[1] Typhoon Morakot (2009), a devastating tropical cyclone (TC) that made landfall in Taiwan from 7 to 9 August 2009, produced the highest recorded rainfall southern past 50 years. This study examines factors contributed heavy rainfall. It is found amount of was nearly proportional reciprocal TC translation speed rather than intensity. Morakot's on occurred concurrently with cyclonic phase intraseasonal oscillation, which enhanced background southwesterly monsoonal flow. The extreme caused...

Abstract According to the thermodynamic theory of cloud top evaporative instability, persistent stratocumulus should be observed only when jumps in equivalent potential temperature θ and total water mixing ratio r satisfy stability condition Δθ > k(L/cp)Δr, where k ± 0.23. Using observations mid‐latitude subtropical we find that above is violated many cases. In an attempt understand how can persist under apparently unstable conditions first review instability then develop a dynamical...

In this study, an ensemble meteorological modeling system is one-way coupled with a hydrological model to predict typhoon rainfall and flood responses in mountainous watershed Taiwan. This framework includes perturbations of the initial conditions, data analysis methods, physical parameterizations. The predicted from then used drive physically distributed for Lanyang basin during landfall Typhoon Nanmadol (2011). forecast provides track forecasts that are comparable operational center more...

Abstract Typhoon Morakot struck Taiwan during 6–9 August 2009, and it produced the highest rainfall (approaching 3000 mm) caused worst damage in past 50 yr. Typhoon–monsoon flow interactions with mesoscale convection, water vapor supply by monsoon flow, slow moving speed of storm are main reasons for record-breaking precipitation. Analysis typhoon track reveals that steering although indeed slow, still exceeded approximately 5 km h−1 (1 = 0.28 m s−1) postlandfall period on 8 August, when was...

Abstract Taiwan, which is in the middle of one most active western North Pacific Ocean’s tropical cyclone (TC) zones, experienced a dramatic increase typhoon-related rainfall beginning twenty-first century. This record-breaking has led to suggestions that it manifestation effects global warming. With significantly influenced by its steep terrain, Taiwan offers natural laboratory study role terrain may play climate change TC rainfall. Here, shown recently observed large increases are result...

We studied the temporal and spatial characteristics of extreme typhoon rainfall in Taiwan using Central Weather Bureau hourly precipitation data from 21 surface stations during past 51 years (1960-2010). Extreme is defined as 95th percentile intensity total rain events, or equivalently, events greater than 9 mm hr-1 which contribute 40% to amount Taiwan. It was found that approximately 70% (20%) season (Mei-Yu) July October (from May June). There are significant variations over annual...

Due to the diminishing Coriolis effect, belt 300 km either side of equator has been considered tropical cyclone‐free. Typhoon Vamei, which developed near Singapore on 27 December 2001, was first recorded cyclone formation within 1.5 degrees equator. The development result two interacting systems, a weak Borneo vortex that drifted into southern tip South China Sea and remained there for four days, strong persistent cold surge created large background cyclonic vorticity at probability similar...

An elliptical eye that rotated cyclonically with a period of approximately 144 minutes in Typhoon Herb 1996 was documented. The region had semimajor axis 30 km and semiminor 20 km. Two complete periods min were observed the Doppler radar data. rotation context barotropic dynamics at three levels explored: linear waves on Rankin vortex, nonlinear Kirchhoff spectral model. wave theory involves existence both high (potential) vorticity gradient near edge cyclonic mean tangential flow typhoon....

Abstract An important issue in the formation of concentric eyewalls a tropical cyclone is development symmetric structure from asymmetric convection. It proposed herein, with aid nondivergent barotropic model, that vorticity structures result interaction between small and strong inner vortex (the core) neighboring weak vortices induced by moist convection outside central cyclone). The results highlight pivotal role strength core maintaining itself, stretching, organizing, stabilizing outer...

A simple zonally symmetric balanced model of the Hadley circulation is presented. The based on potential vorticity arguments and consists a predictive equation for pseudodensity an invertibility principle to diagnose associated wind mass fields. When theory formulated in latitude coordinate, meridional advection implicit coordinate transformation, which makes prediction analytically solvable. For convective heating patterns that simulate ITCZ, produces upper lower tropospheric anomalies...

Abstract This study examines the intensity change and moat dynamics of typhoons with concentric eyewalls using passive microwave data best-track in western North Pacific between 1997 2006. Of 225 examined, 55 62 cases have been identified. The indicate that approximately 57% category 4 72% 5 possessed at some point during their lifetime. While major are most likely to form eyewalls, formation structure may not be necessarily lifetime maximum intensity. Approximately one-third eyewall formed...

