indian ocean Invest 91B

[Vorticity0123]

It seems like a new tropical cyclone has developed in the Indian Basin. Even though the IMD (Indian Meteorological Department) has only classified the system as a 'well marked low pressure area', and the JTWC has set a 'medium' chance of development, satellite imagery loops show a system more like a mid-range tropical storm. (as of 12:00 UTC). Below is a satellite image of the system:

 

 

Satellite image of 91B. (Courtesy: NOAA)

 

On the image, clear cyclonic turning is evident, indicative of a well-defined LLCC (low level circulation centre). Furthermore, a well-defined (though broken) banding feature wraps into the center from the west.

 

Of note is that even though it looks like a tropical cyclone, it is not one until the IMD or the JTWC has upgraded the system to a tropical storm.

 

I'll provide a more extensive post about this possible cyclone later today or tomorrow.

 

Sources:

http://www.imd.gov.in/section/nhac/dynamic/cyclone.htm

http://www.ssd.noaa.gov/PS/TROP/floaters/91B/91B_floater.html
http://www.usno.navy.mil/JTWC/

[Somerset Squall]

JTWC still assess the risk of TC development as MEDIUM, stating that the LLC is still quite broad. I think some land interaction is coming into play here, and this could become an issue for the invest as it tracks very close to southern India. There is a large blow up of convection west of the LLCC, but a lack of organised convection directly over the centre.

[Vorticity0123]

JTWC still assess the risk of TC development as MEDIUM, stating that the LLC is still quite broad. I think some land interaction is coming into play here, and this could become an issue for the invest as it tracks very close to southern India. There is a large blow up of convection west of the LLCC, but a lack of organised convection directly over the centre.

 

Well noted, it looks as if the convection has weakened rapidly during the past few hours. At the time when I checked the image, there appeared to be some very well-defined banding features also curving into the LLCC (low level circulation center). On the last few frames, the convection has a very disorganized apperarance, and indeed the LLCC looks very poorly defined at best. 

 

The land interaction scenario as you mentioned does sound very plausible, as it might block inflow of moist maritime air from reaching the circulation, or prohibit a circulation from becoming established at all. It remains very remarkable to me that even though a cyclone can look well-organized at satellite imagery, it could well be just a poorly defined low pressure area.

Edited May 6, 2014 by Vorticity0123

[Somerset Squall]

Indeed Vorticity, looks can be deceiving. I recall many instances of Atlantic waves looking very much like tropical storms on satellite imagery, even with apparent banding features, and even having winds of storm force, but to not actually be a tropical cyclone due to the lack of a closed LLC. 91B's only chance is if it moves away from land.