Slide 7 of 27
The forecast numbers are based on the 30-year average temperature pattern shown in solid green.
This shows how the winter of 1996/97 fell short of average, and how very warm the winter of 1997/98 was, reflecting El Nino influences.
Roughly speaking, the probability of seeing colder weather in the first 2 months of 1999 than we had for the same period in 1998 approaches a level greater than 95 percent. Perhaps more obviously, there is a 50 percent probability that we will see at least the 8 percent increase in winter (October-March) heating degree-days assumed for the base case forecast.