Tropical Cyclone Recurvature Research Articles

Modulation of high-latitude tropical cyclone recurvature by solar radiation

Modulation of high-latitude tropical cyclone recurvature by solar radiation

Kinetic energy budgets in different quadrants during tropical cyclone recurvature: A case study of Typhoon Rumbia (2018)

The contributions of divergent and rotational winds to the kinetic energy (KE) budget in different quadrants in the domain of Typhoon Rumbia (2018) with record-breaking duration are analyzed during its recurvature. The relative importance of the rotational and divergent kinetic components represented by Kr and Kd, respectively, in the KE budget are investigated. Distinguished from previous kinetic budget analyses over the entire target domain, Kr and Kd are investigated in the four quadrants around typhoon centers to study their individual contributions along typhoon tracks. It is found that the KE budget by the divergent wind is of vital importance during typhoon recurvature. KE, Kr and Kd are asymmetric around Typhoon Rumbia with maximum values occupying in the northern quadrants. The maintenance of the anticyclonic circulation at high levels before Rumbia recurvature is mainly resulted from the increase of Kr and the decrease of Kd. Kd at middle and high levels starts to propagate downwards, especially in the northeast quadrant starts. This phenomenon is prior to the recurvature which leads to the increase of Kd and decrease of KE and Kr at low levels.

Assessing the Climatology and Synoptic Conditions of Tropical Cyclone Recurvature over the Bay of Bengal, Bangladesh

Recurvature in tropical cyclones is not very uncommon, but rare. There are instances of recurved tropical cyclones forming over the Bay of Bengal. Some of them have hit the coastal regions of Bangladesh. In this research, the climatology and synoptic conditions of such events have been assessed. It has been found that 25 recurved tropical cyclones have hit Bangladesh throughout the period from 1891 to 2019. Most of them have occurred during the post-monsoon season. Again, there have been more cases of recurvature in tropical cyclones that hit the southwest coastal region of Bangladesh than the southeast. Although there are some differences between the direction and speed for the two coasts, but there are not much differences between them for their vector or scalar speeds. In addition, further assessment of the wind speeds and the intensities of tropical cyclones have revealed some interesting findings. The analyses of synoptic conditions for the recurved tropical cyclones have also obtained some important results. All these results and findings will aid in better forecasting of recurved tropical cyclones in the future. The Dhaka University Journal of Earth and Environmental Sciences, Centennial Special Volume June 2022: 131-141

Kinetic Energy Budgets in Different Quadrants During Tropical Cyclone Recurvature: A Case Study

Kinetic Energy Budgets in Different Quadrants During Tropical Cyclone Recurvature: A Case Study

Kinetic Energy Budgets in Different Quadrants During Tropical Cyclone Recurvature: A Case Study

Kinetic Energy Budgets in Different Quadrants During Tropical Cyclone Recurvature: A Case Study

Tropical cyclone recurvature: An intrinsic property?

AbstractThe typical track of a tropical cyclone (TC) in the Northern Hemisphere is an initial northwestward movement followed by an eventual turning toward the east. Such turning is referred to as recurvature and often explained by the change of the environmental flow that steers the TC. Here we show that even in the absence of background flow, a TC initiated at a high enough latitude can recurve itself. Differential horizontal advection of the planetary vorticity by the TC circulation at different vertical levels leads to the development of vertical wind shear, upper tropospheric anticyclone, and asymmetric distribution of convection. The flow associated with the upper tropospheric anticyclone on the equatorward side of the TC and the diabatic heating associated with the asymmetric convection combine to cause the TC to recurve. Such knowledge, an intrinsic recurvature property of the TC is important in forecasting the TC track when the environmental flow is weak.

북서태평양에서 여름철 태풍활동에 대한 북태평양 진동의 영향

This study analyzed the change in tropical cyclone (TC) activity according to the fluctuation in July-to-September average North Pacific Oscillation index (NPOI) and its underlying large-scale environment during the last 37 years from 1977 to 2013. For this purpose, seven years with highest index NPOI value (positive NPOI phase) and another seven years with lowest NPOI index value (negative NPOI phase) among the 37 years were selected as sample after excluding the ENSO years. During the positive NPOI phase, TCs were created in the east of tropical and subtropical western North Pacific and moved to the west from the Philippines toward the southern region in China or toward far eastern sea of Japan. Meanwhile, during the negative NPOI phase, TCs tended to proceed to the north toward Korea or Japan passing East China Sea from the eastern sea of the Philippines. As a result, also in the TC recurvature, TCs in positive NPOI phase showed a tendency of recurving toward more eastern direction compared to TCs in negative NPOI phase. Hence, TC intensity was stronger in negative NPOI phase which allowed more time for obtaining energy from the ocean.

