Saturday, September 26, 2009

Monsoon in withdrawal mode, exits W. Rajasthan

India Meteorological Department (IMD) announced on Friday that the Southwest monsoon has withdrawn from many parts of West Rajasthan.

The withdrawal process has been in the making for some time with the skies over Rajasthan and large parts of northwest India clearing up and the mercury consistently peaking to beyond the 40 deg Celsius.

ANTI-CYCLONE

On Friday, weather charts showed the large anti-cyclone (high-pressure area within sinking motion of air that retards cloud formation) sneaking in from across the northwest border.

The withdrawal line passed through Ganganagar, Churu, Jodhpur and Barmer. The monsoon is likely to withdraw from more parts of northwest India during the next four days in fairly fast progression.

The process could get bogged down just over central India as easterly flows from a lately activated Bay of Bengal fill large parts of peninsula and even parts of central India.

The anticipated low-pressure area is expected to materialise over the Bay by Sunday even as a much stronger system is forecast to brew over the South China Sea concurrently.

The Bay system would be forced to let go of some moisture that would feed into the stronger South China Sea system, according to the European Centre for Medium-Range Weather Forecasts (ECMWF).

After walloping the Indo- China coast for a landfall, the South China Sea system could yet again set the Bay on fire, with ECMWF projecting the formation of another `low' during early October.

In this manner, the withdrawal process of the monsoon from the rest of the mainland India may get affected indefinitely.

THUNDERSHOWERS

The US National Centres for Environmental Prediction sees the whole of the peninsula and parts of central India being brought under the cover of thundershower activity until October 11, according to as per latest forecasts.

Monsoon withdrawal has already been delayed by more than 20 days owing to occasional presence of cyclonic circulations and troughs transported in by the westerly flows across northwest India.

But on Friday, towards the southeast, an upper air cyclonic circulation lay in wait over northwest and adjoining west-central Bay of Bengal, an IMD update said.

Under its influence, the anticipated low-pressure area is likely to form during the next two days over west-central Bay of Bengal and neighbourhood.

Scattered rainfall activity has been forecast over the Northeastern States during the next three days before tapering off.

Fairly widespread rainfall activity with isolated heavy fall is likely over peninsular India, including Maharashtra, for five days from Saturday, the IMD update said.

WIDESPREAD RAINS

Satellite pictures showed convective clouds over parts of southeast and west-central Bay of Bengal and the Andaman Sea.

Forecast for the three days ending September 30 said that scattered to fairly widespread rainfall activity with isolated heavy falls is likely over the west coast and peninsular India.

An update from the Chennai Met Centre said that the monsoon has been vigorous over Karnataka during the 24 hours endeding Friday morning.

Rainfall occurred at most places over Karnataka and at a few places over Kerala. Isolated rainfall occurred over Tamil Nadu and Andhra Pradesh.

Forecast for the next two days said that rain or thundershowers are likely to occur at most places over Karnataka; at many places over coastal Andhra Pradesh and at a few places over Kerala, Lakshadweep, Telangana and Rayalaseema.

Isolated rain or thundershowers has been forecast over Tamil Nadu and Puducherry.

A warning valid for the next two days said that isolated heavy rain is likely over coastal Karnataka and the ghat areas of south interior Karnataka.

Chennai - If wind moves in from Sea then we will have a Thunder squall like yesterday afternoon. Sea breeze time window is till 11pm.
Chennai - We might get a Thunder storm after 10 pm.. Now it's warm, humid and literally NO wind.
Chennai - Very HOT saturday evening now 7:01pm, 33.2°C
Nine swine flu deaths in India, toll 286 .. http://ping.fm/27l35
Chennai - All thru the day it was overcast with High dead clouds. Now 5:53pm also no sign of Rain.

Monsoon maintains token presence over peninsula

The India Meteorological Department (IMD) on Thursday maintained the watch for a late-September low-pressure area to churn up the Bay of Bengal around Sunday even as the monsoon retained its token presence over the peninsula.

