scholarly journals On the Rapid Intensification of Hurricane Wilma (2005). Part I: Model Prediction and Structural Changes

2011 ◽  
Vol 26 (6) ◽  
pp. 885-901 ◽  
Author(s):  
Hua Chen ◽  
Da-Lin Zhang ◽  
James Carton ◽  
Robert Atlas
Keyword(s):  
Model Prediction ◽  
Structural Changes ◽  
Inner Core ◽  
Initial Conditions ◽  
Single Case ◽  
Inversion Layer ◽  
Rapid Intensification ◽  
Structural Variations ◽  
Hurricane Wilma ◽  
Intensity Changes

Abstract In this study, a 72-h cloud-permitting numerical prediction of Hurricane Wilma (2005), covering its initial 18-h spinup, an 18-h rapid intensification (RI), and the subsequent 36-h weakening stage, is performed using the Weather Research Forecast Model (WRF) with the finest grid length of 1 km. The model prediction uses the initial and lateral boundary conditions, including the bogus vortex, that are identical to the Geophysical Fluid Dynamics Laboratory’s then-operational data, except for the time-independent sea surface temperature field. Results show that the WRF prediction compares favorably in many aspects to the best-track analysis, as well as satellite and reconnaissance flight-level observations. In particular, the model predicts an RI rate of more than 4 hPa h−1 for an 18-h period, with the minimum central pressure of less than 889 hPa. Of significance is that the model captures a sequence of important inner-core structural variations associated with Wilma’s intensity changes, namely, from a partial eyewall open to the west prior to RI to a full eyewall at the onset of RI, rapid eyewall contraction during the initial spinup, the formation of double eyewalls with a wide moat area in between during the most intense stage, and the subsequent eyewall replacement leading to the weakening of Wilma. In addition, the model reproduces the boundary layer growth up to 750 hPa with an intense inversion layer above in the eye. Recognizing that a single case does not provide a rigorous test of the model predictability due to the stochastic nature of deep convection, results presented herein suggest that it is possible to improve forecasts of hurricane intensity and intensity changes, and especially RI, if the inner-core structural changes and storm size could be reasonably predicted in an operational setting using high-resolution cloud-permitting models with realistic initial conditions and model physical parameterizations.

Fluctuations in inner-core structure during the rapid intensification of Super Typhoon Nepartak (2016)

2020 ◽  
Author(s):  
Sam Hardy ◽  
Juliane Schwendike ◽  
Roger K. Smith ◽  
Chris J. Short ◽  
Michael J. Reeder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Structural Changes ◽  
Inner Core ◽  
Single Case ◽  
Three Dimensional ◽  
Core Structure ◽  
Rapid Intensification ◽  
Budget Analysis ◽  
Tangential Wind ◽  
The Mean

AbstractThe key physical processes responsible for inner-core structural changes and associated fluctuations in the intensification rate for a recent, high-impact western North Pacific tropical cyclone that underwent rapid intensification (Nepartak, 2016) are investigated using a set of convection-permitting ensemble simulations. Fluctuations in the inner-core structure between ring-like and monopole states develop in 60% of simulations. A tangential momentum budget analysis of a single fluctuation reveals that during the ring-like phase, the tangential wind generally intensifies, whereas during the monopole phase, the tangential wind remains mostly constant. In both phases, the mean advection terms spin up the tangential wind in the boundary layer, whereas the eddy advection terms deepen the storm’s cyclonic circulation by spinning up the tangential wind between 1.5 and 4 km. Further calculations of the azimuthally-averaged, radially-integrated vertical mass flux suggest that periods of near-constant tangential wind tendency are accompanied by a weaker eyewall updraft, which is unable to evacuate all the mass converging in the boundary layer. Composite analyses calculated from 18 simulations produce qualitatively similar results to those from the single case, a finding that is also in agreement with some previous observational and modelling studies. Above the boundary layer, the integrated contribution of the eddy term to the tangential wind tendency is over 80% of the contribution from the mean term, irrespective of inner-core structure. Our results strongly indicate that to fully understand the storm’s three-dimensional evolution, the contribution of the eddies must be quantified.

