# Presentation: 323602

## Targeting strategies to improve hurricane track forecasts (JHT 03-05)

- PIs: Dr Sharanya J. Majumdar (University of Miami)
- Dr Sim D. Aberson (NOAA/AOML/HRD)
- Co-PIs: Dr Zoltan Toth (NOAA/NWS/NCEP/EMC),
- Ms Lacey D. Holland (SAIC at EMC),
-  Dr Brian J. Etherton (UNC Charlotte),
- Mr Paul Leighton (NOAA/AOML/HRD)
- (Acknowledgment: Mr Richard Wobus (EMC))

- Interdepartmental Hurricane Conference, Charleston, SC. March 3rd 2004

## Targeted Observations

- Motivation
- To improve tropical cyclone track and intensity forecasts by selective deployments of observations in the storm’s environment.
- NOAA G-IV Synoptic Surveillance missions use targeted GPS dropwindsondes.
- Present strategy: direct aircraft towards locations in which the “spread” (or standard deviation) of an ensemble forecast is large at the observation time.

## Ensemble Spread Fcst for 2003091400: Isabel

**x**

**x** : Isabel’s Center

## New Targeting Strategy

- Ensemble Transform Kalman Filter (ETKF)
- Has been used operationally by NWS for Winter Storm Reconnaissance since 2001
- Theory: Bishop *et al.* (MWR, 2001)
- Targeted Observations: Majumdar *et al.* (QJRMS 2001, MWR 2002, QJRMS 2002)
- Ensemble Initialization: Wang and Bishop (JAS, 2003)
- Data Assimilation: Etherton and Bishop (MWR, 2004)

## How the ETKF works

- ETKF uses operational ensemble forecasts to rapidly predict signal variance = reduction in error variance for any deployment q of adaptive observations:
- Sq = PN – Pq = MPN(ta)HqT (HqPN(ta)HqT+R)-1HqPN(ta) MT
-                          = ZN(tv) TN Cq q (q+I)-1 CqT TNT ZNT(tv)

- ti

- td

- ta

- tv

- Ensemble
- Initialization time

- Decision
- time

- Targeted Observing
- (analysis) time

- Verification
- time

- t

## Summary Maps of Signal Variance

- ETKF predicts signal variance (reduction in forecast error variance) for all feasible deployments of targeted observations.
- Summarize these predictions in the form of a map or bar chart.

##  ETKF Summary Map: Fabian

##  ETKF Summary Map: Isabel

## ETKF predicts the variance of the “signal” : the impact of the targeted observations on the operational forecast.

**ETKF PREDICTED SIGNAL VAR.**

**ACTUAL NCEP GFS SIGNAL**

- Preliminary result from Hurricane Fabian

- 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**

## ETKF predicts the variance of the “signal” : the impact of the targeted observations on the operational forecast.

**ETKF PREDICTED SIGNAL VAR.**

**ACTUAL NCEP GFS SIGNAL**

- 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 Work

- Examine 2003 targeting missions (5 Atlantic, 2 NW Pacific cyclones): Develop ETKF further, e.g. investigate vortex removal techniques and focus on storm asymmetries
- Extend to “norms” of hurricane track and intensity (currently using simple norm of wind speed, which is used in WSR)
- Synoptic assessment of ETKF summary maps and signal variance propagation
- Quantitative tests of ETKF’s ability to predict signal variance and reduction in forecast error variance
- Adapt scripts to run for GFDL and SHIPS models

## Ongoing Work

- ECMWF 1-deg ensembles are now available (Jan 04), and NCEP GFS 1-deg ensembles will soon be produced beyond 84h
- ETKF software is being developed within the framework of Winter Storms: easy interface
- Work in progress disseminated on Web site: http://orca.rsmas.miami.edu/~majumdar/tc/

## Summer 2004 – Summer 2005

- Run improved ETKF for 1-deg ensembles for synoptic surveillance cases in upcoming 2004 hurricane season.
- Regular communication with NHC once satisfactory version of ETKF is developed.
- Communication with Taiwan (Dr Chun-Chieh Wu): Advising targeted observing locations for typhoon reconnaissance.
- Combine ETKF software with flight track design software developed by Dr Sim Aberson under JHT funding.
- Transition of ETKF software to operations.