Shall we learn some weather terminologies?

 Many amateur radio satellite operators are also keen observers of weather satellite data. They regularly post images captured from weather satellite downlinks on various social media. Being in the tropics and going through rainy season currently, I thought of looking at the definitions of some tropical weather events. It may be noted that tropical weather events can occur even beyond the tropics as they spread to higher latitudes before they make landfall. Now what is a landfall? Most of the weather events originate in the sea and the intersection of the centre of a tropical cyclone with a coastline is known as landfall. But the strongest winds may not be exactly at the center. So it is possible get strong winds even before landfall. On the other hand, strongest winds can also be over the water at landfall.


Tropical cyclones originate over tropical or subtropical waters with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, tropical cyclone is maintained by extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. This is in contrast to extratropical cyclones which derive their energy from horizontal temperature contrasts in the atmosphere known as baroclinic effects.

Storm surge is an abnormal rise in sea level accompanying a tropical cyclone. This is caused by water being pushed to the shore by the force of wind. This causes greatest threat to life and property in a tropical storm. Storm surge is over and above the high tide cause by astronomical factors. Actual level of water is called a storm tide which is a combination of astronomical tide and storm surge. Flooding of normally dry land caused by events along the coasts, estuaries and adjoining rivers is called inundation. Heavy rains also contribute to the rise in water level of rivers in addition to the storm surge from the sea driven by heavy winds. Much more interesting information is available at the US National Weather Service website.

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