Hovmollers – synoptic forecast
The hovmöllers shown here represent the time evolution (ordinate) and longitude (abscissa) of the observations for the days preceding the model's initialisation, followed by the 9 days of ECMWF model forecasts. Time runs from top to bottom. The horizontal black line indicates the initialization date, i.e. the start of the forecast. Note that the latitude bands and longitude range considered vary according to the parameter chosen. For example, for the PW-VelPot-StreamFct parameter, the domain is global in longitude.
- PW-Precip:
- Left figure: Average over [10°-18°N] of the PW anomaly (mm colour) and rainfall (contour mm/d) for ECMWF analyses and forecasts. The oblique red line indicates the typical propagation of an African Easterly Wave at 8 ms-1 towards the west.
- Right figure: Same as above, but for IMERG observations.
- PW-VORTICITY:
- Left Figure : Average over [10°-18°N] of the PW anomaly (mm colour) and meridional wind at 925 hPa.
- Right Figure : Average over [10°-18°N] of the relative vorticity at 850 hPa (colour) and the meridional wind at 700 hPa (contours) for the ECMWF analyses and forecast. The oblique red line indicates the typical propagation of an African Easterly Wave at 8 ms-1 towards the west.
- Mean-Vwind-925-600: Average over [10°-18°N] of the integrated meridional wind between 925 and 600 hPa (ms-1).
- Vwind-200: Average over [40°-60°N] of the meridional wind anomaly at 200 hPa (colours, ms-1) and its filtered anomaly at 10-90 days (negative/positive dashed/full line contours, m/s). The figure follows the propagation of extratropical waves along the polar jet, in particular the quasi-stationary Rossby wave, which is relevant for the intraseasonal variability of the HL (Chauvin et al. 2010). The zero contour is thick and a contour every 4 ms-1 is displayed. The straight lines indicate eastward propagation speeds of 4 and 40 ms-1, respectively.
- PW-VelPot-StreamFct-200: Average over different latitude bands of the intraseasonal anomaly (colour) and equatorial wave contributions (favourable to convection in solid line) representing:
- left : velocity potential at 200 hPa (m2s-1)
- in the middle : streamfunction at 200 hPa (m2s-1)
- right : PW (mm).
- Wind-200: Average over different latitude bands of the intraseasonal anomaly (colour) and equatorial wave contributions (favourable to convection in solid line) representing:
- left : zonal wind at 200 hPa
- right : meridional wind at 200 hPa.
- Wind-850: idem for the wind (U,V) at 850 hPa