Tropical Waves Characteristics
- North Africa
- Reflection of mid-upper level disturbances
South-to-North Orientation (Inverted “V”)
Meso-scale Feature of the Lower Atmosphere
- Generally identifiable at 850-700 hPa
On the Tropical Atlantic form between April/May and October/November
Organized convection along the Near Equatorial Trough over North Africa during the Northern Hemisphere Summer results in perturbations forming. Meso-scale Convective Complexes (MCC) and Meso-scale Convective Systems (MCS) over this region are also responsible (if not the primary source) for the generation of tropical waves, also providing in the process cyclonic rotation to these waves.
Mid/Upper level disturbances occasionally manifest on the lower atmosphere. It is easy for meteorologists to confuse these perturbations with an easterly wave, as they will generally have the classic Inverted “V” signature on the satellite imagery. What differentiates the upper level perturbations from “true” tropical waves is the cold core nature, or beginnings, of these mid/upper perturbations. A perfect example is an upper level TUTT low, which is a cold core system. This is not to say that cold core systems can not evolve into a warm core system, but this is mostly a scale interaction issue (synoptic scale favorably interacting with the meso-scale).
It is highly debatable which level is best for tropical waves analysis and forecasting. A tropical wave that manifests to the 700 hPa height indicates a well organized perturbation, with potential for weather generation. However, one at 850 hPa, under favorable conditions, could gradually amplify to the middle atmosphere. Thus is best to analyze both surfaces.