Decision support experiments and evaluations using seasonal to ...

At NCEP, the dynamical tool, CFS, is complemented
by a number of statistical forecast
tools, three of which, Screening Multiple
Linear Regression (SMLR), Optimal Climate
Normals (OCN), and Canonical Correlation
Analysis (CCA), are merged with the CFS to
form an objective consolidation forecast product
(Figure 2.16). While the consolidated forecast
exceeds the skill of the individual tools, the
official seasonal forecast from CPC involves
a subjective merging of it with forecast and
nowcast information sources from a number of
different sources, all accessible to the public at
CPC’s monthly briefing. The briefing materials
comprise 40 different inputs regarding the
past, present and expected future state of the
land, oceans and atmosphere from sources both
internal and external to CPC. These materials
are posted online at: .
The resulting official forecast briefing has been
the CPC’s primary presentation of climate forecast
information each month. Forecast products
are accessible directly from CPC’s root level
home page in the form of maps of the probability
anomalies for precipitation and temperature
in three categories, or “terciles”, representing
below-normal, normal and above-normal values;
a two-category scheme (above and below
normal) is also available. This framework is
used for the longer lead outlooks (Figure 2.17).
The seasonal forecasts are also available in the
form of maps of climate anomalies in degrees
Celsius for temperature and inches for precipitation
(Figure 2.18). The forecasts are released
monthly, have a time-step of three months, and
have a spatial unit of the climate division (Figure
2.19). For users desiring more information
about the probabilistic forecast than is given in
the map products, a “probability of exceedence”
(POE) plot, with associated parametric information,
is also available for each climate division
(Figure 2.20). The POE plot shows the shift of
the forecast probability distribution from the
climatological distribution for each lead-time
of the forecast.
In addition to NCEP, a few other centers, (e.g.,
the International Research Institute for Climate
and Society [IRI]) produce similar consensus
forecasts and use a similar map-based, tercile-
Decision-Support Experiments and Evaluations using Seasonal to
Interannual Forecasts and Observational Data: A Focus on Water Resources
Figure 2.17 The National Center for Enivironmental Predictions CPC seasonal
outlook for precipitation also shown as a tercile probability map. Tan/brown
(green) shading indicates regions where the forecast indicates an increased
probability for precipitation to be in the dry (wet) tercile, and the degree of
shift is indicated by the contour labels. EC means the forecast predicts equal
chances for precipitation to be in the A (above normal), B (below normal),
or N (normal) terciles. Figure obtained from .
Figure 2.18 The National Center for Enivironmental Predictions CPC
seasonal outlook for precipitation shown as inches above or below the total
normal precipitation amounts for the 3-month target period (compare
with the probability of exceedence forecast product shown in Figure 2.20).
Figure obtained from .
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