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• Reviewof2010Atlan1cSeasonalOutlooks• Recapof2010TropicalCycloneAc1vity• Short‐TermTropicalCyclonePredictability
– Genesis,Track,Intensity
• IntraseasonalTropicalCycloneForecasts
CFAN CSU NOAA TSR ECMWF
IssueDate June15 June2 May27 June4 May15
Total 9.3±2.1 10 8‐14 9.5±2.1 20.9±5.4
IssueDate July15 Aug.4 Aug.5 July6 July15
Total 9.0±2.0 9 7‐11 10.4±2.1 9.9±3
HurricaneFrequency
• Above‐normalac1vityforecastbyallwarningagenciesduetoLaNina,recordSSTsinthetropicalAtlan1candCaribbeanSea,andthetropicalmul1‐decadalsignal
• Recordac1vityforecastbyNOAA’sClimateForecastSystemandtheEuropeanSeasonaltoInterannualPredic1onensemble(EUROSIP)
CourtesyofH.‐M.Kim
Predictor patterns
2010 Forecast : Predictors
Dynamical Forecasts
1) Wind Shear 2) NATL SSTs
Forecast
Forecast History
Observation History
Independent Forecast
Hurricane Frequency
Predictors Predictand
Transfer function (Statistical Model)
ObservaCons DynamicalModel WindShear(ERAInterim)SST(ERSST)Hurricanes(HURDAT)
ECMWFSystem3(June/JulyFcst.)
Period:1981‐2009,July‐October
CourtesyofH.‐M.Kim
OBS CFAN CFS CSU NOAA TSR ECMWF
Date Jul(June) Jul‐Aug EarlyAug EarlyAug EarlyAug June
2002 4 3(3) 4 4 4‐6 4 5
2003 7 7(8) 7 8 7‐9 7 8
2004 9 8(7) 7 7 6‐8 8 5
2005 15 9(9) 11 10 9‐11 11 8
2006 5 7(8) 9 7 7‐9 8 13
2007 6 7(7) 9 8 7‐9 8 7
2008 8 9(8) 9 9 7‐10 10 9
2009 3 5(4) 5 4 3‐6 7 4
RMSE
Predictor patterns
June: 9.3 Hurricanes July: 9.0 Hurricanes
CourtesyofH.‐M.Kim
• 18TropicalCyclones• 16NamedStorms(Climatology:9)
• 9Hurricanes(Climatology:6)
• 5MajorHurricanes(Climatology:2)
• AccumulatedCycloneEnergy:142(Climatology:103)
• Records:– Strongesthurricane(JuliaatCat.4)sofareast– TwosimultaneousCat.4+hurricanes(lastset1926)– FourCat.4+hurricanesin20days(lastset1999,24days)– Fastestrateofintensifica1onfromdepressiontohurricane(HRPaula)
– NomajorhurricanelandfallinU.S.for5consecu1veyears(lastsetin1910‐1914)
• TropicalCyclonespreferen1allyformedintheeasterntropicalAtlan1candthewesternCaribbean/BayofCampeche
• WeakerthannormalsubtropicalAtlan1chighcaused‘CapeVerde’hurricanestomoveintotheOpenAtlan1cavoidingtheU.S.Mainland
• CFANprovidesprobabilis1cgenesis,trackandintensityforecaststhatextendoutto15days
• ForecastsarebasedprincipallyontheECMWFVariableEnsemblePredic1onSystem– 51‐membercoupledocean‐atmosphereensemble
– Days1‐10:T699(30km)– Days11‐15:T319(60km)
– Determinis1c:Days1‐10:T1279(16km)
TropicalCyclones
CFAN(indays)30%(60%)
NHC(indays)30%(60%)
HRAlex 5.3(2.5) 3.5(1.0)
TD2 4.0(0.6) 3.8(0.5)
TSBonnie 2.0(0.0) 2.3(0.0)
TSColin 5.0(1.8) 1.8(1.0)
TD5 3.0(0.5) 1.0(0.5)
HRDanielle 9.4(6.1) 1.4(0.1)
MHREarl 3.0(1.6) 1.8(1.5)
TSFiona 5.5(4.5) 4.5(4.5)
TSGaston 1.0(1.0) 1.3(1.0)
MHRIgor 6.0(3.0) 1.4(1.0)
TSHermine 1.6(1.0) 1.8(1.0)
MHRJulia 7.0(5.0) 0.0(0.0)
MHRKarl 7.0(6.0) 1.0(1.9)
HRLisa 6.0(4.0) 3.0(2.3)
TSMafhew 4.0(3.0) 2.0(2.0)
TSNicole 4.0(1.0) 2.0(1.3)
HRO^o 6.0(1.5) 1.0(1.0)
Total CFAN30%(60%)
NHC30%(60%)
AllTCs 4.7(2.5) 2.0(1.2)
Hurricanes 6.2(3.7) 1.6(1.1)
• CFANgenesisverifica1onindicatespredictabilitythrough5days
• CFANprovidedtwicethelead‐1meforTCgenesisthanNHC
CFANFalseAlarmRate– 15%usingmoderate(30‐60%)risk
– 10%usinghigh(60%+)risk
Short‐TermTropicalCycloneForecas1ng
TrackforecastsfromECMWFoutperformothermodelguidanceincludingNHCforDays3+
EnsemblemeandoesNOTmaximizepredictabilityfromensembles,astotaltrackerrorgrowthisNon‐Gaussian
Short‐TermTCForecas1ng:Tracks
Short‐TermTCForecas1ng:Tracks
• Severalhurricanesexperiencedunexpected,rapidintensifica1onincludingJulia,Karl,Igor,andPaula
• NHCintensityperformancesimilartohigh‐resolu1ondynamicalmodelswithaverageintensityerrorscomparabletoperformancefromlast10years
