1. Upper Air Analysis
850, 700, 500, 250 hPa charts

2. Upper Air Charts Objectives Review Upper Charts
Identify features on Upper Charts
00Z CMC 850 hPa
30 Jul 2008

3. Why use Upper Air Charts?
Weather usually develops throughout the depth of the Troposphere
Most Synoptic weather is actually due to forcing aloft (upper lows/trofs/fronts)
These features are often (but not always) reflected in the SFC analysis
Upper charts are vital in overall analysis (3-D diagnosis)

4. Upper Air Charts
Data displayed on a “horizontal slice” of the atmosphere
For each radiosonde launch: one data point
Horizontal slice can be taken at various heights of the atmosphere
However instead of heights the norm is to use “constant pressure levels”
- Ask students if they understand “Constant Pressure” levels… (Covered in Theory hour 3)

5. Why Pressure Levels? Historically A/C flew at Pressure Altitudes
Still true for flights >18Tft (no Altimeter recalibration)
Radiosondes report in terms of pressure (height is calculated from other parameters)
Computation is easier using Pressure levels.
This way: “the Pilot

6. H L 850 hPa Pressure Surface SEA LEVEL 1500 m > 1500 m < 1500 m
Looking at the 850 hPa Pressure surface
It usually sits near 1500 m / 5000 ft. ASL
However, due to Lower than average pressure in the atmosphere the 850 hPa surface can dip below this.
Similarly in an area of High pressure, the 850 hPa surface will be above 1500 m.
So you can see that Heights on Pressure surfaces can be treated the same as Pressure on Height surfaces.
SEA LEVEL

7. L   1380 m 1440 m 1500 m 12Z 29 Jul 2008 850 hPa Upper Air Stations
So if we look at a plot of 850 hPa data we see varying Heights…
YQD shows 1400 m, heights rise to above 1500 m in the SE.
We can use this data to contour the changes in Height along a pressure surface…
Wind blow || to contours just like Isobars
12Z 29 Jul 2008
850 hPa Upper Air Stations

8. Rejected Data Types of rejected data Reasons why data is rejected
Discussion
Exercise - find rejected data

9. Limitations What’s not represented Friction at low levels
Sharpness/ Smoothing Like Td, heights

10. What’s typically analyzed
The standard Pressure Levels used by most
meteorlogical organizations (MSC):
850 hPa (near 5000 ft / 1500 m)
Thermal advection, fronts, low level jets, moisture
700 hPa (near 10,000 ft / 3000 m)
Thermal advection, fronts, moisture
500 hPa (near 18,000 ft / 5000 m)
Steering flow, vorticity advection, fronts
250 hPa (near 34,000 ft / 10,000 m)
Jet Streams
Issued twice daily: 12Z (14-16Z) & 00Z (02-04Z)

11. Examples of height codes: Examples of height codes:
CMC Upper Air Plots
850 hPa
Examples of height codes:
79 means 1790 metres
Height T
50 means 1500 metres
T-Td
24 means 1240 metres
700 hPa
Examples of height codes: T
Height
30 means 3300 metres
T-Td
00 means 3000 metres
74 means 2740 metres

12. Upper air plots
WD - Wind direction (plotted to 36 compass points, or tens of degrees; indicates the direction from whence the wind originates).
WS - Wind speed (knots, where a short barb indicates intervals of 5 knots, a long barb indicates 10 knot increments, and a flag indicates 50 knot increments). 

13. Upper air plots
TT -Ambient air temperature rounded to the nearest whole °C; "-" for T < 0°C.
DD - Dewpoint depression or spread = T - Td, rounded to the nearest whole °C.
This nomenclature maybe only for the US rather than CMC.
CMC includes temperatures and dewpoints less than -41C.
[An "X" indicates air is too dry to measure dewpoint; normally used when DD exceeds 29°C. If TT < -41ºC, DD is left blank because the air is too dry at these temperatures]. This field is omitted in the 300mb and 200mb plots. 

14. K W K 10°C Isotherm 12Z CMC 850 hPa Temperature 29 Jul 2008
Exact same analysis as previous AMX plot
12Z CMC 850 hPa
Temperature
29 Jul 2008

15. Exercise Draw the ___ degree isotherm on 850
Find thermal ridges on 850 hPa

16. 500 hPa charts
500 hPa vorticity
500 hPa thickness

17. Examples of height codes: Fig. D1.2 Plots on upper charts.
CMC Upper Air Plots
Examples of height codes:
500 hPa (Vorticiy)
75 means 5750 metres T
Height
T-Td
40 means 5400 metres
96 means 4960 metres
500 hPa (Thickness) T
Height
T-Td
Fig. D1.2 Plots on upper charts.

