1. Ingrid – Revisiting the Meteorology Michael Foley Severe Weather Section Bureau of Meteorology

2. Satellite Overview: 2 – 17 Mar 2005 first known severe impact in all tropical states/territories

3. Gove Radar: Anatomy of Ingrid eye wall 30 km across gales 180 km across rain band

4. Cat.Mean Strongest gustTypical Effect No.Winds (km/h) Cyclone Severity Categories 163-90 < 125 Negligible house damage Crop/trees/caravan damage Small craft drag moorings Minor house damage 290-120 125-170 Significant crop/tree/caravan damage Small craft break moorings 3120-160 170-225 Some roof/structural damage Some caravans destroyed Power failure likely 4160-200 225-280 Significant roof/structural damage Dangerous airborne debris Widespread power failure 5> 200 > 280 Extremely dangerous Widespread destruction

5. Intensity Assessments in Cyclone Advices for Ingrid LocationCatMax Gust (km/h) Elizabeth Bay4260 Drysdale Island5290 Croker Island5290 Cape Don4235 Melville Island3215 Faraway Bay (WA)5285 max gusts 320 km/h

6. What are intensity estimates based on? 1.Direct Measurement – rare in Australia 2.Inference (satellite, radar, impacts) - usual Tracy 1974

7. Surface Data Received During Ingrid x x x x x x x x x x no data Cape Don anemometer cups blown away

8. Dvorak: Cloud Patterns  Intensity wind speed day

9. Other Types of Wind Speed Data

10. Post-Analysis Process done for every cyclone before input into national database uses data not received in time for Cyclone Warning allows benefit of hindsight Black Point Barograph Drysdale Island Survey

11. Main Outcomes of Postanalysis Ingrid reached Cat 5 just north of Gove, 12 hours earlier than previously thought Ingrid’s winds began to weaken prior to crossing Croker Island at Cat 4 Ingrid only reached Cat 4 in Timor Sea

12. Almost Gove’s Tracy? redeveloped faster than “allowed” in Gulf

13. Loss of Structure along North Coast Ingrid’s structure weakened as it moved north of the north coast operational analysis rule: hold winds steady for 12 hours after weakening first observed (wind drop lags drop in structure) recent studies suggest 6 hour lag better on average – this was used in postanalysis why did Ingrid weaken prior to landfall, in favourable environment?

14. Concentric Eyewalls: Weakening due to Internal Dynamics inner eyewall 14 km across outer eyewall 52 km across

15. Wind Data in Outer Eyewall McCluer Island AWS max 10-min mean wind 154 km/h was at this time max gust: 207 km/h no obs were obtained in inner eye wall Croker Island

16. Timor Sea: Not As Well Structured

17. Reassessments in Intensity OldNew LocationCatMax Gust (km/h) CatMax Gust (km/h) Elizabeth Bay42605325 Drysdale Island52905325 Croker Island52904240 Cape Don42353215 Melville Island32153185 Faraway Bay (WA)52854270

18. Ingrid vs Katrina very similar intensities (max gusts around 320 km/h) both exhibited concentric eyewalls Katrina was far bigger

19. Australian vs US Classification Maximum Gust (km/h) CategoryAustralian (TC)US (Hurricane) 1< 125151-194 2125-169196-224 3170-224226-266 4225-279268-316 5> 280> 318

20. Katrina Concentric Eye Walls

21. Size – the Big Difference IngridKatrinaextent of gales

22. Ingrid – Revisiting the Meteorology cyclone intensity analysis largely based on inference rather than direct measurement evidence from satellite analysis supports Cat 5 maximum intensity for Ingrid however, postanalysis has concluded: –Cat 5: 12 hours earlier than previously thought –Cat 4 prior to crossing Croker Island –Cat 4 in Timor Sea we can’t be complacent about Cat 5 systems e.g. Katrina