The Asian-Australian Monsoon System: Recent Evolution and Current Status

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The Asian-Australian Monsoon System Recent
Evolution and Current Status
Update prepared by Climate Prediction Center /
NCEP 2 May 2008
For more information, visit http//www.cpc.ncep.
noaa.gov/products/Global_Monsoons/Asian_Monsoons/A
sian_Monsoons.shtml
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Outline

• Recent Evolution and Current Conditions
• Monsoon prediction
• Summary
• Climatology

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Rainfall Patterns Last 90 Days
During the past 90 days, heavy precipitation
occurred over much of the maritime continent,
tropical eastern and southern Indian Ocean,
tropical western Pacific, and the North Pacific
storm-track region. Precipitation was above
normal over most of the tropics except the
western Indian Ocean, Papua New Guinea, and the
equatorial Pacific east of 150E. Above-normal
precipitation also appeared over the storm-track
region. Below-normal precipitation was found over
the subtropical Southern Hemisphere including
Madagascar, the Indian Ocean, and central
Australia. Precipitation was also below normal
over the Middle East, western Asia, the coastal
regions of East and Northeastern Asia, and the
subtropical North Pacific.
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Rainfall Patterns Last 30 Days
During the past 30 days, heavy precipitation
occurred over the tropics (except the western
Indian Ocean) and the North Pacific storm-track
region. Precipitation was above normal over the
tropical Bay of Bengal, the maritime continent
(except Papua New Guinea), tropical western
Pacific (except the equatorial Pacific east of
150E), and over the storm-track region.
Below-normal precipitation was found over the
subtropical Southern Hemisphere including
Madagascar, the Indian Ocean, and Australia.
Precipitation was also below normal over the
Middle East, Myanmar, part of Indonesia, the
coastal regions of southern China and eastern
Indo-China peninsula, Northeast Asia, and
subtropical northwestern Pacific.
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Rainfall Patterns Last 5 Days
The precipitation pattern during the last 5 days
was characterized by the above-normal
precipitation over the Bay of Bengal and the
below-normal precipitation over the
tropical-subtropical Southern Hemisphere
(especially over the Indian Ocean), east coast of
Australia, southeastern China, Japan, and Korea.
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Recent Evolution Rainfall
For other boxes, see http//www.cpc.ncep.noaa.gov
/products/ Global_Monsoons/Asian_Monsoons/90d-prec
ip_click_map.shtml

• Upper-right The precipitation over the
  Indo-China peninsula has been above normal for
  weeks. Whether the onset of the local monsoon is
  earlier than normal deserves particular
  attentions.
• Central-right The precipitation over southern
  India has been near normal during the past weeks
  despite that the heavy precipitation in March
  significantly increased the accumulated
  precipitation.
• Bottom-right Over Top End Australia, the
  precipitation has been below normal for weeks
  although the accumulated precipitation for the
  season was above normal.
• The accumulated precipitation over other tropical
  boxes has been mostly above normal during this
  season.

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Recent Evolution OLR

• The convection over the Bay of Bengal has
  intensified and the convection over the
  equatorial eastern Indian Ocean has been
  suppressed after a northward shift of the
  convective center (central and bottom panels).
• Except the dryness over western Indonesia and the
  wetness over the Philippines, convection remains
  mainly normal over the maritime continent and
  adjacent regions (bottom panel).

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Atmospheric Circulation OLR Last Week

• Upper-right An upper-tropospheric anticyclonic
  pattern controlled southern Asia and the
  cross-equatorial flow over eastern Indian Ocean
  was stronger than normal.
• Lower-right Note the cyclonic pattern over the
  Bay of Bengal, which was energized by the strong
  cross-equatorial flow and the northeasterly flow
  over the South China Sea and the Indo-China
  peninsula. The trade winds over the tropical
  central-western Indian Ocean and western Pacific
  were stronger than normal.

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WY Monsoon Prediction

• Upper panel Webster-Yang monsoon index (Webster
  and Yang 1992) defined as the mean U850-U200 over
  0-20N, 40-110E. The NCEP GFS predicts that, in
  the next two weeks, the large-scale monsoon
  circulation will be stronger than normal,
  implying above normal precipitation and westerly
  anomalies at the lower troposphere over tropical
  Asia.

• Lower panel Correlation between precipitation
  and the Webster-Yang monsoon index (Webster and
  Yang 1992 shading) and regression of 850-mb
  winds against the monsoon index (vectors) for May.

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SA Monsoon Prediction

• Upper panel South Asian monsoon index (Goswami
  et al. 1999) defined as the mean V850-V200 over
  10-30N, 70-110E. The NCEP GFS predicts that the
  South Asian monsoon circulation will be mainly
  near normal in the next two weeks.

• Lower panel Correlation between precipitation
  and the South Asian monsoon index (Goswami et al.
  1999 shading) and regression of 850-mb winds
  against the monsoon index (vectors) for May.

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EA-WNP Monsoon Prediction

• Upper panel East Asian Western North Pacific
  monsoon index (Wang et al. 2008) defined as the
  mean difference of U850(5-15N/90-130E)
  U850(20-30N/110-140E). The NCEP GFS predicts
  that, in the next two weeks, the monsoon
  circulation over East Asia and western North
  Pacific will be stronger than normal, meaning
  above normal precipitation over the northern
  maritime continent and the northwestern Pacific.

• Lower panel Correlation between precipitation
  and the East Asian Western North Pacific
  monsoon index (Wang et al. 2008 shading) and
  regression of 850-mb winds against the monsoon
  index (vectors) for May.

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Summary

• Above-normal precipitation occurred over the
  tropical Asian-Australian sector from 15S to 10N
  during the past months, except over the
  equatorial western Pacific (east of 150E) and the
  tropical western Indian Ocean. Above-normal
  precipitation was also found over the subtropical
  western Pacific storm-track region.
• Below-normal precipitation appeared over the
  subtropical southern Indian Ocean, Madagascar,
  central Australia, and the subtropical
  northwestern Pacific high region. The Middle East
  and western Asia were also drier than normal
  during the past months.
• The NCEP GFS predicts that the large-scale Asian
  monsoon circulation and the monsoon over East
  Asia and northwestern Pacific will be stronger
  than normal in the coming two weeks. It also
  predicts near-normal monsoon circulation over
  South Asia.

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Onset Dates of ASM
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Climatology