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The Effect of Latent Heat on the Extratropical Transition of Typhoon Sinlaku (2008)

By: Michael Kevin Hernández

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• What is an extratropical transition (ET)?

• Why is this important to study ETs?

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• What are the current problems in modeling & defining ETs?

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Problem: What is the sensitivity of ET onset and completion to latent heating from the storm and surrounding area?

Hypothesis: The baroclinic processes alone would not suffice to initiate the ET of Typhoon Sinlaku.

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Most extratropical transitions (ET) of tropical cyclones (TC) re-intensify. The area of gale force winds may increase by a factor of 10.

Tropical Storm

Tropical Cyclones

Extratropical Cyclones

Dissipate

~50%

(Hart & Evans 2001; Jones et al. 2003; Guishard 2006)

Other

~10%

~40% 100%

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Extratropical Cyclones can cause loads of localized damage, e.g. 1996 Post-TC Hortense and 2007 Post-TC Noel.

http://www.hurricanecity.com

http://www.hurricanecity.comhttp://www.shunpiking.com

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Even the smallest vortex can trigger and amplify downstream planetary waves.

0 5 10 15 20

2 1 0 -1 -2 Y

[100

0km

]

x [1000km]

Absolute vorticity [10-5s-1]

-2.0 -1.6 -1.2 -0.8 -0.4 0.0 0.4 0.8 1.2 1.6 2.0

(Riemer 2010)

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Joint Typhoon Warning Center’s Best Track of Typhoon Sinlaku (2008)

Sept. 7

Sept. 9

Sept. 12

Sept. 14

Sept. 17

Sept. 19

Sept. 20 Sept. 21Sept. 18

Case study:

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ECMWF best track and model ensemble members of Sinlaku, but with perturbed initial conditions.

Sept. 2008

latit

ude

longitude

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Small perturbations in the initial conditions lead to huge differences in the interaction of the cyclone and the trough.

ensemble member 4

latit

ude

longitude

ensemble member 8

ensemble member 21

ensemble member 5

ensemble member 10

ensemble member 9

72 hour forecast

Hart (2003) definition: Cyclone Phase Space on ECMWF analysis of Typhoon Sinlaku.

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ET onset

ET completion

120 140 160 180

40

20

Baro

clin

city

(B)

100

50

0

-50

Thermal wind at 900-600 hPa (-VLT)

-300 -200 -100 0 100 200 300

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Assuming Hart (2003) definitions of ET onset and completion, a 50 member ensemble forecast model still cannot pinpoint the ET process temporally.

Sept. 13 Sept. 14 Sept. 15 Sept. 16 Sept. 17 Sept. 18 Sept. 19 Sept. 20 Sept. 21 Sept. 22

ECMWF 50 member ensemble for ET onsetECMWF 50 member ensemble for ET completion

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There is no universal definition for ET onset or completion.

ECMWF analysis

ECMWF analysis

Japan Meteorological Agency

Joint Typhoon Warning Center

Joint Typhoon Warning Center

Klein et al. (2000) analysis

Klein et al. (2000) analysis

Japan Meteorological Agency

Sept. 13 Sept. 14 Sept. 15 Sept. 16 Sept. 17 Sept. 18 Sept. 19 Sept. 20 Sept. 21 Sept. 22

Onset

Completion

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Another method for the ET definition is defined by Klein et al. (2000), which uses satellite analysis.

17 Sept 0930 UTC CIRRUS EDGE

POSSIBLE WARM FRONTOGENESIS

EYEWALL EROSION

DRY SLOTDRY SLOT

18 Sept 1130 UTC

19 Sept 1830 UTC

ET onset: 17 Sept 0800 UTCET completion: 19 Sept 1800 UTC

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Question:

What is the sensitivity of extratropical transition onset and completion to latent heating from the storm and surrounding area?

Hypothesis:

The baroclinic processes alone would not suffice to initiate the extratropical transition of Typhoon Sinlaku.

Experiments:

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• WRF (ARW core) V3.0.1 model• Physics (FULL)• 9 km (outer) domain: Kain–Fritsch cumulus

parameterization • 3 km (inner) domain: convection is explicitly resolved

• Physics (Fake Dry Tropical Cyclone - FDTC)• Same as FULL but:• No cumulus parameterization on any domain • Latent heating turned off in the microphysics

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We would want the domain to be from 15-65oN & 120-175oE

longitude

latit

ude

The ideal domain didn’t produce ideal results.

latit

ude

longitude

Moving the domain further south still meant that the trough was still in the domain. But not by much.

latit

ude

longitude

Now the boundaries are feeding a some information about the trough into the simulation.

latit

ude

longitude

There is a lot more information of the trough that is no longer explicit.

latit

ude

longitude

Feeding in the information of the entire trough isn’t producing ideal results either.

latit

ude

longitude

Domain size:

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– First (static) domain:• 740 × 430 points at 9 km horizontal

resolution• centered at 33N and 150E• 36 vertical levels

– Second (vortex following) domain:• 330 × 330 points at 3 km horizontal

resolution• 36 vertical levels

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Varying the physics parameterizations, while keeping the northern boundary at 50oN, led to differences in TC track and intensity.

