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Impact of Horizontal Resolution on Rapid Intensity Change Forecasts using the

Impact of Horizontal Resolution on Rapid Intensity Change Forecasts using the Hurricane Research System. R. Rogers, S. Gopalakrishnan, K. Yeh, and X. Zhang. NOAA/AOML Hurricane Research Division Miami, FL. Motivation.

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Impact of Horizontal Resolution on Rapid Intensity Change Forecasts using the

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  1. Impact of Horizontal Resolution on Rapid Intensity Change Forecasts using the Hurricane Research System R. Rogers, S. Gopalakrishnan, K. Yeh, and X. Zhang NOAA/AOML Hurricane Research Division Miami, FL

  2. Motivation • Advances in forecasts of tropical cyclone (TC) intensity, structure, and rainfall lag advances in TC track forecasts • Multiscale nature of these processes major reason for this • environmental - O(1000 km) - troughs, shear • vortex - O(1-100 km) - symmetric/asymmetric dynamics, VRWs • convective – O(1 km) – convective bursts, vortical hot towers • turbulent – O(1-100 m) - surface fluxes, entrainment/detrainment • microscale – O(1mm) -- hydrometeor production, latent heat release • Numerical model forecasts of rapid intensity change (RI) should improve as resolution increases • For some cases it does, in others it does not – why?

  3. Examples RI RI • Two cases of RI shown here • One that showed improvement with higher resolution, one that did not. All runs had similar (and good) track forecasts. • Hurricane Katrina (2005) • Underwent RI from Cat 3 to Cat 5 as it traversed Gulf of Mexico • Both resolutions produced RI, but both delayed • Good observational coverage (multiple P-3 flights with Doppler) • Hurricane Emily (2005) • Sustained period of RI, from tropical storm to Cat 4 in 48 h • 3-km run produced RI during 1st 24 h, another intensification episode later than Best Track • 9-km run did not intensify • No airborne Doppler sampling

  4. Track and Intensity – Hurricane Katrina track intensity 27:9 km RI 9:3 km

  5. Vortex-scale fields - Hurricane Katrina 9-3 km HRS Doppler 27-9 km HRS 70 150 150 150 150 150 65 60 Wind speed (m/s) at 2-km altitude 55 50 50 100 100 100 100 100 distance (km) distance (km) distance (km) 45 40 35 50 50 50 50 50 30 100 100 100 100 100 0 0 0 0 0 0 50 50 50 50 50 50 150 150 150 150 150 0 0 0 0 0 0 distance (km) distance (km) distance (km) 7 6 5 4 Vorticity (x 10-3 s-1) and w (m/s) at 4-km altitude 3 distance (km) 2 distance (km) distance (km) 1 0 -1 -2 distance (km) distance (km) distance (km) 2038-2231 UTC 8/28 0000 UTC 8/29 0000 UTC 8/29

  6. Vortex-scale fields – Hurricane Katrina Radius-height axisymmetric (R-z mean) plots 9-3 km HRS Doppler 27-9 km HRS 18 18 18 16 16 16 14 14 14 80 70 12 12 12 60 10 10 10 50 height (km) 40 8 8 8 Tangential and radial winds (m/s) 30 6 6 20 6 10 4 4 4 0 2 2 2 0 0 0 20 10 30 40 50 60 70 80 90 100 20 10 30 40 50 60 70 80 90 100 20 10 30 40 50 60 70 80 90 100 radius (km) radius (km) radius (km) 18 18 18 16 16 16 80 14 14 14 70 12 12 12 60 50 10 10 10 height (km) 40 8 8 8 Vorticity (x 10-4 s-1) and vertical motion (m/s) 30 20 6 6 6 10 4 4 4 0 2 2 2 20 10 30 40 50 60 70 80 90 100 20 10 30 40 50 60 70 80 90 100 20 10 30 40 50 60 70 80 90 100 radius (km) radius (km) radius (km) 2038-2231 UTC 8/28 0000 UTC 8/29 0000 UTC 8/29

