• Television weather reports represent weather conditions
with smiling suns, rainy clouds and flashing bolts of
•In studying the weather we need to know where it is raining
and where it is sunny, the wind speed and direction,
humidity, visibility, cloud cover, precipitation, air
pressure, dew point, and temperature.
•To understand these relationships it is best to represent
weather variables in a simple graph.
•Smiling suns do not contain enough information about the
weather. On the other hand too many numbers drawn on a
single map presents a confusing picture.
•Weather conditions observed at a city or town are best
represented on a map using the station model.
Interpreting Weather Station Models
Used to plot a multitude of weather data in a small symbol.
Observed Temperature station reporting symbol
The value highlighted in yellow located in the upper
left corner (in the diagram above) is the temperature
in degrees Fahrenheit. In this example, the reported
temperature is 64 degrees.
is defined as a measure of the average kinetic
energy (or speed) of the molecules in the air.
2. Current weather
The symbol highlighted
in yellow indicates the
occurring at the time the
observation is taken. In
this case, fog was
3. Dew Point
The value highlighted in yellow located in the lower left corner
is the dew point temperature in degrees Fahrenheit. In this
example, the reported dew point temperature is 58 degrees.
Dew points indicate the amount moisture in the air. The higher
the dew points, the higher the moisture content of the air at a
given temperature. Dew point temperature is defined as the
temperature to which the air would have to cool. IT IS NEVER
GREATER THAN THE AIR TEMPERATURE.
4. Cloud Cover
The symbol highlighted in yellow indicates the amount
of cloud cover observed at the time the observation is
taken. In this the case, cloud cover is…
5. Barometric Pressure
*Average sea-level pressure is
1013.25 hPa (mb) or 29.921
inches of mercury (in Hg).
*Average pressure on Earth
ranges between 900 mb and
The value highlighted in yellow located in the upper right corner
represents the last three digits of the barometric pressure at sea
level in millibars (mb).
•The highest recorded atmospheric pressure, 108.6 kPa (1086
mb or 32.06 inches of mercury), occurred at Tosontsengel,
Mongolia, 19 December 20012.
•The lowest recorded non-tornadic atmospheric pressure, 87.0
kPa (870 mb or 25.69 inches of mercury), occurred in the
Western Pacific during Typhoon Tip on 12 October 19792. The
record for the Atlantic ocean was 88.2 kPa (882 mb or 26.04
inches of mercury) during Hurricane Wilma on 19 October 2005.
Barometric Pressure cont…
Interpreting Pressure Reports:
*If reported value is greater than 500: Initial 9 is missing.
Place it on left, then divide by 10.
For example: 827 becomes 982.7 mb.
*If reported value is less than 500: Initial 10 is missing. Place it
on left, then divide by 10.
For example (as in above diagram): 027 becomes 1002.7 mb.
6. Wind Speed
The symbol highlighted in yellow is known as a wind
barb. The wind barb indicates wind direction and wind
Wind barbs point in the direction "from" which the
wind is blowing. In the case of the diagram below,
the orientation of the wind barb indicates winds from
7. Wind Speed
Wind speed is given
here in the units of
"knots" (knt). A "Knot"
is a nautical mile per
1 Knot = 1.15 Miles
Per Hour (MPH)
1 Knot = 1.9
Kilometers Per Hour