Tutorial 19:
The Weather Station Model
Introduction:  Weather patterns are an important aspect of climate.  As such, we must be able to read typical weather maps.  There are many aspects to weather like, temperature, pressure, wind direction and speed, cloud cover....and on.  Weather maps would be too difficult to read if all elements of weather were to be presented for all weather stations.  We will, then, only become familiar with a simplified weather station model as shown below (a diagram similar to this one is found in your handout packet).  The elements are discussed below.

station model example

How to read the Station Model:

1) Cloud Cover: The degree to which the circular station marker is filled in indicates percent cloud cover.  Our example shows 75% cloud cover.

2) Wind Direction: The "stick" that protrudes from the station indicates wind direction. Hint: Imagine that the stick is an arrow shot into the station.  Now ask yourself where the archer must have been standing.  In this instance, the archer stood to the northwest.  That is the indicated wind direction.

3) Wind Speed:  The feathers or flags on the wind direction stick indicate wind speed.  If conditions are calm, then a circle encloses the station marker.  The example shows 15 knot winds.

4) Current Temperature: The number to the upper left of the station shows current temperature.  You must read the map to determine if Celsius or Fahrenheit degrees are being used.  The example shows 31°F.

5) Dew Point Temperature: The number to the lower left of the station marker shows dew point.  The example shows 30°F.  Note: Although the station model doesn't show relative humidity, you may get a feel for %RH by noting how close the current temperature and dew point temperatures are.  Obviously, the closer the two numbers are, the higher the RH.

6) Current Weather: If weather exists, a symbol is shown between the current and dew point temperatures.  The example shows a snow storm.

7) Current Barometric Pressure:  Current pressure is shown in the upper right corner of the station.  Very importantly, the number shown is in SHORTHAND!!  Here is the set of rules:

a.  if the number shown is less than 500, then put 10 out in front and the last digit is always the decimal.  The example is 247 which really means 1024.7mb.

b.  if the number shown is greater than 500, like 883, then put a 9 out in front and treat the last digit as the decimal.  Our example of 883 really means 988.3mb.

8) Pressure Change: The number to the lower right of the model indicates the amount of change in barometric pressure recorded over the last three hours.  Whether the pressure increased or decreased is indicated by a sign (+ or -) respectively.  Since pressure tends not to change very much over a three hour period, the number on the station is also in shorthand notation for tenths of millibars.  The example is +28 which means that pressure had increased by 2.8mb over the last three hours.  Given the current pressure and pressure change data, you may calculate what the pressure was three hours earlier.  Since the change is positive, just subtract the 2.8mb.  This would show that the pressure was 1021.9mb three hours earlier.

9) Trend in Pressure Change: Just how pressure changed over the last three hours is indicated by a trend symbol that is just to the right of the pressure change number.  The example shows constant increase.

Further Trend Line Symbols:
Symbol interpretations:
a. Constant decrease
b. Constant decrease then leveled off
c. Increase then constant decrease
d. Level then decreased
e. Was level, increased briefly, then decreased
f. Constant increase
g. Constant increase then leveled off
h. Decreased then constant increase
i. Level then increased
j. Was level, then decreased briefly, then increased
There are essentially an infinite number of variations or combinations for these symbols.