In December 2000, the IRI
prepared a Climate Outlook for January - June 2001.
Here we provide a subset of the December Net Assessment Forecast
with observed rainfall percentiles for the same period for qualitative
comparison. IRI's June Net assessment forecast for the period July - December
2001 will be available at
http://iri.columbia.edu/climate/forecast/net_asmt/ later this month.
Uncertainties
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.
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).
January-March 2001 Precipitation Probabilities and Observed Precipitation Anomalies. Precipitation anomalies are shaded ONLY for "above-normal" (above 67%-ile) and "below-normal" (below 33%-ile).
Of relevance in the
preparation of this Outlook were the near-average, but slightly cooler than normal,
sea-surface temperatures
(SSTs)
in the central equatorial Pacific Ocean.
Near neutral equatorial Pacific SST conditions are in effect for both seasons of the forecast,
January-February-March 2001 and
April-May-June 2001.
The SSTs of the tropical Indian Ocean were assumed to remain normal.
Tropical Atlantic SSTs are near-normal during the first forecast season and are expected
to become slightly cooler than normal during the second season.
Methods
The following procedures and information were used to
prepare this Climate Outlook:
Coupled ocean-atmosphere model predictions of tropical Pacific SST --
particularly heavy weighting has been given to the NOAA /NCEP, Climate Modeling Branch coupled model
Statistical forecasts of Indian Ocean and Atlantic Ocean sea surface temperature
The response of Atmospheric global circulation model (GCM) predictions to
the present and predicted SST patterns
Statistical analyses
Appropriate Regional Climate Outlook Forum consensus guidance.
Additional 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 Service.