The US Navy’s Joint Typhoon Warning Centre (JTWC) has located Cyclone Thane 555 km to the east of Chennai this morning.
But the system is developing at a below average rate not just because of an increasing ‘shear’ effect on winds in the upper levels but also marginally favourable sea-surface temperatures (SSTs).
‘Shear’ is the sudden change in wind speeds with height, and lops off the top of building storms, undermining their strengths.
Additionally, JTWC says, the satellite image suggests that the umbilical chord with the pool of deep moisture may have been compromised, choking the fuelling mechanism needed to churn the system at high intensity.
The storm strength is built on the SSTs of 27.5 deg Celsius and above, and the convection (the process of cloud building) they initiate.
But SSTs are currently ruling in the 26 to 27.5 deg Celsius range, the JTWC said.
These adverse factors would work against intensification of the Thane beyond a point, with peak strength likely to be attained during the next 24 hours or so.
But JTWC posits Thane with a likely landfall over Chennai, or just to the south of it, expected to materialise by later Thursday night or early Friday morning.