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 11 May 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 During the past 90 days, above-normal precipitation occurred over the tropics east of 90E and over the Coral Sea. Below-normal precipitation was observed over the Middle East, eastern India, southern China, Korea, Australia, Madagascar, and equatorial and southern-subtropical central Indian Ocean.

4. Rainfall Patterns: Last 30 Days During the past 30 days, above-normal precipitation occurred over much of the tropics between 100E and 150E (except Indonesia), Bay of Bengal, and the waters east of Japan. Below-normal precipitation was observed over part of Middle East, India, East Asia, Indonesia, Australia, tropical Indian Ocean (especially the east), Australia, Madagascar, southern-subtropical central Indian Ocean, and western Pacific (east of 150E).

5. Rainfall Patterns: Last 5 Days Rainfall was mainly below normal during the last week, especially over the tropical central-eastern Indian Ocean and East Asia. Above normal rainfall was observed over the South China Sea, Philippines, the Philippine Sea, and subtropical western Pacific 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. • While dry conditions continue to appear over the near-equatorial regions and southern China, above-normal rainfall has occurred over the Southeast Asia regions between the dry zones, especially over the Philippines and the South China Sea.

7. Atmospheric Circulation The most significant feature in the past week was the strong anomalous cyclonic pattern over the Indo-China peninsula, South China Sea, East Asia, the Philippine Sea, and the East China Sea. The trade wind over southern tropical Indian Ocean and the westerly flow over northern Indian Ocean have strengthened.

8. NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Week 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). The NCEP Global Forecast System predicts that the large-scale monsoon circulation will be weaker than normal in the next two weeks. • Lower panel: Correlation between precipitation and the Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850-mb winds on the monsoon index (vectors) for May.

10. 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). The NCEP Global Forecast System predicts that, in the next two weeks, the EAWNP monsoon circulation will be first weakening and then becoming stronger than normal. • Lower panel: Correlation between precipitation and the East Asia – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850-mb winds on the monsoon index (vectors) for May.

11. Summary • Rainfall was mainly below normal during the last week, especially over the tropical central-eastern Indian Ocean and East Asia. Above normal rainfall was observed over the South China Sea, Philippines, the Philippine Sea, and subtropical western Pacific Ocean. • The NCEP GFS predicts that, in the next two weeks, rainfall tends to increase over Southeast and southern East Asia from an overall below-normal condition although the large-scale monsoon circulation is still weaker than normal.

12. Onset of the Asian Monsoon

13. Climatology