circle horizontally even with the indicated value on the
altitude scale (fig. 4-40).
When there is a significant difference between your
station’s elevation and sea level, or if the surface
pressure is greatly different than 1,013 hPa (standard
pressure), then the preplotted dots for the fixed regional
level winds will not be accurately spaced with respect to
the mandatory level wind plots. In these cases, the
forecaster may desire that you plot the fixed-regional
level winds by establishing the altitude using the
pressure-altitude curve, as shown in figure 4-40.
Plotting Tropopause Height
The tropopause information is encoded in Part A or
C of the TEMP coded messages following the
mandatory level information. The three groups of
information start with the indicator 88. The format of
the data is shown in figure 4-32. The reported
tropopause information (pressure level, temperature,
dew-point depression, and wind direction and speed) is
plotted just as a mandatory level. Additionally, in the
uncolored portion of the diagram between the left wind
scale and the diagram, a horizontal line is extended from
the tropopause pressure level, and the block letters
TROP are written above the line. When group 88999 is
reported, the block letters NO TROP are written just to
the right of the colored portion of the diagram at the
100-hPa level. See figure 4-41 for examples of both
plotted tropopause and maximum wind information.
Plotting Maximum Wind
The maximum wind pressure level, wind direction
and speed follows the 77 indicator or the 66 indicator in
Part A or C of the message. At the pressure level
reported, a dashed horizontal line is drawn extending
from the right side of the colored portion of the diagram
and the word MAX is written on the line. The maximum
wind is plotted at that same level on the wind scale.
Wind shear values, if reported, are usually not plotted.
Plotting Supplemental Information
Much of the additional data following the 51515
group in Parts B and D of the TEMP code can be plotted
on the diagram. If the group refers to a single level, a
straight line is usually drawn at the pressure level, and
the remark entered on the diagram. If the code refers to
a layer of the atmosphere, the top and bottom of the
layer are indicated by drawing horizontal lines at the
pressure level, and the comment is entered on the chart.
These coded remarks may refer to the reason for
termination, levels of doubtful or missing data, or
Figure 4-40.—Fixed regional level winds may be plotted on the solid dots on the wind scale, or positioned using the PA curve.
4-34
