Climate Outlook
ASIA July 2001 - December 2001
Issued: June 2001
The IRI has prepared this experimental Climate Outlook for Asia for July
2001 - December 2001. Of relevance in the preparation of this outlook is
the prediction of near-average to slightly warmer than average
conditions in the eastern equatorial Pacific for the next 6 to 9
months. Currently the sea surface temperatures (SSTs) across much of
the eastern and central equatorial are near their long-term average
(SSTs)
, although slightly lower than average SSTs have developed along the
immediate western coast of South America and warmer than average SSTs
persist in the extreme western part of the basin. Near neutral
equatorial Pacific SST conditions are in effect for the first season of
the forecast, July-August-September
2001, while during the second season, October-November-December
2001, they are expected to be slightly above average. The warmer
than average SSTs that continue to dominate much of the Indian Ocean are
expected to decrease slowly through the forecast period. The area of
above-average temperature in the tropical south Atlantic Ocean is
expected to persist through at least the first half of the forecast
period.
METHODS -
This Outlook was prepared using the following procedures and
information:
A) Coupled ocean-atmosphere model predictions of tropical Pacific SST
covering the forecast period. Particularly heavy weighting has been
given to predictions from the coupled model operated by the NOAA
National Centers for Environmental Prediction, Climate Modeling Branch.
This model suggests a continuation of near-average conditions during the
first forecast season. The forecast for near-neutral conditions is
consistent with some, but not all, numerical and statistical forecasts
of central and eastern Pacific SSTs.
B) Forecasts of the tropical Indian ocean using a statistical model
developed by the IRI.
C) Global atmospheric general circulation model (GCM) predictions of the
atmospheric response to the present and predicted sea-surface
temperature patterns.
D) Other sources of information include
NASA's
Seasonal to Interannual Prediction Project (GSFC-NASA).
The procedures, models, and data used to derive this Climate Outlook may
be somewhat different from those used by the national meteorological
services in the region. Thus, this product may differ from the official
forecasts issued in those areas. The Climate Outlook for July-December
2001 is dependent on the accuracy of the SST predictions. For the
tropical Pacific, these predictions can be expected to provide useful
information, but there is some uncertainty concerning the evolution of
SSTs. Spread in global SST predictions is a source of uncertainty in the
Outlook provided here. Note that even if perfectly accurate SST
forecasts were possible, there would still be uncertainty in the climate
forecast due to chaotic internal variability of the atmosphere. These
uncertainties are reflected in the probabilities given in the forecast.
It is stressed that the current status of seasonal-to-interannual
climate forecasting allows prediction of spatial and temporal averages,
and does not fully account for all factors that influence regional and
national climate variability. This Outlook is relevant only to seasonal
time scales and relatively large areas; local variations should be
expected, and variations within the 3-month season should also be
expected. For further information concerning this and other guidance
products, users are strongly advised to contact their National
Meteorological Services.
OUTLOOK -
This Outlook covers two seasons: July - September 2001 and October -
December 2001. Maps are given showing tercile probabilities of
precipitation and temperature. The maps for precipitation indicate the
probabilities that the seasonal precipitation will fall into the wettest
third of the years (top number), the middle third of the years (middle
number), or the driest third of the years (bottom number). The color
shading indicates the probability of the most dominant tercile -- that
is, the tercile having the highest forecast probability. The color bar
alongside the map defines these dominant tercile probability levels. The
upper side of the color bar shows the colors used for increasingly
strong probabilities when the dominant tercile is the above-normal
tercile, while the lower side shows likewise for the below-normal
tercile. The gray color indicates an enhanced probability for the
near-normal tercile (nearly always limited to 40%). As before, numbers
and their associated histograms show the probabilities of the three
terciles. In areas with lots of spatial detail, there may not be
sufficient room on the map, to allow histograms for each region. In
those cases, some idea of the probabilities may be gained from the color
alone. A qualitative outlook of climatology ("C") indicates that there
is no basis for favoring any particular category. Areas that are marked
by "D" represent regions experiencing their dry season (less than 15% of
annual precipitation) and for which less than 5cm of precipitation
typically occurs over the season. Otherwise, for example, in the case of
the Philippines in July - September 2001
(Map A), there is a 40% probability
that the precipitation will be in the wettest third of the years, a 35%
chance it will be in the near-normal third of the years, and a 25%
chance that the precipitation will be in the driest third of the years.
Maps of temperature show expected probabilities that the seasonal
temperatures will fall into the warmest third of the years, the middle
third of the years, or the coldest third of the years
(Map A) . The numbers for each region on the temperature maps
indicate the probabilities of temperatures to fall in each of the three
categories, above-, near-, and below-normal.
