Targeting strategies to improve Targeting strategies to improve hurricane track forecasts (JHT 03-hurricane track forecasts (JHT 03-

05)05)

PIs: PIs: Dr Sharanya J. Majumdar (University of Miami)Dr Sharanya J. Majumdar (University of Miami)Dr Sim D. Aberson (NOAA/AOML/HRD)Dr Sim D. Aberson (NOAA/AOML/HRD)

Co-PIs:Co-PIs: Dr Zoltan Toth (NOAA/NWS/NCEP/EMC), Dr Zoltan Toth (NOAA/NWS/NCEP/EMC),

Ms Lacey D. Holland (SAIC at EMC),Ms Lacey D. Holland (SAIC at EMC), Dr Brian J. Etherton (UNC Charlotte),Dr Brian J. Etherton (UNC Charlotte),Mr Paul Leighton (NOAA/AOML/HRD)Mr Paul Leighton (NOAA/AOML/HRD)

(Acknowledgment: Mr Richard Wobus (EMC))(Acknowledgment: Mr Richard Wobus (EMC))

Interdepartmental Hurricane Conference, Charleston, SC. March 3rd

2004

Targeted ObservationsTargeted Observations• MotivationMotivation

•To improve tropical cyclone track and intensity To improve tropical cyclone track and intensity forecasts by selective deployments of forecasts by selective deployments of observations in the storm’s environment.observations in the storm’s environment.

•NOAA G-IV Synoptic Surveillance missions use NOAA G-IV Synoptic Surveillance missions use targeted GPS dropwindsondes.targeted GPS dropwindsondes.

•Present strategy: direct aircraft towards Present strategy: direct aircraft towards locations in which the “spread” (or standard locations in which the “spread” (or standard deviation) of an ensemble forecast is large at deviation) of an ensemble forecast is large at the observation time.the observation time.

Ensemble Spread Fcst for 2003091400: Ensemble Spread Fcst for 2003091400: IsabelIsabel

x

x : Isabel’s Center

New Targeting StrategyNew Targeting Strategy

• Ensemble Transform Kalman Filter (ETKF)Ensemble Transform Kalman Filter (ETKF)

•Has been used operationally by NWS for Winter Storm Reconnaissance since 2001

•Theory:Theory: Bishop Bishop et al.et al. (MWR, 2001) (MWR, 2001)

•Targeted Observations:Targeted Observations: Majumdar Majumdar et al.et al. (QJRMS (QJRMS 2001, MWR 2002, QJRMS 2002)2001, MWR 2002, QJRMS 2002)

•Ensemble Initialization:Ensemble Initialization: Wang and Bishop (JAS, Wang and Bishop (JAS, 2003)2003)

•Data Assimilation:Data Assimilation: Etherton and Bishop (MWR, Etherton and Bishop (MWR, 2004)2004)

How the ETKF worksHow the ETKF works

ETKF uses operational ensemble forecasts to rapidly ETKF uses operational ensemble forecasts to rapidly predict predict signal variancesignal variance = = reduction in error reduction in error variancevariance for any deployment q of adaptive for any deployment q of adaptive observations:observations:

SSqq = P = PNN – P – Pqq = MP = MPNN(t(taa)H)HqT qT (H(HqqPPNN(t(taa)H)HqTqT+R)+R)-1-1HHqqPPNN(t(taa) M) MTT

= = ZZNN(t(tvv)) TTNN CCq q q q ((qq+I)+I)-1 -1 CCqT qT TTNTNT ZZNTNT(t(tvv))

ttii ttdd ttaa tt

vv

EnsembleEnsemble

Initialization timeInitialization timeDecisionDecision

timetimeTargeted ObservingTargeted Observing

(analysis) time(analysis) timeVerificationVerification

timetime

tt

Summary Maps of Signal Summary Maps of Signal VarianceVariance

ETKF predicts signal variance ETKF predicts signal variance (reduction in forecast error variance) (reduction in forecast error variance)

for all feasible deployments of for all feasible deployments of targeted observations.targeted observations.

Summarize these predictions in the Summarize these predictions in the form of a map or bar chart.form of a map or bar chart.

ETKF Summary Map: ETKF Summary Map: IsabelIsabel

ETKF PREDICTED SIGNAL VAR.ETKF PREDICTED SIGNAL VAR.ACTUAL NCEP GFS SIGNAL ETKF predicts the

variance of the “signal” : the impact

of the targeted observations on the operational forecast.

Preliminary result from Hurricane

Isabel

ETKF uses 20-member 1-degree res NCEP GFS Ensemble, initialized 24-

36h prior to targeted observing time.

Impact on GFS analysis

Impact on 1-day forecast

Impact on 2-day forecast

Ongoing WorkOngoing Work• Examine 2003 targeting missionsExamine 2003 targeting missions (5 Atlantic, 2 NW Pacific cyclones): (5 Atlantic, 2 NW Pacific cyclones):

Develop ETKF further, e.g. investigate vortex removal techniques and Develop ETKF further, e.g. investigate vortex removal techniques and focus on storm asymmetriesfocus on storm asymmetries

• Extend to “norms” of hurricane track and intensityExtend to “norms” of hurricane track and intensity (currently using (currently using simple norm of wind speed, which is used in WSR)simple norm of wind speed, which is used in WSR)

• Synoptic assessmentSynoptic assessment of ETKF summary maps and signal variance of ETKF summary maps and signal variance propagationpropagation

• Quantitative testsQuantitative tests of ETKF’s ability to predict signal variance and of ETKF’s ability to predict signal variance and reduction in forecast error variancereduction in forecast error variance

• Adapt scripts to run for Adapt scripts to run for GFDLGFDL and and SHIPSSHIPS models models

Ongoing WorkOngoing Work

• ECMWF 1-deg ensembles are now available ECMWF 1-deg ensembles are now available (Jan 04), and NCEP GFS 1-deg ensembles will (Jan 04), and NCEP GFS 1-deg ensembles will soon be produced beyond 84hsoon be produced beyond 84h

• ETKF software is being developed within the ETKF software is being developed within the framework of Winter Storms: easy interfaceframework of Winter Storms: easy interface

• Work in progress disseminated on Web site: Work in progress disseminated on Web site: http://orca.rsmas.miami.edu/~majumdar/tc/http://orca.rsmas.miami.edu/~majumdar/tc/

Summer 2004 – Summer Summer 2004 – Summer 20052005

• Run improved ETKF for Run improved ETKF for 1-deg ensembles1-deg ensembles for synoptic surveillance for synoptic surveillance cases in upcoming cases in upcoming 2004 hurricane season2004 hurricane season..

• Regular communication with NHCRegular communication with NHC once satisfactory version of ETKF once satisfactory version of ETKF is developed.is developed.

• Communication with TaiwanCommunication with Taiwan (Dr Chun-Chieh Wu): Advising targeted (Dr Chun-Chieh Wu): Advising targeted observing locations for typhoon reconnaissance.observing locations for typhoon reconnaissance.

• Combine ETKF software with Combine ETKF software with flight track design softwareflight track design software developed developed by Dr Sim Aberson under JHT funding.by Dr Sim Aberson under JHT funding.

• Transition of ETKF software to operations.Transition of ETKF software to operations.