July-September 2001 Seasonal Forecast

Date and Period of Forecast

In March 2001, the IRI has prepared an experimental Climate Outlook for April-September 2001. Presented here is the long-lead Outlook for the period July-September 2001. The complete forecast with discussion can be found at http://iri.ldeo.columbia.edu/climate/forecast/net_asmt/.

This Climate Outlook is dependent on the quality of the sea surface temperature (SST) predictions. For the tropical Pacific, these predictions can be expected to provide useful information, but there is some uncertainty concerning the detailed evolution of SSTs.  Spread in global SST predictions is a source of uncertainty in the Outlook provided here. The procedures, models, and data used to derive this Climate Outlook may be somewhat different from those used by National Meteorological Services in particular regions and may differ from the official forecasts issued in those areas.

Regional Influences

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. For further information concerning this and other guidance products, users are strongly advised to contact their National Meteorological Services.

Precipitation Outlook

The Outlook for April-June 2001 can also be found at http://iri.ldeo.columbia.edu/climate/forecast/net_asmt/. Maps show expected precipitation probabilities in tercile classes. The maps indicate probabilities that seasonal precipitation will fall into the wettest third of the years (top number), the middle third of years (middle number) or the driest third of the years (bottom). An outlook of climatology "C" (light grey) indicates equal probabilities in each class; i.e., there is no basis for favoring the forecast of any particular category. Areas marked "D" (dark grey) experience a pronounced dry season during the forecast period, typically receiving less than 15% of their annual precipitation or less than 5 cm total during this three-month period. Boundaries between sub-regions should be considered transition zones, and their location considered to be only qualitatively correct.

July-September 2001 Precipitation Probabilities

Temperature Outlook

The Outlook for April-June 2001 can also be found at http://iri.ldeo.columbia.edu/climate/forecast/net_asmt/. The temperature map shows expected probabilities that the seasonal temperatures will fall into the warmest third of the years (top number), the middle third of the years, or the coldest third of the years (bottom number). A qualitative outlook of climatology "C" (light grey) indicates equal probabilities in each class; i.e., there is no basis for favoring the forecast of any particular category. Boundaries between sub-regions should be considered transition zones, and their location considered to be only qualitatively correct.

July-September 2001 Temperature Probabilities

Ocean Conditions

Of relevance in the preparation of this Outlook is the predicted decay of the slightly cooler than normal sea-surface temperatures (SSTs) in the central equatorial Pacific Ocean and the forecast development of weak, warmer than normal conditions by the second forecast period.  Near neutral equatorial Pacific SST conditions are in effect for the first season of the forecast, April-May-June 2001, while during the second season, July-August-September 2001, they are expected to be slightly above average. The SSTs of the tropical Indian Ocean were assumed to be near average throughout both forecast periods.

Methods

The following procedures and information were used to prepare this Climate Outlook:

Sources of information include ACMAD, COLA, CPTEC, CPC/NOAA, CMC, Department of Natural Resources (Queensland, Australia), NIWA, ECMWF, Indian Meteorological Department, PAGASA, Bureau of Meterology, and the South African Weather Bureau.

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