Sudden Weather Changes
Date: Tuesday, April 23, 2002
An episode of one weather type usually gives way to
another weather type, very-abruptly, in a single day. Why is this?
When referring to "weather episodes," I assume you mean dry vs
precipitation. Precipitation tends to occur along boundaries of differing
air masses, and areas of precipitation, usually are narrow in width. As
these boundaries (fronts) sweep across a given area, the weather changes can
Here is a link that has some good explanations of what drives weather
systems. Check especially the topic on "Storms and Fronts."
What you describe occurs because so many dramatic
weather events or situations occur along "boundaries"
between different air masses or underneath usually
narrow jet streams. Good examples are the thunderstorm
lines (squall lines) that form a hundred miles or so in
front of a cold front and move very quickly through a
local area or a cold frontal passage with its
accompanying rain or snow, followed within a day by
colder and clear air within the trailing high pressure
area. Even frontal related thunderstorms can be caused by
an overlying jet stream that is aligned with the front; once
this passes or loses strength you get an abrupt change to
another very different weather regime.
Opposite to this are the periods of several consecutive
days of nice weather associated with a high pressure
system, separated by many miles from any meteorological
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
Well, DTuc, most of what we call weather - clouds, wind, rain, snow - is
associated with fronts. A front is where two air masses meet. The
characteristics of one air mass is different from the one taking its
place. The frontal passage can be very abrupt (but not always). Cold
fronts can move at over 50 miles per hour. When one of these comes
through, it could seem very abrupt.
Click here to return to the Weather Archives
Update: June 2012