At last BOB-UAC coming close to the NTN & SAP coasts. So tomorrow onwards rainfall activity with overcast conditions along the coastal NTN & SAP will increase gradually. However this UAC may not be descending to lower-level, which is evident from weak 850 hpa level vorticity & stream lines (Figures 1 & 2). This UAC will start entering Arabian ocean by travelling across TN after June 4th. Overall in-between June 2nd & 4th, rainfall activity along NTN-CTN & SAP coasts will peak and expect some decent rainfall.
The recent increase in SOI & IOD values given life in the form increasing moisture filled trade winds thus stability of present BOB-UAC for longer time. However SOI started again falling down as per lasts values (decreased by 0.5 points). So present BOB-UAC may not strengthen to LPA and will enter Arabian ocean, where it will be getting good MJO-support in phase 1 to strengthen beyond LPA along the west-coast.
From the present BOB-UAC there is fair chance of decent rains along coastal NTN & SAP between June 1 & 4.
However we need to focus on next BOB-UAC (can become rain-bearing strong system) for NTN & AP by June 2nd week under the support of strong MJO entering in phase 2.
Conclusion: Expecting this June month rainfall over Chennai will end up in historical note in similar view with PJ.
Topic courtesy: Rsrao