Wind-induced Surface Heat Exchange Research Articles

A Moist Potential Vorticity Model for Midlatitude Long-Lived Mesoscale Convective Systems over Land

Abstract Mesoscale convective systems (MCSs) bring large amounts of rainfall and strong wind gusts to the midlatitude land regions, with significant impacts on local weather and hydrologic cycle. However, weather and climate models face a huge challenge in accurately modeling the MCS life cycle and the associated precipitation, highlighting an urgent need for a better understanding of the underlying mechanisms of MCS initiation and propagation. From a theoretical perspective, a suitable model to capture the realistic properties of MCSs and isolate the bare-bones mechanisms for their initiation, intensification, and eastward propagation is still lacking. To simulate midlatitude MCSs over land, we develop a simple moist potential vorticity (PV) model that readily describes the interactions among PV perturbations, air moisture, and soil moisture. Multiple experiments with or without various environmental factors and external forcing are used to investigate their impacts on MCS dynamics and mesoscale circulation vertical structures. The result shows that mechanical forcing can induce lower-level updraft and cooling, providing favorable conditions for MCS initiation. A positive feedback among surface winds, evaporation rate, and air moisture similar to the wind-induced surface heat exchange over tropical ocean is found to support MCS intensification. Both background surface westerlies and vertical westerly wind shear are shown to provide favorable conditions for the eastward propagation of MCSs. Last, our result highlights the crucial role of stratiform heating in shaping mesoscale circulation response. The model should serve as a useful tool for understanding the fundamental mechanisms of MCS dynamics.

Application of the rotating-convection paradigm for tropical cyclones to interpreting medicanes: An example

The rotating-convection paradigm for tropical cyclone behaviour is shown to provide an attractive and consistent framework for interpreting the dynamics of formation and intensification of at least some medicanes. The ideas are illustrated by a case study of the medicane that formed over the eastern Mediterranean in mid-December 2020. This case study is based on analyses of data from the European Centre for Medium Range Weather Forecasts (ECMWF), imagery from the European geostationary meteorological satellite, Meteosat Second Generation, and output from a convection permitting numerical simulation of the event using the United Kingdom (UK) Met Office regional model with the RAL2 physics configuration. Limitations of the currently widely accepted interpretation of medicanes in terms of the so-called Wind-Induced Surface Heat Exchange (WISHE) intensification mechanism are discussed.

Sensitivity of Linear Models of the Madden–Julian Oscillation to Convective Representation

Abstract Two analytical models with different starting points of convective parameterizations, the Fuchs and Raymond model on one hand and the Khairoutdinov and Emanuel model on the other, are used to develop “minimal difference” models for the MJO. The main physical mechanisms that drive the MJO in both models are wind-induced surface heat exchange (WISHE) and cloud–radiation interactions (CRI). The dispersion curves for the modeled eastward-propagating mode, the MJO mode, are presented for an idealized case with zero meridional wind and for the realistic cases with higher meridional numbers. In both cases, the two models produce eastward-propagating modes with the growth rate greatest at the largest wavelengths despite having different representations of cumulus convection. We show that the relative contributions of WISHE and CRI are sensitive to how the convection and entropy/moisture budgets are represented in models like these. Significance Statement The Madden–Julian oscillation is the largest weather disturbance on our planet. It propagates eastward encompassing the whole tropical belt. It influences weather all around the globe by modulating hurricanes, atmospheric rivers, and other phenomena. Numerical models that forecast the Madden–Julian oscillation need improvement. Here we explore the physics behind the Madden–Julian oscillation using simple analytical models. Our models are based on the assumption that surface enthalpy fluxes and cloud–radiation interactions are responsible for the Madden–Julian oscillation but it should be borne in mind that other physical mechanisms have been proposed for the MJO. The impact of this research is to better understand the Madden–Julian oscillation mechanism.

Convective self–aggregation in a mean flow

Abstract. Convective self-aggregation is an atmospheric phenomenon seen in numerical simulations in a radiative convective equilibrium framework thought to be informative of some aspects of the behavior of real-world convection in the deep tropics. We impose a background mean wind flow on convection-permitting simulations through the surface flux calculation in an effort to understand how the asymmetry imposed by a mean wind influences the propagation of aggregated structures in convection. The simulations show that, with imposing mean flow, the organized convective system propagates in the direction of the flow but slows down compared to what pure advection would suggest, and it eventually becomes stationary relative to the surface after 15 simulation days. The termination of the propagation arises from momentum flux, which acts as a drag on the near-surface horizontal wind. In contrast, the thermodynamic response through the wind-induced surface heat exchange feedback is a relatively small effect, which slightly retards the propagation of the convection relative to the mean wind.

