mean wave height correlation statistics are within one
Table 5. 1995 Peak Period Statistical Summary
percentage point. Mean period bias statistics in
Buoy Model Mean RMS SI
SS
Cor
Table 4 for NDBC 42001 show that WAM and WIS
Error
Bias
mean periods over the year of measurements tend to
(sec) (sec)
be slightly high. WW3 bias is low. WIS mean RMS
42001 WIS
-0.13 1.17 19.4 0.98
0.63
for mean period is the lowest of the three with 0.59
WAM 0.08
1.36 23.1 0.92
0.55
sec. Skill scores are very close with WIS and WW3
WW3 -0.60 1.15 19.1 0.98
0.58
showing means of 0.99; WAM's mean is 0.96. WIS
42020 WIS
-0.36 1.17 18.3 0.98
0.61
has the highest mean correlation and lowest mean skill
WAM -0.19 1.31 20.6 0.97
0.54
score. NDBC 42001 peak period statistics in Table 5
WW31 -1.01 1.12 16.7 0.98
0.63
show that WIS and WW3 have negative mean biases,
42035 WIS
-0.02 1.54 28.3 0.95
0.53
-0.13 and 0.60 m, indicating under-prediction. WAM
WAM -0.01 1.54 28.4 0.94
0.47
shows a positive bias of 0.08 sec. All RMS means are
WW31 -0.97 1.04 18.7 0.97
0.71
slightly over 1 sec. WIS shows slightly better mean
42036 WIS
-0.45 1.34 24.8 0.96
0.49
statistics for correlation. WW3 and WIS both show a
WAM -0.02 1.53 29.3 0.97
0.56
scatter index of 19 compared to WAM's 23. WIS and
WW31 -0.84 1.01 18.3 0.98
0.68
WAM both have a 0.98 skill score.
Table 3. 1995 Wave Height Statistical Summary
Buoy Model Mean RMS SI
SS
Cor
5.3 HURRICANE OPAL COMPARISONS
Error
Bias
(m)
(m)
Hurricane Opal (a category 4 hurricane) was active in
42001 WIS
0.28
0.28 24.4 0.92 0.91
the Gulf of Mexico September 27-October 6, 1995.
WAM -0.08 0.26 22.4 0.98 0.91
Figure 2 shows the wave comparison results for WAM
at 42001 for October 1995. Figure 3 shows similar
WW3 0.02
0.28 23.6 0.98 0.90
results for WIS, and Figure 4 shows the WW3
42020 WIS
0.08
0.35 25
0.96 0.85
hindcast comparison. Note that both the WAM and
WAM -0.27 0.38 28
0.96 0.80
WIS hindcasts slightly over-predict the maximum
1
WW3 -0.19 0.43 28
0.96 0.77
wave height during Opal. WW3 under-predicts the
42035 WIS
0.17
0.23 26.3 0.93 0.87
maximum wave height and also under-predicts the
WAM -0.20 0.21 24.2 0.96 0.86
energy after the peak has passed. WIS shows an
WW31 -0.15 0.24 25
0.97 0.83
excellent period comparison for this storm.
42036 WIS
0.10
0.30 32.4 0.95 0.90
WAM -0.26 0.32 34.3 0.94 0.84
5.4 WAVE DIRECTION COMPARISONS
WW31 -0.19 0.31 28.3 0.96 0.89
Wave direction comparison results in Figures 2, 3, and
Table 4. 1995 Mean Period Statistical Summary
4 are very similar for all three models. Table 6 shows
Buoy Model Mean RMS SI
SS
Cor
the wave direction statistics for October 1995 for the
Error
Bias
three models. The table contains the mean direction
(sec) (sec)
difference in degrees ( x ), a concentration statistic
42001 WIS
0.18
0.59 10.8 0.99
0.77
^
WAM 0.14
0.74 14.2 0.96
0.70
with 1.00 being perfect correlation, and the number of
WW3 -0.45 0.63 11.6 0.99
0.73
comparisons. These statistics use the circular
42020 WIS
-0.00 0.60 10.8 0.99
0.76
direction techniques discussed in Tracy (2002) which
WAM -0.07 0.72 13.2 0.98
0.66
is an application of Bowers et al. (2000). The
0.75
concentration statistic is a measure of how the two
42035 WIS
0.25
0.73 15.3 0.98
0.69
distributions compare. Values 5.0 and greater for this
WAM -0.06 0.80 16.3 0.98
0.56
statistic indicate that the two directional distributions
WW31 -0.90 0.55 11.0 0.98
0.79
being compared are similar. These direction statistics
42036 WIS
-0.05 0.77 16.0 0.98
0.61
were calculated for waves 1m and above. Note that
WAM 0.00
1.01 12.5 0.91
0.64
mean directional difference results for all three models
1
WW3 -0.65 0.59 11.7 0.98
0.78
indicate hindcast and measurements are within 2 deg.
1
For months of Jan-Mar 1995 only
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