Rapid intensification is a meteorological condition that occurs when a tropical cyclone intensifies dramatically in a short period of time. The United States National Hurricane Center (NHC) defines rapid intensification as an increase in the maximum 1-min sustained winds of a tropical cyclone of at least 30 knots (35 mph; 55 km/h) in a 24-hour period.
In order for rapid intensification 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. Dry air can also limit the strengthening of tropical cyclones.
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.[further explanation needed] Hot towers have been implicated in tropical cyclone rapid intensification, though they have diagnostically seen varied impacts across basins.
Previous nomenclature and definitionsEdit
The United States National Hurricane Center previously defined rapid deepening of a tropical cyclone, when the minimum central pressure decreased by 42 millibars (1.240 inHg) over a 24-hour period. However it is now defined as an increase in the maximum sustained winds of a tropical cyclone of at least 30 knots (35 mph; 55 km/h) in a 24-hour period.
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- Lam, Linda (October 23, 2015). "Multiple Factors Allowed Hurricane Patricia to Rapidly Intensify". The Weather Channel. Retrieved August 6, 2018.
- Lam, Linda (7 September 2018). "Based on Hurricane Florence's Location, We Didn't Expect It to Get So Strong So Soon". The Weather Channel. Retrieved 7 September 2018.
- Diana Engle. "Hurricane Structure and Energetics". Data Discovery Hurricane Science Center. Archived from the original on 2008-05-27. Retrieved 2008-10-26.
- Zhuge, Xiao-Yong; Ming, Jie; Wang, Yuan (October 2015). "Reassessing the Use of Inner-Core Hot Towers to Predict Tropical Cyclone Rapid Intensification*". Weather and Forecasting. 30 (5): 1265–1279. Bibcode:2015WtFor..30.1265Z. doi:10.1175/WAF-D-15-0024.1.
- National Hurricane Center/Tropical Prediction Center (February 7, 2005). "Glossary of NHC/TPC Terms". United States National Oceanic and Atmospheric Administration's National Weather Service. Archived from the original on October 17, 2005. Retrieved April 1, 2014.
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