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Image Description: Upper-Air Station Model
Upper-station model shown. Very similar to the surface station models. However, some information is different. We will be looking at the differences throughout this section.
Upper-Air Station Plots are composed of:
Pressure Level
Wind Speed & Direction
Temperature (°C)
Dew-Point Depression (°C)
Cloud Cover
Height of constant pressure surface (meters MSL)
12 - hour height change (dam)
Wind Speed & Direction
Wind Speed & Direction
Wind speed in the example to the right is 110 knots.
If winds are missing:
"M" is plotted in the height change space.
If winds are light and variable:
"LV" will be plotted in the height change space
Temperature & Dew-Point Depression
Temperature & Dew-Point Depression
Temperature (T) and Dew-Point Depression (Tdd) are reported on an upper-level station model ,and report to the nearest whole degree Celsius.
Dew-Point Depression (Tdd) is calculated using Temperature (T) and Dew-point temperature (Td):
(Tdd) = T – Td
*Note: Temperature (T) is always greater than or equal to the Dew-point temperature (Td). Therefore, the dew-point depression will always be positive
Notes to keep in mind:
Notes to keep in mind:
If the Tdd is less than or equal to 5°C, the circle is filled in.
If the temperature is colder than -41°C, Tdd is left blank.
If the temperature data is missing, the space is left blank.
If the Tdd is greater than or equal to 30°C, 'X' is plotted in that space.
For image above:
For image above:
T = -5°C
Tdd = 14°C
Td = -19°C
Cloud Cover
Cloud Cover
Note: Circle is ONLY filled in if the dew-point depression is less than or equal to 5°C (indicating that we have clouds).
Pressure Surface Height
Pressure Surface Height
Height of a constant pressure surface in meters MSL!
To decode the height, if the pressure surface is
850 mb (~1500 m): Add a 1 in front of the plotted value
700 mb (~3000 m): Add a 2 or 3 in front of the plotted value; whichever brings the height closest to 3000 m
500 mb (~5400 m): Add a 0 behind the plotted value
300 mb (~9000 m): Add a 0 behind the plotted value
200 mb (~12000 m ): Add a 1 in front and a 0 behind the plotted value
Height Example #1
Height Example #1
Pressure Surface: 500 mb
Add a 0 to the end.
Height: 5,650 m
Height Example #2
Height Example #2
Pressure Surface: 700 mb
Add a 2 or 3 to the beginning, whichever brings the height closest to 3000 m.
In this case, add a 2.
Height: 2,975 m
12-Hour Height Change
12-Hour Height Change
Reported in decameters
+ indicates a positive change
- indicates a negative change
This is interpreted the same way for all pressure levels
Here: the height increased 3 decameters over the past 12 hours
Example:
Example:
What are the following variables?
Wind Direction
Wind Speed
Temperature
Dew-Point Depression
Dew Point
Cloud Cover
Height
Height Change
The answer is collapsed in the image.
Wind Direction: West
Wind Speed: 60 kts
Temperature: -5°C
Dew-Point Depression: 10°C
Dew Point: -15°C
Cloud Cover: Clear
Height: 5750 meters
Height Change: Increased 3 decameters
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