on the rapid intensification of hurricane wilma (2005) hua chen committee members: dr. da-lin zhang...

On the Rapid Intensification of Hurricane Wilma (2005)

Hua Chen

Committee members: Dr. Da-Lin Zhang (Advisor) Dr. James Carton

Dr. Chuan Liu (Dean’s Representative) Dr. Xin-Zhong Liang

Dr. Kayo Ide Dr. Takemasa Miyoshi

Overview of Hurricane Wilma (2005)

• Record intensity in the Atlantic basin – 882 hPa

• Record intensification rate: 54 hPa/6 h, 83 hPa/12h, and 97 hPa/24 h (RI Def: > 1.5 hPa/hr)• Record small eye size: 5 kilometer in diameter

• Huge storm surge: 12 - 14 feet surge

• Torrential rainfall: 1600 mm rainfall/24h at Yucatan peninsula

Above the mean fcst errors: track - 160 km/48 h, 250 km/72 h, andlarge intensity underforecast (GFDL: 924 hPa and 50 m s-1).

Outline• Numerical prediciton• Model description• Model Verification

• Diagnostic analysis• The upper level warm core• Small symmetric eyewall

Model Description (WRF-ARW)

• Two-way, movable, quadruply nested (27/9/3/1 km), 55 levels in the vertical;

• Thompson et al. (2004) 3-ice cloud microphysics scheme;• The Betts-Miller-Janjic cumulus scheme for 27 and 9 km;• The YSU PBL scheme;• NOAH surface-layer physics;• Cloud-radiation interaction scheme;• Initial and boundary conditions: The GFDL’s then

operational data, except for the specified daily SST;• Integration period: 0000 UTC 18 ~ 0000 UTC 21 October

2005 (72 h) for all the four meshes.

A

B

C D1

DN

NASA/GSFC, 26 March 2012

The best track (dashed) vs the 72-h predicted track (solid),SST (shaded), SST (00 Z 19 – 00 Z 18; contoured)

Observed

Predicted

0 6 12 18 24 30 36 42 48 54 60 66 72

880

900

920

940

960

980

1000

MA

XIM

UM

SUR

FAC

E W

IND

(M S

-1)

CE

NT

RA

L P

RE

SSU

RE

(hP

a)

MODEL HOUR18/00 19/00 20/00 21/00

10

20

30

40

50

60

70

80

90

VOBS

VPRE

POBS

PPRE

Pre-RI

RI Post-RI

A

BC

D

Visible Satellite picture Predicted reflectivity at 1-km altitude

1900 UTC 18 OCT 1800 UTC 18 OCT

a b

c d

N-S

SE-NW

SW-NE

NE-SW

SE-NW

NW-SE

N-S

SW-NE

W-E

S-N

W-E

W-E

W-E

W-E

W-E

W-E

W-E

W-E

18/2130

19/1800 19/1800

19/2140

20/0512

20/0650

20/1020

20/1845

20/2140

18/1830-18.5

19/1800-42

19/2030-44.5

19/2100-45

19/2300-47

20/0500-53

20/0700-55

20/1030-58.5

20/1800-66

20/2100-69

Radius (km) Radius (km)

Verification against the flight-level observations

RMW = 7 kmRMW = 15 km

Observed Predicted

Hypothesis – upper level warm core

• An upper level warm core is important for RI;• The upper level warm core results from the descending

air in the lower stratosphere due to convective bursts• This upper level warm core is protected by the

symmetric divergent outflow at upper level from ventilation;

• Convective bursts, driven by high SSTs, play an important role in generating the upper-level warm core.

-120

-100

-80

-60

-40

-20

0

20

-120

-100

-80

-60

-40

-20

0

20

0 6 12 18 24 30 36 42 48 54 60 66 72

Pre

ssu

re D

efic

it (h

Pa

)

Time (hour)

380

Hei

gh

t (k

m)

Pre-RI RI Post-RI

A

C

360

340

320

400

B

Shadings: Temperature perturbation with respect to t = 0;

Contours: Potential temperature

Wind barbs

all taken at the eye center.

Total warmingWarming above 380 KWarming below 380 K

a)

b)

380 K

t = 36 h

340 K

vt

z

z

vtsTR

zgzpdzT

R

gzpp

t

b

exp)()exp)( 1

Efficiency of upper level warming

T1+∆T

T2

T1

T2+∆T

21

exp)(

exp)(RT

zg

TTR

zgzpp ta

)(expexp)(

21 TTR

zg

RT

zgzpp tb

))((

))((exp

2121

2121

TTTTTRT

TTTTTzg

p

p

b

a

PaPb

Pt

0

10

20

30

40

50

60

70

80

90

100

0

200

400

600

800

1000

0 6 12 18 24 30 36 42 48 54 60 66 72

Mean

Rad

ius of In

tense U

pd

raftsN

um

ber

of

Inte

nse

Up

dra

fts

Model Hour

AE

ERC

0

10

20

30

40

50

60

70

80

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Pre-RIRIPost-RI

Height (km)

Ave

rage

d O

ccu

rren

ces

No. of updraftsMean radius of updraftsRMW (z = 1 km)RMW (z = 11 km)

