4B.2 A comparison of typhoon best-track data in the western North Pacific: irreconcilable differences. by Mark A. Lander University of Guam Central Guam

4B.2 A comparison of typhoon best-track data in the western North Pacific: irreconcilable differences.

byMark A. Lander

University of Guam

Central Guam mountains after amajor brushfire.

The two primary agencies responsible for basin-wide TC coverage — the Joint Typhoon Warning Center (JTWC) and the Japan Meteorological Agency (JMA) — are so incompatible as to call into question the utility of their best-track TC data for climate studies.

The Joint Typhoon Warning Center (JTWC), now located in Pearl Harbor, Hawaii, has a nearly 50-year record of tropical storms and typhoons for the western North Pacific Basin. The JTWC is jointly manned by the U.S. Navy and U.S. Air Force to provide tropical cyclone reconnaissance and forecast support to the U.S. Military and other U.S. Government agencies and assets in the eastern Hemisphere. The JTWC has a continuous record of tropical cyclone activity in the western North Pacific extending from 1959 to present. Until the year 2000, it also provided the names for the TCs of that basin.

P. J. Webster, G. J. Holland, J. A. Curry, H.-R. ChangScience 16 September 2005:Vol. 309. no. 5742, pp. 1844 – 1846

Examination of hurricane intensity shows a substantial change in the intensity distribution of hurricanes globally. The number of category 1 hurricanes has remained approximately constant but has decreased monotonically as a percentage of the total number of hurricanes throughout the 35-year period. The trend of the sum of hurricane categories 2 and 3 is small also both in number and percentage. In contrast, hurricanes in the strongest categories (4 + 5) have almost doubled in number (50 per pentad in the 1970s to near 90 per pentad during the past decade) and in proportion (from around 20% to around 35% during the same period). These changes occur in all of the ocean basins.

True if one uses JTWCFalse if one uses JMA !!!

In General:

JTWC intensities too high !!

OR

JMA intensities too low !!

1996 Typhoon Season

-20

-10

0

10

20

30

40

50

60T

D 1

An

nT

D3

Bar

tC

am Dan

Eve

Fra

nk

Glo

ria

Her

bIa

nJo

yL

isa

Kir

kT

D 1

5M

arty

Nik

iO

rso

Pip

erT

D 2

1R

ick

Sal

lyT

S 2

4V

iole

tT

om

Wil

lie

Yat

esZ

ane

Ab

elT

D 3

1B

eth

Car

loT

D 3

4T

S 3

5D

ale

Ern

ieT

S 3

8T

D 3

9T

D 4

0T

D 4

1F

ern

Gre

g

-20

-10

0

10

20

30

40

50

60

1996

V max

JTWC Higher than JMA

JMA No Tropical Warnings

JTWC Lower than JMA

Wind speed difference

(kt)

-40

-30

-20

-10

0

10

20

TD

1A

nn

TD

3B

art

Cam Dan

Eve

Fra

nk

Glo

ria

Her

bIa

nJo

yL

isa

Kir

kT

D 1

5M

arty

Nik

iO

rso

Pip

erT

D 2

1R

ick

Sal

lyT

S 2

4V

iole

tT

om

Wil

lie

Yat

esZ

ane

Ab

elT

D 3

1B

eth

Car

loT

D 3

4T

S 3

5D

ale

Ern

ieT

S 3

8T

D 3

9T

D 4

0T

D 4

1F

ern

Gre

g

-40

-30

-20

-10

0

10

20


JTWC Lower than JMA

1996 Minimum SLPJMA No Tropical Warnings

JTWC = 1.5386 x JMA - 7.8015 1

When intercept not set to zero

1 JTWC = 1.4133 x JMAWhen intercept forced to zero

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160

JMA Vmax 10-min kts

JTW

C V

max

1-m

in k

ts1996: JTWC Vmax VS JMA Vmax

Why ??

JTWC uses 1-minute average for sustained wind speed.

JMA uses 10-minute average for sustained wind speed.

Difference between 1-min and 10-min is approximately 115%.

Why ??

JTWC and JMA use different T-number conversion tables.

Dvorak T number/wind speed comparison

T Number JTWC JMA 10 to 1 2 30 30 33.6 2.5 35 35 39.2 3 45 45 50.4 3.5 55 55 61.6 4 65 65 72.8 4.5 77 70 78.4 5 90 77 86.2 5.5 102 85 95.2 6 115 93 104.2 6.5 127 100 112.0 7 140 107 119.8 7.5 155 115 128.8 8 170 122 136.6

JMA can’t getCAT 5 until T8 is reached !!

JTWC = 0.00666492523952 (JMA)2 + 0.52216572124655 (JMA) + 7.70018715792769

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100 120 140 160 180

JMA 10-Min Vmax

JTW

C 1

-Min

Vm

ax

JTWC VS JMADVORAK T-NUMBER

EQUIVALENT WIND SPEEDS

T 4.0

T 5.0

T 4.5

T 5.5

T 6.0

T 6.5

T 7.0

T 7.5

T 8.0

T 3.5

T 3.0

T 2.5T 2.0

0

20

40

60

80

100

120

140

160

180

2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8T NUMBER

Win

d S

pee

d (

Kts

)

JMA10-Min to 1 Min

JTWC 1-Min

JMA

Who is right ???

Anecdotal Evidence.