scholarly journals On the Rapid Intensification of Hurricane Wilma (2005). Part II: Convective Bursts and the Upper-Level Warm Core

2013 ◽  
Vol 70 (1) ◽  
pp. 146-162 ◽  
Author(s):  
Hua Chen ◽  
Da-Lin Zhang
Keyword(s):  
Inner Core ◽  
Static Stability ◽  
Rapid Intensification ◽  
Important Ingredient ◽  
High Resolution Data ◽  
Hurricane Wilma ◽  
Warm Core ◽  
Convective Bursts ◽  
Upper Level ◽  
The Relationship

Abstract Previous studies have focused mostly on the roles of environmental factors in the rapid intensification (RI) of tropical cyclones (TCs) because of the lack of high-resolution data in inner-core regions. In this study, the RI of TCs is examined by analyzing the relationship between an upper-level warm core, convective bursts (CBs), sea surface temperature (SST), and surface pressure falls from 72-h cloud-permitting predictions of Hurricane Wilma (2005) with the finest grid size of 1 km. Results show that both the upper-level inertial stability increases and static stability decreases sharply 2–3 h prior to RI, and that the formation of an upper-level warm core, from the subsidence of stratospheric air associated with the detrainment of CBs, coincides with the onset of RI. It is found that the development of CBs precedes RI, but most subsidence warming radiates away by gravity waves and storm-relative flows. In contrast, many fewer CBs occur during RI, but more subsidence warming contributes to the balanced upper-level cyclonic circulation in the warm-core (as intense as 20°C) region. Furthermore, considerable CB activity can still take place in the outer eyewall as the storm weakens during its eyewall replacement. A sensitivity simulation, in which SSTs are reduced by 1°C, shows pronounced reductions in the upper-level warm-core intensity and CB activity. It is concluded that significant CB activity in the inner-core regions is an important ingredient in generating the upper-level warm core that is hydrostatically more efficient for the RI of TCs, given all of the other favorable environmental conditions.

Inner-core dynamics during the rapid intensification of Hurricane Wilma (2005) with a steady radius of the maximum wind

2020 ◽  
Author(s):  
Nannan Qin ◽  
Da-Lin Zhang ◽  
William Miller ◽  
Chanh Kieu
Keyword(s):  
Inner Core ◽  
Vertical Motion ◽  
Rapid Intensification ◽  
Flux Divergence ◽  
Hurricane Wilma ◽  
Maximum Wind ◽  
Budget Analysis ◽  
Core Dynamics ◽  
Major Process ◽  
Frictional Dissipation

<p>Recent studies show that some hurricanes may undergo rapid intensification (RI) without contracting the radius of maximum wind (RMW). A cloud-resolving WRF-prediction of Hurricane Wilma (2005) is used herein to examine what controls the RMW contraction and how a hurricane could undergo RI without contraction. Results show that the processes controlling the RMW contraction are different within and above the planetary boundary layer (PBL). In the PBL, radial inflows contribute to contraction, with frictional dissipation acting as an inhibiting factor. Above the PBL, radial outflows and vertical motion govern the RMW contraction, with the former inhibiting it. A budget analysis of absolute angular momentum (AAM) shows that the radial AAM flux convergence is the major process accounting for the spinup of the maximum rotation, while the vertical flux divergence of AAM and the frictional sink in the PBL oppose the spinup. During the RI stage with no RMW contraction, the local AAM tendencies in the eyewall are smaller in magnitude and narrower in width than those during the contracting RI stage. In addition, the AAM following the time-dependent RMW decreases with time in the PBL and remains nearly constant aloft during the contracting stage, whereas it increases during the non-contracting stage. These results reveal different constraints for the RMW contraction and RI, and help explain why a hurricane vortex can still intensify after the RMW ceases contraction</p>

Numerical Simulation of Hurricane Bonnie (1998). Part II: Sensitivity to Varying Cloud Microphysical Processes