The Role of Surface Heat Fluxes on the Size of Typhoon Megi (2016)

AbstractThis study attempts to understand how surface heat fluxes in different storm regions affect tropical cyclone (TC) size. The Advanced Research version of the Weather Research and Forecasting (ARW-WRF) Model (version 3.5.1) is used to simulate Typhoon Megi (2016). A series of numerical experiments are carried out, including a control simulation and several sensitivity experiments with surface heat fluxes suppressed in different TC regions [to mimic the reduction of the wind-induced surface heat exchange (WISHE) feedback in the inner and/or outer core]. The results show that with surface heat fluxes suppressed in the entire domain, the TC tends to be smaller. Meanwhile, the TC size is more sensitive to the surface heat flux change in the outer core than to that in the inner core. Suppressing surface heat fluxes can weaken the rainbands around the suppressed area, which in turn slows down the secondary circulation. When the surface heat flux is suppressed in the inner-core region, the weakening of the secondary circulation associated with the diminished inner rainbands is limited to the inner-core region, and only slightly affects the absolute angular momentum import from the outer region, thus having negligible impact on TC size. However, suppression of surface heat fluxes in the outer-core region leads to less active outer rainbands and a more substantial weakening of secondary circulation. This results in less absolute momentum import from the outer region and in turn a smaller TC.

Characteristics and mechanism of vertical coupling in the genesis of tropical cyclone Durian (2001)

The vertical coupling (VC) process and mechanism during the genesis of a tropical cyclone (TC) implied by the weak vertical shear of horizontal wind, one of the key factors impacting TC genesis, constitute important but unanswered fundamental scientific problems. This paper carried out a targeted investigation of this problem through numerical simulation and theoretical analyses. The main conclusions are as follows. Even if TC genesis occurs in a barotropic environment, a VC process still occurs between the trough (vortex) at the middle level and that at the lower level in the TC embryo area. VC mainly occurs at the tropical disturbance (TDS) stage. Only after the VC is accomplished can the tropical depression (TD) organize further by itself and develop into the tropical storm (TS) stage or the stronger tropical typhoon (TY) stage through the WISHE (wind-induced surface heat exchange) mechanism. In the VC process, vortical hot towers (VHTs) play vertical connecting roles and are the actual practitioners of the VC. Through the VHTs’ vertical connections, the middle- and lower-troposphere trough axes move towards each other and realize the VC. VHTs can produce intensive cyclonic vorticity in the lower troposphere, which is mainly contributed by the stretching term. The tilting term can produce a single dipole or double dipole of vorticity, but the positive and negative vorticity pairs offset each other roughly. While the stretching term ensures that the cyclonic rotations of the wind field in the middle and lower levels tend to be consistent, the tilting term acts to uniformly distribute the horizontal wind in the vertical direction, and both terms facilitate the VC of the wind field. With the latent heat of condensation, VHTs heat the upper and middle troposphere so that the 352 K equivalent potential temperature contour penetrates vertically into the 925–300 hPa layer, realizing the VC of the temperature field. While forming cloud towers, VHTs make the ambient air become moist and nearly saturated so that the 95% relative humidity contour penetrates vertically into the 925–400 hPa layer, realizing the VC of the humidity field. Due to the collective contributions of the VHTs, the embryo area develops into a warm, nearly saturated core with strong cyclonic vorticity. The barotropic instability mechanism may also occur during TC genesis over the Northwest Pacific and provide rich large-scale environmental vorticity for TC genesis. The axisymmetric distribution of VHTs is an important sign of TC genesis. When a TC is about to form, there may be accompanying phenomena between the axisymmetric process of VHTs and vortex Rossby waves.

