Oceanic conditions may deter intensification of Cyclone Roanu

May 20, 2016 6:54 PM |

Updated on May 20, 2016 06:30 PM (IST): Oceanic conditions may deter intensification of Cyclone Roanu

It seems that oceanic conditions are not favouring the further intensification of Cyclone Roanu prevailing in westcentral and adjoining northwest Bay of Bengal.

The tropical storm is presently centered at Latitude 18.4°N and Longitude 84.6°E, about 50 km south-southeast Kalingapatnam, Andhra Pradesh. The system is moving at a fast pace of 30 kmph.

We have already stated the fact that the intensification of any weather system developing in sea is largely governed by oceanic parameters.

According to Skymet Weather, there is not much change in the scenario since yesterday and cyclone continues to move along the cold pool off the Odisha coast.

As reiterated by weathermen, the intensity of the cyclonic storms reduce when the storm visits a cold pool. Thus, it is quite possible that Cyclone Roanu may not gain further strength that it had indicated initially.

Moreover, it is a fast moving system and is likely to hit the land mass during next 36 hours. This growing proximity to the coast will further hold the cyclone from intensifying. Hence, chances are there that it may also weaken further before making landfall over the Bangladesh coast.

Though the sea surface temperature which is in the range of 30°C is favourable for further strengthening of the system but ocean mean temperature (OMT) is not favouring the same. OMT is the mean temperature of the layer that has around 100 meters of depth and is indicating that sea is relatively cooler.

TCHP and OMT imageThe May 19 image of the Tropical Cyclone Heat Potential (TCHP) and OMT image depict almost similar picture of May 18.

In this image, the cross marks show the likely track of the storm. The track continues to run in close proximity of the cold pool which is not a healthy sign for the sustenance of the storm.

These cold pools, also known as the cold pool eddies are detrimental for the health of the weather systems.  For instance, a depression that had formed in Bay of Bengal in 2005 had dissipated after entering the cold pool eddy. However, that eddy was far bigger than the present one.


Updated on May 19, 2016 06:30 PM (IST): Cyclone Roanu’s potential may be dictated by oceanic conditions

The cyclones that develop in the Bay of Bengal are notorious in nature and are well known for their changes in terms of both intensity and track. These storms keep upgrading and downgrading as they continue with their movement.

When these storms are in the open sea, they continue to strengthen. Atmospheric conditions such as warm waters and moisture incursion add on to the growth potential of the cyclone.

Reasons for the weakening of a storm

However, there are several reasons responsible for the weakening of the storms

1. When the storm reaches the landmass, drier winds penetrate reducing the moisture levels and is known as entrainment. Due to this, the storm gradually weakens.

2. Frictional forces are also responsible for the weakening of the storm. When the storm enters the land, due to the frictional forces, the intensity of the cyclone tends to weaken.

3. The oceanic temperatures are also responsible for the weakening of the storm. There is no uniformity in the oceanic temperatures. Thus, the intensity of these storms reduce when the storm visits a cold pool.

4. Also, when the storm comes in contact with a strong vertical wind shear, the system tends to decay.

What is a Cold Pool

The cold pool is an area of relatively cooler waters in the warm oceans. In case of smaller areas, this may be called as ocean eddies. Eddies could form over the oceans, over land and in the atmosphere as well. Ocean eddies cold in nature are responsible for the decay of a weather system. The land based eddies are a result of the terrain and atmospheric eddies could form on small scale changes in the environmental conditions.

How oceanic conditions are dictating Cyclone Roanu’s potential

Present Scenario

The weather system has intensified into a cyclonic storm and is likely to become a severe cyclonic storm soon. Skymet has studied the oceanic conditions for the past three days.

The image above shows the Tropical Cyclone Heat Potential (TCHP) of the current Cyclone.

The May 17 slide shows a pool of cool water off the Odisha coast. While surrounding areas have higher temperatures, the cold pool shows lesser temperature. The May 18 slide also depicts a similar picture. This cold pool will not let the system gain strength.

The ocean mean temperature (OMT) image below also confirms the same.

How oceanic conditions are dictating Cyclone Roanu’s potential

In this image, the cross marks show the likely track of the storm. The OMT shows that the temperatures are about one degree lesser than the surrounding areas. The track is running close to the cold pool which is not a healthy sign for the sustenance of the storm. While the latitudinal position is in the favour of the intensification of the cyclonic storm, the presence of the cold pool will negate the positive latitudinal position.


Please Note: Any information picked from here should be attributed to skymetweather.com


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