  7. 16 16 16 14 14 14 40 12 12 12 30 15 10 10 10 5 2 8 8 8 1 6 6 6 .5 .1 4 4 4 .01 2 2 2 0 0 0 -12 -12 -12 -9 -9 -9 -6 -6 -6 -3 -3 -3 0 0 0 3 3 3 6 6 6 9 9 9 12 12 12 15 15 15 -15 -15 -15 Convective-scale statistics – Hurricane Katrina Contoured frequency by altitude diagrams (CFADs) – Variation of distribution with height 18 18 18 vertical motion height (km) 9-3 km HRS Doppler 27-9 km HRS % vertical motion (m/s) vertical motion (m/s) vertical motion (m/s) 2038-2231 UTC 8/28 0900Z 29 Aug 0900Z 29 Aug

  8. Track and Intensity – Hurricane Emily track intensity 27:9 km RI 9:3 km

  9. Environmental-scale fields - Hurricane Emily 850 200 850-200 hPa hodographs and inner-core vertical shear 850 1200 UTC 7/13 200 1200 UTC 7/14

  10. Vortex-scale fields – Hurricane Emily Time-radius Hovmollers of axisymmetric winds at 10-m height 27:9 km 9:3 km 00Z 16 JUL 00Z 16 JUL 12Z 15 JUL 12Z 15 JUL 00Z 15 JUL 00Z 15 JUL 30 20 25 15 20 12Z 14 JUL 12Z 14 JUL 10 15 5 10 00Z 14 JUL 00Z 14 JUL 5 12Z 13 JUL 12Z 13 JUL 00Z 13 JUL 00Z 13 JUL 100 150 200 100 150 200 50 50 radius (km) radius (km)

  11. Vortex-scale fields – Hurricane Emily R-z mean plots of tangential and radial winds (m/s) 16 16 16 14 14 14 35 12 12 12 30 25 10 10 10 20 27:9 km height (km) 8 8 8 15 10 6 6 6 5 4 4 4 0 2 2 2 0 0 0 25 25 50 75 100 25 50 75 100 50 75 100 radius (km) radius (km) radius (km) 16 16 16 14 14 14 35 12 12 12 30 25 10 10 10 20 height (km) 8 8 8 15 9:3 km 10 6 6 6 5 4 4 4 0 2 2 2 0 0 0 25 50 75 100 25 25 50 75 100 50 75 100 radius (km) radius (km) radius (km) 1200 UTC 7/13 1200 UTC 7/14 1200 UTC 7/15

  12. Vortex-scale fields - Hurricane Emily Vorticity (x 10-5 s-1) and vertical motion (m/s) at 4-km altitude 300 300 300 300 200 250 250 250 150 100 200 200 200 75 27:9 km 50 distance (km) 150 150 150 25 10 100 100 100 -10 -25 50 50 50 150 200 150 200 150 200 50 100 250 300 50 100 250 300 50 100 250 300 distance (km) distance (km) distance (km) 300 300 300 300 200 250 250 250 150 100 200 200 200 75 distance (km) 50 9:3 km 150 150 25 150 10 100 -10 100 100 -25 50 50 50 150 200 50 100 250 300 150 200 50 100 250 300 150 200 50 100 250 300 distance (km) distance (km) distance (km) 1200 UTC 7/13 1200 UTC 7/14 1200 UTC 7/15