• ECMWFdeterminis1cperformedbeferthanensemblesforDays3‐5(Impactofresolu7on)
Sta7s7csdonotincludeHurricanePaulaorHurricaneO=o
MainDevelopmentRegion(MDR)
Caribbean(CAR)
GulfofMexico(GoM)
ProducConRegion(PR)
• CFANhasprovidedregionalprobabilis1coutlooksforDays1‐15since2007
• RegionaloutlooksareprovidedforfourregionsoftheAtlan1c
• Reliabilityanalysisshowedacategoricalapproachperformsbeferthandiscreteprobabilityvalues:– Minimal(<10%)– Low(10‐30%)– Moderate(30‐60%)
– High(60%+)
• CFANoutperformedECMWFandclimatologyforallregionsduringDays1‐15
• CFANperformancerela1vetoECMWFisduetoabilitytosubjec1velyiden1fyperiodsofhigher(lower)thannormalpredictabilitywhileaccoun1ngforsystema1cerrors
Regions Days1‐5 Days6‐10 Days11‐15
Produc1onRegion
0.75(0.78) 0.68(0.42) 0.70(0.32)
GulfofMexico 0.63(0.38) 0.53(0.13) 0.53(0.19)
Caribbean 0.57(0.43) 0.25(0.24) 0.42(0.20)
MainDevelop.Region
0.61(0.16) 0.19(0.16) 0.41(0.05)
AllRegions 0.65(0.50) 0.45(0.26) 0.54(0.21)
Format:CFAN(ECMWF);StaCsCcallySignificantValuesat95%levelNote:Values>0ForecastSkilfulRela1vetoClimatology
• WhyAfemptIntraseasonalForecasts?– Someatmosphericmemoryfromini1alcondi1ons– Oceancircula1onbeginsforcingatmosphericvariability
– Addi1onalpredictabilitysource:Madden‐JulianOscilla1on
• BenefitsofaMonthlyForecastSystem– Provideaddi1onallead‐1mefordisastermi1ga1on
– Supportadap1vepoliciesformanagingenergyresources– Develophedgingstrategiesbasedonprobabilis1cforecasts
• ECMWFMonthlyForecast– 51‐memberensemble– Days1‐10:T399(50km)– Days11‐32:T255(80km)– Day10+HOPEOceanModel
• TCTrackingScheme– ModifiedfromVitart(1997)– Variablesinclude:
• 850hPaRela1veVor1city• MeanSeaLevelPressure• 500–200hPaTemperatures• 1000–200hPaThickness
StrongAmplitudeMJOatModelIni1aliza1on
WeakAmplitudeMJOatModelIni1aliza1on
21
€
Brier Skill (BS) =1N
(pi − o)2
i=1
N
∑
Brier Skill Score =1− BSBSref
• Regionswithforecastskillinclude:– NorthernCaribbean(Weeks1‐2)
– WesternSubtropicalAtlanCc(Weeks1‐2)– MainDevelopmentRegion(Weeks1‐4)
• ECMWFMonthlyisskillfulatforecas1ngdeep‐layerver1calshearintheGulfofMexicoandMainDevelopmentRegion
• Weakcorrela1oninCaribbean1edtovariabilityinTUTTstrength
• Frequencyofeasterlywavesexplainsabout10‐20%ofthevarianceinECMWFTCforecasts
• Spa1alpafernofcovariabilitycoincideswithregionsofposi1veBrierskillscores
RegionalCorrelaConCoefficients:
• Ingeneral,predictabilityextendsthrough10to15dayswithlongerskillfulforecastsin2009comparedto2008
Phase1
Phase2
Phase3
Phase4
Phase5
Phase6
Phase7
Phase8
TCAnomaly:Full32DaysTCProbability:Full32Days
Whenac1veMJO(>1SD)iscenteredintheIndianOcean(Western
Hemisphere)atmodelini1aliza1on,TCac1vityintheNorthAtlan1cisenhanced
(suppressed)
MJOphasingandintensitymodulates10‐30%ofTCprobabilityforecastsfortheMainDevelopmentRegionandwestern
Caribbean/southernGulfofMexico
• RegionswithSkillfulTCForecastsinclude:– MainDevelopmentRegion:Full32DayPeriod– SouthernGulfofMexico:Weeks1–3
• RegionalTCpredictability1edtodeep‐layerwindshearforecastsandfrequencyofeasterlywaves
• Ini1alphaseofMJOexplains10–30%varianceinTCforecastsacrossMainDevelopmentRegionandwesternCaribbean– MJOphasingandamplitudemodulatesthereliabilityofECMWFTCpredic1ons
• CFANproducedskillfulforecastsintraseasonalforecastsfortheProduc1onRegionandtheMainDevelopmentRegion
• Rela1vetotheshort‐termforecastperiods,theECMWFforecastprobabili1esforDays16‐32werebias‐adjustedbasedonMJOphasing,whichresultedinhigherBrierSkillScores
Regions Days1‐5 Days6‐10 Days11‐15 Days16‐32
Produc1onRegion
0.75(0.78) 0.68(0.42) 0.70(0.32) 0.22(0.18)
GulfofMexico 0.63(0.38) 0.53(0.13) 0.53(0.19) ‐0.26(‐0.27)
Caribbean 0.57(0.43) 0.25(0.24) 0.42(0.20) 0.04(‐0.01)
MainDevelop.Region
0.61(0.16) 0.19(0.16) 0.41(0.05) 0.45(0.27)
AllRegions 0.65(0.50) 0.45(0.26) 0.54(0.21) 0.08(0.01)