1. Juliane Schwendike and Sarah Jones http://www.sat.dundee.ac.uk/abin/geobrowse/MSG/2006/ The Interaction between Convection and African Easterly Waves: a Model Case Study Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft

2. 13/09/2006, 00 UTC 10/09/2006, 12 UTC 11/09/2006, 00 UTC 11/09/2006, 12 UTC 10/09/2006, 00 UTC 13/09/2006, 12 UTC 14/09/2006, 00 UTC Tropical Depression Tropical Storm Meteosat images: http://www.sat.dundee.ac.uk/abin/geobrowse/MSG/2006/9Channel 5: water vapour 5.35 - 7.15 µm. 17/09/2006, 00 UTC Hurricane Helene

3. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Hovmoeller between 6N and 16N Relative vorticity in 700 hPa 05Sep 09Sep 07Sep 11Sep 13Sep 15Sep 40°W10°E0°20°W TS Helene Tropical Depression The AEW in the 700-hPa ECMWF Analysis Propagation speed: ~10 m s -1 9 Sep: Initiation of convection ahead of the trough of the AEW 10-11Sep: crossing from Land to water 12 Sep: tropical depression 14 Sep: Tropical Storm Helene 16 Sep: Hurricane Helene Convective system in satellite images Developing tropical depression in satellite images

4. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Model simulations with COSMO 4.0 Model regions Forecast model of the Deutscher Wetterdienst (DWD): COSMO 4.0 Horizontal resolution: 28 km and 2.8 km 50 levels No parameterisation of convection with 2.8km resolution 72-h forecasts Initiated with ECMWF analyses 100200400800120010001400180016002000220024002600 orography [m]

5. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft 10E35W 10Sep 11Sep 12Sep 12UTC Hovmoeller between 6N and 16N ECMWF Relative vorticity at 700 hPa 0° 10E Hovmoeller between 6N and 16N COSMO Relative vorticity at 700 hPa 35W 10Sep 11Sep 12Sep 12UTC 0° The AEW in the 700-hPa ECMWF Analysis and in COSMO COSMO, 28 km resolution 72h Forecast initialised at 9 September 2006, 12 UTC ECMWF Analysis

6. 19°W 7°N 17°N 1°W 10/09/2006, 00 UTC 12h forecast initiated at 9 Sep 2006, 12 UTC Height (1000 hPa) COSMO T+12 Vert. integral of humidity, cloud water and ice (kg/m 2 ) + wind (m/s) Convection over West Africa 30h forecast initiated at 9 Sep 2006, 12 UTC Height (1000 hPa) COSMO T+30 Vert. integral of humidity, cloud water and ice (kg/m 2 ) + wind (m/s) 19°W 7°N 17°N 10/09/2006, 18 UTC 1°W Image courtesy for the RTD Product of Météo France. 18°W12°W6°W 8°N 12°N 16°N 18°W12°W6°W 8°N 12°N 16°N

7. 12h forecast initiated at 10 Sep 2006, 12 UTC Height (1000 hPa) COSMO T+12 Vert. integral of humidity, cloud water and ice (kg/m 2 ) + wind (m/s) 21h forecast initiated at 11 Sep 2006, 00 UTC Height (1000 hPa) COSMO T+21 Vert. integral of humidity, cloud water and ice (kg/m 2 ) + wind (m/s) 11/09/2006, 00 UTC 11/09/2006, 12 UTC Convection over West Africa and the Atlantic 24°W18°W12°W 12°N 8°N 5°N 28°W 10°N 22°W16°W 10°W

8. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Becoming a Tropical Depression 12h forecast initiated at 12 Sep 2006, 00 UTC Height (1000 hPa) COSMO T+12 Vert. integral of humidity, cloud water and ice (kg/m 2 ) + wind (m/s) 12h forecast initiated at 13 Sep 2006, 00 UTC Height (1000 hPa) COSMO T+12 Vert. integral of humidity, cloud water and ice (kg/m 2 ) + wind (m/s) 12/09/2006, 12 UTC 32°W 5°N 17°N 11°W 13/09/2006, 12 UTC 32°W 5°N 17°N 11°W 12°W30°W 24°W 18°W 6°N 10°N 14°N 16°W22°W28°W34°W 8°N 12°N 16°N

9. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Tropical Storm Helene 12h forecast initiated at 16 Sep 2006, 00 UTC Height (700 hPa) COSMO T+12 Specific humidity (kg/kg) and wind (m/s) 16/09/2006, 12 UTC Image courtesy of Jason Dunion, HRD & CIMSS. Image courtesy to CIMSS. 56°W50°W44°W 14°N 18°N 22°N TS Helene 16 Sep 2006, 12 UTC Saharan Air Layer (SAL)

10. Convection over Land vs. Ocean West Africa Atlantic zonal wind (contours); vertical velocity (shaded) rel. vorticity (contours); diabatic heating (shaded) B D

11. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Temperature Budget Analysis: Over Land 300 400 ___ vertical advection - - - grid scale moist processes ….. horizontal advection turbulence radiation sum of all tendencies Average over box A

12. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Temperature Budget Analysis: Over Land Average over box B ___ vertical advection - - - grid scale moist processes ….. horizontal advection turbulence radiation sum of all tendencies

13. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Temperature Budget Analysis: Over Land Average over box C ___ vertical advection - - - grid scale moist processes ….. horizontal advection turbulence radiation sum of all tendencies

14. Θ tendency for MCS over West Africa Ascent Descent

15. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Vorticity Budget Potential vorticity (PV): PV budget: Diabatic PV changes Frictional PV changes very small

16. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Vorticity Budget PV budget: Diabatic PV tendency = “Horizontal component” “Vertical component”

17. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft PV tendency for the whole boxes for MCS over West Africa ACB diabatic PV tendency horizontal component vertical component

18. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Temperature Budget Analysis: Over Water Average over box D ___ vertical advection - - - grid scale moist processes ….. horizontal advection turbulence radiation sum of all tendencies

19. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Potential Temperature Budget Analysis: Over Water Average over box E ___ vertical advection - - - grid scale moist processes ….. horizontal advection turbulence radiation sum of all tendencies

20. D D E E Θ tendency for strong ascent region Θ tendency for strong descent region Θ tendency for convective system over the Ocean

21. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft DE Diabatic PV tendency for the whole boxes PV tendency for convective system over the Ocean diabatic PV tendency horizontal component vertical component

22. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft West Africa Eastern Atlantic Mean PV at the beginning and end of the convective system‘s life cycle PV at the beginning PV at the end

23. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Summary Updraught, heating and rel. vorticity are tilted over West Africa and upright over the Atlantic Diabatic PV tendency at low-levels positive and negative at mid and upper levels Increased low-level PV could enhance low-level monsoon flow behind the system and strengthen the AEW trough and AEJ at 700 hPa

24. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Outlook: Interaction with SAL 30h forecast initiated at 17 Sep 2006, 12 UTC Height (700 hPa) COSMO T+30 Specific humidity (kg/kg) and wind (m/s) 18 September 2006, 18UTC Precipitable water (mm) Image courtesy Naval Research Laboratory. www.nrlmry.navy.mil/sat_products.html 28°N 20°N Modelling with COSMO-ART (Aerosol and Reactive Trace gases).

25. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Convection over Land vs. Ocean West Africa Atlantic zonal wind (contours); vertical velocity (shaded) rel. vorticity (contours); diabatic heating (shaded) B D

26. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft PV tendency for the ascent regions for the MCS over West Africa A C B

27. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft PV tendency for the descent regions for the MCS over West Africa A C B

28. Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft D D E E Diabatic PV tendency for strong ascent region Diabatic PV tendency for strong descent region PV tendency for convective system over the Ocean