scholarly journals A Numerical Study of Aviation Turbulence Encountered on 13 February 2013 over the Yellow Sea between China and the Korean Peninsula

2018 ◽  
Vol 57 (4) ◽  
pp. 1043-1060 ◽  
Author(s):  
Dan-Bi Lee ◽  
Hye-Yeong Chun
Keyword(s):  
Yellow Sea ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
The Yellow Sea ◽  
Small Scale ◽  
Mountain Waves ◽  
Frontal System ◽  
Upper Level ◽  
Tropopause Folding

AbstractAt 0247 UTC 13 February 2013, a South Korean commercial aircraft encountered moderate-level clear-air turbulence at ~24 000 ft (~7.3 km) over the Yellow Sea (121.25°E, 38.55°N) en route from Incheon, South Korea, to Tianjin, China. Two crew members were severely injured by this event. To investigate the possible mechanisms of this event, a high-resolution numerical simulation using the Weather Research and Forecasting Model was conducted. In the synoptic-scale flow pattern, one of two bifurcated jet streams passed over the Yellow Sea, and strong horizontal and vertical gradients of the wind occurred on the northern edge of the jet stream near the flight route. An upper-level frontal system on the cyclonic shear side of the jet intensified as it moved northward toward a strengthening upper-level trough in northeastern China. The developed jet–frontal system induced strong vertical wind shear and tropopause folding, which extended down to about z = 5 km, near the observed turbulence region. Despite a relatively high stability with an intrusion of stratospheric air with tropopause folding, the strong vertical wind shear led to a small Richardson number in the incident region, which in turn induced the aviation turbulence through the Kelvin–Helmholtz instability. Although small-scale mountain waves were evident during the passage of flight before the incident time, breaking of these waves was not likely the key factor for the observed turbulence, given that the wave amplitudes were weak and that the strong zonal wind on the upstream of the mountain waves prohibited wave saturation and breakdown.

scholarly journals The Unexpected Rapid Intensification of Tropical Cyclones in Moderate Vertical Wind Shear. Part I: Overview and Observations

2018 ◽  
Vol 146 (11) ◽  
pp. 3773-3800 ◽  
Author(s):  
David R. Ryglicki ◽  
Joshua H. Cossuth ◽  
Daniel Hodyss ◽  
James D. Doyle
Keyword(s):  
Tropical Cyclones ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Convective Cloud ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Brightness Temperatures ◽  
Idealized Modeling ◽  
Hurricane Prediction ◽  
Upper Level

Abstract A satellite-based investigation is performed of a class of tropical cyclones (TCs) that unexpectedly undergo rapid intensification (RI) in moderate vertical wind shear between 5 and 10 m s−1 calculated as 200–850-hPa shear. This study makes use of both infrared (IR; 11 μm) and water vapor (WV; 6.5 μm) geostationary satellite data, the Statistical Hurricane Prediction Intensity System (SHIPS), and model reanalyses to highlight commonalities of the six TCs. The commonalities serve as predictive guides for forecasters and common features that can be used to constrain and verify idealized modeling studies. Each of the TCs exhibits a convective cloud structure that is identified as a tilt-modulated convective asymmetry (TCA). These TCAs share similar shapes, upshear-relative positions, and IR cloud-top temperatures (below −70°C). They pulse over the core of the TC with a periodicity of between 4 and 8 h. Using WV satellite imagery, two additional features identified are asymmetric warming/drying upshear of the TC relative to downshear, as well as radially thin arc-shaped clouds on the upshear side. The WV brightness temperatures of these arcs are between −40° and −60°C. All of the TCs are sheared by upper-level anticyclones, which limits the strongest environmental winds to near the tropopause.

scholarly journals The Unexpected Rapid Intensification of Tropical Cyclones in Moderate Vertical Wind Shear. Part III: Outflow–Environment Interaction

