scholarly journals Dynamical and Physical Processes Leading to Tropical Cyclone Intensification under Upper-Level Trough Forcing

2013 ◽  
Vol 70 (8) ◽  
pp. 2547-2565 ◽  
Author(s):  
Marie-Dominique Leroux ◽  
Matthieu Plu ◽  
David Barbary ◽  
Frank Roux ◽  
Philippe Arbogast
Keyword(s):  
Angular Momentum ◽  
Tropical Cyclone ◽  
Potential Vorticity ◽  
Weather Prediction ◽  
Three Dimensional ◽  
Vertical Wind Shear ◽  
Thick Layer ◽  
Limited Area ◽  
Southwest Indian Ocean ◽  
Upper Level

Abstract The rapid intensification of Tropical Cyclone (TC) Dora (2007, southwest Indian Ocean) under upper-level trough forcing is investigated. TC–trough interaction is simulated using a limited-area operational numerical weather prediction model. The interaction between the storm and the trough involves a coupled evolution of vertical wind shear and binary vortex interaction in the horizontal and vertical dimensions. The three-dimensional potential vorticity structure associated with the trough undergoes strong deformation as it approaches the storm. Potential vorticity (PV) is advected toward the tropical cyclone core over a thick layer from 200 to 500 hPa while the TC upper-level flow turns cyclonic from the continuous import of angular momentum. It is found that vortex intensification first occurs inside the eyewall and results from PV superposition in the thick aforementioned layer. The main pathway to further storm intensification is associated with secondary eyewall formation triggered by external forcing. Eddy angular momentum convergence and eddy PV fluxes are responsible for spinning up an outer eyewall over the entire troposphere, while spindown is observed within the primary eyewall. The 8-km-resolution model is able to reproduce the main features of the eyewall replacement cycle observed for TC Dora. The outer eyewall intensifies further through mean vertical advection under dynamically forced upward motion. The processes are illustrated and quantified using various diagnostics.

scholarly journals Prediction and Diagnosis of Tropical Cyclone Formation in an NWP System. Part III: Diagnosis of Developing and Nondeveloping Storms

2007 ◽  
Vol 64 (9) ◽  
pp. 3195-3213 ◽  
Author(s):  
K. J. Tory ◽  
N. E. Davidson ◽  
M. T. Montgomery
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Deep Convection ◽  
Weather Prediction ◽  
Vertical Wind Shear ◽  
Forecast Model ◽  
Vertical Shear ◽  
Limited Area ◽  
Vortex Interactions ◽  
Secondary Mechanism

Abstract This is the third of a three-part investigation into tropical cyclone (TC) genesis in the Australian Bureau of Meteorology’s Tropical Cyclone Limited Area Prediction System (TC-LAPS), an operational numerical weather prediction (NWP) forecast model. In Parts I and II, a primary and two secondary vortex enhancement mechanisms were illustrated, and shown to be responsible for TC genesis in a simulation of TC Chris. In this paper, five more TC-LAPS simulations are investigated: three developing and two nondeveloping. In each developing simulation the pathway to genesis was essentially the same as that reported in Part II. Potential vorticity (PV) cores developed through low- to middle-tropospheric vortex enhancement in model-resolved updraft cores (primary mechanism) and interacted to form larger cores through diabatic upscale vortex cascade (secondary mechanism). On the system scale, vortex intensification resulted from the large-scale mass redistribution forced by the upward mass flux, driven by diabatic heating, in the updraft cores (secondary mechanism). The nondeveloping cases illustrated that genesis can be hampered by (i) vertical wind shear, which may tilt and tear apart the PV cores as they develop, and (ii) an insufficient large-scale cyclonic environment, which may fail to sufficiently confine the warming and enhanced cyclonic winds, associated with the atmospheric adjustment to the convective updrafts. The exact detail of the vortex interactions was found to be unimportant for qualitative genesis forecast success. Instead the critical ingredients were found to be sufficient net deep convection in a sufficiently cyclonic environment in which vertical shear was less than some destructive limit. The often-observed TC genesis pattern of convection convergence, where the active convective regions converge into a 100-km-diameter center, prior to an intense convective burst and development to tropical storm intensity is evident in the developing TC-LAPS simulations. The simulations presented in this study and numerous other simulations not yet reported on have shown good qualitative forecast success. Assuming such success continues in a more rigorous study (currently under way) it could be argued that TC genesis is largely predictable provided the large-scale environment (vorticity, vertical shear, and convective forcing) is sufficiently resolved and initialized.

