32nd ConferenceonHurricanesandTropicalMeteorology18–22April2016,SanJuan,PR
[email protected] pdf ofthisposter
Poster#80ComparingCI-number/PressureRelationshipsintheWesternPacificusingHURSAT-ADTandHistoricalReconnaissance
CarlJ.Schreck III1,2,K.R.Knapp2,J.P.Kossin2,andC.Velden31NCSU’sCooperativeInstituteforClimateandSatellitesNorthCarolina(CICS-NC),2NOAA’sNationalCentersforEnvironmentalInformation,3Wisconsin-Madison’sCooperativeInstituteforMeteorologicalSatelliteStudies(CIMSS)
Conclusions
• BothDvorakandKoba WPRsareinconsistentwithKnaff–Zehr forstrongerstorms
• Koba’s pressuresaregood,butthewindsaretooweakwhenconvertedtopressure
• Dvorak’spressuresaretoostrong,butthewindsconvertedtopressurearegood
• ThisanalysissupportsoperationalpracticeofusingDvoraktoestimatewindsandthenconvertingtopressureusingKnaff–Zehr
MapoffixeswithbothaircraftandHURSAT-ADTintensityestimates
Data&Methods
Reconnaissancedata• ObtainedfromJTWC
F-Decksfor1978–1987
• Usingpressurecalculatedfromminimumflight-levelheight
HURSAT-ADT• ADTalgorithmappliedtoHURSATdata(seeKossin etal.
2013)• Onlyusesinfrareddatafromgeostationarysatellites• Mayunderestimateintensities,esp.forstormwith
developingeyesorwithverysmalleyes
MatchaircraftpressurewithnearestHURSAT-ADTfixwithin3hours• Koba etal.(1991)manuallyanalyzed855fixesfor50
storms• Ourmethodproduces1972fixesfrom163storms
HURSAT-ADTandAircraftPressure
Top:HistogramofHURSAT-ADTCInumbersandpressuresderivedfromflight-levelheightsBottom: Deviationsfromthemedianobservedpressureforeachtable
BroadagreementforstormsweakerthanT-5.0and960hPa
Tablesdivergeforstrongerstorms• AircraftpressuresroughlyalignwiththosefromKoba• Dvorakpressuresaretoolowforstrongerstorms• Koba winds,whenconvertedtopressurethroughKnaff–Zehr,aretoo
weakforstrongerstorms• Dvorakwinds,convertedtopressurethroughKnaff–Zehr,match
observations
Problem
JTWCandJMAproduceverydifferentestimatesofTyphoonstrength
Histogramof1-minbesttrackwinds(left:JTWC,right:JMA)andaircraftreconnaissancepressures.
• JTWCusestheDvoraktables• JMAusesKoba tables,whichhavelowerwindsforthe
strongeststorms• Differencesextendwellbeyondwindaveragingperiods(10-
minutevs.1-minute)• Aircraftreconnaissanceendedin1987,andeventhenwind
estimateswerecrudebytoday’sstandards
Wind–PressureRelationships
Knaff &Zehr (2007)andKnaff &Sampson(2006):
Vsrm Storm-relativewindspeed Vsrm = Vmax −1.5 c0.63
S Normalizedsize parameter 0.64Penv EnvironmentalPressure 1008.9Φ Latitude 18.85°∆P Penv − MSLPc Stormmotion 9.6
GlossaryandReferencesJTWC:JointTyphoonWarningCenter JMA:JapaneseMeteorologicalAgency ADT:AdvancedDvorakTechniqueDvorak,V.F.,1984:Tropical cycloneintensityanalysisusingsatellitedata.NOAATech.Rep.NESDIS11,45pp.Knaff, J.A.,andC.R.Sampson,2006:ReanalysisofWestPacifictropicalcycloneintensity1966–1987.Preprints,27thConf.onHurricanesandTropical
Meteorology,Monterey,CA,Amer.Meteor.Soc..Knaff, J.A.,andR.M.Zehr,2007:ReexaminationofTropicalCycloneWind–PressureRelationships.Wea.Forecasting,22,71–88,doi:10.1175/WAF965.1.Koba,H.,T.Hagiwara,S.Osano,andS.Akashi,1991:RelationshipsbetweenCInumber andminimum sealevelpressure/maximumwindspeedoftropical
cyclones.Geophys.Mag.,44,15–25.Kossin, J.P.,T.L.Olander,andK.R.Knapp,2013:Trendanalysiswithanewglobal recordoftropicalcycloneintensity.J.Climate,26,9960–9976,doi:10.1175/JCLI-
D-13-00262.1.
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