2019 ◽  
Vol 147 (8) ◽  
pp. 2919-2940 ◽  
Author(s):  
David R. Ryglicki ◽  
James D. Doyle ◽  
Daniel Hodyss ◽  
Joshua H. Cossuth ◽  
Yi Jin ◽  
...  
Keyword(s):  
Wind Shear ◽  
Vertical Wind Shear ◽  
Environmental Flow ◽  
Vertical Wind ◽  
Environment Interaction ◽  
Rapid Intensification ◽  
Field Matching ◽  
Upper Level ◽  
Bernoulli Flow ◽  
Dynamic High Pressure

Abstract Interactions between the upper-level outflow of a sheared, rapidly intensifying tropical cyclone (TC) and the background environmental flow in an idealized model are presented. The most important finding is that the divergent outflow from convection localized by the tilt of the vortex serves to divert the background environmental flow around the TC, thus reducing the local vertical wind shear. We show that this effect can be understood from basic theoretical arguments related to Bernoulli flow around an obstacle. In the simulation discussed, the environmental flow diversion by the outflow is limited to 2 km below the tropopause in the 12–14-km (250–150 hPa) layer. Synthetic water vapor satellite imagery confirms the presence of upshear arcs in the cloud field, matching satellite observations. These arcs, which exist in the same layer as the outflow, are caused by slow-moving wave features and serve as visual markers of the outflow–environment interface. The blocking effect where the outflow and the environmental winds meet creates a dynamic high pressure whose pressure gradient extends nearly 1000 km upwind, thus causing the environmental winds to slow down, to converge, and to sink. We discuss these results with respect to the first part of this three-part study, and apply them to another atypical rapid intensification hurricane: Matthew (2016).

Effect of TC–Trough Interaction on the Intensity Change of Two Typhoons

2005 ◽  
Vol 20 (2) ◽  
pp. 199-211 ◽  
Author(s):  
Hui Yu ◽  
H. Joe Kwon
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
Eddy Flux ◽  
Upper Troposphere ◽  
Shallow Layer ◽  
Upper Level

Abstract Using large-scale analyses, the effect of tropical cyclone–trough interaction on tropical cyclone (TC) intensity change is readdressed by studying the evolution of upper-level eddy flux convergence (EFC) of angular momentum and vertical wind shear for two TCs in the western North Pacific [Typhoons Prapiroon (2000) and Olga (1999)]. Major findings include the following: 1) In spite of decreasing SST, the cyclonic inflow associated with a midlatitude trough should have played an important role in Prapiroon’s intensification to its maximum intensity and the maintenance after recurvature through an increase in EFC. The accompanied large vertical wind shear is concentrated in a shallow layer in the upper troposphere. 2) Although Olga also recurved downstream of a midlatitude trough, its development and maintenance were not strongly influenced by the trough. A TC could maintain itself in an environment with or without upper-level eddy momentum forcing. 3) Both TCs started to decay over cold SST in a large EFC and vertical wind shear environment imposed by the trough. 4) Uncertainty of input adds difficulties in quantitative TC intensity forecasting.

A Numerical Study of Hurricane Erin (2001). Part II: Shear and the Organization of Eyewall Vertical Motion

2007 ◽  
Vol 135 (4) ◽  
pp. 1179-1194 ◽  
Author(s):  
Scott A. Braun ◽  
Liguang Wu
Keyword(s):  
Wind Shear ◽  
Numerical Study ◽  
Vertical Wind Shear ◽  
Vertical Motion ◽  
Vertical Wind ◽  
Small Scale ◽  
Strong Mixing ◽  
Upward Motion ◽  
Asymmetric Flow ◽  
Subsequent Decrease

