Thiruvananthapuram: Indian Meteorological Department under the Union ministry of earth sciences has much explaining to do in the wake of Chief Minister Pinarayi Vijayan's references to deficiencies in its weather forecast. The state has been appalled by the fact that the actual rainfall that it witnessed was three times the quantity forecast by the IMD in the worst deluge of the century.
Sources say that the State, which experiences two monsoons, still does not have a reliable rain gauge network. The Indian Bureau of Standards stipulates a rain gauge every 150 sq km in heavy rainfall areas and 10 per cent these should be automatic for continuous monitoring. Based on this, Kerala, with a land area of 38,800 sq km, should have 258 rain gauges. But there are only 69 gauges and a mere five of them automatic, mostly confined to the coast. Only automatic gauges ensure data every half an hour while data from other gauges are available only the next day. This impairs the system of regular updates for precise (disaster) planning. An adequate number of gauges has to be installed in the hilly regions to enable the state to receive reliable data.
But the MoES had turned its back on the requests to rectify this gross inadequacy. This had resulted in significant errors in the monsoon forecast in the state, sources point out.
Given the disastrous weather warning for cyclone Ockhi, the SDMA braced for the monsoon this year, with the state relief commissioner P.H. Kurian convening a meeting on May 16. The Met regional director assured the meeting that the monsoon long range forecast would be 97 per cent of the average rainfall, with a variation of plus or minus 5 per cent, implying the monsoon would be uneventful in terms of the seasonal precipitation.
One major handicap for the SDMA in preparing for the monsoon was the absence of actionable data from IMD. The authority informed the ministry of earth sciences (MoES) on August 8 that data from Thiruvananthapuram Met office were not available on its website. MoES checked and confirmed that the radar installed at Kochi had a glitch, but the radar in the state capital delivered data every 10 minutes.
However, the weather bulletin available on the IMD site on August 9 at 5.25 pm was the same as that of 8 am the previous day. Following NDMA intervention, the MoES ensured a steady stream of radar data from August 10.
But the weather forecasts were the least helpful in tackling the unprecedented floods. As per IMD standards, heavy rainfall is 7 cm to 11 cm, very heavy rainfall 12 cm to 20 cm and extremely heavy rainfall above 20 cm. There was no extremely heavy rainfall alert during entire August. The mismatch in forecast and the actual rainfall is evident from August 9 and 15. The total rainfall received during the spell was 352.2 mm as against a forecast of 98.5 mm.
The IMD forecast on August 25 for August 27 and 28 was very heavy rainfall. But this was withdrawn on August 26. The alert for August 1 to 10 was isolated heavy rainfall (less than 12 cm). But there was an actual shortfall in August first week and the reservoir level in Idukki dipped since August 4. But, on account of the depression in Bengal, the state witnessed a spell of extremely heavy rainfall on August 8 and 9, belying all expectations. IMD forecast had no mention of an extremely heavy rainfall.
The five-day alert issued by IMD on August 8 at 1 pm showed heavy rainfall in Idukki, Wayanad and Pathanamthitta on August 9 and light to moderate warning (1.5 cm to 6.5 cm) for the rest of the days. But a heavy rainfall followed.
Even on August 14 when it rained a torrent, IMD's 5-day prediction of August 10 was "light to moderate rainfall". There was no suggestion of extremely heavy rainfall district-wise. The special bulletin in the thick of the rains on August 14 did not foresee any extremely heavy precipitation. But it rained 20 cm plus for the next two days in Idukki alone.
