IRI Climate Digest
April-June 2001 Seasonal Forecast
Date and Period of Forecast
In December 2000, the IRI has prepared an experimental Climate Outlook
for January-June 2001. Presented here is the long-lead Outlook for
the period April-June 2001. The complete forecast with discussion can be found at http://iri.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.
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.
The Outlook for January - March 2001 can also be found at http://iri.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.
April-June 2001 Precipitation Probabilities
The Outlook for January - June 2001 can also be found at http://iri.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.
April-June 2001 Temperature Probabilities
Of relevance in the
preparation of this Outlook has been the
near-average but slightly cooler than normal
(SSTs) in the
central equatorial Pacific Ocean.
Near neutral equatorial Pacific SST conditions are
in effect for
both seasons of the forecast,
and April-May-June 2001.
The SSTs of the tropical Indian Ocean were assumed
Tropical Atlantic SSTs are near normal during the
forecast season and are expected to become slightly cooler than normal
during the second season.
The following procedures and information were used to
prepare this Climate Outlook:
Coupled ocean-atmosphere model predictions of tropical Pacific SST
heavy weighting has been given to the NOAA /NCEP, Climate Modeling Branch
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
Appropriate Regional Climate Outlook Forum consensus guidance.
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.