Inflow (meteorology)

Tropical cyclones require a large inflow of warmth and moisture from warm oceans in order to develop significantly, mainly within the lowest 1 kilometre (0.62 mi) of the atmosphere.

When thunderstorms are able to organize into squall lines, a feature known as a rear inflow jet develops to the south of the mid-level circulation associated with its northern bookend vortex.

[4] While an initial warm core system, such as an organized thunderstorm complex, is necessary for the formation of a tropical cyclone, a large flux of energy is needed to lower atmospheric pressure more than a few millibars (0.10 inch of mercury).

[6] Polar front theory is attributed to Jacob Bjerknes, and was derived from a coastal network of observation sites in Norway during World War I.

A portion of this conveyor belt turns to the right (left in the Southern Hemisphere), aligning with the upper level westerly flow.

However, the western portion of this belt wraps around the northwest (southwest in the Southern Hemisphere) side of the cyclone, which can contain moderate to heavy precipitation.

Supercellular thunderstorm image showing cumulus inflow bands
Airflow in and around a supercell with the inflow at the base on right.
Structure of a tropical cyclone with inflow in red.
A weather map of an extratropical cyclone affecting Great Britain and Ireland. The "L" symbol denotes the center of the "low", and the occluded, cold, and warm frontal boundaries are depicted.