Mitsuru Ueno (MMitsuru Ueno (MRIRI/TRD)/TRD)

Recent Advancements in the Understanding of Recent Advancements in the Understanding of Typhoon InnerTyphoon Inner--Core StructuresCore Structures

and its Implication for Typhoon Vortex Initializationand its Implication for Typhoon Vortex Initialization

The 1The 1--st International Workshop on Prevention and Mitigationst International Workshop on Prevention and Mitigationof Meteorological Disasters in Southeast Asia, March 3of Meteorological Disasters in Southeast Asia, March 3--5, 20085, 2008

A number of previous studies suggest thatA number of previous studies suggest thatinnerinner--core processes could play a significantcore processes could play a significantrole in the evolution of TC structure.role in the evolution of TC structure.

●● The structure and evolution of vortexThe structure and evolution of vortex--RossbyRossby wavewave/ / eyewalleyewall mesomeso vortices depend onvortices depend onthe symmetric PV structure in the innerthe symmetric PV structure in the inner--core region.core region.

●● EyewallEyewall mixing occurred associated withmixing occurred associated withvortexvortex--RossbyRossby wave contributes to subsequentwave contributes to subsequentTC structure and intensity changes.TC structure and intensity changes.

If smoothed initial conditions are provided, a vortex If smoothed initial conditions are provided, a vortex spinupspinupwill introduce a delay or incorrect timing/magnitude of thewill introduce a delay or incorrect timing/magnitude of thetriggering of vortex triggering of vortex RossbyRossby waves or waves or eyewalleyewall mixing events.mixing events.

(Elsberry 2002)(Elsberry 2002)

益子さんの図

HydrometeorsHydrometeors VorticityVorticity

Case Study: Case Study: Typhoon Typhoon RusaRusa (2002)(2002)

MashikoMashiko (2005)(2005)

Braun et al.Braun et al.(2006)(2006)

Case Study:Case Study:Hurricane Hurricane Bonnie (1998)Bonnie (1998)

VorticityVorticityVertical motionVertical motionAsymmetric flowAsymmetric flow

Some recent studies suggest that Some recent studies suggest that wavenumberwavenumber--oneoneasymmetries in precipitation in the innerasymmetries in precipitation in the inner--core regioncore regionand vertical tilt of TC vortices are attributable toand vertical tilt of TC vortices are attributable toenvironmental vertical wind shear, and theirenvironmental vertical wind shear, and theiramplitudes depend on the amplitudes depend on the TC strengthTC strength as well asas well asshear magnitude.shear magnitude.

35.0

37.5

40.0

42.5

45.0

FORECAST HOUR = 6-12 composit

2535.0

37.5

40.0

42.5

45.0

FORECAST HOUR = 6-12 composit

25

35.0

37.5

40.0

42.5

45.0

FORECAST HOUR = 6-12 composit

25

Environmental shear can be a significant contributorEnvironmental shear can be a significant contributorto wind and rainfall asymmetries.to wind and rainfall asymmetries.

Case Study:Case Study: Typhoon Typhoon SongdaSongda (2004)(2004)

Not rare case!Not rare case!

MSM analysis

Radar_Composit

RMW~30km

9h integration at a very high resolution of 667 m

RMW~200km

hard to spin up thevortex well in a shortterm even with a veryhigh resolution model

Shallower thanobserved

Steady inintensity

Developingspuriously

Case Study:Case Study: Typhoon Typhoon RusaRusa (2002)(2002)

Braun et al. (2006)Braun et al. (2006)

Case Study:Case Study: Hurricane Bonnie (1998)Hurricane Bonnie (1998)

Vertical motionVertical motion

At present, a feasible option to prepareAt present, a feasible option to preparea realistic typhoon innera realistic typhoon inner--core structurecore structure

in the initial fields for high resolution modelsin the initial fields for high resolution modelsisis

to use a TC to use a TC bogusingbogusing method.method.

