SOLUTION: From Figure 3-27 for constant depth, d
35 feet
for
and
Th en
and
F = 80,000 feet,
U = 50 mph.
H = 6.2 feet, say 6 feet,
T = 4.1 seconds, say 4 seconds.
*************************************
3.62 DECAY IN LAKES, BAYS, AND ESTUARIES
Section 3.33. Decay of A Wave Field applies to water areas contiguous
with land as well as those in the open océan. Most fetches in inland
waters will be limited at the front and at the rear by a land mass and
decay distances will usually be relatively small or nonexistent.
3.7 HURRICANE WAVES
When predicting wave génération by hurricanes, the détermination of
fetch and duration from a wind field is more difficult than for more normal
weather conditions discussed earlier. The large changes in wind speed and
direction with both location and time cause the difficulty. Estimation of
the free air wind field must be approached through mathematical models,
because of the scarcity of observations in severe storms. However, the
vertical température profile and atmospheric turbulence characteristics
associated with hurricanes differ less from one storm to another than for
other types of storms. Thus the relation between the free air winds and
the surface winds is less variable for hurricanes than for other storms.
3.71 DESCRIPTION OF HURRICANE WAVES
In hurricanes, fetch areas in which wind speed and direction remain
reasonably constant are always small; a fully arisen sea State never
develops. In the high-wind zones of a storm, however, long-period waves
which can outrun the storm may be developed within fetches of 10 to 20
miles and over durations of 1 to 2 hours. The wave field in front, or to
either side, of the storm center will consist of a locally generated sea,
and a swell from other régions of the storm. Samples of wave spectra,
obtained during hurricane Agnes, 1972, are shown in Figure 3-31. Most
of the spectra display evidence of two or three distinct wave trains; thus,
the physical implications of a significant wave period is not clear.
Other hurricane wave spectra computed with an analog spectrum analyse*
from wave records obtained during Hurricane Donna, 1959, hâve been publiée
by Bretschneider (1963). Most of these spectra also contained two distinc
î \ » lie
3-52
35 feet
for
and
Th en
and
F = 80,000 feet,
U = 50 mph.
H = 6.2 feet, say 6 feet,
T = 4.1 seconds, say 4 seconds.
*************************************
3.62 DECAY IN LAKES, BAYS, AND ESTUARIES
Section 3.33. Decay of A Wave Field applies to water areas contiguous
with land as well as those in the open océan. Most fetches in inland
waters will be limited at the front and at the rear by a land mass and
decay distances will usually be relatively small or nonexistent.
3.7 HURRICANE WAVES
When predicting wave génération by hurricanes, the détermination of
fetch and duration from a wind field is more difficult than for more normal
weather conditions discussed earlier. The large changes in wind speed and
direction with both location and time cause the difficulty. Estimation of
the free air wind field must be approached through mathematical models,
because of the scarcity of observations in severe storms. However, the
vertical température profile and atmospheric turbulence characteristics
associated with hurricanes differ less from one storm to another than for
other types of storms. Thus the relation between the free air winds and
the surface winds is less variable for hurricanes than for other storms.
3.71 DESCRIPTION OF HURRICANE WAVES
In hurricanes, fetch areas in which wind speed and direction remain
reasonably constant are always small; a fully arisen sea State never
develops. In the high-wind zones of a storm, however, long-period waves
which can outrun the storm may be developed within fetches of 10 to 20
miles and over durations of 1 to 2 hours. The wave field in front, or to
either side, of the storm center will consist of a locally generated sea,
and a swell from other régions of the storm. Samples of wave spectra,
obtained during hurricane Agnes, 1972, are shown in Figure 3-31. Most
of the spectra display evidence of two or three distinct wave trains; thus,
the physical implications of a significant wave period is not clear.
Other hurricane wave spectra computed with an analog spectrum analyse*
from wave records obtained during Hurricane Donna, 1959, hâve been publiée
by Bretschneider (1963). Most of these spectra also contained two distinc
î \ » lie
3-52