University of Wisconsin Convective Initiation (UWCI) Developed by

1. University of Wisconsin Convective Initiation (UWCI) Developed by Justin Sieglaff, Lee Cronce, Wayne Feltz CIMSS UW-Madison, Madison, WI Kris Bedka SSAI, Hampton VA Mike Pavolonis and Andy Heidinger NOAA/STAR/ASPT Madison, WI

2. What does satellite data add to convective detection?

3. UWCI Objectives • Provide a CI nowcast signal during day and night • Minimize false alarm at the expense of some probability of detection • Use alternative method for time trend computation (non-AMV) to minimize pixelation • Provide coherent radar-like satellite-based CI signal as direct AWIPS/N-AWIPS satellite convective initiation decision support aid in field

4. Source of Confusion: More than one CI algorithm exists! • CI from CIMSS • 24-hour coverage • Uses cloud-typing algorithm to detect phase changes • Uses multispectral GOES IR data • Not computational intensive • Being extended via object tracking • CI from UAH (SatCast Ver2) • Daytime Only (improved) • Uses pixel-based mesoscale Atmospheric Motion Vectors • Uses multispectral GOES IR data • Being extended via object tracking

5. What is output from UWCI? • Value of 0: No CI nowcast • Value of 1: “Pre-CI Cloud Growth”: growing liquid water cloud • Value of 2: “CI Likely”: associated with growing supercooled water or mixed phase cloud • Value of 3: “CI Occurring”: Associated with a cloud that has recently transitioned to thick ice – that is, it has glaciated

6. What is output from UWCI? • Value of 0: No CI nowcast • Value of 1: “Pre-CI Cloud Growth”: growing liquid water cloud • Value of 2: “CI Likely”: associated with growing supercooled water or mixed phase cloud • Value of 3: “CI Occurring”: Associated with a cloud that has recently transitioned to thick ice – that is, it has glaciated GROWING means the cloud is cooling, becoming taller

7. What is output from UWCI? • Value of 0: No CI nowcast • Value of 1: “Pre-CI Cloud Growth”: growing liquid water cloud • Value of 2: “CI Likely”: associated with growing supercooled water or mixed phase cloud • Value of 3: “CI Occurring”: Associated with a cloud that has recently transitioned to thick ice – that is, it has glaciated GROWING means the cloud is cooling, becoming taller Once the cloud has glaciated, UWCI not needed

8. Characteristics of UWCI • Nowcasts cloud development in regions not dominated by cirrus • Uses only IR channels from GOES satellite • Results available ~2 minutes after satellite scan (distribution to AWIPS takes an additional 5-10 minutes) • Operates in regular and RSO mode • Large spatial coverage: CONUS/Hawaii/Pacific • Up to 30-45 minutes of lead time before significant radar echoes/lightning strikes • Low FAR, good POD, error sources understood

9. When should you use UWCI with caution? • Algorithm does not work well where cirrus cloud cover exists • Fast-moving clouds can cause false alarms • Thirty minutes between images? False alarm rate increases • CI is more a diagnostic tool – that is, you lose the good lead times – in true maritime Tropical airmasses • Explosive development? UWCI may be more diagnostic

10. When should you use UWCI with caution? • Algorithm does not work well where cirrus cloud cover exists • Fast-moving clouds can cause false alarms • Thirty minutes between images? False alarm rate increases • CI is more a diagnostic tool – that is, you lose the good lead times – in true maritime Tropical airmasses • Explosive development? UWCI may be more diagnostic (a function of time resolution)

11. UWCI: Algorithm logic – an overview in words Box average 11 micron brightness temperature (BT) is calculated for current time and previous time, using specific classes from GOES Cloud Typing product Unfiltered Cloud Top Cooling (CTC) Rate is calculated by differencing box average 11 micron BT for current time from previous time Large/small box approach eliminates most of false CTC due to cloud motion (and additional checks reduce false cooling further) CI Nowcast is assigned to remaining CTC pixels with cooling rates less than or equal to -4.0K/15 minutes by leveraging GOES Cloud Typing product

12. What is Box-Averaging? • Newly developing convective clouds move short distances between successive images due to the high-temporal resolution of current GOES • Clouds remain within a “boxed” region for 2 consecutive GOES scans. Mean IR temperatures and cloud microphysical properties of the clouds (i.e. “box-averaging”) can be differenced to identify new convective initiation • This Eulerian framework means cloud motion is a significant issue: “new” non-convective clouds can enter the boxed region and influence the box-averaged properties, producing false cloud top cooling signal • A set of tests is developed to preserve the signal associated with convective initiation while filtering out signal from rapidly moving and/or non-convective clouds

13. For the center (Yellow) pixel: 13 pixels At each pixel along the perimeter: box-average the cloudy pixels in a 7x7 box; find the minimum TBB for all points along the perimeter (T2) 7 pixels 13 pixels 7 pixels What is the box-average TBB of the cloudy pixels (T1) in the small box at the current time? This is done for every pixel in the image; TBB is the 11-mm brightness temperature

