Weather office lowers expectations of monsoon rainfall to 100% of normal

28 July 2016

With reduced chances of La Nina weather event, monsoon rainfall this year is likely to be normal and not 'above normal' as was predicted by the India Meteorological Department (IMD) earlier.

The IMD in its latest climate outlook says rainfall in July, August and September could be more than 100 per cent of the normal rainfall but not above normal (104 per cent to 110 per cent) of the normal.

This is down from IMD's earlier predictions, which has in its stage forecast issued in June had forecast the average rainfall to be 106 per cent of the normal monsoon rainfall of 89 mm (with +/-4 per cent model error). The met department will issue its second stage forecast in a couple of days.

With rainfall so far much below predictions and the July climate outlook issued by IMD's Regional Climate Centre for south Asia expects July, August, September rainfall over India to be more than 100 per cent of the normal rainfall, overall rainfall could be much below predictions.

Quantitatively, the monsoon seasonal rainfall is likely to be 106 per cent of the Long Period Average (LPA) with a model error of 5 per cent. The LPA of the seasonal rainfall over the country as a whole for the period 1951-2000 is 89 cm.

IMD has a well-established early warning system for monitoring and warning of severe weather events and associated heavy rainfall. Accordingly, watch / alerts / warnings of severe weather are issued regularly.

IMD is also providing its location specific now casting weather service across the country. This service activity currently covers 180 urban centres under which now cast of severe weather (Thunderstorms; heavy rainfall from lows / depressions over the land) in 3-6 hrs range is issued.

Origin, development / movement of severe weather phenomena are regularly monitored through Doppler Weather Radars (DWRs) and with all available other observing systems (Automatic Weather Station-AWSs; Automatic Rain Gauge - ARGs; Automatic Weather Observing Systems-AWOS; satellite derived wind vectors, temperature, moisture fields etc.).

Heavy rainfall warnings are issued to the relevant district administration, state & central government agencies and relief authorities, as well as communicated to the public through radio, newspapers and internet.

The experimental Climate Forecast System model of Indian Institute of Tropical Meteorology (IITM) too indicates slight reduction in rainfall during August, September based on the initial conditions of June as compared to its forecast based on initial conditions of May.

The Australian weather office has said that the Indian Ocean Dipole (IOD) has strengthened in recent weeks and there are only 50 per cent chances of La Nina. A negative IOD can decrease rainfall over India while La Nina event normally helps rainfall over the Indian sub-continent.

DS Pai, head, Long Range Forecasting, IMD said, "The IOD impact has started coming into picture."

However, according to the Ministry of Earth Sciences (MoES), August and September rainfall are still expected to be 'reasonably okay'. "It will help fill up reservoirs by September end," said M Rajeevan, secretary, MoES recently. The reservoir in drought hit Marathwada region have filled up to only 5 per cent from the low of 1 per cent they had hit in June.

Currently, monsoon has entered into a weak phase. However, IMD expects its revival from the first week of August. "We may get good rainfall in first half of August, just like the first half of July as a low pressure system is expected to form in the Bay of Bengal around August 1 or 2," said Sunitha Devi, director (weather forecast), IMD, Pune.

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