All about Upper-Level Station Models

Description of Upper-Air Station Model: Open circle with wind barbs pointing towards the northwest. On the barb, there are 2 triangles and 1 long stick. The upper left number is -05. The bottom left number is 14. The upper right number is 185. The pressure is 500mb.

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 Models 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 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

Description of Upper-Air Station Model: Open circle with wind barbs pointing towards the northwest. On the barb, there are 2 triangles and one long stick. The upper left number is -05. The bottom left number is 14. The upper right number is 185. The bottom right value is LV. This image points out the wind barb and the direction it is coming from. It also gives a review for the barb values: Triangle (flag) - 50 knots ; long stick (full line) - 10 knots ; short stick (half line) - 5 knots.

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:

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.

Description of Upper-Air Station Model: Open circle with wind barbs pointing towards the northwest. On the barb, there are 2 triangles and one short stick. The upper left number is -05. The bottom left number is 14. The upper right number is 185. The bottom right number is +03. This image highlights the values of -05 and 14 as the temperature and dewpoint respectively. Meaning that the upper left value is temperature and the bottom left value is dew point depression.

For image above:

T = -5°C

Tdd = 14°C

Td = -19°C

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).

Description of Upper-Air Station Model: Filled circle with wind barbs pointing towards the northwest. On the barb, there are 2 triangles and one short stick. The upper left number is -05. The bottom left number is 5. The upper right number is 185. The bottom right number is +03. This image highlights the circle being filled in as it relates to cloud cover.

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