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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