18. 500 hPa Vorticity
Troughs and ridges are most easily identified at this pressure level.
Clouds and precipitation frequently accompany upper-level lows and troughs, even without surface frontal systems. Short-wave troughs, are often embedded in the Rossby flow, and will propagate at speeds of 20 to 40 knots.
Most surface lows and fronts are associated with upper-level short-wave troughs.
Rossby = wave pattern in the upper flow, usually the longer wave pattern
Counted the Rossby waves. Low number = retrogression high # progression
Changes around 5 or 6 when you count the #aroung the whole planet

19. CMC 500 hPa
Vorticity
Line of constant
Vorticity

20. 500 hPa Thickness
The dam thickness is an approximate RA/SN line
This is indicative of the average temperature of the column of air under the 500 hPa pressure level. Larger thicknesses indicate warmer air.

22. W K Line of constant 1000-500 hPa Thickness 00Z CMC 500 hPa
This chart can be found on the 0 hr 4 panel model run
Line of constant
hPa Thickness
00Z CMC 500 hPa
Thkns
30 Jul 2008

23. 00 Hr PROG
MSLP & Thkns
Valid 00Z 30 Jul 2008

24. 250 hPa or 300 hpa
Jet Streams

25. Examples of height codes:
PLOTS ON UPPER CHARTS
Examples of height codes:
250 hPa
80 means 10,800 metres
20 means 10,200 metres
90 means 9,900 metres
Height T
T-Td

26. Jet streams
Normally, the greatest winds are found above the regions of strongest horizontal temperature contrasts, and hence, in the tightest contour packing.
A “Jet” is often found in segments
1,000 to 3,000 miles long
miles wide.
3,000-7,000 feet deep
Here we are basically at the top of the troposphere. The charts indicate the strength of features in the lower atmosphere - strong storm systems on the surface are reflected in the patterns contained in these charts. At middle latitudes, the jet stream can usually be found on the 300 hPa and 200 hPa charts.
A "jet" (winds of 50 kts) is most frequently found in segments of 1,000 to 3,000 miles long, 100 to 400 miles wide, and 3,000 to 7,000 feet deep. Such dimensions vary with seasonal change. As a general rule, locations north of a jet associated with a surface front are likely to be cold and stormy; locations south - warm and dry.

27. Isotach (constant wind) Plotted for winds ≥ 60 kts
CYQD – 10,530 m
Isotach (constant wind) Plotted for winds ≥ 60 kts
12Z CMC 250 hPa
Isotachs
29 Jul 2008

28. Enhancing Upper Charts and Exercises

29. Enhancing 850 hPa and 700 hPa CHARTS
High (blue) & Low (red) symbols
0°C isotherm (red)
Areas of moisture:
Any stations reporting T-Td of 4 or less
Highlight the station in Green
Areas of Warm/Cold Advection

30. Thermal Advection
Look for areas where the isotherms cross the contours and form closed “rectangles” (solenoids)
An area of thermal advection is bordered by 2 separate Isotherms & 2 separate height contours
The smaller the solenoid the more intense the advection

31. Thermal Advection Identifying advection type (warm or cold):
Look at the height contours:
find the direction of flow (“Low to your left wind at your back”)
the wind will push the isotherms in that direction
If air blows from warm to cold it is warm air advection
If air blows from cold to warm it is cold air advection
Identifying Warm and Cold “pools” will very helpful in this process

32. TEMPERATURE ADVECTION
-10
-10 L L K -5  H H  5 15 10 W

33. L H W W K W
850 hPa 12Z

34. H L W W K L
700 hPa 12Z L

35. CMC 12Z 700 hPa Analysis L H K W

36. Enhancing 500 hPa Charts 500 hPa is referred to as the “Steering Flow”
500 hPa Vorticity chart:
Analyze S/W Trofs and Ridges

37. 250 hPa
Upper level jets

38. Review Upper Air Charts
850 & 700 hPa
Advections
Moist/saturated stations (T-Td = 4 or less)
0 degree Isotherm
500 hPa (steering flow)
Vorticity: S/W Trofs and Ridge
Thickness: dam thickness area
250 hPa
Jet Isotachs (>60 kts)
Jet Axis(es)

39. NEXT: Upper Chart Exercise

40. Exercises
Highlight the following features on the upper air charts provided:
850 & 700 hPa
Low/High labels
0°C Isotherm
Saturated upper air stations
Warm/Cold pools
Thermal advections

41. Exercises
Highlight the following features on the upper air charts provided:
500 hPa Vorticity chart:
Analyze S/W Trofs and Ridges

42. Highlight the following features on the upper air charts provided:
250 hPa
Isotachs
Jet axes

43. Other websites for the description of upper air charts

44. Online tools WeatherOffice
Aviation Digital Data Service (ADDS)
Storm Chaser Machine