What are “packed isobars”?
Hourly weather observations that include sea-level pressure are plotted or printed on weather maps. Isobars are drawn by connecting points having equal sea-level air pressure, using a specified contour interval, allowing meteorologists not only to pinpoint the location of high and low pressure systems, but also to track them as they move across a given geographical area. When isobars are tightly packed, wind speeds increase. This occurs in areas between low pressure and high pressure systems. The greater the difference in air pressure between the high and the low pressure systems, the closer isobars and the stronger the winds. Tightly-packed isobars are common in hurricanes, nor’easters and in the Midwest when strong arctic high pressure systems follow intense low pressure snowstorms.