Lets first see the postive factors
1. Dipping of Jetstreams – When a jet stream dips, it creates upper divergence and there by increasing convergence at lower levels. These rains are always intense and are associated with hails.
2. The upper trough is caught between two HPA and a valley like trough is created. The sharper the trough the more the intense the rains are.
3. CAPE – 4000 (J/kg) is available near Chennai. So we just need a TS over Chennai. The abundant energy will magnify the TS.
4. Moisture Content – No need to worry about this. You may already felt the sultry feeling. Moisture is available right from upper level to surface levels.
1. All the above are assumed factors
2. The storms should not peak too early before coming to our Bermuda triangle
3. Chennai is located southern coastal part of India. This region not known to get rains in April.
I personally feel that we have more than good chance for rains in Chennai in next two days as the postive factors cannot be ignored.