0

200

400

600

800

1000

0 6 12 18 24 30 36 42 48 54 60 66 72

Nu

mb

er o

f In

ten

se U

pd

raft

s

Model Hour

Pre-RI RI Post-RI

The cloud field at z = 17.5 km and CBs. The red circle is the RMW at z = 1 km

t = 30 h,t = 30.08h

Vertical cross section of cloud hydrometeors (shaded, g kg-1), storm-relative flow vectors, and vertical motion (downward/dashed every 1 m s-1 and

upward/solid every 3 m s-1).





symmetric divergent outflow at upper level from being ventilated;


400

380

360

340

320

400

380

360

340

320

Hei

ght (

km

)

a

b

Radius (km)

880

900

920

940

960

980

1000

880

900

920

940

960

980

1000

0 6 12 18 24 30 36 42 48 54 60 66 72

• Higher altitude of warm core at t =30 h;• Higher outflow layer at t=30 h;• Higher inflow layer at t=30 h;

ab

t = 30 h

t = 54 h• Warm core is located at the same altitude as the outflow layer

Differences:

Common feature:

50

a) 15:15

W

b) 15:30

c) 15:45 d) 16:00

W

W

W

RI onset

Shading: θ

Red contour:Upward motion

Blue contour:Downward motion

Black circle:RMW at Z = 1 km

“W”: warm anomaly

Z = 14 km

W1

W1

W2

W2W2

a) 11:25 b) 11:40

c) 11:55 d) 12:05

40

Pre-RI

Shading: θ

Red contour:Upward motion

Blue contour:Downward motion

Black circle:RMW at Z = 1 km

“W”: warm anomaly

Z = 14 km

Internal gravity wave movie


920

940

960

980

1000

900

920

940

960

980

1000

0 6 12 18 24 30 36 42 48 54 60 66 72

SST-1

CTL

Hei

gh

t (k

m)

Cen

tra

l P

ress

ure

(hP

a)

400

380

360

340

320

400

380

360

340

320

Model Hour

b

a

c

The 18/6/2 km control simulation

The SST-1 sensitivity simulation

CTL: 3.5 hPh/hrSST-1: 1.9 hPa/hr

0

50

100

150

200

0 6 12 18 24 30 36 42 48 54 60 66 72

Nu

mb

er o

f In

ten

se U

pd

raft

s

Time (hour)

2-km control2-km SST-1

Time Series of the number of Intense updrafts

Hypothesis – small symmetric eyewall

• The small eye is important;• The symmetric patter is important

CEN

TRA

L SU

RFA

CE

PRES

SUR

E (

mb)

RA

DIU

S OF M

AXIM

UM

WIN

D (km

)TIME (hours)

0 24 48 72 96 120

Pmin

Rmaxv

1010

1005

1000

995

990

985

180

150

120

90

60

30

0

880

900

920

940

960

980

1000

880

900

920

940

960

980

1000

0 6 12 18 24 30 36 42 48 54 60 66 72

Adapted from Schubert and Hack (1982)

Onset of RI

RMW (km)

DP

(hP

a)

• AAM conservation

• Gradient wind balance

• solid body rotation

Hypothesis – small symmetric eyewall

• The small eye is important;• The symmetric patter is important

Why does the eyewall becomes from asymmetric to symmetric?

40

a) 06:00 b) 15:00

v v v v v v v v v vv

v

v

v

v

v

1

3

5

7

9

11

13

15

13

57

911

13

15

Why symmetric pattern is important for RI?

-25

-15

-5

5

15

25

35

-25

-15

-5

5

15

25

35

3 6 9 12 15 18

1-5 km distancedistance_ydistance_x

Time (hour)

Dis

tan

ce (

km

)

(b) 07:45

(c)08:05 (d)08:45

(a) 07:00

AB

AB

AB B

A

How does the eye size contract fast in pre-RI stage?

Shading: radar reflectivity

contour:Vorticity

“A”, “B” denote the rainbands.

CEN

TRA

L SU

RFA

CE

PRES

SUR

E (

mb)

RA

DIU

S OF M

AXIM

UM

WIN

D (km

)

TIME (hours)0 24 48 72 96 120

Pmin

Rmaxv

1010

1005

1000

995

990

985

180

150

120

90

60

30

0

eyewall closure !Small symmetric eyewall forms!

Conclusion

• WRF model reproduces reasonable well the track, intensity and storm structure given the reasonable configuration;

• An upper level warm core is important for the storm to undergo RI because of its efficiency;

• The upper level warm core results from the descending air in the lower stratosphere due to convective bursts

• This upper level warm core is protected by the symmetric divergent outflow at upper level from ventilation;


Conclusion -continued

• The small eye size is important in determining RI;• The asymmetric pattern is hostile to RI because it

induces tilting and the asymmetric divergent outflow advects warming away from the center;

• The change of vertical wind shear with time is a key factor for the trigger of RI since it prevents the formation of a large symmetric eyewall at early stage.

Future work

• Perform more clear SST sensitivity tests to identify its impact on convective bursts and associated warm core;

• Microphysics sensitivity test.

Any questions?

on the rapid intensification of hurricane wilma (2005) hua chen committee members: dr. da-lin zhang...

Documents