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This report provides an update on the recent evolution and current status of the Asian-Australian monsoon system, along with prediction information. It includes climatology precipitation patterns from the last 90 days, highlighting areas with below-normal and above-normal rainfall. The report also presents atmospheric circulation patterns and model forecasts for the monsoon system.
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The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP March 7, 2011 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 Note: Occasionally when the update date of the land+ocean precip maps are not close enough to the release date of this weekly scheduled monsoon ppt. we use the more recent land -only precip maps. During the past 90 days, precipitation has been generally near normal over much of the monsoon region, except over for below normal rainfall over eastern China and over parts of Papua New Guinea. Over Australia, the seasonal mean precipitation has been above normal.
Precip Patterns: Last 30 Days Please see Note in Slide three. The 30-day precipitation accumulation is seriously deficient over southeastern China. The somewhat deficient precipitation conditions over southeastern Australia is getting better. Elsewhere the precipitation is above normal, particularly over central and western Australia.
Precip Patterns: Last 7 Days Please see Note in Slide three. If land only maps are used, this map corresponds to the last seven days. During the last seven days, monsoon rainfall was below normal over southern Malaysia, maritime Indonesian continent and eastern China.. But rainfall was much above normal over interior Australia.
Rainfall Time Seriesover 5x5 lat-lon boxes Note: This unified land-only daily precipitation dataset is different from the CMAP dataset used in the previous three spatial maps. The time series of precipitation over the various regions is quite consistent with the spatial maps shown earlier, even though as noted above, the precip data sets are from different sources and are processed differently.
Atmospheric Circulation Overall, the weakened monsoon circulation over the region this past week is quite consistent with the below normal rainfall over much of the monsoon region except for the above normal precipitation over northern and interior northern Australia associated with a strong cyclonic circulation over the region.
NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 1 & Week 2 Week-1 Note: The NCEP/GFS based Forecast maps are not updated this week due to technical difficulties. The maps shown here are from prev. week. Week-2
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 suggests slightly above normal rainfall over the region. This index is more appropriate for northern summer monsoon than the during the current winter months now. 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 March. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.
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 be at about normal level in the next two weeks. 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 March Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon.
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 (over northern Australia) indicates much above normal rainfall in the first week followed by near normal rainfall in the second week. 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 March Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. 11
Summary • During the past 90 days, precipitation has been generally near normal over much of the monsoon region, except over for below normal rainfall over eastern China and over parts of Papua New Guinea. Over Australia, the seasonal mean precipitation has been above normal. The 30-day precipitation accumulation is seriously deficient over southeastern China. The somewhat deficient precipitation conditions over southeastern Australia is getting better. Elsewhere the precipitation is above normal, particularly over central and western Australia. • During the last seven days, the weakened monsoon circulation over the region this past week is quite consistent with the below normal rainfall over much of the monsoon region except for the above normal precipitation over northern and interior northern Australia associated with a strong cyclonic circulation over the region. The NCEP’s GFS model continues t o predict above normal rainfall over northern and interior northern Australia in the next week.
