The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology

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Initialization, Prediction and Diagnosis of the
Rapid Intensification of Tropical Cyclones
using the Australian Community Climate and Earth
System Simulator, ACCESS Michael Reeder, Noel
Davidson, Jeff Kepert, Craig Bishop, Peter
Steinle and Kevin Tory with Yi Xiao, Harry
Weber, Yimin Ma, Hongyan Zhu, Xingbao Wang, Mai
Nguyen, Lawrie Rikus, Richard Dare, Ying Jun
Chen And Roger Smith and Michael Montgomery
(Honorary Members) Special thanks to WEP and
ESM Programs, and UKMO
Weather and Environmental Prediction and
Environmental System Modelling Groups CAWCR,
Centre for Australian Weather and Climate
Research A Partnership between CSIRO and the
Bureau of Meteorology Acknowledgments Kamal
Puri, Gary Dietachmayer

The Centre for Australian Weather and Climate
Research A partnership between CSIRO and the
Bureau of Meteorology
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Tropical Cyclone Characteristics in the
Australian Region

• TC behaviour and forecast issues
• Track,
• Genesis,
• Intensification/RI/Decay,
• Structure Change (size, etc),
• ET
• Landfall!!!

Points of Origin
Points with Min. CP
(Dare and Davidson, 2004, MWR)
Points of Final Decay
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Scope of Talk

• Operational ACCESS-TC
• ACCESS-TC System Configuration
• VS, 4DVAR Initialization, Verification
  (track, intensity, structure)
• Related, Diagnostic Projects (Shudder, Points of
  collaboration)
• (Testing new params, new data sources,
  even mechanisms/processes)
• Future Plans

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ACCESS-TC Verification NMOC Real-time Forecasts
2011 WNP Region, 10 TCs Number of
Forecasts Mean Track Error, Mean ABS Central
Pressure Error, (B-corrected), A-TC and
Persistence
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Not All Good News
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Track Forecasts from available operational
systems for Heidi and Iggy (A-TC, EC, UK, JMA,
GFS, NGP, GFDN,
Deficiencies in (a) LSE, and/or (b) Vortex
Structure ???
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ACCESS-TC vs ECMWF for TC IGGY from base times
20120126/12Z and 20120127/00Z Left Panels
Observed and forecast tracks and central
pressures from ACCESS-TC Centre Panels 72-hour
forecasts of MSLP from ACCESS-TC Right
Panels 72-hour forecasts of MSLP from ECMWF
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• ACCESS-TC for Operations and Research
• 1. Resolution
• 0.110X50L, re-locatable grid, with TC near centre
  of domain, option for higher-resolution
  forecasts.
• 2. Vortex Specification
• (a) Structure based on observed location, central
  pressure and size (tuned and validated using
  6000 dropsonde observations from the Atlantic)
• Only synthetic MSLP obs used in the 4DVAR to (a)
  relocate the storm to observed location, (b)
  define the inner-core circulation, and (c) impose
  steering flow asymmetries consistent with the
  past motion.
• 3. Initialization using 4DVAR Assimilation
• 5 cycles of 4DVAR over 24 hours. Uses all
  standard obs data, plus synthetic MSLP obs (no
  upper air synthetic obs).
• 4DVAR then
• Defines the horizontal structure of the
  inner-core at the observed location, (CP, VMAX,
  RMW, R34)
• Builds the vertical structure from MSLP obs,
• Constructs the secondary circulation,

The Centre for Australian Weather and Climate
Research A partnership between CSIRO and the
Bureau of Meteorology
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• Verification of large scale forecasts
• MSLP RMSE Global forecasts over the Australian
  Region
• Improved Prediction of the LSE of storms,
• compared to previous Australian Global System

The Centre for Australian Weather and Climate
Research A partnership between CSIRO and the
Bureau of Meteorology
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OBS Network
Without Vortex Specification Initial
Position/Intensity Errors for TC Anthony were
230km and 5hPa With Vortex Specification Initial
Position/Intensity Errors reduced to 40km and
0hPa VS blue MSLP obs in upper left panel
dense enough to
define Vmax at RMW, extensive enough to merge
with LSE.
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For Anthony at Landfall Obsvd and fcast track
and intensity without and with VS
500 hPa Initial Condition without and with VS
(synthetic MSLP obs only) Note construction of
3-D structure 4DVAR defines depth and tilt,
important for evolution of vortex
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Vortex Specification (Weber, 2011)
Figure 2 Tangential wind v(r) in m s-1 as a
function of radius in km of Hurricane Fran on
September 29, 1996 (top) and Hurricane Floyd on
September 19, 1999 (bottom). Thick lines
represent the average v(r) of all flight passes
and the AVSM output v(r) (smoother curve). The
thin lines define an envelope given by the
minimum and maximum v(r) of all flight passes at
each radial grid point. The input parameters of
AVSM are operational estimates of roci and vm  c
in (e), (f).
Validation of Vortex Structure Use EXBT data
sets for the NA and NP to validate TC structures
obtained from the Vortex Specification (RMW,
R34). (CLOK Charlie Lok)
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• Validation of Vortex Structure. I Cloud Fields
  (Rikus, 20XX)
• Actual and Synthetic Cloud Imagery
• Yasi at t 0 and t 46 hours from base time,
  12Z, 20110131
• 4DVAR initializes the ascent and moisture
  fields.
• Model maintains cloud fields during the
  forecast.

