India Weather 13/09/24: Kerala rain to decrease in onam, know India weather forecast

India Weather 13/09/24: Kerala rain to decrease in onam, know India weather forecast

In the previous week ended at 23.59 hrs on 12th September 2024, the south-west monsoon has been extremely vigorous over east and west Madhya Pradesh, Jharkhand, Bihar ,east and west Rajasthan Chattisgarh,Punjab & Haryana, NCR Delhi, and vigorous over the north- east,Andhra Pradesh and Telengana, Gujarat Uttrakhand ,and active over , North coastal Karnataka, Konkan & Goa, Vidarbha ( Interior Maharashtra) and over some parts of Himachal Pradesh.
It has been very active over sub- Himalayan west Bengal, Odisha , west Bengal, east and west Uttarpradesh, and moderately active over north Kerala, central Kerala, and other parts of the Indian peninsula.

In Tamilnadu isolated rainfall occurred in the Nilgiris , Valparai and over the Manjolai hills in Kanyakumari district as part of the orographic rains over the western ghats and over Tanjavur and Pudukkottai due to wind discontinuity and trough in the easterlies.

The cyclonic circulation over central Bay and a mid tropospheric circulation over north west India caused widespread rains over the north- west and central and south central Indian States. The monsoon trough has been slightly tilted south of its mean position at its north- west end and tiled south of its normal at its south-east end. The western offshore trough remained active from Gujarat to Malabar coast.

With so many back to back depressions and cyclonic circulation occurring, one might be wondering why all these circulations move only
north- west ward and not towards the east. This movement of depressions and cyclonic circulation is due to the physical law of conservation of relative vorticity of the air column and its latitudinal location.

As earth’s west to east spin imparts absolute planetary vorticity as is experienced in the Coriolis force, causing air parcels heading northward to turn right, the relative vorticity of the air parcel tries to balance the shear and curvature vorticities and conserve this and in this process the net effect is that the air column tends to drift poleward towards the west ( beta drifting). As the moment of inertia of the air parcel gets reduced as it moves to higher latitudes, it’s vorticity has to increase to conserve angular momentum.

So long as there is sufficient thermal energy and moisture supplied constantly through latent heat of condensation and evaporation or the latent heat flux which could run into a whopping several millions watts per sq metre. Despite the lower level westerlies, these vorticities happen at upper levels and and are not generally weakened or dissipated by the westerly steering winds.

At the same time due high vertical shear they do not become destructive cyclones either during the peak monsoon months. Nevertheless these depressions are copious rain givers. As the monsoon winds weaken by the end of September, these depressions start to become extremely & destructive. There are more complex factors involved in this process which can only be explained mathematically and numerically which is outside the scope of this blog. However the attached picture would give a general idea of the path that a cyclonic circulation takes.

Forecast: ( Effective from 06:00 hrs from. 13/09/24, to 23:59 hrs on 19/09/24.

The northern monsoon trough may continue to remain active and its north- west end may shift southward in the next 5-6 days. An upper air cyclonic circulation associated with the monsoon depression is likely over west Uttar Pradesh and adjoining parts of NCR Delhi, Uttrakhand from 12th to 14th September triggering exremely heavy rains in these areas.

Meanwhile a fresh monsoon depression is likely on 13 th September over the head of Bay.This system may progress westward accompanied by another spell of very heavy rains in Odisha, Bihar, Jharkhand, east & west Uttar Pradesh, Madhya Pradesh before it finally decays over easy Rajasthan by 19th or 20th September.

On 12th, 13th & 14 th September, fresh alert needed for NCR Delhi , Karnal, Paipat, Hissar and adjoining areas of Haryana, as there is a likelihood of extremely heavy rains . The entire Pauri- Garhwal, Karnaprayag, Joshimutt, Nainital, Mussoorie, and the lower western Himalayas would also be pounded by very heavy rains and micro cloudbursts on 13 th & 14 th September. Extreme caution may be exercised by tourists proceeding to the hills of Uttrakhand on these days.

North east Regions

Due to the fresh mid tropospheric cyclonic circulation associated with the monsoon depression, Meghalaya , upper Assam, sub-Himalayan west Bengal and extremely heavy rains may be expected in Silchar, upper Assam, Meghalaya, and Arunachal Pradesh on 13th and 14 th September. This system may progress westward and merge into the depression from the Bay on 11th September. As a consequence extremely heavy rains may be expected in Bihar, Jharkhand , West Bengal , sub-Himalayan west Bengal, on 14th and 15th.

The system may further move westwards unleashing extreme rains over east Uttar Pradesh , west Uttar Pradesh , east Madhya Pradesh, and west Madhya Pradesh on 16th and 17th September and peter out on 20 th September over western Madhya Pradesh and eastern Rajasthan.

Western, eastern,central and south India

The western offshore trough, may become weaker from 13 th September and as a result moderate rains may be restricted only from coastal Maharashtra to south coastal Karnataka.
The interior regions of Marathwada, and Madhya Maharashtra comprising places like Sholapur, Nashik, Pune, Aurangabad, Jalgaon may receive only light to moderate isolated rains from 13 th to 15 th September and the Vidarbha regions may remain dry.

The Telengana regions may get a respite after extremely heavy rains in the last week and weather is likely to be generally dry.
However due to trough in the easterlies and wind discontinuity Coastal and interior areas of Andhra Pradesh may expect isolated thunder showers on 14 th September.

