# Presentation: 028984

## ETKF PLANNED FLIGHT

**NOAA G-IV AIRCRAFT TRACK AROUND HURRICANE IVAN.**

**ETKF PLANNED FLIGHT**

**ACTUAL G-IV FLIGHT**

## Testing the Ensemble Transform Kalman Filter strategy for targeted observations during the 2004 Atlantic Hurricane Season (JHT 03-05)

- Dr Sharanya J. Majumdar (University of Miami)
- Dr Sim D. Aberson (NOAA/AOML/HRD),
- Dr Brian J. Etherton (UNC Charlotte),
- Mr Paul Leighton (NOAA/AOML/HRD),
- Dr Zoltan Toth (NOAA/NWS/NCEP/EMC).
- TPC/NHC Point of Contact: Mr James Franklin.

- 59th Interdepartmental Hurricane Conference, Jacksonville, FL. March 9th 2005.

## 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: drop sondes in locations in which the “spread” of the NCEP GFS ensemble forecast 850-200hPa deep layer mean wind is large at the observation time.

## Ensemble Transform Kalman Filter (ETKF)

- Used annually by NWS for Winter Storm Reconnaissance since 2001.

- ti

- to

- tv

- Initialization time

- Observing time

- Verification time

- t

- 2 days

- 1-3 days

-   Sq = Pr – Pq = M Pr(to) HqT (Hq Pr(to) HqT+Rq)-1 Hq Pr(to) MT

## 2004 Hurricane Season

- ETKF maps of “reduction in wind forecast error variance” for all feasible deployments of targeted observations were produced in real-time.
- A combination on uniform sampling, ensemble spread and ETKF were used to design G-IV synoptic surveillance tracks.
- ETKF and Ensemble Spread maxima were traversed by “travelling salesman” flight planner code (Aberson and Leighton, prior JHT) to plot coordinates.

## Hurricane Frances: September 2 2004, 00Z

**SPREAD**

**ETKF**

## Hurricane Jeanne: September 24 2004, 00Z

**SPREAD**

**ETKF**

## Hurricane Jeanne: September 25 2004, 00Z

**SPREAD**

**ETKF**

## Evaluation of Targeted Observations

- 4 PARALLEL CYCLES:
- AVNO: operational cycle with all dropwindsonde data
- AVNN: no dropwindsonde data are assimilated
- AVTG: only those dropwindsonde data that meet the targeting requirements of Aberson (2003) are assimilated
- AVET: as in AVTG, but with targets selected by the ETKF
- The removal of between one-third and one-half of the dropwindsonde data from the data assimilation did not appreciably change the errors of the forecasts.
- Testing with the remainder of the 31 cases from the 2004 season is proceeding.

**Notes:**
	In the Charley case (Fig. 2), for the AVTG run, the six dropwindsondes extending from the eastern tip of Cuba to southwest of Jamaica, the two northernmost dropwindsondes to the east of Florida, the dropwindsonde near Cozumel, Mexico, and the eight dropwindsondes extending from the northern tip of the Yucatan peninsula to Tampa (except the one dropwindsonde closes to Key West), were removed from the data assimilation cycle.  For the AVET run, the dropwindsonde at the easternmost tip of Cuba, the two northernmost dropwindsondes east of Florida, the dropwindsonde near Cozumel, Mexico, and the eight dropwindsondes extending from the northern tip of the Yucatan peninsula to Tampa were removed from the data assimilation cycle.  Figure 3 shows the track forecasts for the four runs, and the errors are shown in Table 1. 
	In the Frances case (Fig. 4), for the AVTG run, all dropwindsonde data from the round-robin flight from Keesler Air Force base and the three northeasternmost dropwindsondes were removed from the data assimilation cycle.  For the AVET run, all dropwindsonde data from the round-robin flight from Keesler Air Force base and the two northernmost dropwindsondes northeast of Hurricane Frances were removed from the data assimilation cycle.  Figure 5 shows the track forecasts for the four runs, and the errors are shown in Table 2.  The errors for all four runs are much smaller than those of the Charley case, and only small differences between all the forecasts are evident.

	The results of these two cases, in addition to similar AVTG tests completed for the 2003 hurricane season, continue to suggest that the targeting and sampling strategy described in Aberson (2003) is appropriate for the design of flight tracks for the improvement of tropical cyclone track forecast.  In both of these cases, the removal of between one-third and one-half of the dropwindsonde data from the data assimilation did not appreciably change the errors of the forecasts. The results of these two cases for the AVET version is only preliminary, and no conclusions can yet be drawn.
Testing with the remainder of the 31 cases from the 2004 season is proceeding.
	In the Charley case (Fig. 2), for the AVTG run, the six dropwindsondes extending from the eastern tip of Cuba to southwest of Jamaica, the two northernmost dropwindsondes to the east of Florida, the dropwindsonde near Cozumel, Mexico, and the eight dropwindsondes extending from the northern tip of the Yucatan peninsula to Tampa (except the one dropwindsonde closes to Key West), were removed from the data assimilation cycle.  For the AVET run, the dropwindsonde at the easternmost tip of Cuba, the two northernmost dropwindsondes east of Florida, the dropwindsonde near Cozumel, Mexico, and the eight dropwindsondes extending from the northern tip of the Yucatan peninsula to Tampa were removed from the data assimilation cycle.  Figure 3 shows the track forecasts for the four runs, and the errors are shown in Table 1.  All three runs with dropwindsonde data provided better forecasts than the run with no dropwindsonde data, and only small differences between the forecasts with various combinations of the dropwindsonde data are evident.

