Friday, November 20, 2009

North-East monsoon yields 19% excess rain so far .. except coastal Andhra Pradesh with a 27 per cent deficit ..

North-East monsoon yields 19% excess rain

More than a month-and-a-half into the season, the northeast or winter monsoon has generated excess rainfall of 19 per cent during the season so far (October 1 to November 18).

The season has been normal or above normal over the southern peninsula (except coastal Andhra Pradesh with a 27 per cent deficit), west-central, central, north and east India.


The northwest continued to disappoint, especially the bread baskets of Punjab and Haryana. But the entire Uttar Pradesh, Bihar, Madhya Pradesh, Jharkhand and Maharashtra returned gains in excess of the usual.

Chhattisgarh (22 per cent); Gangetic West Bengal (35 per cent) and Arunachal Pradesh (29 per cent) too have run up varying deficits during this period.

Leading international models had suggested that November would likely see northwest India being left in the lurch while peninsular India would make the most gains.

The India Meteorological Department's (IMD) rainfall maps showed the `gateways' in the northwest - Punjab, Haryana, west Rajasthan and Saurashtra-Kutch - reporting scanty rainfall.

But model predictions favour comparatively better times going further into the winter for these regions.

They get their seasonal rains from western disturbances of significant magnitude with embedded cyclonic whirls.

Most of the rains generated during the season until now have fallen eastward from Uttarkhand, west Uttar Pradesh, east Rajasthan and Gujarat.

Some qualitative change to the scenario was discernible only during the latest week (ending Wednesday) when west Rajasthan alone posted scanty rainfall and Saurashtra-Kutch, deficient - the rest of the country had excess rainfall.


Meanwhile, the US National Centres for Environmental Prediction (NCEP) saw more rain being generated over Sri Lanka and along the Tamil Nadu coast during November 19 to 26.

The entire southeast and southwest Bay of Bengal and adjoining East Indian Ocean, a `hotspot' for quite sometime now, will continue to set up weather for the southern peninsula during this phase.

The realised rains are expected to be normal over Tamil Nadu but in excess over the west coast, especially around coastal Karnataka, according to the NCEP outlook.

The following week (November 27 to December 5) is forecast to see a fresh wave of rains approach the Tamil Nadu coast from the east and the southeast.

The European Centre for Medium-Term Weather Forecasts (ECMWF) too, agrees and picked successive cyclonic circulations patrolling the southeast and adjoining southwest Bay of Bengal from Sunday to Tuesday.

A broad area of lower pressure may get thrown up covering the south Andaman Sea and adjoining southeast Bay of Bengal around midweek next week. This should trigger a conventional `low' in the region the next day or the day after.

This could well be the causative feature of the rains that the NCEP sees falling over India's southeast coast and adjoining Sri Lanka during the next week and possibly into early December.


An update from the Regional Met Centre, Chennai, said that the northeast monsoon has been vigorous over south coastal Andhra Pradesh during the 24 hours ending Thursday morning.

Forecast for the next two days said that rain or thundershowers are likely at a few places over Tamil Nadu, Puducherry, Kerala, Lakshadweep, Andhra Pradesh and Karnataka.

The cyclonic circulation over south Tamil Nadu and adjoining Kerala persisted on Thursday. But the trough from south Konkan coast to Chhattisgarh that emptied rains over central and east-central India during the past few days has weakened.


It has, however, left behind a cyclonic circulation over south Chhattisgarh and adjoining coastal Andhra Pradesh. Another cyclonic circulation lay over Madhya Maharashtra and neighbourhood.

Strong northwesterly to westerly winds are prevailing over the Indo-Gangetic plains. The northwesterly component is what brings in the `chill factor' into focus over the region.

The IMD said that minimum temperatures are likely to fall by 1 to 2 degree Celsius over northwest India and by 2 to 4 degree Celsius over central and adjoining east India during the next three days.
Nagercoil - Raining heavily now 4:15pm
Nagercoil - Kanyakumari district experiencing 2 day of Heavy NE afternoon showers.
South and south-east Bay is getting active ..
Satellite shows:: Heavy showers over south-Tamilnadu, Gulf of Mannar, south Kerala, and coastal Karnataka ..
Latest COLA - GFS: still holds to the Cyclone prediction by Monday .. .. it predicts it even more severe now.
Chennai - Temperature is around 30 deg.. but humidity is high at 72%
Satellite shows.. Moisture push from Bay continues and Expect heavy intermittent showers from tomorrow ..
RT @meteorochennai: chennai-Early morning shower will clear and it will be mostly sunny. Expect rain from tomorrow
Here are some useful TECHNICAL comments for our weather updates .. .. Contact us thru weatherblog(at) for Authoring.

Some useful TECHNICAL comments for our weather updates

Anonymous has left a new comment on your post "Yesterday's moisture push from South-east Bay is s...":

Yesterday [18.11.2009/WEDNESDAY-In CHENNAI]it was given to infer that a sea level high pressure in the WC bay veered with height. This veering wind helped transport moisture in SOUTH-North horizontal plane. This is referred to as 'WARM AIR ADVECTION" This enabled quick cumulus built up in SOUTH-NORTH horizontal plain along 77 to 78 Deg Longitude. Thus it rained heavily from USILAMPATTI, Periyakulam, to Hyderabad. However today [19.11.2009/THURSDAY] WAA moved towards further west.

Anonymous has left a new comment on your post "Chennai - ALERT:: Watch out for a LOCAL heavy show...":

During early morning in Chennai from Beach SRly sub urban station to Chetpet SRLY sub urban station there was rain for atleast 10 min.[Today, the 20 Nov 2009]
The Quciscat sea wind shows winds converging at 10 Degree North Latitude i.e SE of Nagapatinam.
Towering cumulus in NE sector is visible.
The High pressure [1050 hPa] slides through Thai and Easterlies are filled in the Bay East of 80 Deg East. {Refer Thai Meteorological Department analysis]
The low pressure as usual lies beneath Cape Comorin and adjoining SW Bay.
Easterlies generating wave like patterns and give rain to TN coast soon.

Anonymous has left a new comment on your post "Whole of India is moving into a DRY MJO phase from...":

Though SW monsoon is a giant wind [reversal] phenomenon where the winds originate from SOUTH INDIAN OCEAN in Southern Hemisphere, crosses the Equator, then turns to west and blows the western side of INDIA. Most of the Asian countries are benefited by this summer monsoon rainfall.
On contrary, NE monsoon winds emanate from high pressure area over land and winds emanating from this high passes through Bay of Bengal and moisture intake is comparatively less.
Tamilnadu, Coastal AP, Kerala is benefited mostly by this NEM.

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Chennai - ALERT:: Watch out for a LOCAL heavy shower.. in another 1 hr.
Whole of India is moving into a DRY MJO phase from Today.. .typically this phase will not support Cyclone formation
EFS model did not support the formation of Cyclone around 25-Nov, instead it's predicting it around 29-Nov.
All Tamilnadu and Srilankan people should watch this ..
Chennai - Look forward to another showery weekend... this time may be from saturday evening.
Satellite shows, Another heavy weather front from Bay is in striking distance from TN coast ..
Chennai - very warm and cloudy now 9:45am, possibility of a super shower is increasing.