scholarly journals Tropical Transition of the 2001 Australian Duck

2010 ◽  
Vol 138 (6) ◽  
pp. 2038-2057 ◽  
Author(s):  
Luke Andrew Garde ◽  
Alexandre Bernardes Pezza ◽  
John Arthur Tristram Bye
Keyword(s):  
Potential Vorticity ◽  
Large Scale ◽  
Three Dimensional ◽  
Vertical Wind Shear ◽  
Heat Fluxes ◽  
Pressure System ◽  
Surface Heat Fluxes ◽  
Warm Core ◽  
Tasman Sea ◽  
Upper Level

Abstract In March 2001, a hybrid low pressure system, unofficially referred to as Donald (or the Duck), developed in the Tasman Sea under tropical–extratropical influence, making landfall on the southeastern Australian coast. Here, it is shown that atmospheric blocking in the Tasman Sea produced a split in the subtropical jet, allowing persistent weak vertical wind shear to manifest in the vicinity of the developing low. It is hypothesized that this occurred through sustained injections of potential vorticity originating from higher latitudes. Hours before landfall near Byron Bay, the system developed an eye with a short-lived warm core at 500 hPa. Cyclone tracking revealed an erratic track before the system decayed and produced heavy rains and flash flooding. A three-dimensional air parcel backward-trajectory scheme showed that the air parcels arriving in the vicinity of the mature cyclone originated from tropical sources at lower levels and from the far extratropics at higher levels, confirming the hybrid characteristics of this cyclone. A high-resolution (0.15°) nested simulation showed that recent improvements in the assimilation scheme used by the Australian models allowed for accurately simulating the system’s trajectory and landfall, which was not possible at the time of the event. Compared to the first South Atlantic hurricane of March 2004, the large-scale precursors were similar; however, the Duck was exposed to injections of upper-level potential vorticity and favorable surface heat fluxes for a shorter period of time, resulting in it achieving partial tropical transition only hours prior to landfall.

scholarly journals The Conversion of Total Column Ozone Data to Numerical Weather Prediction Model Initializing Fields, with Simulations of the 24–25 January 2000 East Coast Snowstorm

2009 ◽  
Vol 137 (1) ◽  
pp. 161-188 ◽  
Author(s):  
Dorothy Durnford ◽  
John Gyakum ◽  
Eyad Atallah
Keyword(s):  
Numerical Weather Prediction ◽  
Potential Vorticity ◽  
East Coast ◽  
Weather Prediction ◽  
Three Dimensional ◽  
Total Column Ozone ◽  
Numerical Weather ◽  
Upper Level ◽  
Column Ozone ◽  
Total Column

Abstract Satellites are uniquely capable of providing uniform data coverage globally. Motivated by such capability, this study builds on a previously described methodology that generates numerical weather prediction (NWP) model initial conditions (ICs) from satellite total column ozone (TCO) data. The methodology is based on three principal steps: 1) conversion of TCO to mean potential vorticity (MPV) via linear regression, 2) conversion of two-dimensional MPV to three-dimensional potential vorticity (PV) via vertical mapping onto average PV profiles, and 3) inversion of the three-dimensional PV field to obtain model-initializing height, temperature, and wind fields in the mid- and upper troposphere. The overall accuracy of the process has been significantly increased through a substantial reworking of the details of this previous version. For instance, in recognition of the fact that TCO ridges tend to be less reliable than troughs, the authors vertically map an MPV field that is a synthesis of ozone-derived MPV troughs and analysis MPV ridges. The vertical mapping procedure itself produces a more physical three-dimensional PV field by eliminating unrealistically strong features at upper levels. It is found that the ozone-influenced upper-level initializing fields improve the quantitative precipitation forecast (QPF) of the 24–25 January 2000 East Coast snowstorm for two of the three (re)analyses. Furthermore, the best QPF involves ozone-influenced upper-level initializing fields. Its high threat scores reflect a superior placement, amplitude, and structure. This best QPF is apparently superior to a forecast of the same case where TCO data were assimilated using four-dimensional variational data assimilation.

scholarly journals Diagnosis of Track Forecast Errors for Tropical Cyclone Rita (2005) Using GEFS Reforecasts