An additional precipitation
map
is provided for the first season indicating probabilities for extreme
precipitation anomalies. Extremes are defined as anomalies that fall
within the top and bottom 15th percentile of the observed records. A
priori, there is a 15% probability of being within the extremely wet
category, and a 15% probability of being within the extremely dry
category, leaving a 70% probability that the precipitation will not be
extreme. The maps indicate areas of increased risk of extreme
precipitation totals. Three levels of increased risk are defined:
slightly enhanced risk, enhanced risk, and greatly enhanced risk. For
slightly enhanced risk, there is a 25-40% probability that precipitation
will be within the indicated extreme, i.e. wet or dry. This represents
an approximate doubling of the climatological risk. For enhanced risk,
there is a 40-50% probability that precipitation will be within the
indicated extreme. This represents an approximate tripling of the
climatological risk. For greatly enhanced risk, the probability that
precipitation will be within the indicated extreme exceeds 50%, i.e. the
indicated extreme is the most likely outcome. A similar map is provided
in the first season indicating probabilities of
extreme temperature
anomalies.
Boundaries between sub-regions should be considered as transition zones,
and their location considered to be only qualitatively correct.
July - September 2001:
PRECIPITATION
The following regions of enhanced probabilities of precipitation
anomalies are indicated:
Slightly enhanced probabilities for below normal precipitation
(40%-30%-30% and 40%-35%-25%) are forecast in 3 separate areas,
including for much of Syria (off map), much of Iraq (off map), most of
Iran, small parts of Afghanistan and Pakistan, parts of India, Nepal,
and parts of western and northern China.
Slightly enhanced probabilities for near normal precipitation
(35%-40%-25%) are forecast for a very small portion of the northwestern
coast of India.
Slightly enhanced probabilities for above normal precipitation
(30%-30%-40%) are forecast for southern Myanmar, southwestern Thailand,
Cambodia, and southern Vietnam.
Slightly enhanced probabilities for near normal and above normal
precipitation (20%-40%-40%) are forecast for the Andaman Islands, south
of Myanmar.
A greatly enhanced probability for below normal precipitation
(50%-30%-20%) is forecast for central Sumatra. Weaker probabilities for
below normal precipitation (45%-35%-25% and 40%-35%-20%) surround this
region, including the remainder of Sumatra, most of Borneo, southwestern
Malaysia, and Java.
An enhanced probability for above normal precipitation (25%-30%-45%) is
forecast for Halmahera Island and the extreme eastern tip of the
northern Celebes. Weaker probabilities for above normal precipitation
(30%-30%-40% and 25%-35%-40%) surround this region, including most of
Papua New Guinea, eastern Irian Jaya, Buru and Ceram Islands, the
central and northern Celebes, and part of the Federated States of
Micronesia.
Slightly enhanced probabilities for near normal precipitation
(30%-40%-30%) are forecast for part of the Marshall Islands, Nauru
Island, and part of the Federated States of Micronesia.
TEMPERATURE
The following regions of enhanced probabilities of temperature anomalies
are indicated:
Slightly enhanced probabilities for below normal temperatures
(40%-30%-30%) are forecast for central Siberia, Russia.
Slightly enhanced probabilities for below normal temperatures
(40%-35%-20%) are forecast for northeastern Iraq (off map; see map for
Europe), part of northern Iran, part of southern Russia, and small
portions of northern Afghanistan.
Slightly enhanced probabilities for above normal temperatures
(25%-35%-40%) are forecast for portions of southern and central Iran.
An enhanced probability for above normal temperature (25%-30%-45%) is
forecast for part of northern China and southern Mongolia. Weaker
probabilities for above normal temperature (30%-30%-40%) surround this
region, including additional portions of northern China and southern and
central Mongolia.
An enhanced probability for below normal temperature (45%-35%-20%) is
forecast for Kokkaido Island of northern Japan, the southern Kuril
Islands of Russia, and the Sakhalin peninsula of Russia. Weaker
probabilities for below normal temperature (40%-35%-20%) surround this
region, including northern Honshu Island of Japan, the northern Kuril
Islands of Russia, the Kamchatka Peninsula, the Commander Islands, the
Sikhote Alin Range of eastern Russia, northeastern China, extreme
eastern Mongolia and the adjacent portion of Russia.
Slightly enhanced probabilities for near normal temperature
(30%-40%-30%) are forecast for eastern Russia on the shore of the Sea of
Okhotsk.