Frictionally Induced Feedback in a Reduced Dynamical Model of Tropical Cyclone Intensification

AbstractThis study examines the role of frictional feedback in the atmospheric boundary layer during tropical cyclone (TC) development. Using a reduced model of TC dynamics, it is shown that a feedback between frictional convergence and convective heating in the absence of slantwise moist neutrality is capable of producing a stable maximum-intensity limit, even without surface fluxes. However, the efficiency of this frictional-convergence feedback depends crucially on how effectively boundary layer moisture convergence is converted into convective heating, which decreases rapidly as the TC inner core approaches a state of moist neutrality. This decreasing efficiency during TC intensification explains why the effect of the frictional-convergence feedback is generally small compared to that of the wind-induced surface heat exchange (WISHE) feedback under the strict conditions of slantwise moist neutrality. Examination of the reduced TC model with a constant-heating source reveals that TC intensification is not peculiar to any specific feedback mechanism but, rather, is a direct consequence of the inward advection of absolute angular momentum, regardless of feedback mechanism.

The Role of WISHE in the Rapid Intensification of Tropical Cyclones

Abstract This study examines the role of surface heat fluxes, particularly in relation to the wind-induced surface heat exchange (WISHE) mechanism, in the rapid intensification (RI) of tropical cyclones (TCs). Sensitivity experiments with capped surface fluxes and thus reduced WISHE exhibit delayed RI and weaker peak intensity, while WISHE could affect the evolutions of TCs both before and after the onset of RI. Before RI, more WISHE leads to faster increase of equivalent potential temperature in the lower levels, resulting in more active and stronger convection. In addition, TCs in experiments with more WISHE reach a certain strength earlier, before the onset of RI. During the RI period, more surface heat fluxes could provide convective instability in the lower levels, and cause a consequent development in the convective activity. More efficient intensification in a TC is found with higher surface heat fluxes and larger inertial stability, leading to a stronger peak intensity, more significant and deeper warm core in TC center, and the axisymmetrization of convection in the higher levels. In both stages, different levels of WISHE alter the thermodynamic environment and convective-scale processes. In all, this study supports the crucial role of WISHE in affecting TC intensification rate for TCs with RI.

WISHE‐Moisture Mode in a Vertically Resolved Model

AbstractThe Madden‐Julian oscillation is a global phenomenon, a wave with the wavelength of the circumference of the Earth. A theoretical model presented by Fuchs and Raymond (2007, https://doi.org/10.1111/j.1600-0870.2007.00230.x) obtained a mode called the eastward propagating wind‐induced surface heat exchange (WISHE)‐moisture mode that had its largest instability for the longest wavelengths. That model imposed the first baroclinic mode vertical structure. This paper expands the Fuchs and Raymond model by developing a vertically resolved model, a model in which all the variables except the heating vertical profile are calculated. The heating profile is assumed to have a vertical structure of the first baroclinic mode. The model uses the upper boundary radiation condition and thus includes the effects of the stratosphere. The convective parametrization includes wind‐induced surface heat exchange, cloud‐radiation interactions, and moisture closure. The vertically resolved model produces one unstable mode whose dispersion relation characteristics closely resemble the eastward propagating WISHE‐moisture mode. For the longest wavelengths it is more unstable and its phase speed is slightly larger than in the Fuchs and Raymond model. The calculated vertical structure reveals a similar vertical structure to the first baroclinic mode with small differences that to some extent agree with observations.

Essential Ingredients to the Dynamics of Westerly Wind Bursts

AbstractWesterly wind bursts (WWBs) are brief, anomalously westerly winds in the tropical Pacific that play a role in the dynamics of ENSO through their forcing of ocean Kelvin waves. They have been associated with atmospheric phenomena such as tropical cyclones, the MJO, and convectively coupled Rossby waves, yet their basic mechanism is not yet well understood. We study WWBs using an aquaplanet general circulation model, and find that eastward-propagating convective heating plays a key role in the generation of model WWBs, consistent with previous studies. Furthermore, wind-induced surface heat exchange (WISHE) acts on a short time scale of about two days to dramatically amplify the model WWB winds near the peak of the event. On the other hand, it is found that radiation feedbacks (i.e., changes in the net radiative anomalies accompanying westerly wind bursts) are not essential for the development of WWBs, and act as a weak negative feedback on WWBs and their associated convection. Similarly, sensible surface heat flux anomalies are not found to have an effect on the development of model WWBs.

