Strong rain in parts of Delhi catches IMD off-guard again
The showers were in sharp contrast to the India Meteorological Department’s (IMD) forecast on Sunday, when the agency issued till July 16 a ‘green alert’, indicating that no significant weather events are likely in that span.
PA sharp, strong burst of rain in parts of the national capital on Monday caught the Met department off guard once again, a day after the agency predicted “very light rain or drizzle” across the Capital.
Pitampura in northwest Delhi was the city’s wettest neighbourhood, getting 77.5mm of rain till 5.30pm on Monday, a spell classified as ‘heavy rainfall’, while Pusa got 25mm of rain, categorised as a ‘moderate’ spell. South Delhi’s Safdarjung station, considered Delhi’s representative station, got just a millimetre of rain.
The showers were in sharp contrast to the India Meteorological Department’s (IMD) forecast on Sunday, when the agency issued till July 16 a ‘green alert’, indicating that no significant weather events are likely in that span. The weather office over the past week got a string of rain alerts wrong, predicting showers several times till Sunday, even as Delhi continued to received only brief patches of rain in that time.
Met officials called Monday’s showers “convective rainfall”, a phenomenon that takes place when the earth’s surface heats rapidly, vapourising water, with rain clouds forming within a matter of hours. Convective rainfall, Met officials said, is generally unpredictable and can occur in localised parts due to high humidity and temperature.
“We forecast isolated drizzle activity in some places and not much rain was expected. But this was convective rain, which generally takes place when the humidity and temperature are both high. It is difficult to forecast such spells 24 hours in advance, because rain clouds can form in a couple of hours. It is also localised, so while one part of Delhi received just 1mm, another part received heavy rainfall,” said Jenamani.
On Monday, Lodhi Road and Safdarjung logged 1mm of rain each, Ridge and Delhi University 11.4mm each, Najafgarh 4mm, Palam ‘trace’, Pusa 25mm, Jafarpur 0.5mm and Pitampura 77.5mm.
IMD classifies rainfall between ‘trace’ and 2.4mm as ‘very light’, between 2.5 and 15.5mm as ‘light’, between 15.6 and 64.4mm as ‘moderate’, between 64.5mm and 115.5mm as ‘heavy’ and ‘very heavy’.
Delhi’s on Monday meanwhile saw a maximum temperature of 36.9°C — a degree above normal for this time of the year. The relative humidity oscillated between 57% and 88% respectively.
Mahesh Palawat, vice president at the private weather forecaster Skymet, said that till Sunday, Delhi was experiencing humid conditions, but not enough moisture, because the monsoon trough was in central India. However, after spells of rain across Punjab, Haryana, Rajasthan and western Uttar Pradesh over the weekend, moisture was added to Delhi’s air, causing Monday’s showers.
“There were clear skies initially, which led to [the ground] heating, with the moisture quickly turning into thunder clouds in a matter of hours. This then led to intense, but patchy rainfall. Such convective spells may occur till July 13 or 14, but widespread rainfall is not expected,” he said.
The IMD had a yellow alert in place for the weekend, forecasting light to moderate rainfall. However, on both days, Safdarjung failed to record any rainfall, with very light to light rainfall recorded in isolated parts of Delhi. The IMD had then issued a green alert for the next six days, up to July 16, forecasting very light rainfall or drizzle activity for the capital on Monday.
A green alert is generally issued when no significant weather event is expected. In terms of rainfall, it is issued when only very light rainfall or drizzle activity is expected. A yellow alert is issued to alert the public of a weather phenomenon and generally issued when light to moderate rainfall is expected, while an orange alert is issued to warn people to be prepared about a weather event. In terms of rainfall, it is generally issued for moderate to heavy spells of rainfall.
After recording a ‘very heavy’ spell of rainfall between 8.30am on June 30 and 8.30am on July 1, Delhi has failed to see any significant rainfall activity, despite forecasts by the IMD of spells of light to heavy rainfall during this period.
The IMD has a green alert in place until July 17 now, with its forecast for Tuesday showing Delhi will see ‘generally cloudy skies and light rainfall’.