Lack of ‘warm water’ may have weakened Lehar!
VISAKHAPATNAM: Cyclone Lehar may have begun with a bang but ended with a whimper by the time it hit the Andhra Pradesh coast near Machilipatnam in Krishna district on Thursday evening with a wind speed of barely 50-70 kmph as it fizzled out over the sea itself.
The India Meteorological Department (IMD) had predicted that Cyclone Lehar would cross the Andhra Pradesh coast on November 28 noon as a very severe cyclonic storm (VSCS) with a maximum wind speed of 170-200 kmph. IMD's predictions had people from all walks of life in the coastal districts, particularly East Godavari, Visakhapatnam and Srikakulam, as well as the state machinery, right from chief minister Kiran Kumar Reddy, worried as it was coming in the wake of cyclones Phailin and Helen.
Though the weakened system gave the much needed respite to people as well as the state government, it has now become the cynosure of meteorologists of IMD and scientists of the National Institute of Oceanography (NIO), who are now taking Lehar up as a case study to ascertain the reasons behind the sudden weakening of the system and change in path.
"Lehar can be a good case study for oceanography scientists and meteorologists. We may also start work on it but it will take a couple of weeks to gather data available from all corners of the country, including the IMD and analyze the actual cause behind the sudden changes in the strength of the cyclone and its path," said Dr VSN Murthy, scientist in-charge, National Institute of Oceanography, Vizag Regional Centre.
Meanwhile, Prof OSRU Bhanu Kumar, emeritus professor, Department of Meteorology, Andhra University, said that the activeness of a cyclone largely depends on four conditions, namely sea surface temperature (SST) or warm water in the sea, vertical wind shear (VWS), high level divergence (HLD) and low level convergence (LLC). "If any two of the conditions fail to cooperate, the cyclonic system will get weakened. I think in the case of Lehar, SST and VWS might have failed to favour the cyclone," Bhanu Kumar said, explaining that the sea water needs to be warm for any kind of cyclone to sustain. According to Dr Murthy of NIO, an ocean's SST should be a minimum of 26.5 degree Celsius to maintain the warm core that fuels cyclones. SST is nothing but the water temperature close to the ocean's surface. Similarly, VWS is nothing but a change in wind direction. According to Prof Bhanu Kumar, the VWS should always be lower or weak to strengthen the cyclone system. At the same time, the SST, LLC and HLD should also always be strong or higher for strengthening the activeness of any low pressure or cyclonic system, Bhanu Kumar explained.
"We can't say it was a rare case. It routinely happens in the sea. However, Lehar can be chosen for a case study for young scientists, who are interested in oceanography or meteorology by gathering all the data of the track of the cyclone," Bhanu Kumar added.
Meanwhile, a senior Met official from the Cyclone Warning Centre at Visakhapatnam, said that both Phailin and Helen sustained because of favourable SST conditions. "I feel the chilly weather conditions off and along the coast might have been one of the reasons behind the weakening of the cyclone," the officer said.
Source - TOI - http://timesofindia.indiatimes.com/city/visakhapatnam/Lack-of-warm-water-may-have-weakened-Lehar/articleshow/26546308.cms
The India Meteorological Department (IMD) had predicted that Cyclone Lehar would cross the Andhra Pradesh coast on November 28 noon as a very severe cyclonic storm (VSCS) with a maximum wind speed of 170-200 kmph. IMD's predictions had people from all walks of life in the coastal districts, particularly East Godavari, Visakhapatnam and Srikakulam, as well as the state machinery, right from chief minister Kiran Kumar Reddy, worried as it was coming in the wake of cyclones Phailin and Helen.
Though the weakened system gave the much needed respite to people as well as the state government, it has now become the cynosure of meteorologists of IMD and scientists of the National Institute of Oceanography (NIO), who are now taking Lehar up as a case study to ascertain the reasons behind the sudden weakening of the system and change in path.
"Lehar can be a good case study for oceanography scientists and meteorologists. We may also start work on it but it will take a couple of weeks to gather data available from all corners of the country, including the IMD and analyze the actual cause behind the sudden changes in the strength of the cyclone and its path," said Dr VSN Murthy, scientist in-charge, National Institute of Oceanography, Vizag Regional Centre.
Meanwhile, Prof OSRU Bhanu Kumar, emeritus professor, Department of Meteorology, Andhra University, said that the activeness of a cyclone largely depends on four conditions, namely sea surface temperature (SST) or warm water in the sea, vertical wind shear (VWS), high level divergence (HLD) and low level convergence (LLC). "If any two of the conditions fail to cooperate, the cyclonic system will get weakened. I think in the case of Lehar, SST and VWS might have failed to favour the cyclone," Bhanu Kumar said, explaining that the sea water needs to be warm for any kind of cyclone to sustain. According to Dr Murthy of NIO, an ocean's SST should be a minimum of 26.5 degree Celsius to maintain the warm core that fuels cyclones. SST is nothing but the water temperature close to the ocean's surface. Similarly, VWS is nothing but a change in wind direction. According to Prof Bhanu Kumar, the VWS should always be lower or weak to strengthen the cyclone system. At the same time, the SST, LLC and HLD should also always be strong or higher for strengthening the activeness of any low pressure or cyclonic system, Bhanu Kumar explained.
"We can't say it was a rare case. It routinely happens in the sea. However, Lehar can be chosen for a case study for young scientists, who are interested in oceanography or meteorology by gathering all the data of the track of the cyclone," Bhanu Kumar added.
Meanwhile, a senior Met official from the Cyclone Warning Centre at Visakhapatnam, said that both Phailin and Helen sustained because of favourable SST conditions. "I feel the chilly weather conditions off and along the coast might have been one of the reasons behind the weakening of the cyclone," the officer said.
Source - TOI - http://timesofindia.indiatimes.com/city/visakhapatnam/Lack-of-warm-water-may-have-weakened-Lehar/articleshow/26546308.cms