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• Validation of Vortex Structure.
• II Cloud Bands and Convective Asymmetries
• 85GHz Imagery (left panels) and ACCESS-TC 500 hPa
  vertical motion field at t 6 (initialized with
  4DVAR) and t 55 hours for Yasi from base time
  00Z, 20110131
• Note regions of observed active inner
  rainbands and eyewall convection, and
  corresponding forecast regions of strong and weak
  ascent.
• Based on use of synthetic MSLP obs and 4DVAR,
  structures are consistent from even the early
  hours of the forecast.
• Rainfall in TCs (Ying Jun Chen)

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Preliminary Validation of Vortex Structure.
III Intensity and Windfields (Verification of
R34) (Y. Ma) Critical for Storm Surge and
Rainfall For Yasi from base time 00Z,
20110131 Time series of forecast (a) Central
Pressure, (b) Maximum Wind, (c) Radius of
Maximum Wind, (d) Radius of 64, 50 and 34 knot
winds. Symbols indicate estimated values, where
available Encouraging preliminary
verification What defines size and the
RMW? ltltltltlt
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Illustrative Example TC YASI Forecast and
Observed Tracks and Intensities from ACCESS-TC
at 4km resolution
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Tropical Cyclone Projects Verification and
Post-analysis of Operational ACCESS-TC
Enhancements to the Boundary Layer
Parameterization for ACCESS-TC. Secondary
Eyewall Formation and Eyewall Replacement Cycles
in Tropical Cyclone Simulations Genesis
Applications OWZ Diagnostics and
ACCESS-TC Downstream Development during the
Extratropical Transition of Tropical Cyclones
Observational Evidence and Influence on Storm
Structure. Sensitivity of Prediction of
Intensity and Vortex Structure to Initial Vortex
Structure Rainfall in TCs Inner-core Structure
Change during Rapid Intensification Amplifying
Planetary Rossby Waves and Extreme Rain Events in
Current and Future Climates
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ACCESS-TC Improving air-sea exchange
parameterisation, plus inclusion of sea spray
processesYimin Ma and Colleagues
Statistics for track and intensity biases (ME, ME
ABS Mean Error, Mean Absolute Error)

• Realistic physical representation of air-sea
  exchange in high wind conditions in TCs.
• Validate with CBLAST Data
• Small changes in track forecast
• Large improvements in intensity forecast
• Small changes in outer structure

Structure prediction for YASI (2011). Base time
20110131/00Z
The Centre for Australian Weather and Climate
Research A partnership between CSIRO and the
Bureau of Meteorology
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BL Parameterisation in TCs Jeff Kepert

• Previous work has shown a substantial sensitivity
  to choice of parameterisation (Braun and Tao
  2000, Smith and Thomsen 2010).
• Why are they different?
• Which scheme is the most suitable?
• Method
• Use diagnostic 3-d model of TC BL (Kepert and
  Wang 2001) to make interpretation easier all
  simulations are the same above the BL.
• Implement four simplified parameterisations in
  the model, representative of those used in TC
  modelling.
• Compare and work out why.

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Comparing the schemes
Scheme Near-surface log layer? Inflow? Supergrad-ient flow? Recommend-ed for use?
MM5 Bulk and Blackadar No Strongest (exceeds obs) Strongest (exceeds obs) NO!
Louis Yes Moderate Moderate Yes
Higher-order (TKE scheme) Yes Moderate Moderate Yes (but expensive)
K-profile (MRF, YSU) Yes Weaker, depending on BL depth Weaker, depending on BL depth Yes, provided BL depth is ok (check!!).
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Secondary Eyewall Formation and Eyewall
Replacement Cycles in Tropical Cyclone
Simulations Xingbao Wang and Colleagues
Idealized Initial Vortex in an Acquiescent
Environment Nested down to Resolution of 2/3 km.
East-west Diameter-time, Hovmoller diagram of
Radar Reflectivity and Tangential Wind

