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

This report provides an update on the recent evolution and current conditions of the Asian-Australian monsoon system, along with predictions for its future. It includes information on precipitation patterns, atmospheric circulation, and model forecasts.

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

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  1. The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP January 24, 2011 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. Precip Patterns: Last 90 Days During the past 90 days, the west-east dipole in the tropical Indian Ocean precipitation, with dryness to the west and wetness to the east, seems to have established strongly..Further to the east, the precip associated with the east Asian winter monsoon is characterized by more than normal rainfall except over Southern Malaysia, western Indonesian maritime continent and eastern New Guinea. Australia has experienced an overall very wet monsoon season so far particularly to the north and east.

  4. Precip Patterns: Last 30 Days The mean and anomalous pattern of precipitation over the last 30 days is very similar to the 90 day pattern.

  5. Precip Patterns: Last 5 Days Consistent with NCEP GFS prediction, during the five days ending the indicated period, rainfall was overall somewhat below normal over much of the winter monsoon region and even much of the tropical Indian Ocean, except for heavy rain in and around Philippines.

  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. Over a large part of Southeast Asia, the accumulated rainfall has been persistently above average in the past three months. 6

  7. Atmospheric Circulation The anomalous cyclonic circulation near Philippines is the main cause of, and consistent with the above normal rainfall in this region during the indicated period. This region continues to receive heavy rains from a series of tropical systems resulting in floods and loss of lives. Similar conditions prevailed over eastern and south eastern Australia in earlier weeks.

  8. NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 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).Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the Webster-Yang monsoon index will continue to stay at or near normal values. 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 January. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

  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). Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the Southeast Asian and northwestern Pacific monsoon index will stay at around normal levels. 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 January. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.

  11. Prediction of Australian Monsoon Upper panel: Australian monsoon index (Hung and Yanai 2004) defined as U850 averaged over 2.5ºS-15ºS, 110-150ºE. Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the Australian monsoon circulation will slide to near normal values in the next two weeks. Lower panel: Correlation between rainfall and Australian monsoon index (Hung and Yanai 2004; shading) and regression of 850-mb winds on the monsoon index (vectors) for December. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. 11

  12. Summary • The monsoon over southeast Asia has brought excessive rainfall, flooding and devastation this season to many areas of the monsoon region, particularly over northern, eastern Australia in earlier weeks, and in Philippines this recent week. However, the NCEP GFS model predicts the monsoon circulation and associated rainfall winding down to near normal levels over most of these regions and even below normal rainfall in interior Australia in the next two weeks..

  13. Demise of the Asian Monsoon

  14. Onset of the Australian Monsoon

  15. Climatology

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