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 27 July 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 eastern Arabian Sea, west coast of India, the Bay of Bengal, Bangladesh, Myanmar, the South China Sea, Philippines, the Philippine Sea, Korea, and most of the western Pacific. Below-normal precipitation was observed over eastern Africa, southern and northern India, most of the India Ocean, East Asia, eastern Indo-China peninsular, Indonesia, Malaysia, and part of Australia. 3

Rainfall Patterns: Last 30 Days During the past 30 days, above-normal precipitation was observed over the eastern Arabian Sea, western India, the Bay of Bengal, Myanmar, the South China Sea, the Philippine Sea, Korea, and part of the western Pacific. Below-normal precipitation appeared over southeastern and northern India, tropical southern Indian Ocean, much of Southeast Asian land/islands, eastern China, and eastern Australia. 4

Rainfall Patterns: Last 5 Days Monsoon rainfall was above normal over central-western India, eastern Bay of Bengal, eastern China, southern Japan, and around Papua New Guinea and Bismarck Sea regions. Rainfall was below normal over southern and northeastern India, Sri Lanka, southern China, the South China Sea, Philippines, the Philippine Sea, tropical eastern Indian Ocean, and part of Indonesia. 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. • Upper panel: The East Asian Mei-yu fluctuated around normal apparently. • Middle panel: The monsoon rainfall has been persistently below normal over the southwestern maritime continent. • Bottom panel: In spite of the deficient rainfall in June and the past week, the monsoon rainfall over southern India has been near or above normal. 6

Atmospheric Circulation Anomalous anti-cyclonic patterns were over southern India and Philippines, and an anomalous cyclonic pattern was seen over Korea and southern Japan. The monsoon flows over regions from central India, the Bay of Bengal, and the South China Sea to the East China Sea and southern Japan were stronger than normal. 7

NCEP/GFS Model Forecasts Bias-Corrected Precip. Anom. for Weak 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 (020ºN, 40 -110ºE) – U 200 (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 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 August. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. 9

Prediction of South Asian Monsoon Circulation Upper panel: South Asian monsoon index (Goswami et al. 1999) defined as V 850 -V 200 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 August. 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 U 850 (5 -15ºN, 40 -80ºE) – U 850 (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 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 August. Green (brown) shading indicates increase (decrease) in rainfall associated with strong monsoon. 11

Summary • In the past week, monsoon rainfall was above normal over central-western India, eastern Bay of Bengal, eastern China, southern Japan, and around Papua New Guinea and Bismarck Sea regions. Rainfall was below normal over southern and northeastern India, Sri Lanka, southern China, the South China Sea, Philippines, the Philippine Sea, tropical eastern Indian Ocean, and part of Indonesia. • The NCEP Global Forecast System predicts that, in the next two weeks, the monsoon circulation over tropical Asia will be overall near normal with below normal rainfall over southern-central India and much of the maritime continent. 12

Onset of the Asian Monsoon 13

Climatology 14