– Please note that this is a logarithmic scale, ie it is does not indicate the exact risk of an event, and can only be used for severe weather.
– If the confidence equation is between 90 and 100, the condition has maximum confidence.
– Between 75 and 90, the condition has high confidence.
– Between 55 and 75, the condition has solid confidence, some uncertainty.
– Between 40 and 55, the condition has moderate likelihood, moderate uncertainty.
– Between 30 and 40, the condition has weak likelihood, notable uncertainty.
– Between 20 and 30, the condition has high uncertainty.
– Between 10 and 30, the condition has very high uncertainty.
– Between 5 and 10 the condition has even higher uncertainty.
– Less than 5 – negatable confidence – can be disregarded until it’s value comes into the above categories.
The confidence equation
14 – days away
/ severity factor
x model confidence
x 10 (see constants below – variable)
x 0.4
Severity factor (Qualitative – NOT continuous – choose 1 that fits best):
6 – Never happened, would have catastrophic impacts on society
4 – Never happened, but is within conceivable terms. A slight increase on the “max ever recorded” etc.
3 – The max ever recorded, or indistinguishly close, all the way to occurs every decade or so
2 – Occurs every 2 or 3 years in said location, fairly common, “to be expected”
1 – Occurs every year
0.8 – Occurs multiple times a year (frequent)
Model confidence
Continuous: Above 0.7 to 1.0 – Widespread and consistent cross model agreement, higher end = more solid agreement for specific measuring value,
0.6 to 0.7 – agreement in many models, but lacking of pure consistency,
0.4 to 0.6 – suggested in some models, close to 50% of the time, and in only a few runs
0.2 to 0.4 – only suggested in few models / runs – sparsely indicated
0.0 to 0.2 – only suggested in 1 to 3 runs, very limited support
x 10 – a constant. X by 11 if 3 or less days away, by 13 if less 2 days away, and 14 if less than 1 day away.
x 0.4.
Example – 40C in London next Thursday?
14 – 5 days way = 9. 40C in London. has been categorized as 4 severity factor. 9 / 4 = 2.25 x 0.1 (very limited support) = 0.225. x 10 (constant) = 2.25. x 0.4 = 0.9, so 1.
Confidence is low.
Example – 29C in London tomorrow?
14 – 1 = 13. 13 / 0.8. = 16.25 x 1.0 = 16.25. x 14 = 227.5.
X 0.4 = 91 confidence ranking.
Please note that in some cases with a date above 14 days, a negative number may be produced, for this reason this equation is recommended to be used for comparing the statistical probability of weather events for different areas in the medium range time scale.
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