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

Tropical Cyclone Characteristics in the Australian Region

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TC behaviour and forecast issues:

Track, Genesis, Intensification/RI/Decay, Structure Change (size, etc), ET Landfall!!!

(Dare and Davidson, 2004, MWR)

Points of Origin Points with Min. CP Points of Final Decay

Scope of Talk

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Operational ACCESS-TC

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ACCESS-TC System Configuration VS, 4DVAR Initialization, Verification (track, intensity, structure)

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Related, Diagnostic Projects (Shudder, Points of collaboration) (Testing new params, new data sources, even mechanisms/processes)

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Future Plans

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

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

Not All Good News …

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 ???

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

ACCESS-TC for Operations and Research 1. Resolution: 0.11

0 X50L, 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) (b) 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: (a) Defines the horizontal structure of the inner-core at the observed location, (CP, VMAX, RMW, R34) (b) Builds the vertical structure from MSLP obs, (c) Constructs the secondary circulation, (d) Creates a balanced TC circulation at the observed location, with correct (?) structure and intensity.

(e) Creates a structure which is responsive to environmental wind shear without imposing constraints on the vertical-stacking or tilt of the circulation. (important for vortex dynamics and cloud asymmetries) 4. Forecast Model: UKMO Unified Model from ACCESS.

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

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

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.

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

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

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

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)

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

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4DVAR initializes the ascent and moisture fields.

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Model maintains cloud fields during the forecast.

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

Validation of Vortex Structure. II: Cloud Bands and Convective Asymmetries

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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

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Note regions of observed active inner rainbands and eyewall convection, and corresponding forecast regions of strong and weak ascent.

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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)

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

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? <<<<<

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

ACCESS-TC – Improving air-sea exchange parameterisation, plus inclusion of sea spray processes Yimin 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

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.

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

Comparing the schemes

Scheme

MM5 Bulk and Blackadar Louis

Near-surface log layer?

Inflow?

No Strongest (exceeds obs)

Supergrad ient flow?

Strongest (exceeds obs)

Recommend ed for use?

NO!

Yes Moderate Moderate Yes Higher-order (TKE scheme) K-profile (MRF, YSU) Yes Yes Moderate Moderate Weaker, depending on BL depth Weaker, depending on BL depth Yes (but expensive) Yes, provided BL depth is ok (check!!).

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

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

Radar Reflectivity(dBZ) Tangential Wind

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 Secondary Eyewall Formation.

results in the

OWZ Diagnostics for Genesis Vertically-aligned, moist regions with curvature vorticity in low shear Kevin Tory and Colleagues

Application of ACCESS-TC to Genesis Forecasting: 72, 60, 48, 36 hour forecasts verifying at 00UTC, 20111226: ~ Genesis time for Grant.

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

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

LARGE VARIABILITY IN Tropical Cyclone STRUCTURE (Ma and Davidson, 2012) Structure and Structure Change critical for Rainfall and Storm Surge => 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.

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

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.

Rainfall in TCs

:

Ying Jun Chen

, Kevin Walsh, Beth Ebert, Noel Davidson

US14111; 7.45 151.83; atoll site

example 600 correl=0.906

500 400 300 200 100 0 US14111 Gauge:749mm TRMM: 563mm US14419 Gauge: 256mm TRMM: 423mm 02 28 28 01 08 07 13 21 14 22 04 26 19 12 12 16 200108 200202 200206 200207 200207 200212 200304 200305 200308 200311 200404 200406 200410 200412 200503 200612

date

atoll rain TRMM 3B42 US14590 Gauge:223mm TRMM: 204mm US14585; 9.57 138.12; coastal with orographic influence 160 140 120 100 80 60 40 20 0 correl=0.74

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Analyse (TRMM, Atoll rain, rain gauge obs), Verify, Predict TC Rainfall

date pacrain coastal with orographic influence TRMM 3b42

Mai NGUYEN: Rapid Intensification: Inner-Core Processes: Internal Structure Change during RI (Vacillation Cycles, QJRMS, 2011)

33 1000 31 980 960 29 940 27 920 25 900 23 270 6 5 4 3 2 1 0 0 -1 -2 6 272 dVm 12 274 SDM 18 276 24 30 278 36 880 0 6 12 18 24 30 36 42

FCST hour

48 54 60 66 72 42 48 54 60 66

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.

ACCESS-TC: Future Plans

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Upgrades to APS1(more satellite data, higher resolution, improved physics, ….)

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NWP and basic research applications from special experimental data sets: TPARC/TCS08, PREDICT: Genesis and Rapid Intensification (NOPP/ONR)

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Specification, Prediction and Validation of TC Structure (CP, Vmax, RMW, R34, ROCI): Critical for prediction of track, intensity, structure, storm surge and rainfall

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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

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Enhancements with 4DVAR (inner and outer loops) (NOPP/ONR) Impact of extra observation types

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Rainfall in TCs (Ying Jun Chen, Walsh, Ebert, Davidson)

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Influence of Amplifying Rossby Waves on TC structure and intensity (NOPP/ONR)

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Inner-core Dynamics (eg, What defines RMW and R34? Mai Nguyen) (NOPP/ONR)

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Challenge: Initialize CAT 3 - 5 storms without the use of reconnaissance data or vortex specification?

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Happy to collaborate on and/or provide data for (i) testing assimilation of new obs data, (ii) testing new parameterisations, (iii) assessing mechanisms.