Rapid intensification

's 24-hour wind speed increase was the largest of any tropical cyclone on record.|alt=Animated infrared satellite imagery of a tropical cyclone There is no globally consistent definition of rapid intensification. Thresholds for rapid intensificationby the magnitude of increase in maximum sustained winds and the brevity of the intensification periodare based on the distribution of high-percentile intensification cases in the respective tropical cyclone basins. In 2003, John Kaplan of the Hurricane Research Division and Mark DeMaria of the Regional and Mesoscale Meteorology Team at Colorado State University defined rapid intensification as an increase in the maximum one-minute sustained winds of a tropical cyclone of at least in a 24-hour period. This increase in winds approximately corresponds to the 95th percentile of Atlantic tropical cyclone intensity changes over water from 1989 to 2000. These thresholds for defining rapid intensification are commonly used, but other thresholds are utilized in related scientific literature. The U.S. National Hurricane Center (NHC) reflects the thresholds of Kaplan and DeMaria in its definition of rapid intensification. The NHC also defines a similar quantity, rapid deepening, as a decrease in the minimum barometric pressure in a tropical cyclone of at least in 24 hours. == Characteristics ==

Around 20–30% of all tropical cyclones experience at least one period of rapid intensification, including a majority of tropical cyclones with winds exceeding . The tendency for strong tropical cyclones to have undergone rapid intensification and the infrequency with which storms gradually strengthen to strong intensities leads to a bimodal distribution in global tropical cyclone intensities, with weaker and stronger tropical cyclones being more commonplace than tropical cyclones of intermediate strength. Episodes of rapid intensification typically last longer than 24 hours. Patricia also holds the record for the largest pressure decrease in 24 hours based on RSMC data, deepening . In 2019, the Joint Typhoon Warning Center (JTWC) estimated that Cyclone Ambali's winds increased by in 24 hours, marking the highest 24-hour wind speed increase for a tropical cyclone in the Southern Hemisphere since at least 1980. .|alt=Satellite animation of a rapidly intensifying Hurricane Delta Tropical cyclones frequently become more axisymmetric prior to rapid intensification, with a strong relationship between a storm's degree of axisymmetry during initial development and its intensification rate. However, the asymmetric emergence of strong convection and hot towers near within inner core of tropical cyclones can also portend rapid intensification. The frequency and intensity of lightning in the inner core region may be related to rapid intensification. A survey of tropical cyclones sampled by the Tropical Rainfall Measuring Mission suggested that rapidly intensifying storms were distinguished from other storms by the large extent and high magnitude of rainfall in their inner core regions. However, the physical mechanisms that drive rapid intensification do not appear to be fundamentally different from those that drive slower rates of intensification. imagery of Typhoon Jelawat during a period of rapid intensification in March 2018|alt=Animated view of a rapidly intensifying typhoon The characteristics of environments in which storms rapidly intensify do not vastly differ from those that engender slower intensification rates. Waters with strong horizontal SST gradients or strong salinity stratification may favor stronger air–sea fluxes of enthalpy and moisture, providing more conducive conditions for rapid intensification. The presence of a favorable environment alone does not always lead to rapid intensification. Vertical wind shear adds additional uncertainty in predicting the behavior of storm intensity and the timing of rapid intensification. The presence of wind shear concentrates convective available potential energy (CAPE) and helicity and strengthens inflow within the downshear region of the tropical cyclone. Such conditions are conducive to vigorous rotating convection, which can induce rapid intensification if located close enough to the tropical cyclone's core of high vorticity. However, wind shear also concurrently produces conditions unfavorable to convection within a tropical cyclone's upshear region by entraining dry air into the storm and inducing subsidence. These upshear conditions can be brought into the initially favorable downshear regions, becoming deleterious to the tropical cyclone's intensity and forestalling rapid intensification. In such cases, outflow from the sheared tropical cyclone may interact with the surrounding environment in ways that locally reduce wind shear and permit further intensification. The interaction of tropical cyclones with upper-tropospheric troughs can also be conducive to rapid intensification, particularly when involving troughs with shorter wavelengths and larger distances between the trough and the tropical cyclone. == Improving predictability and forecasting ==

s as a key area for improvement.|alt=Graph of trends in intensity errors Rapid intensification is a significant source of error in tropical cyclone forecasting, and the timing of rapid intensification episodes has low predictability. Rapid intensity changes near land can greatly influence tropical cyclone preparedness and public risk perception. Genesis and Rapid Intensification Processes (GRIP) was a field experiment led by NASA Earth Science to in part study rapid intensification. Multiple aircraft including the uncrewed Northrop Grumman RQ-4 Global Hawk were used to probe the rapid intensification events of hurricanes Earl and Karl during the 2010 Atlantic hurricane season. In December 2016, the CYGNSS SmallSat constellation was launched with a goal of measure ocean surface wind speeds with sufficiently high temporal resolution to resolve rapid intensification events. The TROPICS satellite constellation includes studying rapid changes in tropical cyclones as one of its core science objectives. Weather models have also shown an improved ability to project rapid intensification events, but continue to face difficulties in accurately depicting their timing and magnitude. Statistical models show greater forecast skill in anticipating rapid intensification compared to dynamical weather models. Intensity predictions derived from artificial neural networks may also provide more accurate predictions of rapid intensification than established methods. Probabilistic and deterministic forecasting tools have been developed to increase forecast confidence and aid forecasters in anticipating rapid intensification episodes. These aids have been integrated into the operational forecasting procedures of Regional Specialized Meteorological Centers (RSMCs) and are factored into tropical cyclone intensity forecasts worldwide.is utilized by RSMC Tokyo–Typhoon Center, the Australian Bureau of Meteorology (BOM), and the NHC. Intensity forecasting tools incorporating predictors for rapid intensification are also being developed and used in operations at other forecasting agencies such as the Korea Meteorological Administration and the Indian Meteorological Department. == Trends==

The first working group report of the IPCC Sixth Assessment Reportpublished in 2021assessed that the global occurrence of rapid intensification likely increased over the preceding four decades (during the period of reliable satellite data), with "medium confidence" in this change exceeding the effect of natural climate variability and thus stemming from anthropogenic climate change. The likelihood of a tropical cyclone with hurricane-force winds undergoing rapid intensification has increased from 1 percent in the 1980s to 5 percent. Statistically significant increases in the frequency of tropical cyclones undergoing multiple episodes of rapid intensification have also been observed since the 1980s. These increases have been observed across the various tropical cyclone basins and may be associated with the thermodynamic properties of environments becoming increasingly conducive to intensification as a result of anthropogenic emissions. A long-term increase in the magnitude of rapid intensification has also been observed over the central and tropical Atlantic as well as the western North Pacific. However, CMIP5 climate projections suggest that environmental conditions in by the end of the 21st century may be less favorable for rapid intensification in all tropical cyclone basins outside of the North Indian Ocean. == See also ==