Sunday, November 22, 2009

Chennai - A nothing evening, clear skies and temperature will go down.
Gulf of Mannar is active again.
Getting reports of heavy rain in Nilgiris.
Heavy rain again over South-east, central and western TN..
CAPE Convection model indicates more rain over east Arabian sea than south-Bay ..
IMD-MM5 Model also predicts a south-east Bay Low pressure on 24-Nov, .. No movement prediction yet.!
A hotter planet means less on our plates ..

IMD says `low' weakening, but other models don't agree

Rainfall has been reported from a few places over Tamil Nadu, Lakshadweep and coastal Karnataka despite the suppressed phase of a Madden- Julian Oscillation (MJO) wave beginning to assert itself.


The suppressed or `dry' phase of the MJO wave is the reverse of its rain-generating wet phase that has exited equatorial Indian Ocean and is moving into the west Pacific.

The alternating wet and dry phases of the MJO travel from west to east and areknown to significantly impact weather playing out over ground.

The recent wet phase had peaked with the triggering of the rare west coast cyclone, Phyan, and the moderate to widespread rainfall generated in its wake over a wide swathe north-north-east across the peninsula.

A residual area of convection left behind by the eastward bound wet MJO wave is active over the South China Sea, international models suggested. They were also of the view that the dry phase over equatorial Indian Ocean (in the vicinity of Sri Lanka and the southern Indian peninsula) may have just been set off over the West Indian Ocean, as of now.

But the peak phase over equatorial Indian Ocean would be felt from December 1 to 7, according to the Climate Prediction Centre of the US National Weather Services.

This dry phase would last until December 11/12, following which the next wet phase of the MJO, a likely weaker episode than the predecessor, may set in over equatorial Indian Ocean reviving the north-east monsoon yet again over Sri Lanka and southern India.

On Wednesday, India Meteorological Department (IMD) said in its update that the previous day's low-pressure area over south-east Bay of Bengal persisted but showed signs of weakening. But the Fleet Numerical Meteorology and Oceanography Centre of the US Navy has suggested that the `low', tagged 95B Invest, is apparently doing well for itself with estimated wind speeds of 20 knots (37 km/hr).

The NGP model of the US Navy that tracks cyclonic circulations has maintained that the system will sustain and keep travelling to the west to eye Sri Lanka coast for a likely landfall, though not spectacular. The Canadian Meteorological Centre too believes that the system would survive the apparently none-too-helpful environment to track north first before moving west to the Sri Lanka-South-east Tamil Nadu belt.

Significantly, the UK Met Office mode has predicted that the system may fail to make the grade and die out over the south-east Bay.

Easterlies may be weakening but the precipitation forecast by the US National Centres for Environmental Prediction expects the occasional thundershowers over the southern peninsula to hold during the short to medium term.

In its outlook for the next two days, the Chennai Met Centre has said that rain or thundershowers are likely at a few places over Tamil Nadu, Puducherry and Lakshadweep.


Isolated rain or thundershowers are likely over Kerala, coastal Andhra Pradesh, Telangana, coastal and south interior Karnataka.

Satellite cloud imagery showed convective clouds over parts of south Bay of Bengal. The IMD expected a subdued rainfall regime over extreme south peninsular India during the next four days.

North-westerly winds will continue to prevail over the Indo-Gangetic plains while it would be northerlies over east and adjoining central India during the next two days.

Minimum temperatures are likely to fall by over parts of central and east India and plains of north-west India during this period.

On Wednesday, maximum temperatures were below normal over some parts of the Indo-Gangetic plains and adjoining central and east India.

Minimum temperatures are below normal by 2-4øC over many parts of east India. The lowest minimum temperature of 4.5 deg Celsius was recorded at Rohtak.

Why south Tamilnadu is getting more showers??

This post we got thru an anonymous comment to one of our post.

Cloud movement from NORTH w.r.t Chennai is an indication that low pressure area is in down SOUTH. [22.11.2009/0600 UTC]. The Five Degree Latitude belt is active. This can be termed as [Easterly]wave like pattern, where troughs will be a point of formation of vortex or cyclonic circulation [anti clockwise]
This is December pattern and is known to weatherman. But this time the belt is far down south beneath five degree latitude. That is why south tamilnadu and SE coastal Tamilnadu is getting rain.
Extreme south Tamilnadu is receiving some showers now 11:30am .
Chennai - might get one or two local short shower over North-west, west and south-west.
Chennai - Bit humid conditions now 11:50am with medium low cloud formation over North-west and south.. nothing threatening to rain.
RT @chennaiweather: Rain will continue in south TamilNadu. Chennai won't get heavy rain, may be passing showers
What is COLA-GFS?? -- "COLA stands for Centre of Ocean-Land-Atmosphere Studies"
Here's the COLA - GFS model for 28-Nov.. .. which shows a severe Cyclone tracking into central Bay.
COLA - GFS model now suggests a Cyclone East of Andhaman islands around Friday.. and Tamilnadu will dry up around that time (27-Nov-09).
A clear looking Bay till extreme south-east .. Dry MJO is taking control ??? ..
A clear looking India and Bay too.. ODD ..
Chennai - Almost a clear morning .. with minor low cloud movement from almost NORTH.. not a good direction which brings rain.