GUIDE WAVE ANALYSIS AND FORECASTING - WMO

44
30
20
14
10
8
6
5
4
3
2
1.4
1
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.6
Wave height: H c in m
Wind speed u
in m/s
30
1
25
1.5
20
17.5
15
12.5
10
2
7.5
3
5
4
6
GUIDE TO WAVE ANALYSIS AND FORECASTING
100 n. mi. = 185 km; 100 km = 54 n. mi.
1 kn = 0.51 m/s; 1 m/s = 1.94 kn
10
Fetch X in km
15
20
30
40
0.1
0.1 0.5 1 2 2 6 9 12 18 24 36 48 72 96
TABLE 4.1
Specific examples of manual forecasting presented in Chapter 4
and associated sub-section number
Description Sub-section
No.
1 Determining sea-state characteristics for a given wind speed and fetch 4.3.1
2 Determining sea state for an increasing wind speed 4.3.2
3 Extrapolating an existing wave field with further development from a constant wind 4.3.3
4 Extrapolating an existing wave field with further development from an increasing wind 4.3.4
5 Computing when swell will arrive, what periods it will have and how these periods will change for 36 h
after arrival begins 4.4.1
6 Same as 5, except for a long fetch in the generation area 4.4.2
7 Computing swell characteristics at Casablanca for a storm of nearby origin 4.4.3
8 Estimating the swell heights for the cases described in 5, 6 and 7 4.4.4
9 Determining wave number and shoaling factor for two wave periods and several representative depths 4.5.1.1
10 Finding the shallow water refraction factor and angle, for a given deep water wave angle with the bottom,
shallow depth, and wave period 4.5.1.2
11 Finding the refraction factor by Dorrestein’s method 4.5.1.3
12 Finding the shallow water height and period for a given wind speed, shallow water depth, and fetch 4.5.2
60
2
100
200
150
300 400
600
Wave period T c in s
Wind duration in hours
Figure 4.1 — Manual wave forecasting diagram (from Gröen and Dorrestein, 1976)
3
1000
4
1500 2000 3000 4000
5
6
8
7
9
12
11
10
17
16
15
14
13
Wind speed u.
in m/s
30
25
20
17.5
15.0
12.5
10.0
7.5
5