Title: The AsianAustralian Monsoon System: Recent Evolution, Current Status and Prediction
1The Asian-Australian Monsoon System Recent
Evolution, Current Status and Prediction
Update prepared by Climate Prediction Center /
NCEP 16 May 2008
For more information, visit http//www.cpc.ncep.
noaa.gov/products/Global_Monsoons/Asian_Monsoons/A
sian_Monsoons.shtml
2Outline
-
- Recent Evolution and Current Conditions
- Monsoon Prediction
- Summary
- Climatology
3Rainfall Patterns Last 90 Days
During the past 90 days, heavy precipitation
occurred over much of the maritime continent,
tropical eastern Indian Ocean, tropical western
and southwestern 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 145E. 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 Australia.
Precipitation was also below normal over the
Middle East, western Asia, the coastal regions of
East and Northeast Asia, and the subtropical
North Pacific.
4Rainfall Patterns Last 30 Days
Heavy precipitation occurred over the tropics and
the North Pacific storm-track region.
Precipitation was above normal over the Bay of
Bengal, eastern Indian Ocean, the South China
Sea, the maritime continent (except
western-central Indonesia and Papua New Guinea),
tropical western Pacific (except the equatorial
region east of 150E), and over the storm-track
region. Below-normal precipitation was found over
much of the Southern Hemisphere including
Madagascar, the Indian Ocean, and Australia.
Precipitation was also below normal over the
Middle East, eastern India, Bangladesh, the
coastal regions of East and Northeast Asia, and
subtropical northwestern Pacific.
5Rainfall Patterns Last 5 Days
The precipitation pattern during the last 5 days
was characterized by the heavy and above-normal
precipitation over the eastern Bay of Bengal,
western Indo-China peninsula, the South China
Sea, and the subtropical northwestern Pacific
(due to the effects of typhoon and tropical
storms). Below-normal precipitation was observed
over the tropical Indian Ocean, western-central
Indonesia, southern and eastern China, and the
east coast of Australia.
6Recent 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 Before the impact of summer monsoon,
the rainfall over southern China remained below
normal. - Central-bottom right The rainfall over the
southern Indo-China peninsula, the Philippines,
and other northern tropical lands in the AA
monsoon region continued to be above normal. - While the major rain band had shifted to the
northern tropics, the precipitation over the
southern tropics became mainly below normal.
7Recent Evolution OLR
- Convection has been further intensifying over the
South China Sea and most of the (central-eastern)
maritime continent. - Convection has becoming weaker over the eastern
Bay of Bengal and western Indo-China peninsula
and has been further suppressed over the tropical
western-central Indian Ocean and Australia. - Convection has become weaker and been suppressed
over East Asia including southern and eastern
China.
8Atmospheric Circulation 200 mb
- Compared to the last week (left panel), the
upper-level anomalous anti-cyclonic pattern over
southern Asia and the easterly anomalies over its
southern flank and over the Arabian Sea have
become stronger, favoring an earlier
establishment of large-scale Asian summer monsoon
circulation.
9Atmospheric Circulation 850 mb
- Lower-level westerlies have extended eastward
from the Bay of Bengal and the Indo-China
peninsula to the South China Sea (SCS) and the
Philippine Sea. - Westerlies have prevailed over the central SCS
and anomalous westerly flow has clearly appeared
and intensified over southern-central SCS (right
panel), favoring an early onset of the SCS summer
monsoon. - Northward cross-equatorial flow continues to be
stronger than normal over the Indian Ocean.
10W-Y 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 normal or stronger than
normal, implying normal or above normal
precipitation and lower-level westerly anomalies
over tropical Asia including the Indo-China
peninsula and the South China Sea.
- 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.
11SA 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 close to
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.
12EA-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 normal or stronger than normal,
meaning normal or above normal precipitation over
the northern maritime continent and tropical
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.
13Summary
- Above-normal precipitation occurred over most of
the tropical Asian-Australian region during the
past months, except over the equatorial western
Pacific (east of 145E) 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,
Australia, and the subtropical northwestern
Pacific high region. The Middle East and western
Asia were also drier than normal during the past
months. - While major rain belt had shifted to the northern
tropics, the precipitation over the southern
tropics appeared below normal. Below-normal
precipitation was also observed over southern
East Asia during the past several days. - Lower-level westerlies have prevailed over the
Indo-China peninsula and southern-central South
China Sea, favoring an early onset of the South
China Sea summer monsoon. - The NCEP Global Forecast System predicts that the
large-scale Asian monsoon circulation and the
monsoon over East Asia and western North Pacific
will be near normal or stronger than normal in
the coming two weeks. It also predicts
near-normal monsoon circulation over South Asia.
14Onset Dates of ASM
15Climatology