The Basics of Weather..the terminologies we read everyday:
Rain variability ("vagaries")
One of the most commonly used words to describe the erratic nature of the monsoon is "vagaries", used in newspapers, magazines, books, web portals to insurance plans, and India's budget discussions.
In some years, it rains too much, causing floods in parts of India; in others, it rains too little or not at all, causing droughts. In some years, the rain quantity is sufficient but its timing arbitrary. Sometimes, despite average annual rainfall, the daily distribution or geographic distribution of the rain is substantially skewed.
In the recent past, rainfall variability in short time periods (about a week) were attributed to "Climate Change".
Before we announce as "Climate Change" happening all over, let us understand the Basic:
The difference between weather and climate
The difference between weather and climate is neatly summed up in the saying “the climate is what you expect; the weather is what you get”, frequently attributed to Mark Twain.
Climate is the average weather – for example the mean annual rainfall in Mumbai or the average January temperature in Delhi, or how many cyclones usually happen in the Indian Ocean each year.
However in any one year, it might be wetter or drier than usual in Mumbai, colder or warmer than usual in Delhi or there may be more or less cyclones, but this won’t necessarily affect the average unless there is a string of years the same.
When you hear or see "showers" on the forecast do you think, there won’t be very much and when you the term "rain" is used do you think, it will be soaking?
The difference between the two is kind of tricky and subtle. There is no doubt that showers are indeed rain. Taking at face value the term rain or showers, has nothing to do with how much precipitation is going to fall. Instead it tells you how it is going to fall. It has to do with the type of cloud they come from.
A shower is a short duration event, that can last a couple of minutes to perhaps 15 minutes or so. But they can sometime last over half an hour. They typically start quickly and end quickly. There can be heavy downpours when dealing with showers.
Showers come from Cumuliform clouds - Cumulus or Cumulonimbus (thunderstorm) the puffy ones that look like they are bubbling up. often separated by blue sky. Showers are pushed around by the wind, so you only experience a particular shower if you are in its path. Since they are hit and miss, your house could be getting wet, while your next-door neighbor could be dry. Cumulus normally result in lower totals while amounts can get quite high from Cumulonimbus.
The customary way of talking about them is isolated showers or scattered/widespread showers. Because they are hit and miss you will never see 100% chance of showers.
What is rain?
Rain is a moderate to long duration event. That can last for a couple of hours to all day. It typically starts gradually then ramps up and ends gradually.
Rain comes from Stratiform clouds- Altostratus and Nimbostratus. These types of clouds are more or less featureless and cover the sky in a grey, widespread sheet, with little to no blue sky to be seen, and of the two, Nimbostratus is thicker and produces heavier rains.
Rain covers a wide area, so most or everyone over a large area are getting wet. Rain can come down lightly or heavily. Because of its long-lasting duration, it can lead to flooding issues.
Now, another Term..Low Pressure: