Delhi Breach 41 Degrees Celsius, But No Heat Wave Likely

Parts of Delhi/NCR breached a daily temperature of 41 degrees yesterday. Base station Safdarjung registered a maximum temperature of 40.6 degrees, about 3.8 degrees above the normal. Observatories at Ridge and Ayanagar recorded day highs of 41.5 degrees and 41.2 degrees, respectively. Bulandshahr, on the outskirts of Gautam Budh Nagar, scaled 42 degrees. These temperatures are about 3-4 degrees above the average temperature and therefore do not amount to heat wave conditions.

Earlier, Delhi observed heat wave conditions between 07-09 April, when the temperature hovered between 40 and 41 degrees. However, with the similar temperatures now, a heat wave can not be announced because the normal temperature for Delhi has climbed to about 37 degrees, as against 34-35 degrees in the last spell. 

For heat wave conditions in the plains, the maximum temperature needs to exceed 40 degrees Celsius, and the departure from normal necessarily has to be 4.5 degrees or more. For a severe heat wave, the variation has to be 6.5 degrees or more. Also, the severe heat wave is considered when the mercury shoots to 45 degrees or more.

There is an active western disturbance over the northern mountains. Also, there is well-marked induced cyclonic circulation over border areas of Punjab, North Rajasthan and the Pakistan region. An east-west trough is extending from this system, running in close proximity to Delhi. Under the influence of these systems, the lower-level winds have changed over Delhi to easterly. These winds are moist but less hot than the seasonal westerly winds. Therefore, the temperatures may not exceed 40 degrees for the next 2-3 days. Accordingly, a heat wave is unlikely over Delhi/NCR. Yet, the vicinity of the east-west trough may trigger one odd shower in some areas today/tomorrow, late in the evening.