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IMPACT OF TAMDAR DATA ON RUC SHORT-RANGE FORECASTS

IMPACT OF TAMDAR DATA ON RUC SHORT-RANGE FORECASTS. Ed Szoke*, Randy Collander*, Brian Jamison*, Tracy Smith* Stan Benjamin, Bill Moninger, Tom Schlatter**, and Barry Schwartz NOAA/Earth Systems Research Laboratory Global Systems Division

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IMPACT OF TAMDAR DATA ON RUC SHORT-RANGE FORECASTS

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  1. IMPACT OF TAMDAR DATA ON RUC SHORT-RANGE FORECASTS Ed Szoke*, Randy Collander*, Brian Jamison*, Tracy Smith* Stan Benjamin, Bill Moninger, Tom Schlatter**, and Barry Schwartz NOAA/Earth Systems Research Laboratory Global Systems Division *Joint collaboration with the Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO **Cooperative Institute for Research in Environmental Sciences (CIRES), Boulder, Colorado

  2. TAMDAR soundings have been shown to be useful for forecasting Talks at the last SLS Conference and previous Annual Meetings WFO Green Bay helps maintain the official NOAA TAMDAR web page at http://www.crh.noaa.gov/tamdar/ In this talk we focus on the impact on NWP: Evaluation of RUC precipitation forecasts for runs with and without TAMDAR for significant weather events Mostly a subjective evaluation, but objective scoring for 2007 cases Procedure: RUC is run at 20-km horizontal grid resolution Identical runs made hourly to 6 h, and out to 24 h every 3 h Here we will concentrate on shorter term (usually first 6 h to 12 h) forecasts initialized when TAMDAR data is most plentiful 1800 UTC and 0000 UTC initialization times generally used Overview

  3. Typical TAMDAR coverage (shown here 1000 UTC/18 Oct – 0400 UTC/19 Oct 06) Flights into a number of smaller airports in addition to the 3 main hubs And at lower altitudes (generally to 20 kft or so)

  4. Verification areas. Objective scoring is done on both areas, for this study we will show some scores for the inner (blue) box .

  5. Case 1: 4 October 2005 – 2100 UTC Surface analyses and reflectivity Still one of the most dramatic cases...4-5 Oct 2005: heavy precip in the Upper Midwest. Flooding reported in Minnesota to northern Wisconsin.

  6. NPVU estimated precipitation for 6-h ending 0000 UTC 5 October 2005 Very sharp cut off to the precip in WI and a huge gradient with a 2-3” max.

  7. RUC forecasts from the 4 October 2005 1800 UTC runs 6-h total precipitation ending 0000 UTC 5 October Both runs forecast too much precip in southern half of Wisconsin, but the RUC run with TAMDAR correctly forecasts more precip (small spots of >1.00”) across the northern half of the state.

  8. Sounding comparison: RUC 6-h forecasts with (labeled dev2) and without (labeled dev1, in black) TAMDAR, compared to the RAOB for Detroit (green) at 0000 UTC 5 Oct 05. Incorrect dry layer in the dev1 forecast.

  9. Same comparison but for Peoria, Illinois. The RUC run with TAMDAR is closer to the RAOB especially at and below 700 mb.

  10. Case 1/part 2: 5 October 2005 – 0300 UTC Surface analyses and reflectivity Heavy precip continues in the same areas

  11. NPVU estimated precipitation for 6-h ending 0600 UTC 5 October 2005

  12. RUC forecasts from the 5 October 2005 0000 UTC runs 6-h total precipitation ending 0600 UTC 5 October No TAMDAR With TAMDAR For this period the RUC run that used the TAMDAR data is a much better forecast with a very sharp cut off to the precipitation in Wisconsin and a better location for the heavy precip.

  13. Case 2: 20 January 2006 – 2100 UTC Surface analyses and reflectivity

  14. This event impacted an extensive area with winter precipitation Power outages from portions of Iowa to Illinois where snow became freezing rain

  15. Observed snowfall ending ~1200 UTC 21 January 2006 About 5” of snow at O'Hare Airport in Chicago, but a foot just to the northwest.

  16. Most of the snow fell in the 12-h period ending at 0600 UTC, so can compare the amounts observed to the RUC 12-h snowfall forecasts below.

  17. Sounding comparison as before: RUC 6-h forecasts with (labeled dev2) and without (labeled dev, in black) TAMDAR, compared to the RAOB for Green Bay (green) at 0000 UTC 21 Jan 06. dev2 is closer to the observed sounding.

  18. Similar comparison for Peoria, Illinois. Not much difference in these forecasts

  19. Precipitation comparison. NPVU estimated precipitation for 6-h ending 0600 UTC 21 January 2006

  20. RUC forecasts from the 21 January 2006 0000 UTC runs 6-h total precipitation ending 0600 UTC 21 January The RUC run with TAMDAR did a better job of forecasting more precipitation in central Illinois.

  21. Case 3: 13 February 2007 – 1800 UTC Surface analyses and reflectivity

  22. Case 3: This was a high-impact event with huge area of winter weather watches and warnings and even a blizzard warning, plus severe weather

  23. RUC forecasts from the 13 February 2007 1800 UTC runs 6-h total precipitation ending 0000 UTC 14 February Forecasts are pretty close in the snow area (as verified by the objective scoring), but there are some differences farther to the south in the convection ahead of the trailing cold front.