2015 ◽  
Vol 30 (5) ◽  
pp. 1334-1354 ◽  
Author(s):  
Thomas J. Galarneau ◽  
Thomas M. Hamill
Keyword(s):  
Tropical Cyclone ◽  
Weather Prediction ◽  
Weather Research And Forecasting ◽  
Track Forecast ◽  
Forecast Errors ◽  
Subtropical Anticyclone ◽  
Cutoff Low ◽  
Layer Flow ◽  
Upper Level ◽  
Mass Evacuation

Abstract Analysis and diagnosis of the track forecasts for Tropical Cyclone (TC) Rita (2005) from the Global Ensemble Forecast System (GEFS) reforecast dataset is presented. The operational numerical weather prediction guidance and GEFS reforecasts initialized at 0000 UTC 20–22 September 2005, 2–4 days prior to landfall, were all characterized by a persistent left-of-track error. The numerical guidance indicated a significant threat of landfall for the Houston, Texas, region on 24 September. The largest mass evacuation in U.S. history was ordered, with the evacuation resulting in more fatalities than TC Rita itself. TC Rita made landfall along the Texas–Louisiana coastal zone on 24 September. This study utilizes forecasts from the GEFS reforecast and a high-resolution regional reforecast. The regional reforecast was generated using the Advanced Hurricane Weather Research and Forecasting Model (AHW) with the GEFS reforecasts providing the initial and boundary conditions. The results show that TC Rita’s track was sensitive to errors in both the synoptic-scale flow and TC intensity. Within the GEFS reforecast ensemble, the nonrecurving members were characterized by a midlevel subtropical anticyclone that extended too far south and west over the southern United States, and an upper-level cutoff low west and anticyclone east of TC Rita that were too weak. The AHW regional reforecast ensemble further highlighted the role of intensity and steering-layer depth in TC Rita’s track. While the AHW forecast was initialized with a TC that was too weak, the ensemble members that were able to intensify TC Rita more rapidly produced a better track forecast because the TCs followed a deeper steering-layer flow.

scholarly journals Dynamical contribution of mean potential vorticity pseudo-observations derived from MetOp/GOME2 ozone data into short-range weather forecast during high precipitation events

2015 ◽  
Vol 4 (2) ◽  
pp. 206
Author(s):  
Siham Sbii ◽  
Mimoun Zazoui ◽  
Noureddine Semane
Keyword(s):  
Potential Vorticity ◽  
Short Range ◽  
Initial Conditions ◽  
Weather Prediction ◽  
Dynamical Behavior ◽  
Heavy Precipitation ◽  
Limited Area ◽  
Total Column Ozone ◽  
Ozone Data ◽  
Precipitation Events

<p>Satellites are uniquely capable of providing uniform data coverage globally. Motivated by such capability, this study builds on a previously described methodology that generates numerical weather prediction initial conditions from satellite total column ozone data. The methodology is based on two principal steps. Firstly, the studied linear regression between vertical (100hPa-500hPa) Mean Potential Vorticity (MPV) and MetOp/GOME2 total ozone data (O3) generates MPV pseudo-observations. Secondly, the 3D variational (3D-Var) assimilation method is designed to take into account MPV pseudo-observations in addition to conventional observations.</p><p>After a successful assimilation of MPV pseudo-observations using a 3D-Var approach within the Moroccan version of the ALADIN limited-area model, the present study aims to assess the dynamical behavior of the short-range forecast at upper levels during heavy precipitation events (HPEs). It is found that MPV assimilation offers the possibility to internally monitor the model upper-level dynamics in addition to the use of Water Vapor Satellite images.</p>

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.

scholarly journals Variability of the Atlantic Meridional Mode during the Atlantic Hurricane Season

2011 ◽  
Vol 24 (5) ◽  
pp. 1409-1424 ◽  
Author(s):  
Dimitry Smirnov ◽  
Daniel J. Vimont
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Vertical Wind Shear ◽  
Ocean Model ◽  
Atlantic Hurricane ◽  
Hurricane Season ◽  
Meridional Mode ◽  
Upper Level ◽  
Atlantic Meridional Mode ◽  
Sst Anomalies