Development mechanisms for Mediterranean tropical‐like cyclones (medicanes)

Midlatitude cyclones with characteristics similar to tropical cyclones (also known as Tropical‐Like Cyclones, TLCs, or medicanes) are sometimes observed in the Mediterranean region. The Wind Induced Surface Heat Exchange (WISHE) mechanism has been considered responsible for their development, in analogy with tropical‐cyclone theory. However, some recent papers have proposed a different explanation, suggesting that the deep warm core in the TLC is mainly an effect of the seclusion of warm air in the cyclone core. To investigate the latter hypothesis, two case‐studies of Mediterranean TLCs are analysed here by means of high‐resolution numerical experiments. The evolution of the near‐surface equivalent potential temperature is followed along back‐trajectories around the cyclone centre, showing for both cases a strong heating when the parcel moves from the outer part of the cyclone to its inner, warmer core. Sensitivity experiments clarify the mechanism of cyclone intensification and the way the warm‐core structure is generated, showing that sea‐surface fluxes and/or condensation latent heating are fundamental to explain the intensification of the cyclones. However, the importance of air–sea interaction processes is case dependent. For the first cyclone, the intense sea‐surface fluxes, associated with tramontane and cierzo winds over the western Mediterranean Sea, transfer a large amount of energy from the ocean to the atmosphere in the area where the cyclone developed, so that the vortex is able to sustain itself in a barotropic environment and reach a tropical‐like structure at a later stage in its lifetime. For the second cyclone, the cyclone never develops a fully tropical‐like structure, evolving in the baroclinic environment associated with the potential vorticity streamer in which the cyclone formed. Based on the distinction emerging in this and other articles, a classification of medicanes in three different categories is proposed.

Sensitivity of tropical cyclone predictions in the coupled atmosphere–ocean model WRF‐3DPWP to surface roughness schemes

The sensitivity of tropical cyclone simulations in a coupled ocean–atmospheric model WRF‐3DPWP to surface roughness parameterizations is investigated. Six cyclones, Hudhud, Phailin, Helen, Jal, Nilam and Khaimuk, which occurred in the North Indian Ocean (NIO) during 2008–2014, are simulated. Three schemes for drag and enthalpy co‐efficients (control (CNTL): Garrett C d and C k, Opt1: Donelan C d + Constant C k, Opt2: Donelan C d + Garret C k) are used. India Meteorological Department (IMD) best track parameters are used for comparison. The results indicate that the simulated cyclone intensity is highly sensitive to the formulation of drag and enthalpy co‐efficients in all cyclone categories, whereas the simulated tracks for strong cyclones only are affected by these schemes. The results showed that CNTL produced better predictions for track and Opt2 for intensity for the three cyclones. An improvement of 12.3, 35.2 and 34.9% in central sea level pressure (CSLP) and 2.9, 31.5 and 45.9% in maximum surface winds (MSW) at 24, 48 and 72 hr respectively are found with Opt2 over Opt1. Simulations showed the model enthalpy co‐efficients mainly affected the intensity of the cyclones by producing a wind‐induced surface heat exchange (WISHE)‐type of feedback through heat and moisture fluxes and warm‐core structure. Opt1 produced highly intensified cyclones due to simulating large enthalpy fluxes associated with a high C k/C d ratio. The stronger wind‐induced moisture fluxes, higher vorticity and strong vertical motion associated with large enthalpy fluxes all support stronger simulated cyclones in Opt1 compared with CNTL and Opt2. The study shows that the decreasing C k for higher winds in Opt2 produced realistic intensity predictions.

A Simple Model of Convectively Coupled Equatorial Rossby Waves

AbstractIntraseasonal oscillations affect the weather not just in the tropics but all around the globe. The convectively coupled equatorial Rossby wave is observed as the westward‐moving intraseasonal oscillation. The fundamental physics of its coupling is still unknown; thus, many questions remain unanswered. How is its phase speed altered by convection? What makes it unstable? Why is it an intraseasonal oscillation? Using the Fuchs and Raymond model with linearized governing equations on an equatorial beta plane, first baroclinic mode vertical structure, and moisture and wind‐induced surface heat exchange (WISHE) convective parametrizations, this paper seeks a fundamental analytical theory that can explain the basic features of the convectively coupled equatorial Rossby wave. The WISHE‐moisture theory leads to a large‐scale, unstable westward propagating mode in the n = 1 case, which we call the westward propagating WISHE‐moisture mode. We find that the westward propagating WISHE‐moisture mode is indeed the free equatorial Rossby wave in the absence of moisture closure and WISHE. It is propagating westward due to the beta effect, and it slows down when it is convectively coupled. Its phase speed decreases mainly due to WISHE and cloud‐radiation interactions. The x‐y structure of the pressure and horizontal winds is similar to the free and observed Rossby wave, with convergent net flow. The strongest easterlies are to the west of the precipitation maximum increasing the moisture in that area. The mode is unstable due to the interplay of surface fluxes and moisture, which increases as a function of zonal wavelength.