Abstract Concentric eyewall formation can be idealized as the interaction of a tropical cyclone core with nearby weaker vorticity various spatial scales. This paper considers barotropic aspects concentric from modified Rankine vortices. In this framework, following parameters are found to important in formation: strength ratio, separation distance, companion vortex size, and skirt parameter. A on affects filamentation dynamics two ways. First, lengthens time, therefore slows moat region just...

Abstract Analyses of tropical cyclones created in an idealized environment reveal how and why cloud microphysical assumptions can influence storm motion, including speed direction. It is well known that the absence a mean flow, leading factor propagation establishment “beta gyres” owing to planetary vorticity advection by storm’s circulation. Previous research demonstrated tangential winds beyond core motion helping determine gyres’ orientation intensity. Microphysical assumptions,...

Abstract This paper examines the effect of topographically phase-locked convection on motion typhoons across island Taiwan. Data for 84 that reached Taiwan’s eastern coast from 1960 to 2010 are analyzed, with motions compared long-term average overland translation speed. For 61 continuous-track among all cases, 77% slow-moving tropical cyclones (TCs) made landfall northern end coast, while 60% fast storms had southeastern coastal landfalls. geographic asymmetry respect typhoon speeds widened...

Abstract A forced shallow-water model is used to understand the role of diabatic and frictional effects in generation, maintenance, breakdown hurricane eyewall potential vorticity (PV) ring. Diabatic heating parameterized as an annular mass sink variable width magnitude, nonlinear evolution tropical storm–like vortices examined under this forcing. produces a strengthening thinning PV ring time due combined radial advection by induced divergent circulation. If forcing makes thin enough, then...

Abstract An objective method is developed to identify concentric eyewalls (CEs) for typhoons using passive microwave satellite imagery from 1997 2011 in the western North Pacific basin. Three CE types are identified: a with an eyewall replacement cycle (ERC; 37 cases), no (NRC; 17 and that maintained extended period (CEM; 16 cases). The inner (outer eyewall) of ERC (NRC) type dissipates within 20 h after formation. CEM has its structure more than (mean duration time 31 h). Structural...

Abstract The authors survey a series of modeling studies that have examined the influences cloud microphysical processes can on tropical cyclone (TC) motion, strength and breadth wind field, inner-core diabatic heating asymmetries, outer-core convective activity, characteristics TC anvil cloud. These are sensitive to parameterization (MP) in large part owing cloud-radiative forcing (CRF), interaction hydrometeors with radiation. most influential component CRF is due absorption emission...

The interactions between monsoon circulations and tropical disturbances in the Northwest Pacific, where low-level mean flow is westerly west easterly east, are studied with a barotropic model. authors' model results suggest that scale contraction by confluent background flow, nonlinear dynamics, β effect, large-scale convergence important for energy enstrophy accumulation near region zonal reverses. energy/enstrophy can be maintained continuous Rossby wave emanation upstream. largest occurs...

The dispatch of capacitors on a distribution feeder in daily system operation is investigated. objective to reach an optimal capacitor dispatching schedule, based the forecast hourly loads for next day, such that total loss day minimised. constraints must be taken into account include maximum allowable number switching operations each capacitor, and voltage limits feeder. An approach dynamic programming presented schedule. To demonstrate effectiveness proposed approach, within service area...

The potential vorticity principle for a nonhydrostatic, moist, precipitating atmosphere is derived. An appropriate generalization of the well-known (dry) Ertel found to be P = ρ−1(2Ω + ∇ × u) · ∇θρ, where ρ total density, consisting sum densities dry air, airborne moisture (vapor and cloud condensate), precipitation; u velocity air moisture; θρ Tρ(p0/p)Ra/cPa virtual temperature, with Tρ p/(ρRa) p pressure (the partial pressures water vapor), p0 constant reference pressure, Ra gas cPa...

Through the use of a zonal balance model we investigate response mean meridional circulation to specified diabatic forcing for both resting and nonresting flows. The potential latitude coordinate transformed components results in simplified equation which variable coefficients are normalized vorticity inertial stability. Solutions this illustrate how latent heat release away from equator forces winter hemisphere Hadley cell that is more intense than summer cell. This asymmetric due primarily...

Abstract The Madden–Julian oscillation (MJO) identified by Madden and Julian in the early 1970s has been well recognized as most prominent intraseasonal signal tropics. Its discovery its relationship with other weather phenomena such tropical cyclones (TCs) are among significant advancements modern meteorology broad far-reaching impacts. original study used radiosonde data on Canton Island, their spectral analysis revealed of a 40–50-day oscillation. It come to our attention that an earlier...