In the ongoing study, a revised version ofIn the ongoing study, a revised version ofJMA TC JMA TC bogusingbogusing procedure, which is bestprocedure, which is best--tunedtuned

to high resolution models, will be sought.to high resolution models, will be sought.

Distinctive aspects of JMA TC Distinctive aspects of JMA TC bogusingbogusing methodmethod

● Mass fields are specified ahead of wind ones.Mass fields are specified ahead of wind ones.● MSLP profile is the cornerstone of the method.MSLP profile is the cornerstone of the method.● 33--D mass fields are constructed based onD mass fields are constructed based on

an analytical function which containsan analytical function which containssome arbitrary parameters.some arbitrary parameters.

Issues to be tackled in the current methodIssues to be tackled in the current method

● The arbitrary parameters are best tuned toThe arbitrary parameters are best tuned tothe models of tensthe models of tens--ofof--kilometer resolution.kilometer resolution.

● MSLP profile is basically determined fromMSLP profile is basically determined fromgalegale--force wind radius and central pressure,force wind radius and central pressure,therefore, detailed innertherefore, detailed inner--core structures such ascore structures such asRMW are not always correctly specified.RMW are not always correctly specified.

● Vortex tilt is not explicitly considered.Vortex tilt is not explicitly considered.

Possible ways to resolve the listed issuesPossible ways to resolve the listed issues

● To reexamine the validity of current setting To reexamine the validity of current setting of the parameters and best tune themof the parameters and best tune themto high resolution models making use ofto high resolution models making use ofobservational dataobservational data

● To replace the formula for MSLP profile withTo replace the formula for MSLP profile withanother one which has more degree of freedom,another one which has more degree of freedom,so that the information on RMW can be utilizedso that the information on RMW can be utilizedin the in the bogusingbogusing procedureprocedure

● To explore the specification method of innerTo explore the specification method of inner--corecoreasymmetries including vortex tiltasymmetries including vortex tilt

Data collected so far for the studyData collected so far for the study

● Observational dataObservational dataPeriod:Period: 20042004--20072007Surface:Surface: SYNOP, METAR, SHIP, BUOYSYNOP, METAR, SHIP, BUOYUpper:Upper: TEMP, PILOTTEMP, PILOT

● Best track dataBest track dataPeriod:Period: 20042004--20072007Region:Region: NW Pacific, NE Pacific, AtlanticNW Pacific, NE Pacific, Atlantic

● Global analysesGlobal analysesPeriod:Period: 2004 (not all), 2005 (not all)2004 (not all), 2005 (not all)

Verification of Analysis against Verification of Analysis against SondeSonde etc.etc.

36.7138.6820033.0445.4325032.8841.6230034.5936.9640032.3132.8950033.6637.8470037.8740.5785038.9038.90Surf.NewOpe.Level

Verification of Bogus Data against Verification of Bogus Data against SondeSonde etc.etc.in the nearin the near--core areacore area

GPH (m)

7.998.512007.588.312507.748.883008.279.744008.049.125008.989.50700

11.7311.9785016.7716.77Surf.NewOpe.Level

Wind (m/s)

SummarySummary

● Previous studies suggest that a high resolution modelPrevious studies suggest that a high resolution modelis needed to obtain accurate forecasts of TC inneris needed to obtain accurate forecasts of TC inner--corecorestructures (such as detailed wind and rainfallstructures (such as detailed wind and rainfalldistributions in the neardistributions in the near--core region) and theircore region) and theirevolutions.evolutions.

● According to our numerical experiences, conventionalAccording to our numerical experiences, conventionalobservational network is not enough to provide initialobservational network is not enough to provide initialTC fields suited for high resolution models, and anTC fields suited for high resolution models, and anad hoc procedure such as ad hoc procedure such as bogusingbogusing one is neededone is neededto avoid the spinto avoid the spin--up problem arising from the use ofup problem arising from the use ofsmoothed initial conditions.smoothed initial conditions.