Intraseasonal Variability in a Cloud-Permitting Near-Global Equatorial Aquaplanet Model

Abstract Recent studies have suggested that the Madden–Julian oscillation is a result of an instability driven mainly by cloud–radiation feedbacks, similar in character to self-aggregation of convection in nonrotating, cloud-permitting simulations of radiative–convective equilibrium (RCE). Here we bolster that inference by simulating radiative–convective equilibrium states on a rotating sphere with constant sea surface temperature, using the cloud-permitting System for Atmospheric Modeling (SAM) with 20-km grid spacing and extending to walls at 46° latitude in each hemisphere. Mechanism-denial experiments reveal that cloud–radiation interaction is the quintessential driving mechanism of the simulated MJO-like disturbances, but wind-induced surface heat exchange (WISHE) feedbacks are the primary driver of its eastward propagation. WISHE may also explain the faster Kelvin-like modes in the simulations. These conclusions are supported by a linear stability analysis of RCE states on an equatorial beta plane.

The Role of WISHE in Secondary Eyewall Formation

Abstract Numerical simulations are conducted to examine the role of the wind-induced surface heat exchange (WISHE) mechanism in secondary eyewall formation (SEF). The control experiment exhibits a coherent secondary eyewall structure as quantified by various parameters (e.g., the azimuthal-mean tangential wind and vertical velocity). Prior to SEF, an area characterized by increasing diabatic heating, enhanced inertial stability, and increasing supergradient winds at the top of the boundary layer is observed outside the eyewall. While these characteristics offer the possibility of both balanced and unbalanced dynamical pathways to SEF, the focus of this study is to evaluate the impact of WISHE. To examine the sensitivity of SEF to WISHE, the surface wind used for the calculation of surface heat fluxes is capped at several designated values and at different radial intervals. When the heat fluxes are moderately suppressed around and outside the SEF region observed in the control experiment, sensitivity experiments show that the formation of the outer eyewall is delayed, and the intensity of both eyewalls is weaker. When the heat fluxes are strongly suppressed in the same region, SEF does not occur. In contrast, suppressing the surface heat fluxes in the storm’s inner-core region has limited effect on the evolution of the outer eyewall. This study provides important physical insight into SEF, indicating that WISHE plays a crucial role in SEF and tropical cyclone evolution.

WISHE-Moisture Mode in an Aquaplanet Simulation.

This study aims to understand the nature of the tropical intraseasonal oscillations (ISOs) in an aquaplanet simulation performed using Geophysical Fluid Dynamics Laboratory's AM2.1 with a uniform sea surface temperature within the deep tropics. The simulated ISO resembles the observed Madden‐Julian Oscillation in that the spectral peak in precipitation appears at zonal wave number 1 and a period of ~60 days. Vertically integrated moist static energy budget of the simulated ISO shows that enhanced latent heat flux to the east of anomalously active convection causes eastward propagation of the ISO mode, which is weakly opposed by horizontal moisture advection. A series of mechanism denial experiments are conducted either by homogenizing select variables—surface wind stress, longwave radiative heating, and surface evaporation—with their zonal means from the control simulation or by suppressing free‐tropospheric moisture variation. Results of the mechanism denial experiments show that the simulated ISO disappears when the interactive surface evaporation is disabled, suggesting that the wind‐induced surface heat exchange (WISHE) mechanism is essential to the simulated ISO. Longwave cloud‐radiation feedbacks and moisture‐convection feedbacks affect horizontal scale and phase speed of the simulated ISO, respectively. Our results strongly suggest that the simulated ISO is the linear WISHE‐moisture mode of Fuchs and Raymond under horizontally uniform boundary conditions.