  24. NPVU estimated precipitation for 6-h ending 0000 UTC 14 February 2007

  25. Why the similar forecasts in the snow area? Maybe a lack of TAMDAR because of flights canceled by the storm! TAMDAR coverage for the period 1500 to 1800 UTC on 15 February 2007 when conditions were dry in the region. TAMDAR coverage for the period 1500 to 1800 UTC on 13 February 2007

  26. Note the similar forecast soundings for Pittsburgh (6-h forecasts ending at 0000 UTC 14 February with the RAOB).

  27. Not the case for this same sounding comparison at Nashville, Tennessee. Overall, the sounding from the run using TAMDAR (dev2) is closer to the RAOB. The RUC run with TAMDAR had a better forecast in the central Tennessee

  28. Perplexing comparison for Detroit, however, where there was abundant TAMDAR for this day.

  29. Case 4: 22 March 2007 – 0000 UTC Surface analyses and reflectivity Strong spring storm with lots of severe weather

  30. 22 March 2007 – 0300 UTC Surface analyses and reflectivity

  31. SPC severe reports for 24-h ending 1200 UTC/22 March 2007

  32. RUC forecasts from the 22 March 2007 0000 UTC runs 6-h total precipitation ending 0600 UTC 22 March No TAMDAR With TAMDAR Some differences are seen – these are outlined in the forecasts The RUC forecast that uses TAMDAR is generally better except within the orange oval area, where no precipitation fell.

  33. NPVU estimated precipitation for 6-h ending 0600 UTC 22 March 2007

  34. Objective scores for the two RUC forecasts for the small verification area and for the 6-h period ending at 0600 UTC/22 March 2007 The statistics agree with the subjective assessment favoring the RUC run that uses the TAMDAR data.

  35. Case 5: 21 June 2007 – 2100 UTC Surface analyses and reflectivity Strong convection with many reports of severe weather

  36. 22 June 2007 – 0000 UTC Surface analyses and reflectivity

  37. SPC severe reports for 24-h ending 1200 UTC/22 June 2007

  38. RUC forecasts from the 21 June 2007 1800 UTC runs 6-h total precipitation ending 0000 UTC 22 June No TAMDAR With TAMDAR Main difference is the precipitation in IL and IN predicted by the RUC run without TAMDAR compared to almost nothing in the run with TAMDAR. Verification showed that no precipitation fell in the IL/IN area.

  39. Sounding comparison for 6-h forecasts for RUC with TAMDAR (dev2) vs RUC without TAMDAR (dev) compared to the DVN RAOB at 0000 UTC 22 June 2007

  40. Sounding comparison for 6-h forecasts for RUC with TAMDAR (dev2) vs RUC without TAMDAR (dev) compared to the ILX RAOB at 0000 UTC 22 June 2007

  41. Precipitation scores for 2007 broken down by season Scores for 6-h forecasts from 1800 UTC runs Winter season (1 Jan-31 Mar) (56 cases) RUC run without TAMDAR RUC run with TAMDAR Threshold #obs # forecast #hits EQTS Bias #forecast #hits EQTS Bias 0.01 45924 72109 32735 0.310 1.570 72715 32839 0.309 1.583 0.10 12385 17175 7218 0.305 1.387 16695 7033 0.301 1.348 0.25 4901 4962 2055 0.257 1.012 4852 2078 0.265 0.990 0.50 1596 1140 367 0.153 0.714 1111 391 0.167 0.696 1.00 240 80 35 0.123 0.333 77 40 0.144 0.321 1.50 72 8 4 0.053 0.111 11 3 0.037 0.153 2.00 26 0 0 0.000 0.000 0 0 0.000 0.000 Summer/convective season (1 Apr-20 June) (62 cases) Threshold #obs # forecast #hits EQTS Bias #forecast #hits EQTS Bias 0.01 51102 82566 35944 0.293 1.616 84024 36110 0.289 1.644 0.10 15730 23262 8249 0.246 1.479 23217 8122 0.241 1.476 0.25 6716 7499 2371 0.192 1.117 7458 2378 0.193 1.110 0.50 2505 1586 536 0.148 0.633 1632 542 0.148 0.651 1.00 531 115 57 0.097 0.217 130 66 0.111 0.245 1.50 126 17 5 0.036 0.135 16 5 0.036 0.127 2.00 34 4 0 0.000 0.118 5 0 0.000 0.147

  42. When we began to examine precipitation forecasts in late 2005 were impressed by the 4-5 October 2005 case with significantly better forecasts by the RUC run that used TAMDAR But that remains our best case More typically, we see much smaller impacts These tend to favor the RUC run that uses TAMDAR, but not always And sometimes mixed...forecast better in some spots but not in others Objective scoring of the precipitation forecasts that began in 2007 agrees with our overall subjective impression Longer-term statistics show relatively small differences generally favoring the RUC run that uses TAMDAR But on a case by case basis can see greater differences in the scores Summary

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