Intensification of Hurricane Sandy (2012) through Extratropical Warm Core Seclusion

2013 ◽  
Vol 141 (12) ◽  
pp. 4296-4321 ◽  
Author(s):  
Thomas J. Galarneau ◽  
Christopher A. Davis ◽  
Melvyn A. Shapiro
Keyword(s):  
New Jersey ◽  
Rhode Island ◽  
North Atlantic ◽  
Gulf Stream ◽  
Diabatic Heating ◽  
Hurricane Sandy ◽  
Cyclonic Vorticity ◽  
Near Surface ◽  
Warm Core ◽  
Upper Level

Abstract Hurricane Sandy's landfall along the New Jersey shoreline at 2330 UTC 29 October 2012 produced a catastrophic storm surge stretching from New Jersey to Rhode Island that contributed to damage in excess of $50 billion—the sixth costliest U.S. tropical cyclone on record since 1900—and directly caused 72 fatalities. Hurricane Sandy's life cycle was marked by two upper-level trough interactions while it moved northward over the western North Atlantic on 26–29 October. During the second trough interaction on 29 October, Sandy turned northwestward and intensified as cold continental air encircled the warm core vortex and Sandy acquired characteristics of a warm seclusion. The aim of this study is to determine the dynamical processes that contributed to Sandy's secondary peak in intensity during its warm seclusion phase using high-resolution numerical simulations. The modeling results show that intensification occurred in response to shallow low-level convergence below 850 hPa that was consistent with the Sawyer–Eliassen solution for the secondary circulation that accompanied the increased baroclinicity in the radial direction. Additionally, cyclonic vertical vorticity generated by tilting of horizontal vorticity along an axis of frontogenesis northwest of Sandy was axisymmetrized. The axis of frontogenesis was anchored to the Gulf Stream in a region of near-surface differential diabatic heating. The unusual northwestward track of Sandy allowed the cyclonic vorticity over the Gulf Stream to form ahead of the main vortex and be readily axisymmetrized. The underlying dynamics driving intensification were nontropical in origin, and supported the reclassification of Sandy as extratropical prior to landfall.

Future changes in North Atlantic winter cyclones in CESM-LENS: cyclone intensity and horizontal wind speed

2021 ◽  
Author(s):  
Edgar Dolores Tesillos ◽  
Stephan Pfahl ◽  
Franziska Teubler
Keyword(s):  
Wind Speed ◽  
North Atlantic ◽  
Diabatic Heating ◽  
Horizontal Wind ◽  
Horizontal Wind Speed ◽  
Near Surface ◽  
Low Level ◽  
Current Century ◽  
Community Earth System Model ◽  
Upper Level

<p>Strong low-level winds are among the most impactful effects of extratropical cyclones on society.  The wind intensity and the spatial distribution of wind maxima may change in a warming climate, however, the dynamics involved are not clear. Here, structural and dynamical changes of North Atlantic cyclones in a warmer climate close to the end of the current century are investigated with storm-relative composites based on Community Earth System Model Large Ensemble (CESM-LE) simulations. Furthermore, a piecewise potential vorticity inversion is applied, to attribute such changes in low-level winds to changes in PV anomalies at different levels.</p><p>We identify an extended wind footprint southeast of the cyclone centre, where the wind speed tends to intensify in a warmer climate. Both an amplified low-level PV anomaly driven by enhanced diabatic heating and a dipole change in upper-level PV anomalies contribute to this wind intensification. On the contrary, wind changes associated with lower- and upper-level PV anomalies mostly compensate each other upstream of the cyclone center. Wind changes at upper levels are dominated by changes in upper-level PV anomalies and the background flow. All together, our results indicate that a complex interation of enhanced diabatic heating and altered upper-tropospheric wave dynamics shape future changes in near-surface winds in North Atlantic cyclones.</p>

scholarly journals Future changes in North Atlantic winter cyclones in CESM-LENS. Part I: cyclone intensity, PV anomalies and horizontal wind speed

2021 ◽  
Author(s):  
Edgar Dolores-Tesillos ◽  
Franziska Teubler ◽  
Stephan Pfahl
Keyword(s):  
Wind Speed ◽  
North Atlantic ◽  
Potential Vorticity ◽  
Structural Changes ◽  
Diabatic Heating ◽  
Horizontal Wind ◽  
Near Surface ◽  
Cyclone Intensity ◽  
Low Level ◽  
Upper Level