	In the Frances case (Fig. 4), for the AVTG run, all dropwindsonde data from the round-robin flight from Keesler Air Force base and the three northeasternmost dropwindsondes were removed from the data assimilation cycle.  For the AVET run, all dropwindsonde data from the round-robin flight from Keesler Air Force base and the two northernmost dropwindsondes northeast of Hurricane Frances were removed from the data assimilation cycle.  Figure 5 shows the track forecasts for the four runs, and the errors are shown in Table 2.  The errors for all four runs are much smaller than those of the Charley case, and only small differences between all the forecasts are evident.

	The results of these two cases, in addition to similar AVTG tests completed for the 2003 hurricane season, continue to suggest that the targeting and sampling strategy described in Aberson (2003) is appropriate for the design of flight tracks for the improvement of tropical cyclone track forecast.  In both of these cases, the removal of between one-third and one-half of the dropwindsonde data from the data assimilation did not appreciably change the errors of the forecasts. The results of these two cases for the AVET version is only preliminary, and no conclusions can yet be drawn.
Testing with the remainder of the 31 cases from the 2004 season is proceeding.

## Data Impact: Charley 12th Aug 04

**TIME    12h         24h  ****	****36h  ****	****48h  ****	****60h  ****	****72h**
** ****AVNN****	**** 89.  ****	****289.  ****	**** 519.  ****	**** 844. ****	****1234. ****	****1620.**
**AVNO   ****	****46.   ****	****67.  ****	****214.  ****	****368.  ****	****562.  ****	****655.**
**AVET   ****	****46.   ****	****78.  ****	****243.  ****	****427.  ****	****642.  ****	****754.**
**AVTG   ****	****46.   ****	****59.  ****	****184.  ****	****372.  ****	****641.  ****	****751.**

**All 3 runs with dropwindsonde data provided dramatically better forecasts than the run without.**
**Small differences exist between these 3 forecasts.**

## Data Impact: Frances 30th Aug 04

**TIME  ****	****12 h  ****	****24 h  ****	****36 h  ****	****48 h  ****	****60 h  ****	****72 h  ****	****84 h  ****	****96 h** **AVNN   ****	****69.   ****	****94.  ****	****124.   ****	****91.   ****	****46.   ****	****61.  ****	****137.  ****	****188. AVNO   ****	****25.   ****	****44.   ****	****33.   ****	****64.   ****	****62.  ****	****114.  ****	****153.  ****	****203. AVET   ****	****39.   ****	****56.   ****	****30.   ****	****59.   ****	****70.  ****	****124.  ****	****155.  ****	****213. AVTG   ****	****31.   ****	****56.   ****	****35.   ****	****64.   ****	****70.  ****	****124.  ****	****155.  ****	****213.**

**Errors for all 4 runs << those of the Charley case. **

**Notes:**
AVG. TRACK ERRORS (KM) FOR HOMOGENEOUS SAMPLE
AVNN      97.0  150.8  250.3  371.8  494.0  634.6  174.3  212.6  201.9  275.7
AVNO      34.4   52.0  104.8  176.5  258.8  327.8  191.1  216.2  271.7  326.0
AVET      31.7   64.6  113.3  201.5  302.6  367.3  193.5  221.3  247.1  309.9
#CASES      3      3      3      3      3      3      2      2      2      2

## Extensions

- 1. Guidance on DOTSTAR typhoon surveillance (Chun-Chieh Wu, National Taiwan University)
- 2. Comparison with targeted Singular Vectors from ECMWF and NOGAPS

## Typhoon Mindulle: June 27 2004, 12Z

- (DOTSTAR)

- SPREAD

- ETKF

## A comparison between targeted observing strategies for tropical cyclones

- S. J. Majumdar (RSMAS/MPO, U. Miami), S. D. Aberson (NOAA/AOML/HRD), C. H. Bishop (NRL Monterey), R. Buizza (ECMWF), M. S. Peng (NRL Monterey), C. A. Reynolds (NRL Monterey)

## Summary

- ETKF provides a theoretical improvement over ensemble spread as an objective targeted observing strategy.
- In practice, ETKF guidance is often very similar to ensemble spread guidance (70% of cases)
- End-to-end product has been created, from input of surveillance time to output of ETKF sensitivity map and automated flight track.

## To be completed

- Continued evaluation of data impact from 2004 season.  Preliminary results are promising.
- Quantitative tests of ETKF’s ability to predict signal variance and reduction in forecast error variance.
- Automate ETKF at EMC for use in 2005 season.
- Investigation of problems with Ivan forecasts.
- Results will continue to be disseminated on _[http://www.aoml.noaa.gov/hrd/data_sub/assessment.html](http://www.aoml.noaa.gov/hrd/data_sub/assessment.html)_ and http://orca.rsmas.miami.edu/~majumdar/tc/