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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction. Update prepared by Climate Prediction Center / NCEP June 1, 2010. 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 Update prepared by Climate Prediction Center / NCEP June 1, 2010 For more information, visit:http://www.cpc.ncep.noaa.gov/products/Global_Monsoons/Asian_Monsoons/Asian_Monsoons.shtml
Outline • Recent Evolution and Current Conditions • Monsoon Prediction • Summary • Climatology
Precip Patterns: Last 90 Days During the past 90 days, precipitation was above average over 10S-10N, with below-average precipitation to both northern and southern sides of the latitude band (e.g. 20S-10S and 10N-20N) especially the Indo-China Peninsula. Above-average precipitation was also observed over Bangladesh, East Asia, and the western North Pacific storm track region.
Precip Patterns: Last 30 Days During the past 30 days, precipitation was above average over 10S-10N, with below-average precipitation to the north and the south especially over the Indo-China Peninsula and subtropical southern Indian Ocean. Above-average precipitation was also observed over Bangladesh, northern Bay of Bengal, part of East Asia, and the western North Pacific storm track region.
Precip Patterns: Last 5 Days Above-average rainfall was observed over the Bay of Bengal, Bangladesh, and East Asia. Below-average precipitation occurred over the tropical southern Indian Ocean, Indo-China Peninsula, northern South China Sea, northern Philippines, and subtropical-extratropical northwestern Pacific.
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: The rainfall over southeastern China and much of East Asia has been mostly above average in the past 90 days. Middle panel: In the past 90 days, rainfall has been mostly below average over much of the Indo-China Peninsula. Lower panel: The pre-monsoon rainfall over southern India has been mostly above average.
Atmospheric Circulation A strong Somali jet and an anomalous cyclonic pattern over southern India and northern Bay of Bengal were observed, associated with anomalously strong cross-equatorial flow over the western and central Indian Ocean. The southwesterly anomalies over East Asia, suggesting a larger-than-normal water vapor supply, were linked to the above-average regional rainfall.
NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 1 & Week 2 Week-1 Week-2
Prediction of Large-Scale Monsoon Circulation Right 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 be near normal in the next two weeks. Left 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.
Prediction of South Asian Monsoon Circulation Right panel: South Asian monsoon index (Goswami et al. 1999) defined as v850 (10-30ºN, 70-110ºE) – v200 (10-30ºN, 70-110ºE).Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that the monsoon circulation over South Asia will be near normal or weaker than normal in the next two weeks. Left 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.
Prediction of East Asia – NW Pacific Monsoon Right 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 monsoon circulation over Southeast Asia and northwestern Pacific will be changing from near normal to stronger than normal. Left 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.
Prediction of East Asian Monsoon Right panel: East Asian monsoon index (Li and Zeng 2002; GRL). Positive (negative) values indicate strong (weak) than normal monsoon. The NCEP Global Forecast System predicts that, in the next two weeks, the East Asian monsoon circulation will be above normal for the first upcoming week and at or below normal the following week. Left panel: Correlation between rainfall and East Asian monsoon index (Li and Zeng 2002; 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 Bay of Bengal, Bangladesh, and East Asia. Below-average precipitation occurred over the tropical southern Indian Ocean, Indo-China Peninsula, northern South China Sea, northern Philippines, and subtropical-extratropical northwestern Pacific. • The pre monsoon rainfall totals during the last 90 days over the Indian regions is above normal. Over eastern China also the 90 day rainfall accumulation is above normal. The NCEP Global Forecast System predicts that the actual summer monsoon onset is likely to be during the second week of June over southern India.