Abstract. Strong low-level winds associated with extratropical cyclones can cause substantial impacts on society. The wind intensity and the spatial distribution of wind maxima may change in a warming climate; however, the involved changes in cyclone structure and dynamics are unclear. Here, such structural changes of strong North Atlantic cyclones in a warmer climate close to the end of the current century are investigated with storm-relative composites based on Community Earth System Model Large Ensemble (CESM-LENS) simulations. Furthermore, a piecewise potential vorticity inversion is applied to associate such changes in low-level winds to changes in potential vorticity (PV) anomalies at different levels. Projected changes in cyclone intensity are generally rather small. However, using cyclone-relative composites, we identify an extended wind footprint southeast of the center of strong cyclones, where the wind speed tends to intensify in a warmer climate. Both an amplified low-level PV anomaly driven by enhanced diabatic heating and a dipole change in upper-level PV anomalies contribute to this wind intensification. On the contrary, wind changes associated with lower- and upper-level PV anomalies mostly compensate each other upstream of the cyclone center. Wind changes at upper levels are dominated by changes in upper-level PV anomalies and the background flow. All together, our results indicate that a complex interaction of enhanced diabatic heating and altered non-linear upper-tropospheric wave dynamics shape future changes in near-surface winds in North Atlantic cyclones.

Synoptic- and Frontal-Scale Influences on Tropical Transition Events in the Atlantic Basin. Part I: A Six-Case Survey

2009 ◽  
Vol 137 (11) ◽  
pp. 3605-3625 ◽  
Author(s):  
Andrew L. Hulme ◽  
Jonathan E. Martin
Keyword(s):  
North Atlantic ◽  
Vertical Shear ◽  
Structure Characteristic ◽  
Sea Level Pressure ◽  
Near Surface ◽  
Warm Core ◽  
Warm Front ◽  
Surface Cyclone ◽  
Upper Level ◽  
Baroclinic Zone

Abstract The process by which a baroclinic, vertically sheared, extratropical cyclone is transformed into a warm-core, vertically stacked tropical cyclone is known as tropical transition. Six recent tropical transitions of strong extratropical precursors in the subtropical North Atlantic are compared to better understand the manner by which some of the canonical structures and dynamical processes of extratropical cyclones serve to precondition the cyclone for transition. All six transitions resulted from the interaction between a surface baroclinic zone and an upper-level trough. During the extratropical cyclogenesis of each storm, a period of intense near-surface frontogenesis along a bent-back warm front occurred to the northwest of each sea level pressure minimum. Within the resultant circulation, diabatic redistribution of potential vorticity (PV) promoted the growth of a low-level PV maximum near the western end of the warm front. Concurrently, the upper-level PV anomaly associated with each trough was deformed into the treble clef structure characteristic of extratropical occlusion. Thus, by the end of the transitioning process and just prior to its becoming fully tropical, each cyclone was directly beneath a weakened upper-level trough in a column with weak vertical shear and weak thermal contrasts. The presence of convection to the west and southwest of the surface cyclone at the time of frontogenesis and upper-level PV deformation suggests that diabatic heating contributes significantly to the process of tropical transition in a manner that is consistent with its role in extratropical occlusion. Thus, it is suggested that tropical transition is encouraged whenever extratropical occlusion occurs over a sufficiently warm ocean surface.

Numerical Study on the Extremely Rapid Intensification of an Intense Tropical Cyclone: Typhoon Ida (1958)

2015 ◽  
Vol 72 (11) ◽  
pp. 4194-4217 ◽  
Author(s):  
Sachie Kanada ◽  
Akiyoshi Wada
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Numerical Study ◽  
Vertical Wind Shear ◽  
Leading Edge ◽  
Central Pressure ◽  
Rapid Intensification ◽  
Near Surface ◽  
Warm Core ◽  
Upper Level

