1. The document discusses using the Ensemble Transform Kalman Filter (ETKF) to target observations around hurricanes and tropical cyclones to improve forecasts. 2. Preliminary results on Hurricane Isabel showed the ETKF could predict the reduction in forecast error variance from targeted observations and identified key regions to observe. 3. During the 2004 hurricane season, the ETKF was used alongside ensemble spread to design synoptic surveillance flights around several hurricanes in the Atlantic basin.

1. Hurricane synoptic surveillance using the Ensemble Transform Kalman Filter Sharanya J. Majumdar (RSMAS/MPO Univ. of Miami) Collaborators: Sim Aberson (HRD), Craig Bishop (NRL Monterey), Brian Etherton (UNC Charlotte), James Franklin (TPC/NHC), Istvan Szunyogh (U.Maryland), Zoltan Toth (EMC), Chun-Chieh Wu (National Taiwan University) Acknowledgment: NOAA Joint Hurricane Testbed NOAA/NCEP/EMC, October 28th 2004

2. Florida: Under the Gun in 2004

4. NOAA G-IV AIRCRAFT TRACK AROUND HURRICANE IVAN. ETKF PLANNED FLIGHT ACTUAL G-IV FLIGHT

9. Signals and Signal Variance Squared NCEP MRF signal 1/2 (u’ 2 +v’ 2 ) + (c p /T r ) T’ 2 valid at analysis time t a Predicted ETKF signal variance S q , using ensembles initiated 36h prior to analysis time t a

11. Aim: to improve a 24-hr forecast on the West Coast t a t a ETKF Summary map of Signal Variance S q , for many different q. Summary bar chart t v t v Good Poor

14. Serial adaptive sampling during Winter Storm Reconnaissance Flight track number Flight track number

16. Evolution of operational signal over 84h

17. Evolution of predicted ETKF signal variance over 84h

20. Answer to Question 1 YES : a linear, increasing relationship is found to exist between the ETKF predicted signal variance, and the sample variance of operational signal realizations. Q2: Is the operational signal variance related to the reduction in operational forecast error variance?

21. Signal realization versus forecast error reduction , at verification time t v

22. WSR01: Signal Variance vs Reduction in Forecast Error Variance

23. Rescaled ETKF Signal Variance Reduction in NCEP forecast error variance Final Result from WSR01

26. Typhoon Nida: May 17 2004, 12Z SPREAD ETKF

27. Typhoon Conson: June 8 2004, 12Z SPREAD ETKF

28. Typhoon Aere: August 24 2004, 12Z SPREAD ETKF SPREAD ETKF

29. Latest ETKF Summary for Aere

30. Latest flight tracks for 12Z August 24th 2004, based on ETKF and ensemble spread output. Maps produced during Sim’s seminar!

31. NOGAPS Singular Vector Sensitivity Summary, first 5 SVs. T79L30 (+48h, -48h) (Courtesy M. Peng, C. A. Reynolds of NRL Monterey) ISABEL: 00Z 14 Sep 2003 SPREAD ETKF

32. SPREAD ETKF

33. ETKF PREDICTED SIGNAL VAR. ACTUAL NCEP GFS SIGNAL ETKF predicts the variance of the “signal” : the influence of the targeted observations on the operational forecast. Preliminary result from Hurricane Isabel ETKF used 20-member 1-deg res NCEP GFS Ensemble, initialized 24-36h prior to targeted observing time. Influence on GFS analysis Influence on 1-day forecast Influence on 2-day forecast

35. Isabel maintained a westward motion until 13 September 2003, moving along the south side of the Azores-Bermuda High. Isabel approached a weakness in the western portion of the High, which allowed the hurricane to turn to the WNW on the 13th, NW on 15th, and NNW on 16th. At 00Z 14th, there were several features in the deep layer mean flow around Isabel. A cyclonic circulation was located near the Carolina coastline. And anti-cyclonic circulation was located to the south of Newfoundland. Just to the south of this feature was a smaller anti-cyclonic circulation. The cyclonic circulation over the eastern US seaboard and the anti-cyclonic circulation in the north Atlantic would help guide Isabel to the northwest over time. In addition, there was another cyclonic circulation to the east of Isabel, and a short-wave trough moving into the Central United States. Ensemble spread at 00Z 14th was mostly associated with Isabel. In addition, there was a lesser amount of ensemble spread to the northwest of Isabel, associated with the cyclonic circulation near the eastern US seaboard. There were also regions of spread to the east of Isabel, to the northeast of Isabel, and over the south-central United States. None of these regions was appropriate for aircraft observations, but the area of spread associated with the cyclonic circulation near the eastern US seaboard was sampled. The ET KF selection for observing sites on the 14th at 00Z concentrated on two areas: Isabel, and the anti-cyclone to the North of Isabel. These were considered to be the two most important and poorest observed features. While the trough in the eastern United States was important, the ET KF did not select it as a target area, in contrast to the ensemble spread, which did depict uncertainty in the east coast cut-off low. Hurricane Isabel: Targeting Discussion, 00Z 14 Sep 2003

36. NOGAPS Singular Vector Sensitivity Summary, first 5 SVs. T79L30 (+48h, -48h) (Courtesy M. Peng, C. A. Reynolds of NRL Monterey) ISABEL: 00Z 15 Sep 2003 SPREAD ETKF

38. At 00Z on the 15th, the deep layer mean flow had changed since the 14th. Now there were two primary features of interest (in addition to Isabel) - the anti-cyclonic circulation to the north of Isabel, and a trough along the eastern United States. The shortwave in the central US caught up to the cut-off low along the east coast to form one feature. Also of importance was a long-wave trough over the central United States. Isabel was to travel between this trough in the central United States and the anti-cyclone off the coast of the Maritime Provinces of Canada. Ensemble spread at 00Z on the 15th was greatest near Isabel, to the east of Isabel, and near the short-wave trough over the eastern United States. The ET KF gave the greatest support to sampling the storm. Secondary targets were (a) the east coast US short wave, (b) the anti-cyclone south of the Canadian Maritimes, and (c) an anti-cyclone to the east of Isabel. Given logistical constraints, the anti-cyclone to the east of Isabel could not be a target area, though the flight did go as far east as possible. The short-wave trough in the eastern US was sampled, however, the anti-cyclone to the north of Isabel was not. Hurricane Isabel: Targeting Discussion, 00Z 15 Sep 2003

39. SPREAD ETKF

40. NOGAPS Singular Vector Sensitivity Summary, first 5 SVs. T79L30 (+48h, -48h) (Courtesy M. Peng, C. A. Reynolds of NRL Monterey) ISABEL: 00Z 16 Sep 2003 SPREAD ETKF

41. SPREAD ETKF

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45. SPREAD ETKF

47. SPREAD ETKF

48. SPREAD ETKF

49. SPREAD ETKF

50. Typhoon Mindulle: June 27 2004, 12Z (DOTSTAR) SPREAD ETKF

51. Typhoon Aere: August 23 2004, 12Z (DOTSTAR) SPREAD ETKF

52. NOAA G-IV AIRCRAFT TRACK AROUND HURRICANE IVAN. ETKF PLANNED FLIGHT ACTUAL G-IV FLIGHT

53. Hurricane Ivan: September 15 2004, 00Z

54. SPREAD ETKF Hurricane Jeanne: September 24 2004, 00Z

55. Hurricane Jeanne: September 25 2004, 00Z