2006 ◽  
Vol 63 (1) ◽  
pp. 109-126 ◽  
Author(s):  
Tong Zhu ◽  
Da-Lin Zhang
Keyword(s):  
Large Scale ◽  
Structural Changes ◽  
Inner Core ◽  
Cloud Microphysics ◽  
Cloud Water ◽  
Heat Of Fusion ◽  
Hurricane Intensity ◽  
Cloud Band ◽  
Intensity Changes ◽  
Hurricane Bonnie

Abstract In this study, the effects of various cloud microphysics processes on the hurricane intensity, precipitation, and inner-core structures are examined with a series of 5-day explicit simulations of Hurricane Bonnie (1998), using the results presented in Part I as a control run. It is found that varying cloud microphysics processes produces little sensitivity in hurricane track, except for very weak and shallow storms, but it produces pronounced departures in hurricane intensity and inner-core structures. Specifically, removing ice microphysics produces the weakest (15-hPa underdeepening) and shallowest storm with widespread cloud water but little rainwater in the upper troposphere. Removing graupel from the control run generates a weaker hurricane with a wider area of precipitation and more cloud coverage in the eyewall due to the enhanced horizontal advection of hydrometeors relative to the vertical fallouts (or increased water loading). Turning off the evaporation of cloud water and rainwater leads to the most rapid deepening storm (i.e., 90 hPa in 48 h) with the smallest radius but a wider eyewall and the strongest eyewall updrafts. The second strongest storm, but with the most amount of rainfall, is obtained when the melting effect is ignored. It is found that the cooling due to melting is more pronounced in the eyewall where more frozen hydrometeors, especially graupel, are available, whereas the evaporative cooling occurs more markedly when the storm environment is more unsaturated. It is shown that stronger storms tend to show more compact eyewalls with heavier precipitation and more symmetric structures in the warm-cored eye and in the eyewall. It is also shown that although the eyewall replacement scenarios occur as the simulated storms move into weak-sheared environments, the associated inner-core structural changes, timing, and location differ markedly, depending on the hurricane intensity. That is, the eyewall convection in weak storms tends to diminish shortly after being encircled by an outer rainband, whereas both the cloud band and the inner eyewall in strong storms tend to merge to form a new eyewall with a larger radius. The results indicate the importance of the Bergeron processes, including the growth and rapid fallout of graupel in the eyewall, and the latent heat of fusion in determining the intensity and inner-core structures of hurricanes, and the vulnerability of weak storms to the influence of large-scale sheared flows in terms of track, inner-core structures, and intensity changes.

Diagnosis of the Initial and Forecast Errors in the Numerical Simulation of the Rapid Intensification of Hurricane Emily (2005)

2009 ◽  
Vol 24 (5) ◽  
pp. 1236-1251 ◽  
Author(s):  
Zhaoxia Pu ◽  
Xuanli Li ◽  
Edward J. Zipser
Keyword(s):  
Numerical Simulation ◽  
Short Range ◽  
Inner Core ◽  
Initial Conditions ◽  
Forecast Errors ◽  
Rapid Intensification ◽  
Convective Structures ◽  
Level Data ◽  
Arw Model ◽  
Flight Level

Abstract A diagnostic study is conducted to examine the initial and forecast errors in a short-range numerical simulation of Hurricane Emily’s (2005) early rapid intensification. The initial conditions and the simulated hurricane vortices using high-resolution grids (1 and 3 km), generated from the Advanced Research version of the Weather Research and Forecasting (ARW) model and its three-dimensional variational data assimilation (3DVAR) systems, are compared with the flight-level data acquired from the U.S. Air Force C-130J aircraft data. Numerical simulation results show that the model fails at predicting the actual rapid intensification of the hurricane, although the initial intensity of the vortex matches the observed intensity. Comparing the model results with aircraft flight-level data, unrealistic thermal and convective structures of the storm eyewall are found in the initial conditions. In addition, the simulated eyewall does not contract rapidly enough during the model simulation. Increasing the model’s horizontal resolution from 3 to 1 km can help the model to produce a deeper storm and also a more realistic eye structure. However, even at 1 km the model is still not able to fully resolve the inner-core structures. To provide additional insight, a set of mesoscale reanalyses is generated through the assimilation of available satellite and aircraft dropsonde data into the ARW model throughout the whole simulation period at a 6-h interval. It is found that the short-range numerical simulation of the hurricane has been greatly improved by the mesoscale reanalysis; the data assimilation helps the model to reproduce stronger wind, thermal, and convective structures of the storm, and a more realistic eyewall contraction and eye structure. Results from this study suggest that a more accurate representation of the hurricane vortex, especially the inner-core structures in the initial conditions, is necessary for a more accurate forecast of hurricane rapid intensification.

