The AsianAustralian Monsoon System Recent Evolution Current Status

The Asian-Australian Monsoon System: Recent Evolution, Current Status and Prediction Update prepared by Climate Prediction Center / NCEP 4 May 2009 For more information, visit: http: //www. cpc. ncep. noaa. gov/products/Global_Monsoons/Asian_Monsoons. shtml 1

Outline • Recent Evolution and Current Conditions • Monsoon Prediction • Summary • Climatology 2

Rainfall Patterns: Last 90 Days During the past 90 days, above-normal precipitation occurred over the tropics east of 90 E and over the Coral Sea. Below-normal precipitation was observed over the Middle East, eastern India, southern China, Korea, Australia, Madagascar, and equatorial and southern-subtropical central Indian Ocean. 3

Rainfall Patterns: Last 30 Days During the past 30 days, above-normal precipitation occurred over much of the tropics between 100 E and 150 E (except Indonesia) and the waters east of Japan and Madagascar. Below-normal precipitation was observed over part of Middle East, India, East Asia, Australia, tropical western Indian Ocean, southern-subtropical central Indian Ocean, and western Pacific. 4

Rainfall Patterns: Last 5 Days Rainfall was mainly below normal during the last week, especially over the tropical central-eastern Indian Ocean, East Asia, and the Indonesia – New Guinea regions. Above normal rainfall was observed over part of South China Sea, Philippines, and the Philippine Sea. 5

Rainfall Time Series over 5 x 5 lat-lon boxes *This unified land-only daily precipitation dataset is different from the CMAP dataset used in the previous three spatial maps. • While dry conditions continue to appear over the near-equatorial regions and southern China, above-normal rainfall has occurred over the Southeast Asia regions between the dry zones, especially over the Philippines. 6

Atmospheric Circulation The most eye-capturing feature is the strong anomalous cyclonic pattern over the South China Sea and the Philippine Sea. A weak anomalous anticyclonic pattern was observed over the tropical eastern Indian Ocean and easterly anomalies were seen over the equatorial Indian Ocean. 7

NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Week 1 & Week 2 Week-1 Week-2 8

Prediction of Large-Scale Monsoon Circulation • Upper panel: Webster-Yang monsoon index (Webster and Yang 1992) defined as U 850 (0 -20ºN, 40 -110ºE) – U 200 (0 -20ºN, 40 -110ºE). The NCEP Global Forecast System predicts that the large-scale monsoon circulation will be near or weaker than normal in the next two weeks. • Lower panel: Correlation between precipitation and the Webster-Yang monsoon index (Webster and Yang 1992; shading) and regression of 850 -mb winds on the monsoon index (vectors) for May. 9

Prediction of East Asia – NW Pacific Monsoon • Upper panel: East Asia – Western North Pacific (EAWNP) monsoon index (Wang et al. 2008) defined as U 850 (5 -15ºN, 40 -80ºE) – U 850 (2030ºN, 70 -90ºE). The NCEP Global Forecast System predicts that the EAWNP monsoon circulation will change from a strong phase to a weak phase in the next two weeks. • Lower panel: Correlation between precipitation and the East Asia – Western North Pacific monsoon index (Wang et al. 2008; shading) and regression of 850 -mb winds on the monsoon index (vectors) for May. 10

Summary • Rainfall was mainly below normal during the last week, especially over the tropical central-eastern Indian Ocean, East Asia, and the Indonesia – New Guinea regions. Above normal rainfall was observed over part of South China Sea, Philippines, and the Philippine Sea. • The NCEP GFS predicts that the rainfall over Southeast and East Asia will be mainly below normal in spite of the above-normal rainfall over the Philippines and its adjacent regions. 11

Onset of the Asian Monsoon 12

Climatology 13