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The May 24 Shamrock cold front

The May 24 Shamrock cold front. A King Air/ WCR close-up view Bart Geerts & Dave Leon University of Wyoming.

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The May 24 Shamrock cold front

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  1. The May 24 Shamrock cold front A King Air/ WCR close-up view Bart Geerts & Dave Leon University of Wyoming

  2. Synoptic situation at 18 UTC on 24 May 2002, based on the ETA initialization. Equivalent potential temperature (color field) and winds (blue, a full barb equals 10 kts) at 900 mb, sea level pressure (yellow contours), and 300 mb geopotential height (red contours).

  3. 21 Z 18 Z 8 dropsondes, 20:22 - 20:57 Z GOES 8 visible satellite image, operational surface observations, and subjective frontal analysis

  4. mixing ratio q pressure (mb) cold front east west total distance: 217 km

  5. TX OK cold front dryline radial velocity reflectivity 19:00 Z Td=9°C r = 7.4 g/kg Smart-R and mobile mesonet data

  6. 19:30 Z Td=15°C r =11.4 g/kg

  7. 20:00 Z

  8. 20:30 Z

  9. 5/24, 21:07 UTC

  10. 19:42 UTC AMA 19:52 UWKA N 19:43 cold front dryline WCR up-looking, flight level 165 m

  11. WCR vertical velocities dryline cold front

  12. Triple point transect 20:12 Flight level: ~2300 m AGL King Air cold front @20:09 20:07 frontal motion SSE 164 NNW 344 front & dryline moist air cold air

  13. Flight level: 2300 m AGL WCR nadir antenna reflectivity frontal motion dBZ

  14. reflectivity 1:1 aspect ratio

  15. Height above flight level (m) total length: 11.2 km aspect ratio: 1:1 NW 315 flight level: 360 m AGL frontal motion SE 135 19:33 - 19:35:33 possibly stratus clouds frontal motion WNW 344 ESE 164 km 20:21:50 - 20:25:40 km -5 NNW 344 SSE 164 2.0 1.5 1.0 0.5 8 6 dBZ -45 20:27:00 - 20:30:48 km NW 300 SE 120 20:42:43 - 20:46:18

  16. 21:06:36-21:13:20 Gravity waves in the cold-frontal stratus frontal motion This is a cloud whose towering tops had grown well above 4 km AGL, part of a line of storm cells aligned with the cold front mixing ratio 9 km Deep convection develops 9 km ahead of sfc cold front w 21:05 21:15 wind direction 21:32 q qe WNW 290 ESE 110

  17. summary • An airborne W-band radar sampling at 30 Hz & a resolution of ~25 m can measure echoes in the opticaly-clear warm-season CBL. • Dual-Doppler synthesis at close range is feasible. • The WCR echo and velocity transects confirming kinematic aspects of a cold front that have been simulated in the lab and by hi-res numerical models, but have never been observed before.

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