Abstract Extremely rapid intensification (ERI) of Typhoon Ida (1958) was examined with a 2-km-mesh nonhydrostatic model initiated at three different times. Ida was an extremely intense tropical cyclone with a minimum central pressure of 877 hPa. The maximum central pressure drop in 24 h exceeded 90 hPa. ERI was successfully simulated in two of the three experiments. A factor crucial to simulating ERI was a combination of shallow-to-moderate convection and tall, upright convective bursts (CBs). Under a strong environmental vertical wind shear (>10 m s−1), shallow-to-moderate convection on the downshear side that occurred around the intense near-surface inflow moistened the inner-core area. Meanwhile, dry subsiding flows on the upshear side helped intensification of midlevel (8 km) inertial stability. First, a midlevel warm core appeared below 10 km in the shallow-to-moderate convection areas, being followed by the development of the upper-level warm core associated with tall convection. When tall, upright, rotating CBs formed from the leading edge of the intense near-surface inflow, ERI was triggered at the area in which the air became warm and humid. CBs penetrated into the upper troposphere, aligning the areas with high vertical vorticity at low to midlevels. The upper-level warm core developed rapidly in combination with the midlevel warm core. Under the preconditioned environment, the formation of the upright CBs inside the radius of maximum wind speeds led to an upright axis of the secondary circulation within high inertial stability, resulting in a very rapid central pressure deepening.

scholarly journals Physical Process Contributions to the Development of a Super Explosive Cyclone Over the Gulf Stream

2021 ◽  
Vol 9 ◽  
Author(s):  
Shuqin Zhang ◽  
Chunlei Liu ◽  
Jianjun Xu ◽  
Shaojing Zhang ◽  
Ruoying Tang ◽  
...  
Keyword(s):  
Gulf Stream ◽  
Diabatic Heating ◽  
Rapid Development ◽  
Cyclonic Vorticity ◽  
Upper Troposphere ◽  
Explosive Cyclone ◽  
Weather Forecasts ◽  
Vorticity Advection ◽  
Medium Range ◽  
Water Vapor Convergence

Contributions of different physical processes to the development of a super explosive cyclone (SEC) migrating over the Gulf Stream with the maximum deepening rate of 3.45 Bergeron were investigated using the ERA5 atmospheric reanalysis from European Centre for Medium-Range Weather Forecasts (ECMWF). The evolution of the SEC resembled the Shapiro-Keyser model. The moisture transported to the bent-back front by easterlies from Gulf Stream favored precipitation and enhanced the latent heat release. The bent-back front and warm front were dominated by the water vapor convergence in the mid-low troposphere, the cyclonic-vorticity advection in the mid-upper troposphere and the divergence in the upper troposphere. These factors favored the rapid development of the SEC, but their contributions showed significant differences during the explosive-developing stage. The diagnostic results based on the Zwack-Okossi equation suggested that the early explosive development of the SEC was mainly forced by the diabatic heating in the mid-low troposphere. From the early explosive-developing moment to maximum-deepening-rate moment, the diabatic heating, warm-air advection and cyclonic-vorticity advection were all enhanced significantly, their combination forced the most explosive development, and the diabatic heating had the biggest contribution, followed by the warm-air advection and cyclonic-vorticity advection, which is different from the previous studies of ECs over the Northwestern Atlantic. The cross section of these factors suggested that during the rapid development, the cyclonic-vorticity advection was distributed and enhanced significantly in the mid-low troposphere, the warm-air advection was strengthened significantly in the mid-low and upper troposphere, and the diabatic heating was distributed in the middle troposphere.

SST fronts along the Gulf Stream and Kuroshio affect the atmospheric winter climatology primarily in the absence of storms

2021 ◽  
Author(s):  
Thomas Spengler ◽  
Leonidas Tsopouridis ◽  
Clemens Spensberger
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Heat Fluxes ◽  
Cyclone Activity ◽  
Surface Heat Fluxes ◽  
The North ◽  
Upper Level ◽  
Upper Level Jet ◽  
Kuroshio Region

