Saturday, March 23, 2024

After the drought - welcome rains in mid - March2024 but also the adverse impact on NH10

After the devastating Teesta valley GLOF of 04Oct2023, our region went in for a four and a half month drought where we did not get a drop of rain:

Both the post-monsoon and  winter season rains went missing and with the vegetation and forests bone dry, we had forest fires much earlier than usual (SHWB is Sub-Himalayan W Bengal)
Screenshot of my post in our What'sApp group, 'Hazard Alerts' showing forest fires in Jan2024.
Forest fire in Sikkim: 16Mar2024

The drought-like conditions continued right upto mid-March2024 with acute drinking water scarcity in many of the urban centres in our region - in Kalimpong there was a 3 day waiting list for anyone wanting to buy water from the water tankers and also, I believe people have started drilling for ground water again. In the rural areas, springs dried up.

Winter rains are caused by Western Disturbances (WDs) which originate around the Mediterranean sea.
reported on the matter, excerpts of which are placed below:
'There has been a lack of rainfall during the post-monsoon season and next to no winter snowfall in some of the north Indian states as a result of a lack of intense western disturbances. This can affect the yield of Rabi crops in these regions and also availability of water in the mountains in general. The lack of snowfall in the mountains could also lead to a warmer than normal pre-monsoon season, with excess rainfall that could affect the harvesting period of Rabi crops. 
Winter precipitation in north India is essential to ensure people’s food and water security. While Rabi is the major cropping season encouraged by rainfall, the glacial streams and rivulets in the Himalayas are fed by melting snow and ice later in the season. 
The only source of rainfall and snowfall in the region are extratropical storms known as western disturbances (WD), which travel from the Mediterranean region. They induce cyclonic circulations in the lower layers of the atmosphere, which cause rainfall in the plains and snowfall in the mountains. They also interact with other wind systems such as the easterlies (winds blowing from the east) to cause rainfall in central India.
The WDs have been showing a decline in intensity in the past few years due to changing climate. The trend continued in the post-monsoon and winter seasons of 2023 as well.
From October 1, 2023 to January 2, 2024, 16 WDs have affected India — five in October, five in November and six in December — out of which only three have been intense and caused rainfall, according to data from the India Meteorological Department (IMD), analysed by Down To Earth (DTE).
This has caused rainfall deficits in states like Uttarakhand and Himachal Pradesh. While Uttarakhand experienced 47 per cent less rains than normal from October 1 to December 27, the deficit in Himachal Pradesh was 40 per cent, according to data from IMD.
Eight out of the 13 districts of Uttarakhand had deficient rainfall (20-59 per cent less rainfall than normal) and four of them suffered from large deficient (greater than 60 per cent deficit) rainfall. Udham Singh Nagar district had the maximum deficit of 87 per cent. 
In Himachal Pradesh, four districts had deficient rainfall and two had large deficient rainfall. Lahaul and Spiti district had the maximum deficit of 73 per cent.
“Himachal Pradesh and Uttarakhand received deficient precipitation since western disturbances during the post-monsoon were weak in nature,” Akshay Deoras, a research scientist at the National Centre for Atmospheric Science and Department of Meteorology, University of Reading, United Kingdom, told DTE.
“The western disturbance activity witnessed a southward dip in December, causing good rainfall over central India, but either deficient or scanty rainfall over most of northern India in December,” he added. 
Towards the end of November, a moderately intense WD interacted with a lower level trough in the easterlies and chased significant rainfall in central and western Indian states of Gujarat, Maharashtra and Rajasthan.
“The northwest rainfall reduction is consistent with the general decreasing trend in western disturbances and the precipitation drop over the region. But the El Nino also tends to produce colder winters over parts of this region,” Raghu Murtugudde, a climate scientist at the University of Maryland and Indian Institute of Technology Bombay, told DTE.
Murtugudde predicted that the pre-monsoon season will be warmer and probably get more rainfall because of the Arabian Sea warming. “If the summer transitions to a La NiƱa then we should have excess rainfall during the monsoon season,” he concluded.

The drought mercifully ended on 20March2024 in Kalimpong and also the rest of
.Sub - Himalayan WB and SIkkim with thundershowers commencing at 2.30am.
The weather systems which affected us and the cloud image is shown below:

For the past few days we have had welcome light rain in our region. Rainfall totals from 20-22Mar2024 are given below:
Darjeeling 118.6mm  Kalimpong  67.2mm  Bagdogra  92.1mm  Gangtok 46.2mm

NH10 status
We have reported extensively on the impact of the GLOF on roads and bridges in our earlier blogs including one exclusively on the part of NH10 which is now causing massive traffic jams here.
What is alarming is that after absolutely no rain for months, the first light/moderate rainfall can disrupt our communication lines so much - an issue which was pointed out by us in the report submitted to the NDMA & SDMAs of W Bengal and Sikkim on 10Nov2023.
Excerpt of the report is below

I shudder to think what will be the condition and status of NH10 when the SW monsoons set in a few months time.

Traffic jams today at Chitrey (top) and Teesta bazar on NH10
Landslide at Likhu Bhir (NH10) on 21Mar2024
(Images from Hazard Alerts What'sApp group - many thanks:)

NH10 and alternate routes in the Kalimpong- Sikkim area
Kalimpong District Administration's What'sApp message on 21Mar2024 advising alternate routes

Praful Rao
Kalimpong district
Darjeeling-Sikim Himalaya


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