa) , Overall temperatures in the troposphere are expected to be higher than normal, particularly on the lower latitudes side of the sub tropical jet. 11th FOCRAII

12. summary of Numerical prediction and its interpretation ・It is likely that El Niño conditions will redevelop by the boreal summer 2015. ・Predicted atmospheric circulation anomalies are as follows, • Asian summer monsoon will be generally weaker than normal. • The sub-tropical jet will shift southward compared to the normal latitude. This means weak Tibetan high. • North pacific high will not extend to north, but around southeast of Japan, it will be not weaker than normal. • These characteristics are consistent with those observed during past El Niño events. ・Additionally, it is necessary to consider that overall temperatures in the troposphere are expected to be higher than normal, particularly on the lower latitudes side of the sub tropical jet, reflecting recent warming tendency and high SSTs in the equatorial Pacific. 11th FOCRAII

13. Schematic chart of outlook for East Asian circulation in JJA 2015 11th FOCRAII

14. 30 30 20 30 30 30 40 40 40 30 40 40 Climatology 33 33 33 Probability forecast of seasonal mean temperature for JJA 2015 in Japan Northern Japan High Low Normal Eastern Japan WesternJapan 40 40 Summer mean temperatures are expected to be both near normal and above normal with 40% probabilities in eastern Japan. Okinawa & Amami 11th FOCRAII

15. 30 30 30 30 30 40 30 Climatology 33 33 33 Probability forecast of seasonal precipitation for JJA 2015 in Japan Northern Japan Below normal Normal Above normal Western Japan Eastern Japan 40 40 Summer precipitation amounts are expected to be both near normal and above normal with 40% probabilities in northern Japan. Okinawa & Amami 20 40 40 11th FOCRAII

16. Thank you 11th FOCRAII

17. Predicted sub-tropical circulation in JJA (4) 500hPa height 850hPa temperature SLP 11th FOCRAII

18. Predicted sub-tropical circulation in JJA (3) 850hPa stream function and anomalies Prediction accuracy ( verification result by the 30-year hindcast ) Rossby Response 11th FOCRAII

19. Predicted sub-tropical circulation in JJA (3) Precipitation and anomalies # above normal rainfall is predicted around Philippines. # These anomalies have significant skill. Prediction accuracy ( verification result by the 30-year hindcast ) 95% significant Anomaly correlation coefficients 11th FOCRAII

20. Linear Regression SST in (-5-5,210-270) and rain JJA 1979-2008 Precipitation and anomalies JRA25 # Meanwhile, JMA’s CGCM probably tend to predict more active convections around Philippines in El Nino conditions. JMA’s CGCM by the 30-year hindcast Intial; April 11th FOCRAII