1. 1 The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP July 12, 2010 For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml

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

3. 3 Precip Patterns: Last 90 Days During the past 90 days, precipitation was above average over the Arabian Sea, Bay of Bengal, Bangladesh, equatorial Southeast Asia and eastern Indian Ocean, southern China, Japan, maritime Indonesia, and the northwestern Pacific storm track region. On the other hand, below-average precipitation occurred over India, Indo-China peninsula, the Philippines, equatorial western Pacific, and subtropical Southern Indian Ocean.

4. 4 Precip Patterns: Last 30 Days During the past 30 days, precipitation was above average over much of tropical Asia except India, Indo-China peninsula, and the Philippines. Above-average precipitation was also observed over the eastern Arabian Sea, Bay of Bengal, tropical eastern Indian Ocean, and the northwestern Pacific storm track region. However, below- average also occurred over the tropical-subtropical western Southern Indian Ocean, equatorial western Pacific, and northeastern Asia.

5. 5 Precip Patterns: Last 5 Days This past week, rainfall seems to be generally deficient everywhere, except along equatorial western Indian Ocean, southeastern China, where it is above normal.

6. 6 Rainfall Time Series over 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 heavy rainfall over southern and southeastern China in the second half of June contributed to the clearly above-average values of the accumulated regional rainfall. The Mei-yu over eastern China has been particularly week so far this year (not shown) Middle panel:. Rainfall deficits continue to deepen over Indo-China peninsula. Lower panel: Accumulated rainfall has been below average over central- northern India. Rainfall deficits also continue to build up over the Gangetic plains in eastern India(not shown)

7. 7 Atmospheric Circulation The trade wind over tropical western Pacific was stronger than normal and an intensified subtropical high affected northwestern Pacific and the South China Sea. An anomalous anti-cyclonic pattern was centered over the head Bay of Bengal thus contributing to the decreased precipitation over the eastern Gangetic plains south of the Himalayas.

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

9. 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. 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 July. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. The NCEP Global Forecast System predicts that the large-scale monsoon circulation over tropical Asia will continue to be below normal. Lately, the GFS predictions of monsoon rainfall vary considerably from week to week.

10. 10 Prediction of South Asian Monsoon Circulation Upper panel: South Asian monsoon index (Goswami et al. 1999) defined as v850 (10-30ºN, 70-110ºE) – v200 (10-30ºN, 70-110ºE). Positive (negative) values indicate strong (weak) than normal monsoon. 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 July. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. The NCEP Global Forecast System predicts that the large-scale monsoon circulation over tropical Asia will be overall near normal to slightly above normal in the next two weeks.

11. 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. 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 July. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the monsoon circulation over Southeast Asia and northwestern Pacific will continue to be weaker than normal.

12. 12 Summary Above-average rainfall was observed over the eastern Arabian Sea, Bay of Bengal, western Indonesia, and tropical-eastern Southern Indian Ocean. Below-average rainfall was found over the southern hill of the Tibetan plateau, part of the Indo-China peninsula, and a band extending from southern China, northern South China Sea, the Philippines, to the equatorial western Pacific. Even though the southwest summer monsoon rains have covered all of India, the season-to -date rainfall continues to be below normal, especially along the eastern Gangetic plains. The weekly rainfall forecasts by the NCEP GFS continue to vary from week to week, and is now predicting below normal rainfall in the coming two weeks.

13. 13 Onset of the Asian Monsoon

14. 14 Climatology