23rd Posting:

Rainfall in Kerala  from UAC ...Creating only " Pseudo Monsoon Effect"

Last 24 hrs:

Kozhikode AP 193mm

Kochi 137mm

Kochi AP 101mm

Alappuzha 122mm

Kozhikode 83mm

Thrissur 71mm

Kerala seeing heavy rains due to the UAC over south peninsula and Tamil Nadu region and wind convergence along the coast. 

Vagaries had mentioned this in our earlier forecast. 

While south tip of Kerala is seeing rain bands from West/Southwest, Central and North Kerala seeing thunderstorm-type rains with steering winds from the east.

Vagaries' thoughts regarding the present weather dynamics:

• Although probably the IMD parameters for SWM onset may have been satisfied objectively (for Thiruvananthapuram region)...this westerly surge for south tip Kerala feels more like a pseudo onset type ...flared up due to the UAC.
• 
  
• Monsoon Vortex also absent, as Vortex should have "Depression" type wind isobars and Depth.
• 
  
• Note: The onset criteria do not consider this pull effect westerly surge...this is where the human element for analysis and large scale weather dynamics interpretation comes into picture
• Winds at mid levels (600-700 hPa) are forecasted to reverse to North/Northeasterly for entire Kerala from tomorrow night. 
• Usually after SWM onset, westerlies extend till a depth of 600 hPa and do not reverse in direction within 48 hours (mid-level winds can change in break phase, but not just after onset). 

• So a more subjective analysis suggests the SW Monsoon to be at the doorstep of Indian mainland, having advanced to Maldives and most of Sri Lanka. 

.Kerala onset could happen around 29th May to 1st June time frame - may not be accompanied by heavy rains like what is observed now.

. Monsoon established over Sri Lanka.

Weekend Outlook 24th-27th:

Mumbai will see partly cloudy, muggy weather with humid days at 35c and warm stuffy nights at 28c. Few localized passing showers possible in MMR region and near Ghats due to strengthening westerly winds and increased clouding in evening/early morning hours.

Heavier Pre monsoon showers (which may add to the humidity) can start from early June. Proper Monsoon onset around 10th June.

Pune: Hot days at 38/39c, with cloudiness increasing by afternoon. Pre Monsoon showers in 1st week of June.