The Analysis of Tropical Cyclone Tracks in the Western North Pacific through Data Mining. Part I: Tropical Cyclone Recurvature

AbstractThis paper is the first of a two-part series of papers that employs the data-mining approach to analyze tropical cyclone (TC) movement in the western North Pacific Ocean. Part I unravels conditions under which TCs tend to recurve, and Part II uncovers conditions leading to TCs making landfall. Here in Part I, a detailed study is carried out into TC recurvature over the South China Sea and western North Pacific. The investigation focuses on the unraveling of rules governing TC recurvature hidden in TC data. The historical TC track database comprises recurving TCs and straight movers. Potential parameters affecting TC recurvature are categorized into three groups: large-scale circulation, circulations surrounding TCs, and variables characterizing TCs. The tree construction algorithm, C4.5, is applied to classify recurving and straight-moving TCs. Parameters measuring large-scale circulation patterns and characterizing TCs play significant roles in building the classification tree. Altogether, 18 rules are discovered from the processed database. Most of the 18 rules can be explained by existing theories and are supported by various empirical findings on TC recurvatures. Rules governing TC recurvature discovered by the present study contain quantitative descriptions of factors such as composite wind fields, geopotential heights, and deep-layer mean winds that are essential to the understanding, interpretation, and prediction of TC recurvatures.

Singular Vector Structure and Evolution of a Recurving Tropical Cyclone

Abstract In this study, the structure and evolution of total energy singular vectors (SVs) of Typhoon Usagi (2007) are evaluated using the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) and its tangent linear and adjoint models with a Lanczos algorithm. Horizontal structures of the initial SVs following the tropical cyclone (TC) evolution suggest that, relatively far from the region of TC recurvature, SVs near the TC center have larger magnitudes than those in the midlatitude trough. The SVs in the midlatitude trough region become dominant as the TC passes by the region of recurvature. Increasing magnitude of the SVs over the midlatitude trough regions is associated with the extratropical transition of the TC. While the SV sensitivities near the TC center are mostly associated with warming in the midtroposphere and inflow toward the TC along the edge of the subtropical high, the SV sensitivities in the midlatitude are located under the upper trough with upshear-tilted structures and associated with strong baroclinicity and frontogenesis in the lower troposphere. Given the results in this study, sensitive regions for adaptive observations of TCs may be different following the TC development stage. Far from the TC recurvature, sensitive regions near TC center may be important. Closer to the TC recurvature, effects of the midlatitude trough become dominant and the vertical structures of the SVs in the midlatitude are basically similar to those of extratropical cyclones.

An Examination of a Model's Components during Tropical Cyclone Recurvature

Abstract The main goal of this study is to investigate the relative contributions from the components of dynamics and physics of a forecast model, toward the understanding of the recurvature dynamics of hurricanes. A number of experiments were conducted using the Florida State University Global Spectral Model (FSU GSM), run at a global resolution of 126 waves. The method of physical initialization was used to “spin up” the model, 24 h prior to the 5-day forecast period to better define the initial water vapor, sensible heat fluxes, and rainfall rates. The usage of the FSU GSM employed a partitioning of the dynamics and physics into separate components, that assumes a residue-free budget of the models' components. The model dynamics were broken down into a nonlinear advective component and also a linear dynamics (rest of the dynamics) partition. The model physics were partitioned into four components: deep convective heating, large-scale precipitation (nonconvective stable rain), total radiation, and shall...

Momentum Transports Associated with Tropical Cyclone Recurvature

Abstract This study attempts to investigate the linear momentum budget responsible for tropical cyclone (TC) recurvature. Using the operational analyses from the U.K. Meteorological Office global model, the environmental flow associated with recurving TCs over the western North Pacific for the years 1991–95 is composited. In general, the dominant features include an eastward-retreating subtropical ridge (STR) and an approaching westerly trough during the recurvature. While the southeasterly flow associated with the STR changes to southerly in the northeast quadrant of the TC in the mid- to upper troposphere, the southwesterly flow associated with the trough penetrates into the northwest quadrant of the TC, especially in the upper troposphere. These changes of the environmental flow throughout the recurvature alter the linear momentum of the TC from southeasterly to southwesterly. To understand the dynamical processes responsible for the linear momentum changes, individual momentum tendency terms are calcu...