Investigate individual TCs

Tropical Storm Greg (43W 96)

Strongest Westerly Wind Burst ever Observed ! (December 1996)

Impacts of TS Greg1996 JTWC Annual TC Report

“Greg was responsible for loss of life and extensive damage to property in the East Malaysian State of Sabah (located on the northwest coast of Borneo). At least 124 lives were reported lost with another reported missing primarily due to flooding from torrential rains. In Kota Kinabalu, The capital of the State of Sabah, high wind scattered billboards and other debris, and broke windows in the 30-story government building.”

Typhoon Vamei

EQ

2 N

4 N

108 E104 E

Singapore

Typhoon Vamei00Z 27 DEC 2001TRMM 85 GHz

Typhoon Vamei. Microwave image courtesy of NRL Monterey:(http://www.nrlmry.navy.mil/tc_pages/tc_home)

JTWC: 75 kt

JMA 45 kt

JTWC Annual Tropical Cyclone report for 2001:

“At 270000Z, JTWC classified the system as a typhoon based on naval ship observations indicating sustained winds within the small eyewall of 75 knots with gusts to 105 knots.”

Even today problems persist.

October 2007: Two midget typhoons

Haiyan

Podul

Midget typhoon Haiyan

JTWC:No Warning.20 kt on ABPW

JMA:40 kt.

TC Podul (Midget Typhoon)

JTWC:No Warning.20 kt on ABPW

JMA: 55 kt

Annual comparisons

Here it gets messy.

1996 Typhoon Season

-20

-10

0

10

20

30

40

50

60T

D 1

An

nT

D3

Bar

tC

am Dan

Eve

Fra

nk

Glo

ria

Her

bIa

nJo

yL

isa

Kir

kT

D 1

5M

arty

Nik

iO

rso

Pip

erT

D 2

1R

ick

Sal

lyT

S 2

4V

iole

tT

om

Wil

lie

Yat

esZ

ane

Ab

elT

D 3

1B

eth

Car

loT

D 3

4T

S 3

5D

ale

Ern

ieT

S 3

8T

D 3

9T

D 4

0T

D 4

1F

ern

Gre

g

-20

-10

0

10

20

30

40

50

60

1996

V max



JTWC Lower than JMA

Wind speed difference

(kt)

-40

-30

-20

-10

0

10

20

TD

1A

nn

TD

3B

art

Cam Dan

Eve

Fra

nk

Glo

ria

Her

bIa

nJo

yL

isa

Kir

kT

D 1

5M

arty

Nik

iO

rso

Pip

erT

D 2

1R

ick

Sal

lyT

S 2

4V

iole

tT

om

Wil

lie

Yat

esZ

ane

Ab

elT

D 3

1B

eth

Car

loT

D 3

4T

S 3

5D

ale

Ern

ieT

S 3

8T

D 3

9T

D 4

0T

D 4

1F

ern

Gre

g

-40

-30

-20

-10

0

10

20


JTWC Lower than JMA

1996 Minimum SLPJMA No Tropical Warnings

-40

-30

-20

-10

0

10

20T

ess

Vio

la

Win

nie

Ali

ce

Bet

ty

Co

ra

Do

ris

Els

ie

Flo

ssie

Hel

en Ida

Kat

hy

Mar

ie

Ru

by

Sal

ly

Til

da

Vio

let

Wil

da

Cla

ra

Do

t

Ho

pe

Iris

Joan

Kat

e

Lo

uis

e

Op

al

-40

-30

-20

-10

0

10

20

1964

JTWC MSLP Lower than JMA

JTWC MSLP Higher than JMA

Minimum SLP


JTWC TYPHOONS ONLY

JTWC = 1.5386 x JMA - 7.8015 1

When intercept not set to zero


0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160

JMA Vmax 10-min kts

JTW

C V

max

1-m

in k

ts1996: JTWC Vmax VS JMA Vmax

1JTWC = 1.4143 x JMAWhen intercept not forced to zero

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160

JMA Vmax 10-min kts

JTW

C V

max

1-m

in k

ts

1997: JTWC Vmax VS JMA Vmax

JTWC = (1.5379 x JMA) - 7.7465 1

When intercept forced to zero


0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160


JTWC = (1.4544 x JMA) - 17.463 1

When intercept not forced to zero

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160

JMA Vmax (10-Min)

JTW

C V

max

(1-

Min

)


JTWC = (1.5412 x JMA) - 15.832 1


1JTWC = 1.3214 x JMAWhen intercept forced to zero

JTWC = (1.5973 x JMA) - 22.637 1


1 JTWC = 1.3028 X JMAWhen intercept forced to zero

JTWC = 0.0067 (JMA)2 + 0.5222 (JMA) + 7.7002

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160


JTWC = (1.2661 x JMA) - 7.832 1



0

20

40

60

80

100

120

140

160

0 20 40 60 80 100 120 140 160


Conclusions:

(1) The differences of wind intensities between the JTWC and the JMA are irreconcilable. There is no uniform or physically meaningful correction that can be applied to the two data sets to bring them into line with each other.

(2) Establish a working group of tropical cyclone diagnostic experts to undertake a project similar to the HRD Hurricane Reanalysis Project for the historical record of the tropical cyclones of thewestern North Pacific.

Documents

4B.2 A comparison of typhoon best-track data in the western North Pacific: irreconcilable differences. by Mark A. Lander University of Guam Central Guam