• Tangential Wind

Radar Reflectivity(dBZ)
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Radar return from 63 to 86 h
Note SEF and start of ERC in bottom 8
panels Hypothesis As a dynamic response to an
UnBalanced Force in the boundary layer (sum of
pressures gradient, centrifugal, Coriolis,
friction forces, etc), a secondary maximum
convergence zone (SMCZ) in the radial flow is
generated in the boundary layer at a radius of
about double the RMW. In the moist,
conditionally-unstable atmosphere, the vertical
updraft induced by the SMCZ triggers moist
convection, which results in the Secondary
Eyewall Formation.
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OWZ Diagnostics for Genesis Vertically-aligned,
moist regions with curvature vorticity in low
shear Kevin Tory and Colleagues
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Application of ACCESS-TC to Genesis Forecasting
72, 60, 48, 36 hour forecasts verifying at
00UTC, 20111226 Genesis time for Grant.
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Downstream Development during the Extratropical
Transition of Tropical Cyclones Lili Liu, Noel
Davidson and Hongyan Zhu Time-longitude series of
Stream Function Anomaly (deviation from zonal
mean) at 45N on 250hPa level for (a) Hurricane
Michael, (b) Hurricane Wilma, (c) Hurricane
Maria, and (d) Hurricane Rita (non-ET). The arrow
is the propagation direction of trough/ridge wave
train and the black dot is the position of the
hurricane around ET time. ET is often associated
with Downstream Development Events
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Capture and ET of Hurricane Maria Fig.10 Dry,
No-Initial-Vortex Simulation of MSLP for Maria.
(a) Base time 00UTC 3 Sep 2005. (b) , (c), (d)
are 24-, 48- and 72- hour MSLP simulations. The
black dot is the position of Hurricane Maria at
the valid simulation time. DD Dynamics can
establish the large scale environment and
capturing trough for ET
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LARGE VARIABILITY IN Tropical Cyclone STRUCTURE
(Ma and Davidson, 2012)
Structure and Structure Change critical for
Rainfall and Storm Surge gt
Need for Mesoscale DA and Correct Initial Vortex
Structure. LARGE NATURAL VARIABILITY IN Tropical
Cyclone STRUCTURE (VMAX, CP, RMW, R34,
ROCI) What determines the variability? What
determines the RMW? Is storm structure important
for the evolution of the storm? Correct
prediction of CP and Vmax (intensity) does not
imply correct prediction of structure.
Visualize the differences in rainfall and storm
surge associated with different structures.
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Initialized and 48-hour forecasts of the radial
profiles of tangential wind from the 7 synthetic
structures at t 0 (top panels) and t 48 hours
(bottom panels) for Bonnie, Ivan and Katrina from
base times 12UTC 23 August 1998, 00UTC, 12
September 2005 and 00UTC, 27 August 2005. Plotted
symbols indicate estimated values of Vmax, R64,
R50 and R34. Units are m/s for wind and kms for
radius.
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example
Rainfall in TCs Ying Jun Chen, Kevin Walsh,
Beth Ebert, Noel Davidson
Analyse (TRMM, Atoll rain, rain gauge obs),
Verify, Predict TC Rainfall
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Mai NGUYEN Rapid Intensification Inner-Core
Processes Internal Structure Change during RI
(Vacillation Cycles, QJRMS, 2011)
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Amplifying Planetary Rossby Waves and Extreme
Rain Events in Current and Future Climates
Left panel Analysis of 24-hour rainfall
accumulations for 29 January 1990. Centre and
right panels 500 hPa wind valid 24 and 29
January 1990, respectively. X marks the
approximate location of Tropical Cyclone Tina at
the analysis times, as it moves to the southeast
and is captured and transitions into a
midlatitude system.
Figure 1 (a) Number of extreme rain events by
month, and (b) percentage of events occurring
within each latitude zone, by month.
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• ACCESS-TC Future Plans
• Upgrades to APS1(more satellite data, higher
  resolution, improved physics, .)
• NWP and basic research applications from
  special experimental data sets
• TPARC/TCS08, PREDICT Genesis and Rapid
  Intensification (NOPP/ONR)
• Specification, Prediction and Validation of TC
  Structure (CP, Vmax, RMW, R34, ROCI)
• Critical for prediction of track,
  intensity, structure, storm surge and rainfall
• Experiments with High Resolution Initialization
  and Prediction
• Experiments with Ensemble Prediction
• Experiments with Revised and New
  Physics
• Diagnostics for TC boundary
  layer and moist processes
• Enhancements with 4DVAR (inner and outer loops)
  (NOPP/ONR)
• Impact of extra observation types
• Rainfall in TCs (Ying Jun Chen, Walsh, Ebert,
  Davidson)