The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction

1. The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP 14 September 2009 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml

2. Outline • Recent Evolution and Current Conditions • Monsoon Prediction • Summary • Climatology

3. Rainfall Patterns: Last 90 Days Below-normal monsoon rainfall was observed over India, Indo-China peninsula, southern China, Northeast China, and the East China Sea. Below-normal rainfall was also observed over the equatorial region of Southeast Asia, tropical southern Indian Ocean (along 10S), and eastern Australia. However, over eastern Arabian Sea, Bangladesh, Myanmar, northern Bay of Bengal, the South China Sea, the Philippine Sea, western Pacific, and equatorial Indian Ocean, rainfall was above normal.

4. Rainfall Patterns: Last 30 Days During the past 30 days, monsoon rainfall was below normal over much of East Asia, Southeast Asia, eastern Australia, and far northwestern Pacific Ocean. On the contrary, rainfall was above normal over the west coast of India, Bangladesh, Myanmar, the Bay of Bengal, central-eastern tropical Indian Ocean, central South China Sea, and the western Pacific east of 140E.

5. Rainfall Patterns: Last 5 Days Rainfall was mainly below or near normal over the Asian monsoon region and western Pacific except the above-normal rainfall over northern India and northern Philippines as well as the water domains to its east and west. Above-normal rainfall was also observed over the central tropical Indian Ocean.

6. Rainfall Time Seriesover 5x5 lat-lon boxes • *This unified land-only daily precipitation dataset is different from the CMAP dataset used in the previous three spatial maps. • Upper panel: The rainfall related to tropical depression Mujigae was helpful for overcoming the deficit in the seasonally-accumulated rainfall over southern China. • Middle panel: In spite of the deficient rainfall over much of India, the monsoon rainfall over Bangladesh and adjacent regions has been mostly above normal. • Bottom panel: The recent heavy rainfall could hardly bring the seasonally-accumulated rainfall over southern Indo-China peninsula back to normal.

7. Atmospheric Circulation Monsoon flow was stronger than normal over South Asia and the tropical Indian Ocean. An anomalous cyclonic pattern was observed over the South China Sea and northern Philippine Sea and an anomalous anti-cyclonic pattern was found over East Asia.

8. NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 1 & Week 2 Week-1 Week-2

9. Prediction of Large-Scale Monsoon Circulation Upper panel: Webster-Yang monsoon index (Webster and Yang 1992) defined as U850 (0-20ºN, 40-110ºE) – U200 (0-20ºN, 40-110ºE).Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the large-scale monsoon circulation over tropical Asia will be near or below normal in the next two weeks. Lower panel: Correlation between rainfall and Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850-mb winds on the monsoon index (vectors) for September. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

10. Prediction of South Asian Monsoon Circulation Upper panel: South Asian monsoon index (Goswami et al. 1999) defined as V850-V200 over 10-30ºN, 70-110ºE.Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the South Asian monsoon circulation will be near or below normal in the next two weeks. Lower panel: Correlation between rainfall and South Asian monsoon index (Goswami et al. 1999; shading) and regression of 850-mb winds on the monsoon index (vectors) for September. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

11. Prediction of East Asia – NW Pacific Monsoon Upper panel: East Asia – Western North Pacific (EAWNP) monsoon index (Wang et al. 2008) defined as U850 (5-15ºN, 40-80ºE) – U850 (20-30ºN, 70-90ºE). Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the EAWNP monsoon circulation will be near normal. Lower panel: Correlation between rainfall and East Asia – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850-mb winds on the monsoon index (vectors) for September. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

12. Prediction of East Asian Monsoon Upper panel: East Asian monsoon index (Li and Zeng 2002; GRL). Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the East Asian monsoon circulation will be near normal. Lower panel: Correlation between rainfall and East Asian monsoon index (Li and Zeng 2002; shading) and regression of 850-mb winds on the monsoon index (vectors) for September. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

13. Summary • In the past week, rainfall was mainly below or near normal over the Asian monsoon region and western Pacific except the above-normal rainfall over northern India and northern Philippines as well as the water domains to its east and west. Above-normal rainfall was also observed over the central tropical Indian Ocean. • The NCEP Global Forecast System predicts that, in the next two weeks, the Asian monsoon circulation tends to be near normal or weaker than normal.

14. Onset of the Asian Monsoon

15. Climatology