14. For the center (Yellow) pixel: 13 pixels At each pixel along the perimeter: box-average the cloudy pixels in a 7x7 box; find the minimum TBB for all points along the perimeter (T2) 7 pixels 13 pixels 7 pixels What is the box-average TBB of the cloudy pixels (T1) in the small box at the current time? This is done for every pixel in the image; TBB is the 11-mm brightness temperature

15. For the center (Yellow) pixel: 13 pixels At each pixel along the perimeter: box-average the cloudy pixels in a 7x7 box; find the minimum TBB for all points along the perimeter (T2) 7 pixels 13 pixels 7 pixels What is the box-average TBB of the cloudy pixels (T1) in the small box at the current time? If (T1-T2) < 0 K, then convective cooling is occurring ; More than 1 pixel must be cloudy in the 7x7 box This is done for every pixel in the image

21. Which of these cooling points reflects cloud growth (in the vertical) and which reflects cloud motion (in the horizontal)?

22. Which of these cooling points reflects cloud growth (in the vertical) and which reflects cloud motion (in the horizontal)? Also: Convective Initiation should ignore cooling cirrus clouds (where the initiation happened a while ago!)

24. Look at the phase change, as well

26. Supercooled or mixed Glaciation has occurred All liquid & warmer than 32 F

28. Convection develops where CI predicted it along warm front

29. 10.7 mm data Cloud Mask finds cloudy pixels 13.0 mm data Cloud typing determines the type of cloud 3.9 mm data Surface Emissivity Surface Temperature 6.7 mm data Clear-Sky Atmospheric Absorption/Emission information

30. Unknown Cloud Mask finds cloudy pixels Clear Fog Cloud typing determines the type of cloud Thick Ice Water Mixed Phase Supercooled Water Cirrus Cirrus overlap

31. Unknown Cloud Mask finds cloudy pixels Clear Fog Cloud typing determines the type of cloud Thick Ice Water Mixed Phase Supercooled Water Cirrus Cirrus overlap

32. CI not computed for these pixels Unknown Cloud Mask finds cloudy pixels Clear Fog Cloud typing determines the type of cloud Thick Ice Water Mixed Phase Supercooled Water Cirrus Cirrus overlap

33. Cloud Mask finds cloudy pixels Cloud typing determines the type of cloud Thick Ice Water Mixed Phase Supercooled Water Cirrus Cirrus overlap

34. Cloud Mask finds cloudy pixels Cloud typing determines the type of cloud Thick Ice Water Mixed Phase Supercooled Water Cirrus Cirrus overlap Determine percentages of each cloud type in 7x7 and 13x13 box Determine cooling rate of cloudy pixels (normalized to a 15-minute dt) Throw out pixels that show warming relative to the values around the perimeter of the larger box Throw out pixels if >50% of pixels in large box are ice clouds

35. UWCI tests to reduce FAR • Throw out pixels that show warming relative to the values around the perimeter of the larger box • Throw out pixels if >50% of pixels in large box are ice clouds • Throw out pixels if the number of cirrus/overlap pixels exceeds the number of water cloud pixels • Throw out pixels if the number of overlap pixels exceeds the number of water/supercooled/mixed phase pixels. Cloud-top cooling might mean thin cirrus are simply becoming thicker. • Throw out pixels if the number of cirrus/overlap pixels exceed water/supercooled/mixed phase pixels at the earlier time and the number of water/supercooled/mixed phase pixels exceeds the number of cirrus/overlap pixels at the later time. CI means the relative number of ice compared to water pixels should be increasing.

37. Is there cooling due to Cloud Motion?

38. IS THE COOLING OUTSIDE THE MAIN UPDRAFT?

39. ARE THERE TOO MANY ICE PIXELS?

40. Is there mostly thin Cirrus when many cloud types are present?

41. ARE THE MICRO-PHYSICAL CHANGES ‘WRONG’ ?

42. ARE THERE TOO MANY ‘OVERLAP’ PIXELS – CIRRUS PIXELS OVER LOW CLOUDS?

43. IS THE INFERRED THUNDER-STORM UPDRAFT IS TOO WEAK?

44. Examples!

45. 20090429 Dryline CI Case

46. 20090429 2015 UTC Instantaneous CI Nowcast CI Occurring CI Likely CI Possible

47. 20090429 2015 UTC Instantaneous CI Nowcast CI Occurring (Glaciation) CI Likely (Supercooled/Mixed Phase) CI Possible (All ‘warm’ liquid) (N-AWIPS Screengrab)

48. 29 April 2009 CI nowcast at 2015 UTC KAMA 2018 UTC Base Reflectivity CI likely Non-detection due to cirrus CI occurring KAMA 2035 UTC Base Reflectivity KAMA 2103 UTC Base Reflectivity First echo >= 35 dBZ, 17 minutes after nowcast

49. 20090506 0545 UTC Nocturnal Instantaneous CI Nowcast SD/NE Border Warm Frontal 0545 UTC 0546 UTC 0606 UTC 0615 UTC

50. Nebraska 090724: Nocturnal Case IR4 image and CTC at 0245Z Radar reflectivity at 0246Z IR4 image and CTC at 0315Z Radar reflectivity at 0311Z