On October 11, Cyclone Titli made a landfall in the Andhra Pradesh coast, entered Gajapati district of Odisha, made a surprise turn towards adjoining districts and continued as a severe cyclonic storm and deep depression for more than 48 hours, leaving 59 people dead in its wake before finally dissipating over West Bengal.
Titli's track is unprecedented in 200 years of the cyclone’s record, observes a report of the Regional Integrated Multi-Hazard Early Warning System for Asia and Africa (RIMES) on the post-landfall impacts of Titli.
Cyclonic storms generally lose strength after landfall. So far, only two cyclones in 200 years of recorded history that struck the Odisha coast retained strength after landfall: the 1999 Super Cyclone and Titli.
The Super Cyclone remained near the coast for 36 hours and reentered the ocean before finally dissipating. It managed to retain its intensity due to the presence of moist coastal winds, thus inducing prolonged rainfall. Nevertheless, the Super Cyclone largely remained a coastal and marine hazard.
On the other hand, Titli re-curved in land and travelled to southern and central Odisha districts far from the coastal zone. It retained its destructive potential after landfall for more than two days, causing heavy rainfall and landslides. Thus, Titli proved to be an all-dimensional hazard: non–coastal, coastal and marine.
Also according to the RIMES report, a cross-country assessment of cyclones reveals that although cyclones associated with secondary hazards are not uncommon, the unexpected track movement of Titli for two days baffled everyone --a pattern meteorologists, disaster managers, and residents never saw before.
It also retained its destructive potential as it moved far away from coasts and towards the interior districts.
Why did Titli surprise the Indian Meteorological Department (IMD) Odisha received some heavy rainfall spells, that too towards the end of the monsoon season in September.
The spells were brought by the low pressure area in the morning of September 5 over northwest Bay of Bengal and the vicinity that eventually became a well-marked low pressure area by the evening of the same day.
It evolved into a depression and further intensified into a deep depression on September 6.
It gradually weakened as it crossed the West Bengal coast and moved north-westwards. Under the influence of the system, widespread and very intense rainfall activity occurred over Odisha. Such events leave the land surface in a very moist condition that supports and enhances the lifetime of post-landfall tropical cyclones.
Since land surface processes are still inadequately parameterised in Numerical Weather Prediction models, these interactions are not properly captured and, hence, not predicted well. As such, the IMD calls Titli the rarest of rare cyclones.
Why OSDMA was taken aback
Despite the unprecedented nature of Titli, the coastal districts achieved zero-casualty. This is a remarkable dividend of the investments made by the Odisha Government in strengthening cyclone preparedness and response since the 1999 Super Cyclone that killed 10,000 people.
Armed with the legacy of successfully managing the 2013 Phailin cyclone with near zero-casualty and guided by IMD forecasts, the Odisha State Disaster Management Authority (OSDMA) evacuated around 300,000 people to safe places well before the Titli's landfall.
IMD’s forecast until the Titli's landfall on October 10 did not indicate a re-curvature track far into the interior zones. Secondary hazards such as landslides were also not indicated. Reports indicating landslide-related deaths from remote and mountainous areas were, therefore, not expected.
Why residents were surprised
Excess end-season September rains enhanced the risk of landslides and flash floods due to the near saturation of soil.
This provided an ideal condition for Titli to trigger floods and landslides.
Previously, public awareness and early warning information communication experience were confined to coastal zones; and remote inhabitants of non-coastal zones were unfamiliar with cyclone risks.
“We saw a lot of casualties and damage in the interior districts because there's no experience managing a cyclone-associated secondary hazards of such kind," observes the RIMES report
Learning from Titli and moving forward.
But every surprise comes with a critical opportunity to improve the current system. Translating impacts into actionable and location-specific early warning information for disaster managers and residents remains a challenge for rare cyclones that cause secondary impacts away from coastal region, such as localized landslides.
On top of the agenda, the RIMES report states that this gap should be addressed to develop a system for translating cyclone movement and strength into sector and location-specific impacts. This needs a robust system for risk assessment and impact-based early warning.
The writer is AR Subbiah Director, RIMES, Bangkok
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