Typical Northeast Monsoon Bursts Still Awaited, Current Spell May Go Weak After Mid Week

Northeast monsoon has largely remained on the back foot this season.  Monsoon made a silent start with absolutely mild current on 21^stOctober. Conspicuously, it failed to gather momentum for sufficiently long, leaving enormous deficiency in the month of October. There is an uptick of weather activity for the last 4 days. However, typical outbursts of seasonal downpour, at least over coastal Tamil Nadu still go missing.  Somewhat active monsoon conditions persisting over South Peninsula now, will go mute after about 3 days.

The onset criteria of northeast monsoon had some gaps this  season. The onset announcement is made after ascertaining the requisite condition : Withdrawal of Southwest Monsoon up to 15°N, onset of persistent surface easterlies over Tamil Nadu coast, Depth of easterlies up to a height of 5,000 feet over Tamil Nadu coast and most importantly fairly wide spread rainfall over coastal Tamil Nadu, South Coastal Andhra Pradesh and adjoining area.

Climatological Northeast Monsoon date is 22^ndOctober with standard deviation of 7 days.  Most delayed onset was on 02^ndNovember in 1988, 1992 and 2000.  The mean duration of northeast monsoon is about 75 days. The smallest duration occurred in 1992 (51 days) and longest (98 days) in 2005.  However, there is no statistical correlation of NE monsoon seasonal rainfall with either monsoon onset, withdrawal or duration.

An off shore cyclonic circulation over southwest Bay of Bengal, in the proximity of Sri Lanka to start with and later shifting over Lakshadweep and Southeast Arabian Sea has triggered weather activity for the last about 3-4 days. An east-west trough from this system is still extending till North Tamil Nadu, cutting across interiors of Peninsular India. This weather system will keep the monsoon activity ‘on’ for another 3 days. The spread and intensity will substantially reduce on 10^thNovember and get further limited to small areas on 11^th Nov. This wet spell will marginally recover the huge deficit so far over the core meteorological sub divisions of northeast monsoon.