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Weather conditions as assessed by the Chennai Met Office of the India Meteorological Department on Tuesday mid-morning point to partly cloudy conditions with no hint of rain
The temperature was at 31.7 degrees Celsius, dew point lower, at 25.7 degrees Celsius and humidity at 70 per cent. The wind was variable being south-easterly but near-calm at 10.15 am.
Dew point temperature
The dew point temperature is the temperature at which the air can no longer hold all of the water vapour mixed with it, and some of the water vapour must condense into liquid water. The dew point is always lower than (or equal to) the air temperature.
If the air temperature cools to the dew point, or if the dew point rises to equal the air temperature, then dew, fog or clouds begin to form. At this point, where the dew point temperature equals the air temperature, the relative humidity is 100 per cent.
If there is then further cooling of the air, say because the air parcel is rising to higher (and thus colder) levels in the atmosphere, even more water vapour must condense as additional dew, fog, or cloud, so that the dew point temperature then falls along with the air temperature.
This is how precipitation forms...when water vapour is removed from the air so rapidly that the liquid water drops grow to a size where they fall out of the cloud.
The wind pattern for the rest of the day is northerly-to-north-easterly, which is helpful for any upcountry to mix in and bring to bear part of the smog load. Various agencies have assessed the city’s air quality to be unhealthy.
Private forecaster Skymet Weather agrees with this outlook:
International forecaster Weather.com, an IBM Business, recorded trending conditions at 10.15 am as follows:
WeatherBug, too, made similar observations:
The increasingly polluted air in the city, the weak North-East monsoon, and lack of any hint of rain engaged Chennai’s bloggers, who tweeted their concerns.
Here are some Reader Responses to BusinessLine’s daily Chennai weather column:
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