Convective-scale diagnostics

Rob RogersNOAA/AOML Hurricane Research Division

• Advances in forecasts of tropical cyclone (TC) intensity, and rapid intensity change (RI) in particular, lag advances in TC track forecasts

• Multiscale nature of these processes major reason for this• environmental - O(1000 km) - troughs, shear• vortex - O(1-100 km) - symmetric/asymmetric dynamics, VRWs• convective – O(1 km) – convective bursts, vortical hot towers• turbulent – O(1-100 m) - surface fluxes, entrainment/detrainment• microscale – O(1mm) -- hydrometeor production, latent heat release

• Large-scale fields generally explain about 35% of skill in RI forecasts (e.g., RI index). How much can smaller-scale processes explain?

• Numerical model forecasts of rapid intensity change (RI) should improve as resolution increases

• For some cases it does, in others it does not – why?

• Robust diagnostic techniques for isolating impacts of physical processes of various scales on RI important for improved physical understanding, model evaluation and improvement

Motivation

Kaplan et al. 2009

35% of skill explained by Rapid Intensification

Index (RII)

Motivation

Summary of diagnostics

Vortex-scale diagnostics• test of initial vortex structure, environment-vortex-convective interactions, resolution• symmetric structure of tangential, radial, vertical wind

• radial distribution• vertical structure• time evolution

Convective-scale diagnostics• test of physical parameterizations (microphysical, convective), resolution • statistics of vertical motion, mass flux

• time-height vertical profiles• vertical structure of distributions• time evolution of distributions

• masking with 0.1 g/kg hydrometeor concentration used to approximate Doppler sensitivity and facilitate comparison with observations

40

60

80

100

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160

2005

-08-

27_0

0:00

:00

2005

-08-

27_0

6:00

:00

2005

-08-

27_1

2:00

:00

2005

-08-

27_1

8:00

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2005

-08-

28_0

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2005

-08-

28_0

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2005

-08-

28_1

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2005

-08-

28_1

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2005

-08-

29_0

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:00

2005

-08-

29_0

6:00

:00

2005

-08-

29_1

2:00

:00

Peak

win

d (k

t)

27-9 km

9-3 km

BT

40

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100

120

140

160

RI BTRI 9:3 km RI 27:9 km

• Hurricane Katrina (2005) • Underwent RI from Cat 3 to Cat 5 as it traversed Gulf of Mexico• Both resolutions produced RI, but both delayed• Good observational coverage (multiple P-3 flights with Doppler)

Example

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

50 100 150 200

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

50 100 150 20000Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

50 100 150 200

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radius (km)

radius (km) radius (km)

RI

RI

RI

Time-radius Hovmoller of axisymmetric 10-m wind from H*Wind and HWRF-x

Vortex-scale diagnostics: Wind field size & structure

H*Wind

HWRF-x 27:9 km HWRF-x 9:3 km

IKE

0

20

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140

8/27

00Z

8/27

03Z

8/27

06Z

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09Z

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8/27

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8/27

21Z

8/28

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21Z

8/29

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03Z

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06Z

8/29

09Z

8/29

12Z

IKE

(TJ)

IKE_H values for Hurricane Katrina

IKE_H 9:3km

IKE_H 27:9km

IKE_H H*Wind

0

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250

8/27

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8/27

03Z

8/27

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09Z

8/27

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8/27

21Z

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8/28

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8/28

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8/29

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IKE

(TJ)

IKE_TS values for Hurricane Katrina

IKE_TS 9:3km

IKE_TS 27:9km

IKE_TS H*Wind

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obs 9:3 km obs 9:3 km27:9 km 27:9 km

Time series of integrated kinetic energy (IKE) for 10-m winds thresholded by tropical storm and hurricane force winds from H*Wind and HWRF-x

Vortex-scale diagnostics: Wind field size & structure

IKE thresholded by tropical storm-force winds IKE thresholded by hurricane-force winds

25 50 75 100

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hei

gh

t (k

m)

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25 50 75

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hei

gh

t (k

m)

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radius (km)

radius (km)

radius (km)

radius (km)

radius (km)

radius (km)

Axisymmetric tangential (shaded, m s-1) and radial wind (contour, m s-1) for Doppler and HWRF-x