Abstract A high-resolution numerical simulation of Hurricane Erin (2001) is used to examine the organization of vertical motion in the eyewall and how that organization responds to a large and rapid increase in the environmental vertical wind shear and subsequent decrease in shear. During the early intensification period, prior to the onset of significant shear, the upward motion in the eyewall was concentrated in small-scale convective updrafts that formed in association with regions of concentrated vorticity (herein termed mesovortices) with no preferred formation region around the eyewall. Asymmetric flow within the eye was weak. As the shear increased, an azimuthal wavenumber-1 asymmetry in storm structure developed with updrafts tending to occur on the downshear to downshear-left side of the eyewall. Continued intensification of the shear led to increasing wavenumber-1 asymmetry, large vortex tilt, and a change in eyewall structure and vertical motion organization. During this time, the eyewall structure was dominated by a vortex couplet with a cyclonic (anticyclonic) vortex on the downtilt-left (downtilt-right) side of the eyewall and strong asymmetric flow across the eye that led to strong mixing of eyewall vorticity into the eye. Upward motion was concentrated over an azimuthally broader region on the downtilt side of the eyewall, upstream of the cyclonic vortex, where low-level environmental inflow converged with the asymmetric outflow from the eye. As the shear diminished, the vortex tilt and wavenumber-1 asymmetry decreased, while the organization of updrafts trended back toward that seen during the weak shear period. Based upon the results for the Erin case, as well as that for a similar simulation of Hurricane Bonnie (1998), a conceptual model is developed for the organization of vertical motion in the eyewall as a function of the strength of the vertical wind shear. In weak to moderate shear, higher wavenumber asymmetries associated with eyewall mesovortices dominate the wavenumber-1 asymmetry associated with the shear so that convective-scale updrafts form when the mesovortices move into the downtilt side of the eyewall and dissipate on the uptilt side. Under strong shear conditions, the wavenumber-1 asymmetry, characterized by a prominent vortex couplet in the eyewall, dominates the vertical motion organization so that mesoscale ascent (with embedded convection) occurs over an azimuthally broader region on the downtilt side of the eyewall. Further research is needed to determine if these results apply more generally.

scholarly journals Comments on “Multiscale Structure and Evolution of Hurricane Earl (2010) during Rapid Intensification”

2017 ◽  
Vol 145 (4) ◽  
pp. 1565-1571 ◽  
Author(s):  
Russell L. Elsberry ◽  
Myung-Sook Park
Keyword(s):  
Vortex Structure ◽  
Wind Shear ◽  
Environmental Control ◽  
Vertical Wind Shear ◽  
Special Kind ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Structure Changes ◽  
Maximum Period ◽  
Upper Level

Abstract This comment addresses the Tropical Storm (TS) Earl upper-level vortex structure changes during a critical stage leading to the onset of rapid intensification as described by Rogers et al. Whereas the first NOAA WP-3D mission in TS Earl provided evidence of a shallow, broad vortex structure, the second WP-3D mission just 12 h later documented a deep, vertically stacked vortex undergoing rapid intensification. The authors attribute this vortex structure change to vertical alignment processes between the low-level Earl vortex and an upper-tropospheric mesoscale vortex about 50 km to the east in the mission 1 analyses. An alternate environmental control explanation is proposed in which a special kind of upper-tropospheric vertical wind shear (VWS) associated with the outflow of Hurricane Danielle to the northwest of TS Earl is the primary factor. Two estimates of the vertical wind shear changes are interpreted relative to the diurnal convective maximum/minimum to explain how the shallow vortex during mission 1 may have been created. It is proposed that the vigorous convection over sea surface temperatures of about 30°C during the diurnal convective maximum period between mission 1 and mission 2 was able to offset the moderate VWS as Hurricane Danielle had moved farther away from Earl. Thus, an explanation for the vertically stacked TS Earl vortex observed during mission 2 in terms of an environmental VWS modulation of the diurnally varying convective processes is proposed as an alternative to a vortex realignment.

scholarly journals The Influence of Environments on the Intensity Change of Typhoon Soudelor

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 162
Author(s):  
Leo Oey ◽  
Yuchen Lin
Keyword(s):  
Tropical Cyclones ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Intensity Variation ◽  
Vertical Wind ◽  
Intensity Change ◽  
Rapid Intensification ◽  
Philippine Sea ◽  
Anomalous Anticyclone ◽  
Upper Level

