Model output statistics MOS 
9 
4. Wind surge: wind components of 295 ±10 degrees and exponent 1, 1.5 or 2 derived from GFS 
model (KALNAY et al., 1990). Correlations from 0.8 to 0.7. 
5. Basic set of other GFS predictors and derived variables (about 150 potential predictors) with best 
correlations from 0.75 to 0.65 for U components of (geostrophic) wind between 950 hPa and 10 m 
above mean sea level. 
6. Wind surge observations at Aberdeen in its double function as a signal provider for external surges 
coming in from the Atlantic Ocean (CORKAN, 1950) and provider of general information about the 
North Sea's current water volume, with correlations from 0.6 to 0.5. External surges are measurable 
at the Cuxhaven gauge after about 12 hours. 
7. Pers2D_korr: this is the most important predictor in the system: the correction of the last known 
initialisation error of the 2D model. Correlation of predictor and predictand is low, but correlation of 
the predictor with the residuum (error) of the 1-predictor MOS equations with the initialisation error 
of DMO of the last corresponding surge event in some cases is greater than 0.6. 
In the discussion of MOS equations below, the symbiosis of physics (2Dv4 model and GFS model), 
synoptics (in the selection and transformation of predictors), and statistics (multiple linear screening 
regression) has been described exemplarily. The standard MSWR regression table format used for this 
purpose has only been explained to the extent required to understand the explanatory texts. A more 
detailed description of the table outputs is provided in KNUPFFER (1996) and HOFFMANN (2008). 
3.2 Predictands 
The following predictands are forecast: 
Surge 
SurgeH 
SurgeL 
Surge+ 
Surge- 
StH+ 
StH- 
StL+ 
StL- 
Kombi 
unclassified predictand 
high water surge classified by HW/LW 
classified by HW/LW 
classified by surge+/surge- 
classified by surge+/surge- 
classified by StH+/StH-/StN+/StN- 
classified by StH+/StH-/StN+/StN- 
classified by StH+/StH-/StN+/StN- 
classified by StH+/StH-/StN+/StN- 
Suitable combination of the latter four predictands if ABS(surge - 4 cm) 
> 2*Abs_Err_surge, otherwise Kombi=surge. Abs_Err_surge is the 
MOS-computed absolute error of the MOS prediction of the surge predictand. 
low water surge 
positive surge 
negative surge 
surge+ at HW 
surge- at HW 
surge+ at LW 
surge- at LW