National capital has observed single digit minimum temperature for the 7th day in a row. Base observatory at Safdarjung recorded temperature </= 9°C between 09th and 15thDecember. The lowest temperature of 6.4°C so far, was recorded on 12thDec. The temperatures will continue to remain less than 9°C for the next one week. However, cold wave conditions are not expected to be witnessed till X-mas and quite likely towards last days of the month.
For the plains, cold wave conditions are announced when the minimum temperature is 10°C or below and is 4.5 notches less than the normal for 2 consecutive days. However, for small areas such as Delhi, even if criteria is fulfilled for a day, cold wave may be declared. The other criteria for cold wave is when minimum temperature drops to 4°C or less for plains.
In the recent past, maximum number of cold wave was recorded in 2018 on 08days and nil days in 2011, 2012, 2015,2016 and 2017. Last year, 06 cold wave days were recorded and minimum temperature of less than 5°C was recorded on 12days. All these were witnessed in the 2nd half of the month and the lowest of all, 3.3°C was observed on 31stDec.
The mean minimum temperature(MMT) for the 1st half of the month (01-15 Dec 2021) stands at 9.9°C against the normal of 9°C. Normal MMT for the month of December is 8.3°C. On an average, month of December begins with a minimum of 10°C and ends with a low of 7°C. The temperatures is likely to remain between 6°C and 9°C till 22ndDecember.
No significant weather is expected for the national capital till 22ndDeceber. Yes, there is an outside chance of having few clouds tomorrow evening and night which may result ‘hit and miss’ drizzle in some pockets. Western disturbance is moving across Jammu& Kashmir and a cyclonic circulation is induced over Haryana and NCR. Wind pattern has changed to easterly in the lower levels.
After the passage of this system, another active western disturbance is expected around 22ndDecember. Night temperatures are expected to rise over the plains of north India including Delhi. This weather system will hang around for 3 days till 24-25 December. Post Christmas, the temperatures are likely to drop significantly with a chance of resulting cold wave towards fag end of the month.