  13. 18 18 16 16 14 14 40 40 12 12 30 30 15 15 10 10 5 5 height (km) height (km) 8 8 2 2 1 1 6 6 .5 .5 .1 .1 4 4 .01 .01 2 2 0 0 -12 -12 -12 -12 -12 -12 -9 -9 -9 -9 -9 -9 -6 -6 -6 -6 -6 -6 -3 -3 -3 -3 -3 -3 0 0 0 0 0 0 3 3 3 3 3 3 6 6 6 6 6 6 9 9 9 9 9 9 12 12 12 12 12 12 15 15 15 15 15 15 -15 -15 -15 -15 -15 -15 Convective-scale statistics – Hurricane Emily CFADs of vertical motion 18 18 16 16 % 14 14 12 12 27:9km 10 10 8 8 6 6 4 4 2 2 0 0 vertical motion (m/s) vertical motion (m/s) vertical motion (m/s) vertical motion (m/s) vertical motion (m/s) vertical motion (m/s) 18 18 16 16 % 14 14 12 12 10 10 8 8 9:3 km 6 6 4 4 2 2 0 0 1200 UTC 7/13 1200 UTC 7/14 1200 UTC 7/15

  14. Summary • Katrina case showed little improvement in predicting rapid intensity change at higher resolution, Emily case showed improvement • Katrina • Storm larger than observed in both runs • Better eyewall slope, secondary circulation features in 3-km • More realistic vorticity structures, stronger updrafts/downdrafts in 3-km • Emily • Shear, RMW same in both runs prior to 1200 UTC 7/14 • Well-defined secondary circulation in 3-km, poorly-defined in 9-km HRS • Inner-core vorticity stronger, more strong positive and negative vorticity cores in 3-km • More strong (12-15 m/s) updrafts in 3-km Questions • What was difference between Katrina and Emily runs? • Secondary circulation, RMW • What is importance of convective-scale fields? Is ability to resolve them vital for improved rapid intensity change forecasts? • What is robustness of physical parameterizations (e.g., surface fluxes, microphysics)?

  15. Future work • Perform more diagnostics • Additional vortex-scale evaluations (e.g., asymmetric fields) • Additional convective-scale evaluations (e.g., mean profiles and mass flux evolution) • Finer-scale diagnostics (turbulent, microphysical scale) • Extend evaluations to more cases, both with and without improvements at higher resolution • Include 1-km HRS runs • Evaluate runs with additional components (e.g., air-sea coupling, inner-core data assimilation) • Test alternate physical parameterizations, formulations • Evaluate impact of resolution, parameterizations using observations

  16. Supplemental slides

  17. Vortex-scale fields - Hurricane Emily 100 100 100 200 200 200 500 500 500 600 600 600 300 300 300 400 400 400 700 700 700 800 800 800 Wind speed at 10-m height 800 800 800 700 700 700 40 35 600 600 600 30 500 500 500 25 20 distance (km) 400 400 400 27:9 km 15 300 300 300 10 5 200 200 200 100 100 100 distance (km) distance (km) distance (km) 600 600 600 500 40 500 500 35 30 400 400 400 25 distance (km) 20 300 300 300 15 9:3 km 10 200 200 200 5 100 100 100 100 200 500 600 300 400 100 200 500 600 300 400 100 200 500 600 300 400 distance (km) distance (km) distance (km) 1200 UTC 7/13 1200 UTC 7/14 1200 UTC 7/15

  18. 16 16 16 16 16 16 14 14 14 14 14 14 12 12 12 12 12 12 10 10 10 10 10 10 8 8 8 8 8 8 6 6 6 6 6 6 4 4 4 4 4 4 2 2 2 2 2 2 0 0 0 0 0 0 Vortex-scale fields – Hurricane Emily R-z mean plots of vorticity (x 10-4 s-1) and vertical motion (m/s) 50 45 40 height (km) height (km) 27:9 km 35 30 25 20 15 10 5 0 100 100 100 50 50 50 25 75 25 75 25 75 radius (km) radius (km) radius (km) 50 45 40 35 30 25 9:3 km 20 15 10 5 0 100 100 50 50 25 75 100 25 75 50 25 75 radius (km) radius (km) radius (km) 1200 UTC 7/13 1200 UTC 7/14 1200 UTC 7/15

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