, also known as rapid intensification
, is a meteorological
condition that occurs when the minimum sea-level atmospheric pressure
of a tropical cyclone
decreases drastically in a short period of time. The National Weather Service
describes rapid deepening as a decrease of 42 millibars
in less than 24 hours. However, this phrase is liberally applied to most storms undergoing rapid intensification.
In order for rapid deepening to occur, several conditions must be in place. Water temperatures
must be extremely warm (near or above 30°C, 86°F), and water of this temperature must be sufficiently deep such that waves do not churn deeper cooler waters up to the surface. Wind shear
must be low; when wind shear is high, the convection
and circulation in the cyclone will be disrupted. Usually, an anticyclone
in the upper layers of the troposphere
above the storm must be present as well — for extremely low surface pressures to develop, air must be rising very rapidly in the eyewall
of the storm, and an upper-level anticyclone helps channel this air away from the cyclone efficiently.
Explosive intensification is a more extreme case of rapid deepening that involves a tropical cyclone deepening at a rate of at least 2.5 mbar
per hour for a minimum of 12 hours.<ref name="NHC... Read More