scholarly journals Dramatic Inner-Core Tropopause Variability during the Rapid Intensification of Hurricane Patricia (2015)

2018 ◽  
Vol 146 (1) ◽  
pp. 119-134 ◽  
Author(s):  
Patrick Duran ◽  
John Molinari
Keyword(s):  
Cross Sections ◽  
Lower Stratosphere ◽  
Inner Core ◽  
Inversion Layer ◽  
Potential Temperature ◽  
Naval Research ◽  
Maximum Magnitude ◽  
Rapid Intensification ◽  
Office Of Naval Research ◽  
Upper Level

Abstract Dropsondes with horizontal spacing as small as 4 km were released from the stratosphere in rapidly intensifying Hurricane Patricia (2015) during the Office of Naval Research Tropical Cyclone Intensity experiment. These observations provide cross sections of unprecedented resolution through the inner core of a hurricane. On 21 October, Patricia exhibited a strong tropopause inversion layer (TIL) across its entire circulation, with a maximum magnitude of 5.1 K (100 m)−1. This inversion weakened between 21 and 22 October as potential temperature θ increased by up to 16 K just below the tropopause and decreased by up to 14 K in the lower stratosphere. Between 22 and 23 October, the TIL over the eye weakened further, allowing the tropopause to rise by 1 km. Meanwhile over Patricia’s secondary eyewall, the TIL restrengthened and bulged upward by about 700 m into what was previously the lower stratosphere. These observations support many aspects of recent modeling studies, including eyewall penetration into the stratosphere during rapid intensification (RI), the existence of a narrow inflow layer near the tropopause, and the role of subsidence from the stratosphere in developing an upper-level warm core. Three mechanisms of inner-core tropopause variability are hypothesized: destabilization of the TIL through turbulent mixing, weakening of the TIL over the eye through upper-tropospheric subsidence warming, and increasing tropopause height forced by overshooting updrafts in the eyewall. None of these processes are seen as the direct cause of RI, but rather part of the RI process that includes strong increases in boundary layer moist entropy.

How Does Hurricane Edouard (2014) Evolve toward Symmetry before Rapid Intensification? A High-Resolution Ensemble Study

2020 ◽  
Vol 77 (4) ◽  
pp. 1329-1351 ◽  
Author(s):  
George R. Alvey ◽  
Ed Zipser ◽  
Jonathan Zawislak
Keyword(s):  
High Resolution ◽  
Inner Core ◽  
Initial Conditions ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Tropical Storm ◽  
Sea Surface ◽  
Rapid Intensification ◽  
Upper Troposphere ◽  
Stratiform Precipitation

Abstract A 14-member high-resolution ensemble of Edouard (2014), a moderately sheared tropical storm that underwent rapid intensification (RI), is used to determine causes of vortex alignment and precipitation symmetry prior to RI. Half the members intensify similarly to the NHC’s best track, while the other seven ensemble members fail to reproduce intensification. Analyses of initial conditions (vertical wind shear, sea surface temperatures, relative humidity, vortex structure) reveal that lower humidity and weaker, more tilted vortices in nonintensifying members likely increase their susceptibility to boundary layer flushing episodes. As the simulations progress, vortex tilt, inner-core humidity, and azimuthal variations in the structure of precipitation best differentiate the two ensemble subsets. Although all members initially are slowly intensifying asymmetric storms, the RI members are unique in that they have more persistent deep convection downshear, which favors vortex alignment via the stretching term and/or precession. As deep convection transitions to stratiform precipitation and anvil clouds in the upshear quadrants, evaporation and sublimation of condensate advected from the downshear quadrants moisten the middle to upper troposphere. This is hypothesized to promote an increase in precipitation symmetrization, a necessary precursor for RI.

