1 The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP 14 July 2008 For more information, visit:

2 Outline Recent Evolution and Current Conditions Monsoon Prediction Summary Climatology

3 Rainfall Patterns: Last 90 Days During the past 90 days, heavy precipitation occurred over the Bay of Bengal, Bangladesh, southern China, Philippines, the southern Philippine Sea, southern Japan, and the North Pacific storm-track region. Precipitation was above normal over most of the equatorial regions, tropical-subtropical Asia, and the western Pacific except over southern India, the eastern Indo-China peninsula, western-central Indonesia, and Papua New Guinea. Precipitation was below normal over the tropical-subtropical Southern Hemisphere including Madagascar, the Indian Ocean, and Australia.

4 Rainfall Patterns: Last 30 Days During the past 30 days, heavy precipitation occurred over the west coast and northeast of India, northern Bay of Bengal, Bangladesh, southern China, and southern Japan. Precipitation was above normal over most of the equatorial regions and the Northern Hemisphere, especially over the equatorial western Indian Ocean, northern Bay of Bengal, northeastern India, southern China, the East China Sea, southern Philippines, and the southern Philippine Sea. However, precipitation was below normal over southern India, eastern Indo-China peninsula, and the eastern tropical Southern Indian Ocean.

5 Rainfall Patterns: Last 5 Days Above-normal precipitation occurred over northern India, northern Bay of Bengal, southern-central China, northern South China Sea, equatorial western-central Indian Ocean, and the subtropical North Pacific east of 150E during the last 5 days. Below-normal precipitation was observed over southern India, the tropical eastern Indian Ocean, southern Philippines, the Philippine Sea, the tropical western Pacific, eastern Nepal, southwestern China, the northern East China Sea, Korea, southern Japan, and the extratropical northwestern Pacific east of Japan.

6 Recent Evolution: Rainfall Upper right: The rainfall over southern Japan has been below normal during the past 2-3 weeks. Central right: Heavy rainfall has occurred over southern China during the past several days. Bottom right: The monsoon rainfall over northern India (and Nepal) has been continuously above normal. For other boxes, see: Global_Monsoons/Asian_Monsoons/90d-precip_click_map.shtml

7 Atmospheric Circulation The cross-equatorial flow over the western-central Indian Ocean was stronger than normal, and an anomalous anti-cyclonic pattern was observed over the eastern Arabian Sea, southern India, and the Bay of Bengal. Anomalous cyclonic pattern controlled southern East Asia and southern China and anti- cyclonic pattern was over the South China Sea and Philippines.

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

9 W-Y Monsoon Prediction Upper panel: Webster-Yang monsoon index (Webster and Yang 1992) defined as the mean U850-U200 over 0-20N, E. The NCEP GFS predicts that, in the next two weeks, the large-scale Asian monsoon circulation will continue to 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 July.

10 SA Monsoon Prediction Upper panel: South Asian monsoon index (Goswami et al. 1999) defined as the mean V850-V200 over 10-30N, E. The NCEP GFS predicts a normal South Asian monsoon 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 July.

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/ E). The NCEP GFS predicts that, in the next two weeks, the monsoon circulation over East Asia and the western North Pacific will be weaker than normal. 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 July.

12 Summary During the past 90 days, heavy precipitation occurred over the Bay of Bengal, Bangladesh, southern China, Philippines, the southern Philippine Sea, southern Japan, and the North Pacific storm-track region. Precipitation was above normal over most of the equatorial regions, tropical-subtropical Asia, and the western Pacific except over southern India, the eastern Indo-China peninsula, western-central Indonesia, and Papua New Guinea. Precipitation was below normal over the tropical-subtropical Southern Hemisphere including Madagascar, the Indian Ocean, and Australia. During the past 30 days, heavy precipitation occurred over the west coast and northeast of India, northern Bay of Bengal, Bangladesh, southern China, and southern Japan. Precipitation was above normal over most of the equatorial regions and the Northern Hemisphere, especially over the equatorial western Indian Ocean, northern Bay of Bengal, northeastern India, southern China, the East China Sea, southern Philippines, and the southern Philippine Sea. However, precipitation was below normal over southern India, eastern Indo-China peninsula, and the eastern tropical Southern Indian Ocean. Above-normal precipitation occurred over northern India, northern Bay of Bengal, southern- central China, northern South China Sea, equatorial western-central Indian Ocean, and the subtropical North Pacific east of 150E during the last 5 days. Below-normal precipitation was observed over southern India, the tropical eastern Indian Ocean, southern Philippines, the Philippine Sea, the tropical western Pacific, eastern Nepal, southwestern China, the East China Sea, Korea, southern Japan, and the extratropical northwestern Pacific east of Japan. Cross-equatorial flow was stronger than normal over the western-central Indian Ocean. Anomalous anti-cyclonic patterns were observed over the eastern Arabian Sea, southern India, and the Bay of Bengal and over southern East Asia and southern China. An anti- cyclonic pattern was over the South China Sea and Philippines The NCEP GFS predicts a weak large-scale Asian monsoon and a normal South Asian monsoon, but above-normal rainfall over southern China and the East China Sea, for the next two weeks.

13 Onset Dates of ASM

14 Climatology