The northern and southern extremes of the country are once again coming under the influence of an incoming western disturbance and an eastern wave, respectively, leading to heavy rain, snowfall, high winds, lightning, and hail in the respective regions.
The India Meteorological Department (IMD) said a passing easterly wave will trigger isolated heavy rainfall over south Tamil Nadu and Kerala & Mahe on Tuesday and Wednesday. Scattered moderate rainfall, thunderstorms, and lightning are likely over Tamil Nadu, Puducherry & Karaikal on these days. Light to moderate rainfall, accompanied by thunderstorms and lightning, is expected over Kerala & Mahe, as well as Coastal and South Interior Karnataka, for three days from Tuesday.
Isolated heavy to very heavy rainfall is likely over south Tamil Nadu on Tuesday, with heavy rainfall over Kerala & Mahe on Tuesday and Wednesday. Satellite images on Sunday afternoon showed thunderclouds from the easterly wave locked over the Andaman & Nicobar Islands. The IMD has predicted scattered to fairly widespread light to moderate rainfall over the Andaman & Nicobar Islands for the next seven days, indicating the robust structure and dynamics of the easterly wave.
Rain for North-West
An incoming western disturbance, despite being more than 3,500 km away over Iraq on Sunday, will trigger scattered to fairly widespread light to moderate rainfall or snowfall over Jammu, Kashmir, Ladakh, and Himachal Pradesh on Sunday. It is likely to intensify, bringing fairly widespread to widespread light to moderate rainfall or snowfall, along with thunderstorms and lightning, over Jammu, Kashmir, and Ladakh for nearly a week until Saturday.
Scattered to fairly widespread light to moderate rainfall or snowfall, along with thunderstorms and lightning, is likely over Himachal Pradesh, while Uttarakhand will see isolated to scattered light to moderate rainfall or snowfall, thunderstorms, and lightning during the same period. Isolated heavy rainfall or snowfall is likely over Jammu, Kashmir, and Ladakh on Monday. Isolated light to moderate rainfall, thunderstorms, and lightning are expected over Punjab, Haryana, and West Uttar Pradesh on Wednesday and Thursday; over West Rajasthan for three days from Thursday; and over East Rajasthan on Saturday.
Western disturbance impact
Mostly known for their weather-generating capacity during winter over North and Northwest India, western disturbances persist beyond the season, arriving in ones and twos even into spring. They subside with the arrival of the southwest monsoon in June, which also brings a reversal of winds. In contrast, easterly waves travel across the Bay of Bengal toward Sri Lanka and South India, carrying a rain head directed mainly at the east coasts of Sri Lanka and Tamil Nadu. They often feature a cyclonic circulation, a low-pressure area, or even a cyclone, extending moderate to heavy rainfall westward over Kerala as well.
Towards the south, an easterly wave packing flaring thunderstorms (in red and blue) have locked in over Andaman & Nicobar Islands on Sunday afternoon, and are expected to roll in towards Sri Lanka and south-east Tamil Nadu coast in India.
| Photo Credit: www.meteologix.com/in
Rainfall spurt in south
A preceding easterly wave last week triggered a rainfall spurt over the South Peninsula, leading to surplus rainfall. However, records have since declined, though the meteorological subdivisions of Lakshadweep (+281 per cent), Tamil Nadu, Puducherry & Karaikal (+94 per cent), and Kerala & Mahe (+34 per cent) have posted a surplus so far during the pre-monsoon period (March 1 to 8).
Northwest India has recorded an above-normal rainfall of eight per cent, the only core geographic region to do so, aided by heavy rainfall or snowfall (and even avalanches) over the hill states of Uttarakhand (+145 per cent) and Himachal Pradesh (+72 per cent). The rest of the meteorological subdivisions in this region are either just normal or below normal during this period.
Worst over Central India
Central India remained the worst-hit, with practically no rain (-100 per cent) across all meteorological subdivisions and a large deficit (-99 per cent) in West Madhya Pradesh, which alone received a sprinkling, if any. Rainfall records for East and Northeast India also worsened, with no rain recently in the plains of West Bengal, large deficits in Bihar, Jharkhand, and Nagaland-Manipur-Mizoram-Tripura, and shortfalls in Arunachal Pradesh, Assam & Meghalaya, and the hills of West Bengal & Sikkim.
Thunderstorms in east
Towards the east, a cyclonic circulation stationed over Assam has shifted to northeast Bangladesh and is expected to sustain seasonal thunderstorms over Northeast India. The IMD has forecast that ongoing isolated to scattered light to moderate rainfall or snowfall may intensify to scattered to fairly widespread light to moderate rainfall or snowfall, along with thunderstorms and lightning, over Arunachal Pradesh, Assam & Meghalaya, and Nagaland, Manipur, Mizoram & Tripura for five days from Tuesday.
Isolated heavy rainfall is likely over Arunachal Pradesh for three days from Tuesday, while isolated light to moderate rainfall or snowfall is predicted for Sikkim for the next seven days. In this manner, thunderstorm activity over Northeast India will receive a boost under the influence of the incoming western disturbance as it moves east from Northwest India later this week.
