Unusually cool and wet April takes weather office by surprise
NEWDELHI: It is the end of April but it is unusually pleasant in Delhi. The maximum temperature has touched 40°C here only once compared to eight days by this time last year. Even in other parts of the country, maximum temperatures are mostly below normal or normal, according to the India Meteorological Department (IMD). No heat waves have been recorded so far except in isolated pockets of Gujarat and Marathwada (and only for a day in both), which is unusual for this time of the year.
IMD scientists are also surprised by intermittent wet spells that have kept maximum temperatures down when the rest of the world is recording above normal temperatures.
In northwest India, this pattern is linked to back-to-back active western disturbances (WDs), which are not supposed to be around in April. By this time, these disturbances which start as low-pressure systems in the Mediterranean, weaken and move to northern latitudes. Scientists said such changes may be due to weather anomalies in Europe. They could also be linked to favourable sea temperatures over the Pacific.
The WDs brought a lot of rain to northwest India; there is also moisture incursion in east and northeast India from the Bay of Bengal, which has been bringing good rains in the pre-monsoon season. According to IMD’s rainfall data, between March 1 and April 26, 13 states have recorded “large excess” of rains (60% above normal).
“Our models show wind patterns will not support development of heat waves till end of the first week of May. Rains will not subside immediately. There will be another strong wet spell in northwest India from May 4 to 6,” said RK Jenamani, senior scientist, National Weather Forecasting Centre. In Delhi and the National Capital Region, the below normal temperature has meant pleasant days and mildly cool nights. The maximum temperature on Saturday in Delhi was 7°C below normal and minimum 5 degrees C below normal. “We had six WDs in March and six in April. Not all WDs brought rain but it has been mostly cloudy and winds are good which doesn’t allow maximum temperature to spike. In 2013 and 2014, we saw similar weather in April,” explained Kuldeep Srivastava, head of the regional weather forecasting centre.
Roxy Mathew Koll, climate scientist from the Indian Institute of Tropical Meteorology, said: “The ocean temperatures over the Pacific are also favourable since El Niño conditions have not developed. Usually if El Niño conditions (anomalously warm ocean temperatures) are present in the central-east Pacific, it can drive heat waves over India during April-May months. It seems that both these factors have been favourable for below normal temperatures over north India.”