isallobar

noun

1. A line joining points of equal pressure change during a specific time interval, especially over three hours.

   “Seasonal variations of atmospheric pressure are illustrated by the isallobaric chart […] which gives the differences between mean pressure in July–August, and in January–February. The position of the isallobars on this chart is largely indicative of the role of monsoonal factors […]”

   “Successive values of pressure provide figures for the barometric tendency, permitting the plotting of isallobars […] This is called tendency analysis.”

   “If your barometer has dropped 0.05 of an inch in the last three hours, you are on the -0.05 isallobar.”