HAZUS and Hurricane Ivan

1. HAZUS and Hurricane Ivan Model predictions and measured wind speeds Greg Gaston Ph.D. gggaston@una.edu Associate Professor Geography Department University of North Alabama Training and Travel supported by a Research Grant from the UNA College of Science

3. Ivan: “Alabama’s Hurricane” of 2004

4. September 2004

5. September 2004

12. May 2005...

13. July 2005...

14. 2005 July

16. 100,000 years of simulated storms...extrapolated from historic storm tracks

17. http://www.aoml.noaa.gov/hrd/tcfaq/mh05.jpg

18. Hurricanes in the Atlantic Basin: 1851-2004 http://www.aoml.noaa.gov/hrd/tcfaq/E11.html

19. What is HAZUS? • GIS-based software tools (ArcGIS) • Loss estimation software that estimates physical damage from earthquakes, hurricanes, and floods • Available from FEMA free of charge (www.fema.gov/hazus)

20. Why HAZUS? • Earthquakes, floods, and hurricanes generate billions of dollars in losses • Knowing potential losses: • Enables better planning • Allows for improved infrastructure to protect people and reduce economic losses • HAZUS can estimate potential future losses

21. Damage estimation/responseand planning • The Federal Emergency Management Agency (FEMA) has spent over $40 million developing and improving a model for damage prediction in the built environment • Originally, only used for earthquake damage, the HAZUS MH has been expanded to include multiple hazards (hurricane winds and flooding)

22. Earthquake Flood Hurricane HAZUS-MH Loss Estimation Methodology

23. D e s i g n P e a k G u s t H u r r i c a n e W i n d S p e e d s ( m p h ) I n O p e n T e r r a i n 9 0 - 1 0 0 1 0 0 - 1 1 0 1 1 0 - 1 2 0 1 2 0 - 1 3 0 1 3 0 - 1 4 0 1 4 0 - 1 5 0 0 1 5 0 - 1 6 Hurricane Model - Hazard • Track model for storms affecting the Gulf and Atlantic coasts, and Hawaii • Hurricane wind field model developed with NSF funding • Regional mappings of land-use to surface roughness

24. Hurricane Hazard Model • Storms initiated in: • Atlantic • Caribbean • Gulf of Mexico • Eastern Pacific • Central Pacific • Storm curvature • Multiple land falls • Changes in intensity • design wind speeds in ASCE-7-98

25. Wind Field Model • Solves full non-linear equations of motion for translating hurricane; then establishes parameters for fast running simulation • Storm asymmetries • Changing sea-surface roughness • Air-sea temperature difference • Translation speeds

26. Hurricane Model – Building Classification • Building components determine degree of damage • 1,884 building classes • Building Type • Number of stories • Roof Straps • Wall Construction • Roof Covering • Etc.

27. ±70% ±10% Example: Sensitivity to Wind Speed

28. User Defined (Single Storm) Scenario Type • 3 options: • Define manually • Import from exported file (other HAZUS users) • Import storm advisory from the Hurrevac FTP site

29. Questions and Assumptions • How well does HAZUS predict peak wind gusts from a hurricane as it tracks inland? • Working Assumption: As the HAZUS model integrates accepted NOAA hurricane models (Hurwind, Hursim). The accuracy of the wind predictions will be highest very near landfall. Accuracy will degrade as the storm tracks inland.

30. Limitations and Caveats • Ivan (2004) is the only hurricane examined (for this presentation) • Peak Wind gust data from Alabama stations • Data were taken from NOAA’s National Hurricane Center http://www.nhc.noaa.gov/2004ivan.shtml

31. Mesonet Data Stations Regional Airport Weather Stations (ASOS)

32. Spatial locations... • Spatial location data for each reporting station was collected either from Auburn University (Mesonet stations) or from the AirNav website for ASOS sites.

33. Stations used to evaluate Ivan’s Wind Gusts

35. Ivan’s Actual Track... Re-formed and back into Texas

37. Size of the circle at each station indicates the magnitude of the difference between the model prediction and the observed wind speeds

38. Magnitude of difference between model prediction and station records and distance from the coast.

39. % Difference between model predictions and observed peak gusts. Color bands indicate 50 mile increments from the coast.

41. % Difference and Distance from Coast

42. Distance Number of stations Average Error

43. Analysis and General Observations: • From these data HAZUS model over-estimates wind speed. • Stations closer to the coast have a greater over-estimation. • At distances 200-300 miles inland, the agreement between the model and actual values is very high. • In the case of Ivan, the model results are in many cases twice as high as the actual winds measured.

44. Is Ivan a special case? Does the HAZUS model accurately predict damage/loss in spite of over estimating wind velocity?

45. Peak Wind Gusts Final Hurrevac track (red line) Black line... Final corrected track

46. “... Final Corrected Track...” • By using the parameters contained in the NWS forecast advisory with no modification, HAZUS overestimates wind velocity. • An experimental NWS model H*wind provides a better solution

47. Final Corrected track uses H*WIND landfall parameters and NHC track coupled with surface wind speed and pressure measurements from C-MAN stations, Buoys, ASOS and FCMP tower data

48. Comparison of NHC and H*WIND Wind Speeds – Hurricane Ivan

49. Hurricane Ivan Wind Field Validation Example

50. Model results from the “Final Corrected Track” released just after landfall... Much higher accuracy