1. 1 The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP 6 October 2008 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 Rainfall Patterns: Last 90 Days The CMAP precipitation dataset shows that, during the past 90 days, above normal precipitation occurred over the central tropical Indian Ocean, the Bay of Bengal, northern India along the Gangetic Plains, the South China Sea, the Philippines, and most of the maritime continent. Precipitation was below normal over central, northwestern, and southern India, and over eastern Indo-China peninsula. It was also below normal over the tropical southeastern Indian Ocean and tropical western Pacific. The east-west dipole in tropical Indian Ocean precipitation is a prominent feature this monsoon season.

4. 4 Rainfall Patterns: Last 30 Days During the past 30 days, above normal precipitation occurred over most of the regions east of 100E. Above normal precipitation also occurred over eastern Arabian Sea, west coast of India, and northwestern Bay of Bengal. However, below normal precipitation appeared over much of the tropical Indian Ocean and East Asia. The nature and polarity of the tropical Indian Ocean dipole were different between the past 30 days and the last 90 days.

5. 5 Rainfall Patterns: Last 5 Days In the past five days, rainfall was below normal over central-southern India, the Bay of Bengal, southern China, and part of tropical western Pacific. Above normal rainfall appeared over the equatorial central Indian Ocean and south of Japan.

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. (top right) Over southern China, intraseasonal variability of rainfall has been clearly observed this season. (mid right) Dry conditions have been seen over much of the Indo- China peninsula. (bottom right) The rainfall over central-southern India has been continuously below normal in spite of the above-normal accumulated rainfall in the past 90 days.

7. 7 Atmospheric Circulation During the past week, the subtropical northwestern Pacific high was stronger than normal and an anomalous anti-cyclonic pattern appeared over southern Asia with a center over the east coast of southern India and western Bay of Bengal. These conditions were consistent with the generally below normal precipitation over much of the tropical Asia and western Pacific sector.

8. 8 NCEP/GFS Model Forecasts Bias-Corrected Precipitation for Week 1 & Week 2 Week-1 Week-2

9. 9 W-Y Monsoon Prediction Upper panel: Webster-Yang monsoon index (Webster and Yang 1992) defined as the mean U850-U200 over 0-20N, 40- 110E. The NCEP Global Forecast System predicts that, in the next two weeks, the large-scale Asian monsoon circulation will be weaker than normal. Lower panel: Correlation between precipitation and the Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850-mb winds against the monsoon index (vectors) for October.

10. 10 SA Monsoon Prediction Upper panel: South Asian monsoon index (Goswami et al. 1999) defined as the mean V850-V200 over 10-30N, 70-110E. The NCEP Global Forecast System predicts that the South Asian monsoon circulation will be in a near normal or below normal condition in the next two weeks. Lower panel: Correlation between precipitation and the South Asian monsoon index (Goswami et al. 1999; shading) and regression of 850-mb winds against the monsoon index (vectors) for October.

11. 11 EA-WNP Monsoon Prediction Upper panel: East Asian – Western North Pacific monsoon index (Wang et al. 2008) defined as the mean difference of U850(5- 15N/90-130E) – U850(20-30N/110-140E). The NCEP Global Forecast System predicts that, in the next two weeks, the monsoon circulation over East Asia and the western North Pacific will be heading towards normal from a below normal condition. Lower panel: Correlation between precipitation and the East Asian – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850-mb winds against the monsoon index (vectors) for October.

12. 12 Summary The summer monsoon in 2009 was characterized by near normal precipitation over the lands and above normal precipitation over the tropical oceans. Over India, the accumulated monsoon rainfall was above normal along the Gangetic Plains but below normal over the southern, central, and northwestern India. The eastern Indo-China peninsula is among the regions where most serious deficit of monsoon rainfall occurred. A prominent precipitation dipole occurred over the tropical Indian Ocean during the past 90 days, with above normal rainfall over the west and below normal precipitation over the east. However, the dipole has undergone a significant change in the past 30 days, in both spatial extent and strength. Eastern Indian ocean has been receiving above normal rains with less rainfall to the west, thus weakening the dipole substantially. During the past week, precipitation was below normal over much of southern Asia. The NCEP Global Forecast System predicts that the Asian monsoon will continue to be below or near normal in the next two weeks, although rainfall tends to be above normal over the equatorial regions when heavy monsoon rainfall is about to shift from the northern hemisphere to the southern hemisphere.

13. 13 Retreat Dates of ASM

14. 14 Climatology