IRI Climate Digest July 2001
July - September 2001 Seasonal Forecasts
Date and Period of Forecast
In June 2001, the IRI prepared a Climate Outlook
for July - December 2001. Here we provide a subset of the June Net Assessment
Forecast. The entire IRI June Net assessment forecast for the period
July - December 2001 is available 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 other regions of the globe for the seasons July-August-September
and October-November-December 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.
Boundaries between sub-regions should be considered transition zones, and
their location considered to be only qualitatively correct. Color
shading indicates which tercile class has the greatest probability of occurrence
with darker shading indicating greater likelihood as shown by the
legend to the right of the plots.
July-September 2001 Precipitation Probabilities for Africa
July-September 2001 Precipitation Probabilities for Asia
July-September 2001 Precipitation Probabilities.
This forecast consists of expected probabilities of temperature in tercile
The terciles refer to the seasonal temperature falling into the warmest
third of the years (top tercile), the middle third of years (middle tercile)
or the coldest third of the years (bottom tercile). Boundaries between
sub-regions should be considered transition zones, and their location considered
to be only qualitatively correct. Color shading indicates which tercile
class has the greatest probability of occurrence with darker shading indicating
greater likelihood as shown by the legend on the bottom of the plots.
The IRI is in the process of implementing new graphics for its forecast
products. Currently, global maps only indicate (by shading) the tercile
class with the greatest probability of occurrence.
Please consult the regional maps at http://iri.columbia.edu/climate/forecast/net_asmt/
for the probabilities of each tercile class.
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.
The following procedures and information were used to prepare this Climate
Coupled ocean-atmosphere model predictions of tropical Pacific SST -- particularly
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.
|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 Meteorology, and the
South African Weather Service.