<p>The Gulf Stream and Kuroshio regions feature strong sea surface temperature (SST) gradients that influence cyclone development and the storm track. Smoothing the SSTs in either the North Atlantic or North Pacific has been shown to yield a reduction in cyclone activity, surface heat fluxes, and precipitation, as well as a southward shift of the storm track and the upper-level jet. To what extent these changes are attributable to changes in individual cyclone behaviour, however, remains unclear. Comparing simulations with realistic and smoothed SSTs in the atmospheric general circulation model AFES, we find that the intensification of individual cyclones in the Gulf Stream or Kuroshio region is only marginally affected by reducing the SST gradient. In contrast, we observe considerable changes in the climatological mean state, with a reduced cyclone activity in the North Atlantic and North Pacific storm tracks that are also shifted equator-ward in both basins. The upper-level jet in the Atlantic also shifts equator-ward, while the jet in the Pacific strengthens in its climatological position and extends further east. Surface heat fluxes, specific humidity, and precipitation also respond strongly to the smoothing of the SST, with a considerable decrease of their mean values on the warm side of the SST front. This decrease is more pronounced in the Gulf Stream than in the Kuroshio region, due to the amplified decrease in SST along the Gulf Stream SST front.  Considering the pertinent variables occurring within different radii of cyclones in each basin over their entire lifetime, we find cyclones to play only a secondary role in explaining the mean states differences between smoothed and realistic SST experiments.</p>

Double warm-core structure and potential vorticity diagnosis during the rapid intensification of Supertyphoon Lekima (2019)

2021 ◽  
Author(s):  
Donglei Shi ◽  
Guanghua Chen
Keyword(s):  
Potential Vorticity ◽  
Diabatic Heating ◽  
Inner Core ◽  
Deep Layer ◽  
Rapid Intensification ◽  
Latent Heat Release ◽  
Wind Fields ◽  
Warm Core ◽  
Upper Level ◽  
Pv Generation

AbstractThe rapid intensification (RI) of supertyphoon Lekima (2019) is investigated from the perspective of balanced potential vorticity (PV) dynamics using a high-resolution numerical simulation. The PV budget shows that the inner-core PV anomalies (PVAs) formed during the RI mainly comprise an eyewall PV tower generated by diabatic heating, a high-PV bridge extending into the eye resulting from the PV mixing, and an upper-tropospheric high-PV core induced by the PV intrusion from stratosphere. The inversion of the total PVA at the end of the RI captures about 90% of changes in pressure and wind fields, indicating that the storm is quasi-balanced. The piecewise PV inversion further demonstrates that the eyewall and mixed PVAs induce the upper-level and midlevel warm cores in the eye region, respectively. The two warm cores cause nearly all the balanced central pressure decrease and thus dominate the RI, with the contribution of the upper warm core being twice that of the midlevel one. In contrast, the upper-tropospheric PV core induces significant warming near the tropopause and deep-layer cooling beneath, reinforcing the upper-level warm core but causing little surface pressure drop.By comparing the diabatic PV generation due to the convective burst (CB) and non-CB precipitation, we found that the non-CB precipitation accounts for a larger portion for the eyewall PVA and thus the associated upper-level warming, distinct from previous studies that primarily attributed the upper-level warm-core formation to the CB. Nevertheless, CBs act to be more efficient PV generators due to their vigorous latent heat release and are thus favorable for RI.

On the Warm Core of a Tropical Cyclone Formed near the Tropopause

2015 ◽  
Vol 72 (2) ◽  
pp. 551-571 ◽  
Author(s):  
Tomoki Ohno ◽  
Masaki Satoh
Keyword(s):  
Diabatic Heating ◽  
Lower Stratosphere ◽  
Potential Temperature ◽  
Numerical Results ◽  
Forced Flow ◽  
Mature Stage ◽  
Warm Core ◽  
Budget Analysis ◽  
Tangential Wind ◽  
Upper Level

Abstract On the basis of numerical results of a three-dimensional model diagnosed using balance dynamics, a mechanism by which the upper-level warm core of tropical cyclones (TCs) forms is proposed. The numerical results reveal that an upper-level warm core develops when TCs intensify just prior to reaching the mature stage. Potential temperature budget analysis reveals that for the tendency of potential temperature, the azimuthal-mean component of advection is dominant at the upper level of the eye at the mature stage. Sawyer–Eliassen diagnosis shows that tendencies due to forced flow by diabatic heating and diffusion of tangential wind are dominant in the eye and are negatively correlated to each other. The distributions of the diabatic heating in the simulated TC are not peculiar. Therefore, it is unlikely that the heating distribution itself is the primary cause of the flow from the lower stratosphere. The analyses of forced circulations of idealized vortices show that the upper-level subsidence is enhanced in the eye when the vortex is sufficiently tall to penetrate the statically stable stratosphere. This result is deduced because the stronger inertial stability extends the response to the heating of the lower stratosphere and causes upper-level adiabatic warming. Therefore, the upper-level warm core emerges if angular momentum is transported into the lower stratosphere due to processes such as convective bursts. The present analysis suggests that TCs can be even stronger than that expected by theories in which the TC vortex is confined in the troposphere.

