If any one is interested this is where the number for verifications come from
Sum( forecast data points - avg forcast data points) * ( observed data points - avg observed data points)
All divided by
Standard deviation of forecast points * standard deviation of observed points.
There is also a correction factor that accounts for latitude.
The bit on the top is actually the covariance of forecast vs obersvation which tells you how much one variable changes wrt the other. The bit on the bottom basically normalises it so everything is on a scale between -1 and 1
-1 is a perfect negative coralation
1 is a perfect positive coralation.
a corralation of 0.6 and above is recommended by the ECMWF as useful for long wave patterns
and 0.8 and above for short wave patterns.
Based on this for 500mb heights (which is the most accurate parameter)
'short wave' FI is 168 hours for the ECMWF and 159 hours for the GFS
'long wave' FI is 216 hours for the ECMWF and 204 hours for the GFS
For surface pressure, probably take 12 hours off these figures.
EDIT: sorry posted this in the media thread by mistake :(
EDIT: just realised I made a careless error in the top part of the equation. This ofc should be covarience.
Note: The FI figures are based on the most recent model verification data averaged over the last 30 days. Sometimes the 10day ECMWF can have verification figures as high as 0.8, other times as low as 0.25.
Most recently the ECMWF and GFS have been performing better than usual for long timescales.
Edited by user
18 January 2014 14:54:13
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Reason: Not specified
Twitter: @QuantumOverlord (general), @MedicaneWatch (medicane/TC stuff)
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
Total: 8 days with snow/sleet falling.
2022/2023 Snow days (approx 850hpa temp):
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
Total: 7 days with snow/sleet falling.
2021/2022 Snow days (approx 850hpa temp):
26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.