Tracks

JTWC

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Latent heating affects whether the TC dies early, follows the best track, and the intensity of the storm.

Tracks

JTWC best trackMin pressure [hPa]

pres

sure

over land

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Deep layer mean (DLM) winds influence TC tracks and the DLM in each simulation varies: 900-200 hPa layer for FULL; 800-500 hPa layer for FDTC. While the JTWC best track is the arrow in black.

FULL

FDTC

1: The synoptic flow pattern at 700-200 hPa was influenced by a lack of latent heating.

FULL FDTC17 Sept

18 Sept

19 Sept

50o

40o

30o

20o

50o

40o

30o

20o

50o

40o

30o

20o

120o 140o 160o 175o 120o 140o 160o 180o

H H

2: The synoptic flow pattern at 700-200 hPa was influenced by a lack of latent heating.

FULL FDTC

20 Sept

21 Sept

19 Sept

50o

40o

30o

20o

50o

40o

30o

20o

50o

40o

30o

20o

120o 140o 160o 175o 120o 140o 160o 180o

H

H

H

H

H H

8070

60

50

4030

2010

0Sept. 17 18 19 20 21

FULL case: TC weakens (KE decrease) once the 500 hPa trough has passed by.

HH H

50o

40o

30o

20o

120o 140o 160o 175o 120o 140o 160o 175o 120o 140o 160o 175o

m2 S

-2 a

rea-2

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8070

60

50

4030

2010

0Sept. 17 18 19

FDTC case: TC weakens still (KE decreases) even as the 500 hPa trough has passed by.

50o

40o

30o

20o

120o 140o 160o 175o 120o 140o 160o 175o 120o 140o 160o 175o

H H H

m2 S

-2 a

rea-2

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The core of the storm within 6 hours and out between both simulations also are influenced by latent heat.

+6 hrs

17 Sept 00 UTC

17 Sept 06 UTC 20 Sept 12 UTC

17 Sept 06 UTC 18 Sept 12 UTC

First 6 hrs

+30 hrs

+78 hrs

FULL

FDTC

weak core

cold air seclusion

warm frontogenesis

cold

frontogenesis

strong core

banding

Near the end of the TC life

+6 hrs

Near the end of the simulation

In summary, modeling ET of TC is hard even if we had a universal definition.• Tracks • Dynamically

• Temporally

• Boundary placement • Choice of model physics

Sept. 13 Sept. 14 Sept. 15 Sept. 16 Sept. 17 Sept. 18 Sept. 19 Sept. 20 Sept. 21 Sept. 22

ECMWF 50 member ensemble for ET onsetECMWF 50 member ensemble for ET completion

Latent heating is needed to maintain the TC and allow the TC to undergo ET.

• Synoptics

• KE

19 Sept21 Sept

w/ latent heat w/o latent heat

• Inner core

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Future work:

Questions?

• Two more new simulations: 1) Remove TC with FULL Physics 2) Remove TC with FDTC Physics

• FDTC simulation suggests an opportunity to explore the evolution of the 500 hPa trough in the absence of TC and Latent Heating.

Hypothesis: ConfirmedThe baroclinic processes alone would not suffice to initiate the extratropical transition of Typhoon Sinlaku.

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Supplementary slides

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Varying the physics parameterizations, while keeping the northern boundary at 50oN, led to differences in TC track and intensity.

Physics set name Microphysics SW radiation PBL Similarity

theoryCumulus scheme

GKF Goddard Goddard Pleim-Xu Pleim-Xu Kain-Fritsch

GGD Goddard Goddard Pleim-Xu Pleim-Xu Grell-Devenyi

WSM5KF WSM 5 class Goddard MYJ ETA Kain-Fritsch

WSM6KF WSM 6 class MM5 YSU MM5 Kain-Fritsch

WSM6GD WSM 6 class MM5 YSU MM5 Grell-Devenyi

Hernandez et al. (‘09) WSM 5 class Goddard YSU MM5 Kain-Fritsch

track differences

JTWC

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Model Configurations:• WRF (ARW core) V3.0.1• Physics (FULL)

• WSM 5 class microphysics• Goddard SW radiation• RRT LW radiation• 5-layer thermal diffusion Land-surface • MYJ PBL• ETA Surface Model• KF Cumulus parameterization

• turned off for domains with resolution exceeding 5 km

• Physics (FDTC)• Same as FULL but

• No cumulus parameterization• Latent heating turned off in the microphysics

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How I calculated the Deep layer mean (DLM) winds.

FULL

FDTC

Z = 0

Z = h

…weighted average