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Andrew Burton Bureau of Meteorology , Perth, Australia

Use of Scatterometer Winds in TC Forecasting Tropical Cyclone Warning Centre Perth. Andrew Burton Bureau of Meteorology , Perth, Australia. Application of Scatterometer to Tropical Cyclone Forecasting. Formation Size (radius of gales) Wind distribution Not for absolute intensity

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Andrew Burton Bureau of Meteorology , Perth, Australia

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  1. Use of Scatterometer Winds in TC Forecasting Tropical Cyclone Warning Centre Perth Andrew Burton Bureau of Meteorology, Perth, Australia

  2. Application of Scatterometer to Tropical Cyclone Forecasting • Formation • Size (radius of gales) • Wind distribution • Not for absolute intensity (winds saturate at >60 90? knots)

  3. Where to Get Scatterometer Data • NRL Monterey http://www.nrlmry.navy.mil/tc_pages/tc_home.html • NOAA/NESDIS QuikSCAT http://manati.wwb.noaa.gov/quikscat Storms page – includes ambiguities: http://manati.wwb.noaa.gov/cgi-bin/qscat_storm.pl Alternative NOAA site, with SSMI wind speeds: http://polar.wwb.noaa.gov/winds/globdata.html • FNMOC http://152.80.49.210/PUBLIC/SCAT or http://www.fnmoc.navy.mil/PUBLIC/SCAT • Remote Sensing Systems http://www.ssmi.com

  4. NRL Montereyhttp://www.nrlmry.navy.mil/tc_pages/tc_home.html

  5. NOAA/NESDIS QuikSCAThttp://manati.wwb.noaa.gov/quikscat

  6. FNMOChttp://152.80.49.210/PUBLIC/SCAT/ FNMOC Ambiguity Removal over SSMI Near Real-Time Ambiguity Removal

  7. Remote Sensing Systemshttp://www.ssmi.com

  8. Scatterometer Coverage

  9. QuikSCAT: SeaWinds Measurements V-pol H-pol From Dr. M. Freilich, Oregon State University

  10. SeaWinds: Swath Geometry Subtrack View (4 solns,but small angle var) Forward Look Red = V-pol Blue = H-pol EdgeView (2 solns) V-pol only Ideal View (4 solns, 90 deg var) Backward Look From Dr. M. Freilich, Oregon State University

  11. Scatterometry: 2-Look Solutions 1 2 3 4 Solution: wind ~10m/s at ?? deg From Dr. M. Freilich, Oregon State University From Dr. M. Freilich, Oregon State University

  12. Scatterometry: 4-Look Solution(s) 1 2 3 4 Most-likely solution: 10m/s at 40deg From Dr. M. Freilich, Oregon State University From Dr. M. Freilich, Oregon State University

  13. Ambiguities: The Chicken-Scratch Diagram

  14. Location, Intensity, Wind Distribution Source: Tropical storms discussion group

  15. Small system (X) analysed for 3 days --no help from NWP model 20S 170W 170W O O X X X O 25 Jan 1800Z 26 Jan 0517Z 26 Jan 1800Z 170W 160W 170W 160W O X O 27 Jan 1712Z 28 Jan 0427Z

  16. Interpretation Challenges • Edge of swath (~ 7 wind vector cells) • Rain effects • Sensitivity to errors in NWP • Practical wind regime 3-45? m/s (problems with both very light and very strong winds) • Resolution (25km) – impact in tight gradients • Ambiguity Removal Process and rain flag process can affect final solution

  17. Edge Problems Along the whole edge…or small portion… FNMOC DISPLAY

  18. Rain Effects – “tear drop” • Position using the curvature outside ‘rain block’ region. • Look for good north-south winds.

  19. Streamlines Beware of winds perpendicular to the swath, even when they are not flagged X Look for non-rain flagged winds TC Chris 03/02/02 0914Z

  20. Isotachs X Look for min speed near centre TC Chris 04/02/02 1002Z

  21. Errorsin NWP TC Guillaume 19/02/02 1341Z Wrong Model Position?

  22. Where is TC HUDAH?No circulation! Try to fix in trough equator-ward of the strongest winds ? Max Winds 95knots

  23. Model initialization errors In this case, poor model initialization combined with a lower skill nadir position, picks proper wind speed, but NO circulation center 20/2356Z AVN 19/12Z tau 24 (Light winds?) -----low skill c 10S c 10S ? MaxWind 55 KTS ? 20S TC Paul 20S

  24. Comparing Different Solutions FNMOC-NRT FNMOC-NOGAPS

  25. NRCS imageryNormalised Radar Cross Section

  26. Microwave Imageryvs Quikscat Scatterometer winds give wrong estimate for centre 10 S 14 S 18 S 88 E 92 E 84 E 84 E 88 E 92 E Comparisonbetween Quikscat solution from NESDIS 30/11/2001 at 0023Z and fair LLCC seen in SSMI near 14.4S 89.1E 30/11/2001 at 0218Z

  27. Analysis Methods - Summary • Ignore the bad - streamline the good • Tear-drop – curved end • TC’s – equatorward side of max wind • Compare different solutions • Isotach method – ignore direction

  28. Conclusions • Provides coverage over data sparse areas • Wind speeds generally good – useful for areas of gales etc • Use the data if it makes sense • Be aware of low skill areas and different ambiguity removal processes (compare!) • Do not use in isolation

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