In Chattisgarh and Odisha scattered heavy rains may be expected from 13th & 14 th due to the low pressure system associated with the monsoon depression over the Bay.

The western offshore trough may go weak with only light rains forecast for north coastal Karnataka and coastal Maharashtra. The Malabar regions of Kerala may remain generally dry and sunny woth occasional.light showers. But the eastern pockets of central and south Kerala, especially , eastern pockets of Ernakulam, Kottayam, and Idukki may expect isolated heavy thunder showers or rains on 14 th & 15 th September .

In Tamil Nadu, due to wind disntinuity and trough in the easterlies, isolated heavy thinderstorm activity may be expected in pockets like Ramanathapuram, Madhurai, Thirunelveli, Karaikudi, Peraiyur, Dindigul on 14 th and 15th September.

General distribution of rainfall and pockets of heavy rainfall alerts for the upcoming week:
North west India:( Moderate to heavy) Chandigarh, NCR Delhi , 12 th to 14 th September.

North- East India ( Heavy to very Heavy) Meghalaya, Imphal, Aizwal, As ilchar, Jorhat, Upper Assam, Guwahati on 14th & 15 th September 2024.

Uttrakhand & Himachal Pradesh:( Moderate to heavy) Uttarkashi, Mandi, Dharamshala, Pauri-Gharwal, Ranikhet, Chamoli, Mukteshwar, Halwani, Almora, Pithoragarh Mussoorie, Nainital, Karnaprayag on 12th 13 th and 14 th September.

Uttar Pradesh:( Heavy to very heavy) Bareilly, Faizabad, Agra, Jhansi , Moradabad, Meerut on 13 th September and in Prayagraj, Varanasi, Kanpur , Shahganj from 15 th to 17 th September.

Madhya Pradesh: ( Heavy to very heavy) Gwalior, Itarsi, Jabalpur, Nainpur, and Sagar from 16th to 18th September.

Gujarat: Nil.

Maharashtra & Goa: Nil

Andhra Pradesh & Telengana:
Nil

Karnataka:( Moderate to heavy)
Nil

Tamilnadu: No alert for very heavy rains.

KERALA

There is no specific alert for extreme heavy rainfall events anywhere in Kerala.

SPECIAL WEATHER ALERT FOR TRAVELLERS AND TOURISTS

North East India
Darjeeling, Gangtok, Siliguri, Arunachal Pradesh, Shillong Meghalaya likely to be rainy from 14/9/24 to 16/9/24. Heavy rains may be expected in Bongaigaon , Goalpara Guwahati, Jorhat and6b Herr f Silchar on these days .
Maximum and minimum temperature: 26°C & 20°C.

Uttrakhand:(Moderate to heavy)
Tourists bound for the hills in Uttrakhand may be on high alert on 13 th and 14th September as Uttarkashi, Pauri, Gharwal and Mussoorie, Nainital , and adjoining hill stations on the eastern Himalayas may expect extremely heavy rains on 13th & 14 th September.

Maximum day temperature 19°C and minimum 15°C in lower Himalayas and 11°C and 6°C in the greater Himalayas lying above 2500 metres above MSL.

The Kedarnath and Badrinath hill shrines in the Gharwal Himalayas may expect moderate to heavy snow or rain from 13th to 14 th September. Maximum day temperature in Kedarnath is likely to be 11°C and minimum 3-4°C. In Badrinath the maximum day temperature is likely to be 10°C and minimum at 3°C.

The Hemkund Sahib Gurudwara in the Gharwal Himalayas may expect heavy snow or rain from 13th to 14 th September. The maximum day temperature may be 7°C and minimum may range from 3°C to minus 2°C .

Himachal Pradesh .
Manali, Shimla, Bilaspur, Mandi , Kangra valley may expect heavy rains on 13 th and 14th September. Isolated extreme rainfall events, or flash floods and landslides may occur and holiday makers are advised to exercise some caution on these days while driving to the hills. Maximum & minimum temperature:
22°C and 15°C in lower Shivalik ranges and 15°C and 7°C in the upper Himalayas and Kinnaur ranges.

Jammu& Kashmir

Light rains on 13/9/24 . No heavy rain alerts. Maximum and minimum temperature 24°C and 15°C in Srinagar and 16°C and 6°C in the higher reaches of the Karakoram Pir Panjal and Ladakh ranges.

South India

Hillstations of Ooty and Kodaikanal may be pleasant with generally overcast skies. However Kodaikanal may expect isolated moderate to heavy thunder showers or rains on 14th September Maximum and minimum temperature: 20°C and 12°C in Ooty and 22°C and 12°C in Kodaikanal.

In Kerala the main hillstations of Kerala, , Wayanad , Munnar, Devikulam, Vagamon and Peerumade may expect moderate thunder showers rains on 14th September with maximum day temperature at 25°C and minimum in the range from to 20°C to 17°C depending on the altitude. In Kanthalloor , Vattavada the maximum temperature is likely to be in the range 19°C to 22°C and minimum temperature around 14°C to 16°C with chance of light rains on 14/9/24 . The backwaters in Alappuzha and Kumarakom may expect moderate spells of rains on 13th & 14th September.

(NB: Next weekly post on 20/09/24)

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