Previous studies have shown that background oceanic and atmospheric environments can influence not only the formation but also the intensity of tropical cyclones. Typhoon Soudelor in August 2015 is notable in that it underwent two rapid intensifications as the storm passed over the Philippine Sea where the 26 °C isotherm (Z26) was deeper than 100 m and warm eddies abounded. At the same time, prior to the storm’s arrival, an anomalous upper-level anticyclone developed south of Japan and created a weakened vertical wind shear (Vs) environment that extended into the Philippine Sea. This study examines how the rapid intensification of Typhoon Soudelor may be related to the observed variations of Z26, Vs and other environmental fields as the storm crossed over them. A regression analysis indicates that the contribution to Soudelor’s intensity variation from Vs is the largest (62%), followed by Z26 (27%) and others. Further analyses using composites then indicate that the weak vertical wind shear produced by the aforementioned anomalous anticyclone is a robust feature in the western North Pacific during the developing summer of strong El Ninos with Oceanic Nino Index (ONI) > 1.5.

A Statistical Perspective on Wind Profiles and Vertical Wind Shear in Tropical Cyclone Environments of the Northern Hemisphere

2017 ◽  
Vol 145 (1) ◽  
pp. 361-378 ◽  
Author(s):  
Peter M. Finocchio ◽  
Sharanya J. Majumdar
Keyword(s):  
Tropical Cyclone ◽  
Northern Hemisphere ◽  
Wind Shear ◽  
Deep Layer ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Vertical Shear ◽  
Intensity Change ◽  
Upper Level ◽  
Wind Profiles

Abstract A statistical analysis of tropical cyclone (TC) environmental wind profiles is conducted in order to better understand how vertical wind shear influences TC intensity change. The wind profiles are computed from global atmospheric reanalyses around the best track locations of 7554 TC cases in the Northern Hemisphere tropics. Mean wind profiles within each basin exhibit significant differences in the magnitude and direction of vertical wind shear. Comparisons between TC environments and randomly selected “non-TC” environments highlight the synoptic regimes that support TCs in each basin, which are often characterized by weaker deep-layer shear. Because weaker deep-layer shear may not be the only aspect of the environmental flow that makes a TC environment more favorable for TCs, two new parameters are developed to describe the height and depth of vertical shear. Distributions of these parameters indicate that, in both TC and non-TC environments, vertical shear most frequently occurs in shallow layers and in the upper troposphere. Linear correlations between each shear parameter and TC intensity change show that shallow, upper-level shear is slightly more favorable for TC intensification. But these relationships vary by basin and neither parameter independently explains more than 5% of the variance in TC intensity change between 12 and 120 h. As such, the shear height and depth parameters in this study do not appear to be viable predictors for statistical intensity prediction, though similar measures of midtropospheric vertical wind shear may be more important in particularly challenging intensity forecasts.

Observed Processes Underlying the Favorable Vortex Repositioning Early in the Development of Hurricane Dorian (2019).

2021 ◽  
Author(s):  
George R. Alvey ◽  
Michael Fischer ◽  
Paul Reasor ◽  
Jonathan Zawislak ◽  
Robert Rogers
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Doppler Radar ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
In Situ Data ◽  
Upper Level

AbstractDorian’s evolution from a weak, disorganized tropical storm to a rapidly intensifying hurricane is documented through a unique multi-platform synthesis of NOAA’s P-3 tail-Doppler radar, airborne in situ data, and Meteo-France’s Martinique and Guadeloupe ground radar network. Dorian initially struggled to intensify with a misaligned vortex in moderate mid-tropospheric vertical wind shear that also allowed detrimental impacts from dry air near the inner core. Despite vertical wind shear eventually decreasing to less than 5 m/s and an increasingly symmetric distribution of stratiform precipitation, the vortex maintained its misalignment with asymmetric convection for 12 hours. Then, as the low-level circulation (LLC) approached St. Lucia, deep convection near the LLC’s center dissipated, the LLC broadened, and precipitation expanded radially outwards from the center temporally coinciding with the diurnal cycle. Convection then developed farther downtilt within a more favorable, humid environment and deepened appreciably at least partially due to interaction with Martinique. A distinct repositioning of the LLC towards Martinique is induced by spin-up of a mesovortex into a small, compact LLC.It is hypothesized that this somewhat atypical reformation event and the repositioning of the vortex into a more favorable environment, farther from detrimental dry mid-tropospheric air, increased its favorability for the rapid intensification that subsequently ensued. Although the repositioning resulted in tilt reducing to less than the scale of the vortex itself, the pre-existing broad mid-upper level cyclonic envelope remained intact with continued misalignment observed between the mid-level center and repositioned LLC even during the early stages of rapid intensification.

