Monday, December 09, 2013

Monday Night Post:

"Madi" is still a Severe Cyclone, with core winds at 60 knts and pressure 970 mb at T4.8...Located , having moved due North in last 12 hrs, at 15.3N and 84.7E. 
Will track NNE slowly and weaken.

A comparatively dry patch of air also runs along the Eastern coast, and is seen seeping into the southern half of the cyclone semi circle. However, the wrapping around the cyclone is slow. 
Since large patches of dry air are to the West, Madi is going to encounter dry air and weaken rapidly after 24 hrs. System most likely to dissipate in the West-Central Bay itself. ( Before hitting land as a system).

Very dry humidity conditions were observed along the West Coast of India, North of Goa. Maily due to strong NE winds blowing from the land into the sea. NE winds due to HPA in NW India.
Ratnagiri had an unusual low humidity of 8%, Mumbai low humidity was 16 % and inland Pune was very dry at 9% humidity !
This extremely dry patch runs from South Gujarat to Goa. Dry air (too a lesser extent) runs Southwards towards the Kerala coast, (Less humid as winds are Northerly here) and covering the Southern Seas around Sri Lanka. 
from Vagaries

RT @IWMpolichalur: Polichalur, #Chennai - Temp: 21.8°C, Wind: 0.0kph from NNW, Pressure: 1007.5hpa "Rising", Rain Today: 0.0mm

Beta drift [?] or backward drift

Cyclones in north Indian Oceans [i.e in Bay of Bengal &  Arabian Sea which are the real extension of Indian Ocean in the east and west side of India] generally tend to move in North & north westerly direction.  That is why the eastern coast of India is more prone to cyclone hit than its western counterpart.  Similarly recarvature i.e movement in NEly direction is also a common feature of a cyclone movement.  But there is rare evidence that the cyclone drifted south west wards. Will this drift be caused by the advection of the background potential vorticity field by the storm circulation?


[1] The SST from Cape Comorin to Puducherry, especially in Mannar Bay and in  Coramandal coast at least between Vedaranyam and Marakanam is relatively high than compare to elsewhere in the Bay.

[2] The horizontal warm air advection in the above said coastal stretch will lead to the formation of vortex.

[3] This formation may be in SWly direction to the current location of VSCS.
Beta Drift
The drift of a tropical cyclone through the large-scale background wind in which it is embedded is known as Beta drift. The drift is caused by the advection of the background potential vorticity field by the storm circulation. Beta drift generally causes tropical cyclones to move pole ward and westward relative to the motion they would have if the background potential vorticity field were unperturbed by the storms. This drift speed is generally around 1–2 m/s.
Courtesy:  American Meteorological Society. .

Madi - NO movement above 14N for past 6hrs

ADT analysis of Madi at 6:30pm shows that pressure has dropped even more to 970mb and NO movement during past 6hrs.
MADI - Satellite IR, 7pm suggest that convective activity is seen over S,S-W quadrants .. showing signs of weakening 

GFS model expects MADI to "Stop and Weaken" at this present location in next 18hrs.
MADI - Before taking S-W movement the system is expected to degrade to Deep Depression on Tuesday night.. 
Degraded Cyclone MADI as a LOW may reach central Tamilnadu coast on Thursday, 12-Dec.

A weak W.D system is affecting Kashmir today... expected to persist with scattered rain/snow till 11-Dec.

Today morning cold over N #India ... Ludhiana = 5 C, Lucknow = 7 C, New Delhi (airport) = 11 C.

Adampur records 4.4 C today morning.

RT @astrostation: #Nagpur  -  9.3 C today morning !
#Chennai - 7:24pm, temperature around 26 C. Winds have reduced.

Bangalore - 6:27pm, "very cold and dry here at Koramangala. slight breeze.."

Madi - noon update, moved North again

ADT analysis of Cyclone Madi at 1pm suggests that it has drifted North and intensified.
Now pressure around 975mb.
1:30pm, Latest visible shot of Cyclone Madi ... shows deep convective activity over N,N-W quadrant ... 
1pm, Cyclone Madi position is 14.42 N , 85.28 E.

Almost ALL models except COAMPS predict a S-W re-curve in next 24 to 36hrs... 

Madi - intensified with less movement to North

10am, ADT analysis show that Cyclone Madi has intensified to a great extent.
Now pressure around 977mb.
Winds upto 142 kmph.
Latest poistion is 13.57N , 84.35E... Madi has not drifted N-N-E during past 12hrs... but has intensified ... 

Madi - visible shot at 10:30am reveals that the center is almost parallel to #Chennai ... 

Latest models and JTWC expects that mid level ridge will make Very severe Cyclone Madi to stop, weaken and then re-curve to S-W after 36hrs.
GFS, expects Cyclone Madi to weaken while taking S-W movement and hit central Tamilnadu coast as Depression .. 
During next 24hrs, almost NO rain expected for most of Tamilnadu and #Chennai.
Except for S, S tip Tamilnadu.