The weather-driving northsouth trough extended from Bihar to coastal Karnataka through Jharkhand, Chhattisgarh, Telangana and interior Karnataka with an embedded cyclonic circulation over Bihar.

BEVY OF TROUGHS

Alargely sea-bound trough extended south from the circulation over Bihar and adjoining West Bengal up to southwest Bay of Bengal. This will have some say in the churning of the Bay and associated birth of the `low.'

The cyclonic circulation over the east-central Arabian Sea off the Karnataka coast has become less marked as of Thursday, but a trough extended south from Konkan towards the Kerala coast.

Satellite pictures showed convective clouds over parts of the north Bay of Bengal, north Andaman Sea and east-central Arabian Sea.

An update from the Chennai Met Centre said the monsoon has been active over interior Karnataka and Rayalaseema during the 24 hours ending Thursday morning.

Rainfall occurred at many places over Kerala, Rayalaseema and interior Karnataka and at a few places over Tamil Nadu and coastal Karnataka. Isolated rainfall occurred over coastal Andhra Pradesh and Telangana.

The forecast for the next two days said that rain or thundershowers are likely at many places over the Andaman and Nicobar Islands.

Rain or thundershowers are likely at many places over Kerala and coastal Karnataka and at a few places over Tamil Nadu, Puducherry, interior Karnataka and coastal Andhra Pradesh.

Isolated rain or thundershowers are likely to occur over Telangana, Rayalaseema and Lakshadweep.

WIDESPREAD RAIN

Given the influence of the varied meteorological features on the immediate vicinity, the IMD has forecast scattered to fairly widespread rainfall activity along the west coast and over interior south peninsular India during the next 24 hours before going into a lull.

This lull would be broken with the formation of the `low' in the Bay from when rains are forecast for peninsular and adjoining central India.

Isolated heavy rainfall is likely over the Andaman and Nicobar Islands, Konkan, Goa and coastal Karnataka during the next 24 hours.

The forecast for the next three days projects the possibility of fairly widespread rainfall with isolated heavy falls over the North-Eastern States.

The three days starting from Sunday until September-end would see the initiation of the `low' over west-central and adjoining northwest Bay. This will lead to an increase in the rainfall along the east coast, peninsular and adjoining central India.

Meanwhile, a forecast about the withdrawal of monsoons from northwest India has become uncertain with the presence of cyclonic circulations - `in situ' or those crossing in from the border.

Any declaration of the withdrawal pre-supposes the total absence of cyclonic circulations over the region and sinking motion of air associated with the setting in of the seasonal anti-cyclone that drives away clouds of any kind.

Dry North-West

Otherwise, dry conditions have settled over the region with many places in Rajasthan recording maximum day-time temperatures of over 40 degrees Celsius.

On Thursday, the IMD traced a `nuisance' cyclonic circulation over north Pakistan and adjoining Jammu and Kashmir, once again preventing the monsoon withdrawal process from getting entrenched.

Meanwhile, the US National Centres for Environmental Prediction (NCEP) has in updated forecasts indicated that the rains over the peninsula may last as late as October 10.

The NCEP expects the churn in the Bay of Bengal to continue at least till such time, with a core wave of rainfall looking to wade its way into Sri Lanka and adjoining south Tamil Nadu and Kerala during this period.

The rest of the peninsula is expected to receive comparatively lesser amount of rain, it said.

Dry conditions have settled over the region with many places in Rajasthan recording maximum day-time temperatures of over 40 degrees Celsius.
US NCEP has updated forecasts indicated that the rains over the peninsula may last as late as October 10.
RT @unknown82dodo: well. S-West monsoon retreating back.lets hope for good monsoon next year
Chennai - Today also touched a high of 37.9°C (1:28pm)
But, latest satellite shows that south-west and Central BAY is active all thru the night .. http://yfrog.com/3djwvj
Latest GFS shows nothing abt the Sep-28 LOW or Depression over the Bay.. http://yfrog.com/0hzswp