scholarly journals Simulation of Rapid Intensification of Super Typhoon Lekima (2019). Part I: Evolution Characteristics of Asymmetric Convection Under Upper-Level Vertical Wind Shear

2021 ◽  
Vol 9 ◽  
Author(s):  
Qijun Huang ◽  
Xuyang Ge ◽  
Melinda Peng
Keyword(s):  
Wind Shear ◽  
Inner Core ◽  
Thermal Structure ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Rapid Intensification ◽  
Super Typhoon ◽  
Storm Center ◽  
Upper Level

The role of the upper-level vertical wind shear (VWS) on the rapid intensification (RI) of super typhoon Lekima (2019) is investigated with a high-resolution numerical simulation. Our simulation shows that under moderate upper-level easterly VWS, the tilting-induced convective asymmetry is transported from the initially downshear quadrant to the upshear quadrant and wrapped around the storm center by the cyclonic flow of the storm while moving inward. This process enhances upward motions at the upshear flank and creates upper-level divergent flow. As such, the establishment of outflow acts against the environmental flow to reduce the VWS, allowing vertical alignment of the storm. The organized outflow plays an important role in sustaining the inner-core deep convection by modulating the environmental upper-level thermal structure. Accompanying deep convective bursts (CBs), cold anomalies are generated in the tropopause layer due to the adiabatic cooling by the upward motion and radiative process associated with the cloud anvil. Physically, cold anomalies at the tropopause locally destabilize the atmosphere and enhance the convections and the secondary circulation. The CBs continue to develop episodically through this process as they wrap around the storm center to form a symmetric eyewall. The results suggest that deep convections are capable of reducing the upper-level VWS, promoting the development of upper-level outflow. Lekima overcame the less favorable environment and eventually intensified to become a super typhoon.

scholarly journals Influence of Environmental Vertical Wind Shear on the Intensity of Hurricane-Strength Tropical Cyclones in the Australian Region

2005 ◽  
Vol 133 (12) ◽  
pp. 3644-3660 ◽  
Author(s):  
Linda A. Paterson ◽  
Barry N. Hanstrum ◽  
Noel E. Davidson ◽  
Harry C. Weber
Keyword(s):  
Tropical Cyclones ◽  
Wind Shear ◽  
Time Lag ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
Negative Effects ◽  
Australian Region ◽  
Upper Level ◽  
The Impact

Abstract NCEP–NCAR reanalyses have been used to investigate the impact of environmental wind shear on the intensity change of hurricane-strength tropical cyclones in the Australian region. A method of removing a symmetric vortex from objective analyses is used to isolate the environmental flow. A relationship between wind shear and intensity change is documented. Correlations between wind shear and intensity change to 36 h are of the order of 0.4. Typically a critical wind shear value of ∼10 m s−1 represents a change from intensification to dissipation. Wind shear values of less than ∼10 m s−1 favor intensification, with values between ∼2 and 4 m s−1 favoring rapid intensification. Shear values greater than ∼10 m s−1 are associated with weakening, with values greater than 12 m s−1 favoring rapid weakening. There appears to be a time lag between the onset of increased vertical wind shear and the onset of weakening, typically between 12 and 36 h. A review of synoptic patterns during intensification-weakening cycles revealed the juxtaposition of a low-level anticyclone on the poleward side of the storm and an approaching 200-hPa trough to the west. In most cases, intensification commences under weak shear with the approach of the trough, but just prior to the onset of high shear. Further, based on described cases when wind shear was weak but no intensification occurred, it is suggested that weak shear is a necessary but not a sufficient condition for intensification. It is illustrated here that the remote dynamical influence of upper-level potential vorticity anomalies may offset the negative effects of environmental shear.

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