In the following station plot the temperature is
76F, the dew point 55F, the wind direction is northeast at about 20 knots.
The pressure is 1013.8 mb, and it has increased then decreased and is now
lower by 0.3 mb than three hours ago. The cloud cover is overcast
and it is raining.
TT - Temperature: In
the United States surface temperature is expressed in units of degrees
Fahrenheit. In most other countries of the world it is expressed in degrees
- Dew point temperature: Expressed in the same units as temperature .
N - Cloud cover: Total
cloud amount represents the fraction of sky covered by cloud.
VV - Visibility: How
far we can see, expressed in units of miles.
dd - Wind direction:
The line drawn represents the direction from which the wind is blowing.
ff - Wind speed: The
barbs on the lines representing wind direction give us information on the
wind speed. Wind speed is measured in knots (1 knot =1.15 miles per hour).
One long barb equals 10 knots, a short barb 5 knots and a triangle represents
a wind speed of 50 knots.
ww - present weather
conditions: Symbols are used to convey information on the type of weather
that was observed when the observations were made. The
next page of this lesson and your book list
some of these symbols. A more extensive list does exist.
PPP - Surface Pressure
adjusted to sea level. The units are coded in mb. The leading 9 or
10 are dropped as is the decimal. So 234 represents a pressure of
1023.4 mb while 834 represents a pressure of 983.4 mb.
pp - Change in surface
pressure over the last three hours. The change in pressure is represented
by a value and a line that tells us how the pressure was changing.
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Written by Steve Ackerman and Tom Whittaker