20:08Z 8/27

19:23Z 8/28

00Z 8/28

03Z 8/29

00Z 8/28

03Z 8/29

27:9 km 9:3 kmDoppler

27:9 km 9:3 kmDoppler

Vortex-scale diagnostics: Vertical structure of axisymmetric vortex

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2005

-08-

27_0

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:00

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-08-

27_0

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2005

-08-

27_1

2:00

:00

2005

-08-

27_1

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2005

-08-

28_0

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-08-

28_0

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:00

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-08-

28_1

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-08-

28_1

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2005

-08-

29_0

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2005

-08-

29_0

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2005

-08-

29_1

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:00

2-km

RM

W (k

m)

RMW (27-9 km)RMW (9-3 km)RMW (Dop)

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obs 9:3 km 27:9 km

Time series of radius of peak axisymmetric tangential wind at 2 km altitude (km) from Doppler and HWRF-x

Vortex-scale diagnostics: Time evolution of vortex size

50 100 150 200

radius (km)

25 75 125 17550 100 150 200

radius (km)

25 75 125 175

50 100 150 200

radius (km)

25 75 125 17550 100 150 200

radius (km)

25 75 125 175

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

RI RI

RI RI

Time-radius Hovmoller of axisymmetric tangential wind and vertical velocity at 5.1 km altitude

27:9 km

9:3 km

27:9 km

9:3 km

ut

ut

w

w

Vortex-scale diagnostics: Time evolution of axisymmetric vortex size

50 100 150 200

radius (km)

25 75 125 17550 100 150 200

radius (km)

25 75 125 175

50 100 150 200

radius (km)

25 75 125 17550 100 150 200

radius (km)

25 75 125 175

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hei

gh

t (k

m)

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hei

gh

t (k

m)

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hei

gh

t (k

m)

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hei

gh

t (k

m)

18

Axisymmetric tangential wind (shaded, m s-1) and vertical velocity (contour, m s-1)

27:9 km

27:9 km

9:3 km

9:3 km

00Z 8/28

03Z 8/29

00Z 8/28

03Z 8/29

Vortex-scale diagnostics: Vertical structure of axisymmetric vortex

-3

-2

-1

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2005

-08-

27_0

0:00

:00

2005

-08-

27_0

6:00

:00

2005

-08-

27_1

2:00

:00

2005

-08-

27_1

8:00

:00

2005

-08-

28_0

0:00

:00

2005

-08-

28_0

6:00

:00

2005

-08-

28_1

2:00

:00

2005

-08-

28_1

8:00

:00

2005

-08-

29_0

0:00

:00

2005

-08-

29_0

6:00

:00

2005

-08-

29_1

2:00

:00

eyew

all s

lope

(km

/km

)2-8 km slope (27-9 km)2-8 km slope (9-3 km)2-8 km slope (Dop)

-3

-2

-1

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obs 9:3 km 27:9 km

Time series of 2-8 km altitude eyewall slope (km km-1) from Doppler and HWRF-x

Vortex-scale diagnostics: Time evolution of vortex vertical structure

Outward slope with height

Inward slope with height

Wind speed (m/s) at 2-km altitude

Vorticity (shaded, x 10-3 s-1) and w

(contour, m/s) at 4-km altitude

Doppler 27:9 km HWRF-x 9:3 km HWRF-x

5010

015

00

5010

015

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5010

015

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5010

015

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5010

015

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500

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-1

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distance (km)

dis

tan

ce (

km)

distance (km)

dis

tan

ce (

km)

distance (km)

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tan

ce (

km)

distance (km)

dis

tan

ce (

km)

distance (km)

dis

tan

ce (

km)

distance (km)

dis

tan

ce (

km)

2038-2231 UTC 8/28 0000 UTC 8/29 0000 UTC 8/29

Vortex- and convective-scale diagnostics: Wind speed, vertical motion, and vorticity

Time series of mean updraft/downdraft velocity (m s-1) profiles in 4° box with maskingh

eig

ht

(km

)

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14 Updraft 27:9 kmRI

hei

gh

t (k

m)

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14 Updraft 9:3 kmRI

hei

gh

t (k

m)

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14 Downdraft 27:9 kmRI

hei

gh

t (k

m)

2

4

6

8

10

12

14 Downdraft 9:3 kmRI

Convective-scale diagnostics: Time evolution of vertical profiles

Time series of aggregate updraft/downdraft vertical mass flux (x 1010 kg s-1) profiles in 4° box with masking

hei

gh

t (k

m)

