•  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)