Southwest monsoon has set in over Kerala, today, the 29th May 2018
- Today, the southwest monsoon has further advanced into remaining parts of southeast Arabian Sea, Comorin – Maldives area, entire Lakshadweep, most parts of Kerala, some parts of Tamil Nadu and some more parts of southwest, central and northeast Bay of Bengal.
- Thus the southwest monsoon has set in over Kerala, today, the 29th May 2018, 3 days ahead of its normal date.
- The Northern Limit of Monsoon (NLM) passes through Lat. 120N/ Long 600E, Lat 120N/ Long 650E, Lat.120N/ Long 700E, Kannur, Coimbatore, Kodaikanal, Tuticorin, Lat. 090N/ Long 800E, Lat. 130N/ Long 850E, Lat.180N/ Long 900E, Lat. 210N/ Long 930E. Figure-1 shows the Northern Limit of Monsoon (NLM) as on today.
Prevailing meteorological conditions leading to onset of monsoon over Kerala.
- Widespread rainfall occurred over Kerala, during the past 3-4 days. The 14 rainfall monitoring stations for Monsoon onset over Kerala have reported more than 60% rainfall from 25th May. (Fig-2).
- Westerly winds have strengthened in the lower levels (more than 30 knots) and deepened with Westerly/ West-southwesterly winds upto 600 hPa (approximately upto 4.5km) over the south Arabian Sea (equator to Lat. 10oN and Long. 55oE to 80oE) from today morning.
- There is persistent convection (cloudiness indicated by Outgoing Long-wave Radiation values <200 Wm-1) from 23rd May. The Satellite (INSAT-3D) derived Outgoing Long wave Radiation value in the box confined by Lat. 5-10oN, Long. 70-80oE is 187 W/m2. (Fig-2).
- In addition to the above features, the following developments are also noticed:
- An east-west shear zone runs roughly along latitude 120N (across south peninsula) at 3.1 km above mean sea level.
- A well marked low pressure area lies over southeast and adjoining eastcentral Arabian Sea off north Kerala- Karnataka coasts.
- Another well marked low pressure area lies over eastcentral and adjoining northeast Bay of Bengal. It is likely to concentrate into a Depression during next 12 hours.
Further advance during next 48 hours
Conditions are favorable for further advance of Southwest Monsoon into some parts of central Arabian Sea, remaining parts of Kerala, some parts of coastal and south interior Karnataka, some more parts of eastcentral and northeast Bay of Bengal, and some parts of northeastern states during next 48 hours.
Fig 1: Northern Limit of Monsoon 2018 as on 29th May 2018
Fig.2: Parameters for declaring onset of monsoon over Kerala