2

4

6

8

10

12

14 Downdraft 9:3 km

hei

gh

t (k

m)

2

4

6

8

10

12

14 Updraft 27:9 kmRI

hei

gh

t (k

m)

2

4

6

8

10

12

14 Downdraft 27:9 kmRI

hei

gh

t (k

m)

2

4

6

8

10

12

14 Updraft 9:3 kmRI

RI

Convective-scale diagnostics: Time evolution of vertical profiles

hei

gh

t (k

m)

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-6 -4 -2 0 2 4 6 8 10

vertical velocity (m/s)

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1 km

-2 -1 0 1 2 3 4 5

vertical velocity (m/s)

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0

per

cen

tag

e

14 km

-2 -1 0 1 2 3 4 5 6vertical velocity (m/s)

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0

per

cen

tag

e

vertical velocity

Convective-scale diagnostics: Contoured frequency by altitude diagram (CFAD)

hei

gh

t (k

m)

hei

gh

t (k

m)

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-6 -4 -2 0 2 4 6 8 10 12

vertical velocity (m/s)

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-6 -4 -2 0 2 4 6 8 10 12

vertical velocity (m/s)

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vertical velocity (m/s)

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vertical velocity (m/s)

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vertical velocity (m/s)

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-6 -4 -2 0 2 4 6 8 10 12

vertical velocity (m/s)

Vertical velocity CFADs for Doppler radar and HWRF-x with masking

20:08Z 8/27

22:31Z 8/28

12Z 8/27

12Z 8/28

12Z 8/27

12Z 8/28

27:9 km

27:9 km

9:3 km

9:3 km

Doppler

Doppler

Convective-scale diagnostics: Contoured frequency by altitude diagram (CFAD)

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 30

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 30

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 30

00Z Aug 27

12Z Aug 27

00Z Aug 28

12Z Aug 28

00Z Aug 29

12Z Aug 29

00Z Aug 30

-6 -4 -2 0 2 4 6 8 10 12 -6 -4 -2 0 2 4 6 8 10 12

-6 -4 -2 0 2 4 6 8 10 12 -6 -4 -2 0 2 4 6 8 10 12

vertical velocity (m/s) vertical velocity (m/s)

vertical velocity (m/s) vertical velocity (m/s)

14 km alt 27:9 km

5 km alt 27:9 km

14 km alt 9:3 km

5 km alt 9:3 km

Time series of vertical velocity distribution (%) at 5- and 14-km altitudes with masking

RI

RI

RI

RI

Convective-scale diagnostics: Time evolution of distributions

0

0.5

1

1.5

2

2.5

3

3.5

4

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0.5

1

1.5

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2.5

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3.5

4

area

(x

104 k

m2)

area

(x

104 k

m2)

Time series of areal coverage (x 104 km2) of threshold values of 3-7 km vertical velocity in 4x4 deg box with masking

27:9 km 9:3 km1 m s-1

2 m s-1

3 m s-1

1 m s-1

2 m s-1

3 m s-1RI RI

Convective-scale diagnostics: Time evolution of convective coverage

Summary• convective- and vortex-scale diagnostics can reveal much about inner-core structure and evolution from model and observations

• RMW, size of wind field at various thresholds, integrated kinetic energy• secondary eyewall, outer rainband evolution, eyewall slope• vertical velocity and mass flux profiles• vertical structure of vertical velocity distributions• time evolution of vertical velocity distributions

• differences between HWRF-x and observations for Katrina case• both resolutions produced RI, but both were delayed. 9:3 km was sooner, stronger than 27:9 km • vortex-scale

• RMW broader, outer wind field smaller in model compared to observations• both resolutions produced outer updraft maxima, 9:3 km produced hint of

contracting secondary eyewall• eyewall slope generally less for 9:3 km than 27:9 km, more time evolution

• convective-scale • mean updraft profiles peaked at higher altitude, downdrafts stronger in 9:3 km• stronger updraft and downdraft mass flux in 9:3 km• stronger updraft/downdraft, vorticity cores in 9:3 km

• all these quantities readily calculated from HWRF-x, airborne Doppler, and H*Wind analyses

Future work

• include azimuthal asymmetries

• partition into precipitation structure regimes (eyewall/rainband/stratiform)

• finer-scale diagnostics (turbulent, microphysical) from model and observations

• broaden to multi-case diagnostics – normalization issues?

• ensemble-based diagnostics