## 453: Exceedance Probabilities

The exceedance probabilities indicate the probability that the value on the
*
x
*
-axis will be exceeded. The exceedance
probabilities are calculated using the climatological data (see
Climatology
for details
on setting the climatological period) and are shown by the thick red line, as well as by a smoothed thin red line that
represents a normal distribution fit to the data. (If the
Transform Y Data
option is
switched on the fitted distribution will not be smooth, but it will not be stepped either). The probabilities indicated by the
green curve are calculated using the current forecast. The values on the
*
x
*
-axis can be shown as anomalies, standardised
anomalies of % of average (if the
Zero Bound
option is switched on) by selecting the
appropriate standardisation option from the
Customise
menu item. The shading and vertical
dashed lines show the thresholds for the "above" and below" categories.

If more than one forecast is produced, the forecasts can be cycled using the up and down arrows (which will work better than attempting to type in the year, although CPT occasionally loses track of the year if they are cycled through too quickly). Similarly, the curves for different gridpoints / stations / series can be viewed by setting the appropriate number at the prompt. A series that has been omitted in the calculations will be skipped.

The forecasts can be saved by selecting the
**
Forecasts
**
tab from the
File _Output
Results
) menu. The graph itself can be exported as a graphics file by right-clicking anywhere in the child window and
selecting
Export
from the pop-up menu. A default name is given to the graphics file, but this name
can be changed using the browse button. The image quality for all the graphics formats can be improved by increasing the size
of the image (see
Options ~ Graphics ~ Graph Scaling
). The graphic title can be
set using the
**
Customise
**
option upon right-clicking in the child window.

The y-axis limits can be set by right-clicking on the image and then selecting the
**
Customise ~ Y-Axis Limits
**
option. The
maximum and minimum values on the y-axis are indicated and can be reset. Resetting these axis limits will in turn automatically
reset the tick-mark interval and number of tick marks. Greater flexibility for setting the tick marks is planned for future
releases. Further options for customising the graph, including adjusting the size of the fonts, and the size of the images, are
available from
Options ~ Graphics
.