INTERPRETATION

BENEFIT AND LIMITATION

GLOSSARY

Local 3-Month Temperature Outlook - Probability of Exceedance Graph

The Local Three-Month Temperature Outlook (L3MTO) Probability of Exceedance (POE) Graph provides the most detailed outlook information. It shows the expected chance (y-axis, in percent) that the average three-month temperature will exceed (i.e. be higher than) the temperatures shown on x-axis in degrees Fahrenheit.

The graph contains two curves: a red curve, representing the POE for the 1981-2010 reference period and a green curve, representing the forecasted POE. As you move along each curve from left to right, the probability decreases and the temperature increases, indicating that it is less likely to exceed higher temperature values. The vertical colored lines represent the average three-month temperatures observed during past five years. The legend on the right provides a reference to the year of observation.

Additionally, an interactive worksheet is available to the right of the POE Graph called the 'Customized Confidence Interval Worksheet'. The selection of confidence intervals is made by using a pull-down menu located to the right of the graph, with choices of: 99%, 95%, 90%, 75%, and 50%. The results for the temperature range associated with the selected confidence interval are displayed below the pull-down menu.

The "XML Data" button provides access to the numeric data for the POE Graph in XML format. The data will be displayed in a new web browser page.

Probability of Exceedance Outlook Interpretation Example for July through September 2006:

Graph Summary: The expected POE (green curve) is shifted to the right of the 1981-2010 POE (red curve) Possible Interpretations: 1. The expected three-month temperature (green dots) of a particular POE is higher than such temperature in the 1981-2010 reference period (red dots). For example, for 1981-2010, there was a 90% chance that the average three-month temperature was higher than 60.8°F; the outlook expects a 90% chance for the average three-month temperature to be higher than 61.4°F	Graph Summary: The Forecast POE (green curve) overlaps with the 1981-2010 POE (red curve) Possible Interpretations: 1. The chances that any particular average temperature will be exceeded are the same as the chances of 1981-2010 reference period.
2. To identify the expected POE increase from the 1981-2010 POE, choose a particular temperature (for example, 62.3°F), move vertically to intersect of the red curve (50%), and then continue to the green curve (69%): there is 19% (69%-50%) greater chance that the observed average three-month temperature will be higher than 62.3°F	2. Users should take this information as guidance only. They need to determine whether the temperature distribution for the 1981-2010 reference period provides sufficient information for their decision making.