Delhi was expected to slip in to cold wave or even severe cold wave conditions in the 1st week of January 2023, commencing 02nd Jan. However, extreme cold has evaded the capital city and the night temperature remain close to or above normal for the last 3 days. Base observatory at Safdarjung recorded minimum temperature of 8.5deg today, above the average by couple of notches.
Delhi has pentad normal temperature of 7 degree for the 1st three weeks of January and rises to about 8deg around fag end of the month. City has recorded lowest temperature of 5 degree so far, on 26th Dec2022. Last 2 days, city is recording below normal day temperature by small margins. Minimum temperature continue to be above normal by a degree or two, therefore escaping cold wave criteria.
Cold wave is considered for a place when the normal minimum temperature is less than 10 degree and the departure from normal is 4.5deg or more. Also, when the mercury plunges to 4 degree or below, cold wave conditions are stated to have set in. Neither of these criteria is met for the capital city and therefore no cold wave so far in the season.
Much awaited and predicted cold wave during the initial days of January 2023 continue to give amiss for the city and neighbourhood of NCR. The western disturbance had earlier cleared the northern mountains and adjacent plains on 31st Dec 2022. In the wake of the system, icy cold winds invariably sweep the northern plains, including the capital city, Delhi. Plains of Punjab, Haryana and Delhi/NCR are experiencing dense fog at many places. This envelop of fog has lifted slightly up in the lower layers of the atmosphere. This situation has resulted sky obscured conditions for the last few days. This sheet of fog is not allowing the sun to shine brightly.
Also, the surface winds are very light and unable to churn and disperse the obscurity in the friction layers of the atmosphere. This is resulting lower than average day temperatures across most parts of Delhi and suburbs. During night, this dome of fog, placed little above the earth surface in the lower layers of atmosphere, restricts the escape of terrestrial radiations. Otherwise, during clear nights, outgoing radiations lead to sharp cooling and more so during wee hours.
The hiatus of meteorological conditions is expected to continue for the next few days. As such, fresh western disturbance is arriving on 06/07 Jan over the hills of north India. Plains will witness some clouds between o6th and 09th Jan 2023. This situation may still not permit 'true' cold wave conditions over and around the capital city. Earliest, such a cold snap is likely only after 2nd week of January. Minimum temperature for Delhi is not likely to drop to 4deg or below, till then.