1. Aviation Department 02 - 2009 © DWD......Preconditions for the development of mountain waves General weather conditions Surface –anticyclonal curve of the isobars on the edge of a high pressure area (  inversion between 1500 and 2500 m) –Gradient of wind  36 km/h –Weak frontal system in parallel to the isobars (  increase of wind with the height constant wind direction)

2. Aviation Department 02 - 2009 © DWD Mountain Waves © Copyright: Bernhard Mühr

3. Aviation Department 02 - 2009 © DWD Kinds of waves Mountain Waves –Obstacles for the undisturbed airstream are hills or mountains Shear waves –Caused by vertical or horizontal wind shear Thermal waves –Obstacle is a thermal updraft

4. Aviation Department 02 - 2009 © DWD Preconditions for the development of mountain waves Topographical Conditions –Mountain ridge located diagonally to the wind direction (deviation of the wind direction max. +/- 30º from the perpendicular direction) Vertical profile of temperature –stable layer of air mass at and above the height of the mountain ridges Vertical profil of wind –Perpendicular components 15-27 kt –Linear increase of wind with the height (min. constancy)

5. Aviation Department 02 - 2009 © DWD...... Preconditions for the development of mountain waves General weather conditions Higher levels –anticyclonal flank of the yet stream –Constant wind direction above mountain level –Wind speed at 500 hPa level: 60-115 km/h –Wind speed at 300 hPa level: 80-150 km/h –Narrow trough (SW-stream at the front of a trough)

6. Aviation Department 02 - 2009 © DWD Yearly statistic of days with mountain waves In Europe

7. Aviation Department 02 - 2009 © DWD Ideal Mountain Wave

8. Aviation Department 02 - 2009 © DWD Vertical profile of the Wind speed and there effect on the air stream a.laminar air stream b.standing eddy c.mountain wave stream d.rotor stream e.Rotor stream

9. Aviation Department 02 - 2009 © DWD Influence of the profiles of obstacles on the development of waves (Wallington ) to short to long ideal obstacle to long despite height ideal chain of obstacles with resonance effects = wave length

10. Aviation Department 02 - 2009 © DWD Possibilities to forecast mountain waves Surface weather forecast charts, upper level forecast charts (500 und 300 hPa) Lester-Harrison-Nomogram Analysis of TEMPs: –Vertical profile –Scorer parameter Direct model output (SkyView, SkyView LMK)

11. Aviation Department 02 - 2009 © DWD LME 7 kmGME 40 km LMK 2.8 km The operational model chain of DWD, consisting of GME, LME und LMK

12. Aviation Department 02 - 2009 © DWD 2,8 km grid 40 km grid DWD – model LMK

13. Aviation Department 02 - 2009 © DWD Forecast of vertical movement with LMK m NN Thüringer WaldErzgebirge

14. Aviation Department 02 - 2009 © DWD Example of 26.10.06: Harz` wave up to 5000 m more than 100 wave flights in the NW part of Germany

15. Aviation Department 02 - 2009 © DWD Example 21 November 2006: Max. altitude Riesengebirge up to 7000 m 500 km out and return flight Klix- Riesengebirge and back home

16. Aviation Department 02 - 2009 © DWD Cross section of the Riesengebirge 16 November 2007

17. Aviation Department 02 - 2009 © DWD Thermal Waves

18. Aviation Department 02 - 2009 © DWD The cumulus wave

19. Aviation Department 02 - 2009 © DWD The cloud street wave