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

The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction. Update prepared by Climate Prediction Center / NCEP 8 June 2009. For more information, visit: http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml. Outline.

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

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  1. The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP 8 June 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 mainly occurred over the region of 10S-20N/100-150E (except Indonesia) and the Bay of Bengal. Below-normal precipitation was observed over eastern Africa, the Middle East, the India Ocean, southern China, southern Japan, and Australia.

  4. Rainfall Patterns: Last 30 Days During the past 30 days, above-normal precipitation was mainly observed over Bangladesh, the Bay of Bengal, the South China Sea, Philippines, the Philippine Sea, south of Java, and part of the maritime continent. Below-normal precipitation appeared clearly over eastern Africa, Madagascar, the Indian Ocean, East Asia, the East China Sea, western-central Indonesia, and Australia.

  5. Rainfall Patterns: Last 5 Days Above-average rainfall was observed over the eastern Bay of Bengal, the Philippine Sea, and New Guinea last week. The rainfall over the tropical Indian Ocean, East Asia, the East China Sea, and subtropical northwestern Pacific was below normal.

  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: In spite of the heavy rainfall in mid-late May, the rainfall over southern China has been mostly below normal since the onset of the local monsoon. • Middle panel: The monsoon rainfall over southern India has been overall near normal. • Bottom panel: Below-normal rainfall appeared persistently over western-central Indonesia.

  7. Atmospheric Circulation The cross-equatorial flow over the Indian Ocean was stronger than normal. Monsoon westerlies were stronger than normal over the Bay of Bengal, Indo-China peninsula, the South China Sea, and the western Pacific. Anomalous cyclonic patterns were observed over the South China Sea and the East China Sea.

  8. NCEP/GFS Model Forecasts Bias-Corrected Precip. for Week 2 Total Anomaly

  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 continue to 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 June. 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 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 June. 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 stronger than normal or 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 June. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

  12. Summary • Above-average rainfall was observed over the eastern Bay of Bengal, the Philippine Sea, and New Guinea last week. The rainfall over the tropical Indian Ocean, East Asia, the East China Sea, and subtropical northwestern Pacific was below normal. • The NCEP Global Forecast System predicts that, in the next two weeks, the large-scale Asian monsoon circulation (measured by the Webster-Yang monsoon index) and the South Asian monsoon circulation will be near normal or slightly below normal. The Southeast Asian monsoon circulation will be near normal or stronger than normal.

  13. Onset of the Asian Monsoon

  14. Climatology

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