Abstract An observational and modeling study is conducted to investigate the structure of the Atlantic Meridional Mode (AMM) during the Atlantic hurricane season, and the relationship between AMM-related SST anomalies and environmental conditions that influence seasonal tropical cyclone activity. The observational analysis shows that during the Atlantic hurricane season the AMM exhibits a similar SST and low-level wind structure as during boreal spring (when the AMM is most active). Observed AMM SST variations are accompanied by air temperature and moisture anomalies that are limited to the boundary layer and an anomalous baroclinic circulation structure in the northern subtropical Atlantic with an anomalous lower-level cyclonic circulation residing under an anomalous upper-level anticyclone during a warm phase. This baroclinic structure contributes to a reduction in vertical wind shear over the tropical Atlantic that is dominated by changes in the upper-level flow. Two sets of model experiments were conducted, in which the NCAR Community Atmospheric Model version 3.1 (CAM3.1) was coupled to a slab ocean model or a data ocean model. In each experiment, the model was either initialized with or forced by AMM-like SST anomalies during boreal summer. The simulations yielded a similar spatial structure to that in the observations, including the baroclinic atmospheric circulation and associated reduction in vertical wind shear. The similarity between the modeled and observed AMM structures strongly suggests a causal relationship in which the AMM-like SST anomalies are responsible for generating environmental conditions that can strongly influence seasonal tropical cyclone variability.

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 (&gt;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 Deterministic methods for prediction of tropical cyclone tracks

MAUSAM ◽  
2021 ◽  
Vol 48 (2) ◽  
pp. 257-272
Author(s):  
U.C. MOHANTY ◽  
AKHILESH GUPTA
Keyword(s):  
Tropical Cyclone ◽  
Weather Prediction ◽  
Horizontal Resolution ◽  
Limited Area ◽  
Deterministic Models ◽  
Global Circulation ◽  
Global Circulation Models ◽  
Structure And Motion ◽  
Cyclone Tracks ◽  
Tropical Cyclone Tracks

ABSTRACT. The paper presents a state-of-art review of different objective techniques available for tropical cyclone track prediction. A brief description of current theories of tropical cyclone motion is given. Deterministic models with statistical and dynamical methods have been discussed. Recent advances in the understanding of cyclone structure and motion aspects have led to improved prediction of tropical cyclones. There has been considerable progress in the field of prediction by dynamical methods. High resolution Limited Area Models (LAM) as well as Global Circulation Models (GCM) are now being used extensively by most of the leading operational numerical weather prediction (NWP) centres in the world The major achievements towards improvement of such models have come from improved horizontal resolution of the models, inclusion of physical processes, use of synthetic and other non-conventional data in the data assimilation schemes and nudging method for initial matching of analysed cyclone centres with corresponding observations. A brief description of further improvement in deterministic approach for prediction of tropical cyclone tracks is outlined.  

The Tropical Cyclone as a Divergent Source in a Background Flow

2020 ◽  
Vol 77 (12) ◽  
pp. 4189-4210
Author(s):  
David R. Ryglicki ◽  
Daniel Hodyss ◽  
Gregory Rainwater
Keyword(s):  
Tropical Cyclone ◽  
Shallow Water ◽  
Vertical Wind Shear ◽  
Water Model ◽  
Rapid Intensification ◽  
Shallow Water Model ◽  
Background Flow ◽  
Analytical Expression ◽  
Budget Analysis ◽  
Upper Level

AbstractThe interactions between the outflow of a tropical cyclone (TC) and its background flow are explored using a hierarchy of models of varying complexity. Previous studies have established that, for a select class of TCs that undergo rapid intensification in moderate values of vertical wind shear, the upper-level outflow of the TC can block and reroute the environmental winds, thus reducing the shear and permitting the TC to align and subsequently to intensify. We identify in satellite imagery and reanalysis datasets the presence of tilt nutations and evidence of upwind blocking by the divergent wind field, which are critical components of atypical rapid intensification. We then demonstrate how an analytical expression and a shallow water model can be used to explain some of the structure of upper-level outflow. The analytical expression shows that the dynamic high inside the outflow front is a superposition of two pressure anomalies caused by the outflow’s deceleration by the environment and by the environment’s deceleration by the outflow. The shallow water model illustrates that the blocking is almost entirely dependent upon the divergent component of the wind. Then, using a divergent kinetic energy budget analysis, we demonstrate that, in a full-physics TC, upper-level divergent flow generation occurs in two phases: pressure driven and then momentum driven. The change happens when the tilt precession reaches left of shear. When this change occurs, the outflow blocking extends upshear. We discuss these results with regard to prior severe weather studies.

Sign in / Sign up

Export Citation Format

Share Document