Slightly enhanced probabilities for near normal temperature
(35%-40%-25%) are forecast for part of northeastern China, North Korea,
South Korea, Shikoku and Honshu Islands of Japan, and Taiwan.
Slightly enhanced probabilities for above normal temperature
(25%-35%-40%) are forecast for a portion of central Pakistan and a small
portion of northwestern India.
Slightly enhanced probabilities for above normal temperature
(25%-35%-40%) are forecast for eastern India, Nepal, portions of
southwestern and south-central China, Bangladesh, most of Burma,
northern Laos and northern Vietnam.
Slightly enhanced probabilities for near normal temperature
(25%-40%-35%) are forecast for Hainan Island of China, southern Vietnam,
eastern Cambodia, southern Myanmar and southern Thailand. This region
extends southward into Indonesia, where the probabilities become
35%-40%-25% over Java.
An enhanced probability for above normal temperature (25%-30%-45% and
20-35%-45%) is forecast for all of the Philippines except for the
northernmost tip, Palau Island, and the northern portion of the
Indonesian part of Malaysia. Weaker probabilities for above normal
temperature (25%-35%-40%) surround this region, including the
northernmost tip of the Philippines, a central portion of the Indonesian
part of Malaysia, Brunei, and the northernmost arm of the Celebes.
October - December 2001:
PRECIPITATION
The following regions of enhanced probabilities of precipitation
anomalies are indicated:
Slightly enhanced probabilities for above normal precipitation
(30%-30%-40%) are forecast for southwestern Iran (off map), as well as a
separate area in northeast Iran, Afghanistan and central and southern
Pakistan.
Slightly enhanced probabilities for near normal precipitation
(25%-40%-35%) are forecast for extreme northern Afghanistan, northern
Pakistan, extreme northern India, and small portions of southern Russia
and western China.
An enhanced probability for below normal precipitation (45%-35%-20%) is
forecast for portions of southeastern China. Weaker probabilities for
below normal precipitation (40%-35%-25%) surround this region, including
a larger portion of southeastern China and South Korea.
Slightly enhanced probabilities for below normal precipitation
(40%-30%-30%) are forecast for Sri Lanka.
Slightly enhanced probabilities for above normal precipitation
(30%-30%-40%) are forecast for southern Myanmar, southern Thailand and
northwestern Malaysia.
A greatly enhanced probability for above normal precipitation
(20%-30%-50%) is forecast for central Indonesia, including Timor, the
southernmost and northernmost Celebes, and some of the Moluccas Islands.
Weaker probabilities for above normal precipitation (20%-35%-45% and
25%-35%-40%) surround this region, including the Philippines, Palau
Island, Papua New Guinea, Irian Jaya, eastern Java, Vanuatu Island, New
Caledonia, some of the Federated States of Micronesia, western Kiribati
and Tuvalu Island.
A greatly enhanced probability for below normal precipitation
(50%-30%-20%) is forecast for southeastern Sumatra and western Java.
Weaker probabilities for below normal precipitation (40%-35%-25%)
surround this region, including south-central Sumatra, central Java and
extreme southwestern Borneo.
TEMPERATURE
The following regions of enhanced probabilities of temperature anomalies
are indicated:
lightly enhanced probabilities for below normal temperature (40%-30%-30%
and 40%-35%-25%) are forecast for most of southeast Asia from eastern
India to eastern China, stretching northeastward through Korea, Japan,
northeast China, the adjacent portion of Russia, and a large region
covering much of northeastern Russia with the exception of the extreme
eastern tip near Bering Strait.
Slightly enhanced probabilities for above normal temperature
(30%-30%-40%) are forecast for the eastern tip of northeast Russia.
An enhanced probability for above normal temperature (20%-35%-45%) is
forecast for Guam and vicinity, the Marshall Islands, and Wake Island.
Weaker probabilities for above normal temperature (25%-35%-40%) surround
this region, including the Solomon Islands, the westernmost Federated
States of Micronesia, extreme southeastern Papua New Guinea, Palau
Island, and the southern and central Philippines, and the western part
of Kiribati in which near normal shares an enhanced likelihood
(20%-40%-40%).
OBSERVED CLIMATOLOGY DATA for Jul-Aug-Sep and
Oct-Nov-Dec
CLIMATOLOGICAL AVERAGE: Temperature
Precipitation
TERCILE THRESHOLDS (33%-ile & 67%-ile): Temperature
Precipitation
EXTREME THRESHOLDS (15%-ile & 85 %-ile): Temperature
Precipitation
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