The Madden‐Julian Oscillation and the Indo‐Pacific Warm Pool

AbstractA minimal model of the interaction of the Madden‐Julian oscillation (MJO) with the Indo‐Pacific warm pool is presented. This model is based on the linear superposition of the flow associated with a highly simplified treatment of the MJO plus the flow induced by the warm pool itself. Both of these components parameterize rainfall as proportional to the column water vapor, which in turn is governed by a linearized moisture equation in which WISHE (wind induced surface heat exchange) plays a governing role. The MJO component has maximum growth rate for planetary wavenumber 1 and is equatorially trapped with purely zonal winds. The warm pool component exhibits a complex flow pattern, differing significantly from the classical Gill model as a result of the mean easterly flow. The combination of the two produce a flow that reproduces many aspects of the observed global flow associated with the MJO.

Acceleration of tropical cyclogenesis by self-aggregation feedbacks

Idealized simulations of tropical moist convection have revealed that clouds can spontaneously clump together in a process called self-aggregation. This results in a state where a moist cloudy region with intense deep convection is surrounded by extremely dry subsiding air devoid of deep convection. Because of the idealized settings of the simulations where it was discovered, the relevance of self-aggregation to the real world is still debated. Here, we show that self-aggregation feedbacks play a leading-order role in the spontaneous genesis of tropical cyclones in cloud-resolving simulations. Those feedbacks accelerate the cyclogenesis process by a factor of 2, and the feedbacks contributing to the cyclone formation show qualitative and quantitative agreement with the self-aggregation process. Once the cyclone is formed, wind-induced surface heat exchange (WISHE) effects dominate, although we find that self-aggregation feedbacks have a small but nonnegligible contribution to the maintenance of the mature cyclone. Our results suggest that self-aggregation, and the framework developed for its study, can help shed more light into the physical processes leading to cyclogenesis and cyclone intensification. In particular, our results point out the importance of the longwave radiative cooling outside the cyclone.

On the role of convective available potential energy (CAPE) in tropical cyclone intensification

This study addresses the role of convective available potential energy (CAPE) in the intensification of simulated tropical cyclones. Additionally, it also examines the ‘wind-induced surface heat exchange’ (WISHE) theory in which CAPE is non-existent during intensification. We use a hierarchy of models with different complexity. A low-order tropical cyclone model forms the simplest model. It is found that the damping of CAPE by fast convective exchange as assumed in the WISHE theory inhibits substantial intensification in the model. This result can be explained by the dominance of the secondary circulation over surface heat transfer in the growth stage. It leads to entrainment of low entropy air into the eyewall resulting in the weakening of the cyclone. Other simulations reveal that the intensification rate increases with increasing initial CAPE and that the inner core CAPE is smaller than that of the ambient region. Investigations with the more complex Ooyama model yield qualitatively similar results. In this model, two types of convection are considered. The first one is based on frictional convergence in the boundary layer and the second one describes a convective adjustment including a precipitation efficiency. Only frictionally induced convection supports tropical cyclone intensification while the second one strongly acts to dampen the cyclone. Finally, the complex nonhydrostatic cloud model CM1 is used where the initial CAPE is varied. This model also exposes the existence of radially increasing CAPE during intensification. The experiments of this study indicate a positive relationship between the radial CAPE gradient and the intensification rate which disagrees with the basic assumption of WISHE models. The results emphasise the role of the secondary circulation for transporting high entropy air into the tropical cyclone inner core, and therefore should be considered in a proper intensification theory as has been done in the rotating convection paradigm by Montgomery and Smith.

On the movement of tropical cyclone LEHAR

In this paper, an attempt has been made to delineate the physical processes which lead to the westward movement of the North Indian Ocean tropical cyclone LEHAR. The Advanced Weather Research and Forecasting (ARW) model is used to simulate LEHAR with 27 and 9 km resolutions. In addition to that, all terms of the complete vorticity equation are computed to obtain the contribution of each term for the vorticity tendency. The vorticity tendency is calculated in four sectors, namely northwest, northeast, southwest, and southeast and assumed that the cyclone moves from its existing location to the nearest point where the vortices tendency is maximum. The results indicate that the model performed well in simulating the characteristics of cyclone compared with the Satellite and other observations. It is noticed that the vorticity stretching term contributes most to the positive vorticity tendency. The second highest contribution is from the horizontal advection thus indicating the secondary importance of steering. The distribution of lightning flash rates are higher in the SW and followed by NW sectors of the cyclone indicate more strong convective clouds are in SW sector. The equivalent potential temperatures (θ e) at different stages of before, during and after the mature stage of the cyclone reveals that the wind-induced surface heat (WISH) exchange process is a plausible mechanism for the intensification of LEHAR.