A Climatological Analysis of Tropical Cyclone Rapid Intensification in Environments of Upper-Tropospheric Troughs

2019 ◽  
Vol 147 (10) ◽  
pp. 3693-3719 ◽  
Author(s):  
Michael S. Fischer ◽  
Brian H. Tang ◽  
Kristen L. Corbosiero
Keyword(s):  
Tropical Cyclone ◽  
Clustering Algorithm ◽  
Inner Core ◽  
Rapid Intensification ◽  
The North ◽  
Warm Core ◽  
Dimensionality Reduction Technique ◽  
Intensity Changes ◽  
Cutoff Low ◽  
Environmental Air

Abstract Tropical cyclone (TC)–trough interactions are a common occurrence in the North Atlantic basin and lead to a variety of TC intensity changes, from rapid intensification (RI) to rapid weakening. To test whether certain TC–trough configurations are more favorable for RI than others, the upper-tropospheric troughs involved in such interactions were objectively classified into one of three clusters through the implementation of a machine-learning, dimensionality-reduction technique in conjunction with a k-means clustering algorithm. Through composite analyses, the upper-tropospheric potential vorticity structure, the TC convective structure, and the TC environment were examined for both rapidly intensifying TCs and nonrapidly intensifying (non-RI) TCs. As a whole, RI episodes were associated with upper-tropospheric troughs of shorter zonal wavelengths and greater upstream TC–trough displacements than non-RI episodes. RI was found to occur most frequently when an upper-tropospheric cutoff low was located approximately 500–1000 km southwest of the TC location. RI occurred preferentially in environments associated with less ventilation of the TC warm core with low-entropy environmental air. An examination of potential trough-induced forcing for convection revealed little relationship between RI and eddy flux convergence of angular momentum. Nonetheless, RI episodes were associated with anomalously vigorous convective activity within the TC inner core, as diagnosed by infrared and passive microwave satellite imagery.

scholarly journals A Numerical Study of Typhoon Megi (2010). Part I: Rapid Intensification

2014 ◽  
Vol 142 (1) ◽  
pp. 29-48 ◽  
Author(s):  
Hui Wang ◽  
Yuqing Wang
Keyword(s):  
Large Scale ◽  
Structural Changes ◽  
Inner Core ◽  
Numerical Study ◽  
Convective Available Potential Energy ◽  
Heat Content ◽  
Vertical Shear ◽  
Rapid Intensification ◽  
Upper Troposphere ◽  
Spiral Rainbands

Abstract Typhoon Megi (15W) was the most powerful and longest-lived tropical cyclone (TC) over the western North Pacific during 2010. While it shared many common features of TCs that crossed Luzon Island in the northern Philippines, Megi experienced unique intensity and structural changes, which were reproduced reasonably well in a simulation using the Advanced Research Weather Research and Forecasting Model (ARW-WRF) with both dynamical initialization and large-scale spectral nudging. In this paper processes responsible for the rapid intensification (RI) of the modeled Megi before it made landfall over Luzon Island were analyzed. The results show that Megi experienced RI over the warm ocean with high ocean heat content and decreasing environmental vertical shear. The onset of RI was triggered by convective bursts (CBs), which penetrate into the upper troposphere, leading to the upper-tropospheric warming and the formation of the upper-level warm core. In turn, CBs with their roots inside of the eyewall in the boundary layer were buoyantly triggered/supported by slantwise convective available potential energy (SCAPE) accumulated in the eye region. During RI, convective area coverage in the inner-core region was increasing while the updraft velocity in the upper troposphere and the number of CBs were both decreasing. Different from the majority of TCs that experience RI with a significant eyewall contraction, the simulated Megi, as the observed, rapidly intensified without an eyewall contraction. This is attributed to diabatic heating in active spiral rainbands, a process previously proposed to explain the inner-core size increase, enhanced by the interaction of the typhoon vortex with a low-level synoptic depression in which Megi was embedded.

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