scholarly journals Development of North Atlantic Tropical Disturbances near Upper-Level Potential Vorticity Streamers

2015 ◽  
Vol 72 (2) ◽  
pp. 572-597 ◽  
Author(s):  
Thomas J. Galarneau ◽  
Ron McTaggart-Cowan ◽  
Lance F. Bosart ◽  
Christopher A. Davis
Keyword(s):  
Water Vapor ◽  
North Atlantic ◽  
Potential Vorticity ◽  
Synoptic Climatology ◽  
Primary Role ◽  
Synoptic Scale ◽  
Near Surface ◽  
The North ◽  
The North Atlantic ◽  
Upper Level

Abstract Tropical cyclone (TC) development near upper-level potential vorticity (PV) streamers in the North Atlantic is studied from synoptic climatology, composite, and case study perspectives. Midlatitude anticyclonic wave breaking is instrumental in driving PV streamers into subtropical and tropical latitudes, in particular near the time-mean midocean trough identified previously as the tropical upper-tropospheric trough. Twelve TCs developed within one Rossby radius of PV streamers in the North Atlantic from June through November 2004–08. This study uses composite analysis in the disturbance-relative framework to compare the structural and thermodynamic evolution for developing and nondeveloping cases. The results show that incipient tropical disturbances are embedded in an environment characterized by 850–200-hPa westerly vertical wind shear and mid- and upper-level quasigeostrophic ascent associated with the PV streamer, with minor differences between developing and nondeveloping cases. The key difference in synoptic-scale flow between developing and nondeveloping cases is the strength of the anticyclone north of the incipient tropical disturbance. The developing cases are marked by a stronger near-surface pressure gradient and attendant easterly flow north of the vortex, which drives enhanced surface latent heat fluxes and westward (upshear) water vapor transport. This evolution in water vapor facilitates an upshear propagation of convection, and the diabatically influenced divergent outflow erodes the PV streamer aloft by negative advection of PV by the divergent wind. This result suggests that the PV streamer plays a secondary role in TC development, with the structure and intensity of the synoptic-scale anticyclone north of the incipient vortex playing a primary role.

scholarly journals The Basic Ingredients of the North Atlantic Storm Track. Part II: Sea Surface Temperatures

2011 ◽  
Vol 68 (8) ◽  
pp. 1784-1805 ◽  
Author(s):  
David James Brayshaw ◽  
Brian Hoskins ◽  
Michael Blackburn
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Storm Track ◽  
Horizontal Wind ◽  
Near Surface ◽  
Continental Scale ◽  
The North ◽  
The North Atlantic ◽  
The Impact ◽  
Sst Gradient

Abstract The impact of North Atlantic SST patterns on the storm track is investigated using a hierarchy of GCM simulations using idealized (aquaplanet) and “semirealistic” boundary conditions in the atmospheric component (HadAM3) of the third climate configuration of the Met Office Unified Model (HadCM3). This framework enables the mechanisms determining the tropospheric response to North Atlantic SST patterns to be examined, both in isolation and in combination with continental-scale landmasses and orography. In isolation, a “Gulf Stream” SST pattern acts to strengthen the downstream storm track while a “North Atlantic Drift” SST pattern weakens it. These changes are consistent with changes in the extratropical SST gradient and near-surface baroclinicity, and each storm-track response is associated with a consistent change in the tropospheric jet structure. Locally enhanced near-surface horizontal wind convergence is found over the warm side of strengthened SST gradients associated with ascending air and increased precipitation, consistent with previous studies. When the combined SST pattern is introduced into the semirealistic framework (including the “North American” continent and the “Rocky Mountains”), the results suggest that the topographically generated southwest–northeast tilt in the North Atlantic storm track is enhanced. In particular, the Gulf Stream shifts the storm track south in the western Atlantic whereas the strong high-latitude SST gradient in the northeastern Atlantic enhances the storm track there.

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