EM 1110-2-1100 (Part II)
(Change 1) 31 July 2003
Figure II-2-15.
Common wind direction conventions
θmet ' 270 & θvec
(II-2-14)
where
θmet = direction in standard meteorological terms
θvec = direction in a Cartesian coordinate system with the zero angle wind blowing toward the east
(m) Wind estimates based on kinematic analyses of wind fields. In several careful studies, it has been
shown that one method of obtaining very accurate wind fields is through the application of "kinematic
analysis" (Cardone 1992). In this technique, a trained meteorological analyst uses available information from
weather charts and other sources to construct detailed pressure fields and frontal positions. Using concepts
of continuity along with this information, the analyst then constructs streamlines and isotachs over the entire
analysis region. Unfortunately, this procedure is very labor-intensive; consequently, most analysts combine
kinematic analyses of small subregions within their region with numerical estimates over the entire region.
This method is sometimes referred to as a man-machine mix.
g. Meteorological systems and characteristic waves. Many engineers and scientists working in marine
areas do not have a firm understanding of wave conditions expected from different wind systems. Such an
understanding is helpful not only for improving confidence in design conditions, but also for establishing
guidelines for day-to-day operations. Two problems that can arise directly from this lack of experience are
(1) specification of design conditions with a major meteorological component missing, and 2) underestimation
of the wave generation potential of particular situations. An example of the former situation might be the
neglect of extratropical waves in an area believed to be dominated by tropical storms. For example, in the
southern part of the Bay of Campeche along the coast of Mexico, one might expect that hurricanes dominate
the extreme wave climate. However, outbursts of cold air termed "northers" actually contribute to and even
control some of the extreme wave climate in this region. An example of the second situation can be found
in decisions to operate a boat or ship in a region where storm waves can endanger life and property.
Table II-2-2 assists users of this manual in understanding such problems. Potentially threatening wind and
wave conditions from various scales of the meteorological system are categorized.
Meteorology and Wave Climate
II-2-23
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