Baroclinic Dynamics of Simulated Tropical Cyclone Recurvature

Abstract The mechanisms associated with tropical cyclone recurvature are investigated using a five-level primitive equation model and an idealized environment with characteristics observed in cyclone recurvature conditions. All cyclones moved generally with the flow in the lower and middle troposphere, but the precise motion occurs by a combination of divergence and of advection in both the horizontal and the vertical. The horizontal advection arises from a combination of the initial environmental flow and local changes from rearrangement of the potential vorticity field by cyclone-environment interaction (the so-called,β effect). The balance between these mechanisms changes as the vortex recurves. Since the gradients of potential vorticity increase sharply poleward of the subtropical ridge, this is the preferred region for development of an anticyclonic gyre. This gyre is advected eastward and becomes the dominant anticyclonic system. Recurvature is aided by horizontal deformation of the cyclone in the v...

An Observational Analysis of Tropical Cyclone Recurvature

Abstract Data for 21 years (1957–77) of North Pacific rawinsondes were examined to investigate the interaction between the synoptic-scale circulation and tropical cyclones prior to, and during, the recurvature process. This study is believed to be the first to quantitatively examine how the environmental wind fields at all levels of the troposphere are related to tropical cyclone motion prior to, and during, recurvature. For tropical cyclones that recurve, significant changes in the upper-tropospheric zonal wind fields were observed 1–2 days prior to beginning recurvature in the environmental sector northwest of the storm. Cyclones actually began to recurve when positive zonal winds (westerlies) penetrated the middle and upper troposphere to within 6° of the cyclone's center. Tropical cyclones that did not recurve consistently showed negative zonal winds at this radius. From the results of this study, a recurvature forecasting scheme was developed that uses environmental wind field data for the region nor...

Forecasting Tropical Cyclone Recurvature. Part I: Evaluation of Existing Methods

Abstract The ability of three objective tropical cyclone track prediction aids and of the official forecast to indicate that recurvature will occur within 72 h is evaluated. Recurvature is defined as the change of direction from northwest through north to northeast. For the recurvers, the timing of recurvature is assessed within 12-h categories. The evaluation of a homogeneous set of 366 western North Pacific forecasts from 1979 to 1984 provides a standard of comparison for measuring the relative skill of a new objective recurvature prediction technique in Part II of this study. The one-way influence tropical cyclone model is shown to have the highest skill in predicting recurvature for this sample.

Forecasting Tropical Cyclone Recurvature. Part II. An Objective Technique Using an Empirical Orthogonal Function Representation of Vorticity Fields

Abstract An empirical orthogonal function (EOF) representation of relative vorticity is used to forecast recurvature (change in storm heading from west through north to cast of 360°) of western North Pacific tropical cyclones. A pattern recognition approach is adapted in which the synoptic conditions at recurvature time and each 12-h interval up to 96 h prior to recurvature are to be distinguished from the synoptic pattern for straight-mover storms. Synoptic descriptors are defined in terms of the time-dependent principal components of the vorticity fields for the individual maps. A standard discriminant analysis approach using 250-mb vorticity fields correctly identifies recurvers and straight movers in 80% and 66%, respectively, of the 782 cases. For a specific discriminant analysis that is derived to separate recurvers (74% correct) from straight movers (81% correct), the accuracy is higher than for the operational track prediction techniques and the official forecasts considered in Part I of this stud...

Tropical Cyclone Recurvature and Nonrecurvature as Related to Surrounding Wind-Height Fields

Abstract Ten years of rawinsonde data for 30 stations in the western North Pacific have been composited relative to tropical cyclone center positions. This is the same data set described in a previous paper by the same authors. These data were used to study prior (12–72 h) differences in surrounding environmental fields between tropical cyclones which recurved and those which did not. Differences in the wind, height and temperature fields out to 21° radius to the north between these two classes of storms are presented. A strong recurvature correlation is found in the 200 mb wind and height fields at large radii to the north. It is suggested that an operational long-range (2–3 days) tropical cyclone recurvature forecast scheme can be developed using upper tropospheric wind-height data.