1. The LAMP/HRRR MELD FOR AVIATION FORECASTING Bob Glahn, Judy Ghirardelli, Jung-Sun Im, Adam Schnapp, Gordana Rancic, and Chenjie Huang Meteorological Development Laboratory, National Weather Service, NOAA 1

2. OUTLINE LAMP forecasts HRRR forecasts Ceiling and Visibility Meld – Method – Verification – Example Conclusions Plans 2

3. CEILING HEIGHT AND VISIBILITY FORECASTS Ceiling height and visibility forecasts are contained in weather forecast products for the aviation community, including the TAFs. – Ceiling in hundreds (hds) ft above ground. – Visibility in miles. Guidance based partly on numerical models is needed to produce the final forecasts. LAMP provides forecasts for aviation products 3

4. LAMP (LOCALIZED AVIATION MOS PROGRAM) LAMP Guidance Products: – Forecasts produced each hour, for most weather elements contained in aviation and public weather products, including ceiling and visibility, in hourly increments out to 25 hours. – Forecasts of convection and lightning potential. Forecasts are available in text and gridded forms. 4

5. LAMP LAMP Forecasts are statistically produced as a combination of: – current observations, – simple advective models, and – MOS forecasts (based on NCEP’s Global Forecast System). Ceiling and visibility forecasts are in terms of: – categories (e.g., ceiling 400-900 ft) and – the probability of each category. 5

6. LAMP CEILING HEIGHT FORECAST, 7-H PROJECTION FROM APRIL 11, 2013, 1200 UTC 6

7. SEA LEVEL PRESSURE AND FRONTS APRIL 11, 2013, 1200 UTC 7

8. HRRR MODEL (HIGH RESOLUTION RAPID REFRESH MODEL) HRRR is a 3-km dynamic model – Forecasts produced each hour, for a variety of weather elements, including ceiling and visibility, in hourly increments out to 15 hours. Ceiling in terms of meters above sea level. Visibility in meters. 8

9. HRRR CEILING HEIGHT FORECAST FOR APRIL 11, 2013, 8-H PROJECTION FROM 1100 UTC 9

10. CEILING AND VISIBILITY AS A MELD OF LAMP AND HRRR Both LAMP and HRRR produce ceiling and visibility forecasts – LAMP in terms of categorical forecasts and the probability of each category (e.g., ceiling 400-900 ft; visibility 3-5 mi) at 1552 specific sites (stations). – HRRR in terms of specific values of ceiling in meters above sea level and visibility in meters on a grid. Ceiling (Visibility) Meld forecasts are produced as a combination of LAMP and HRRR ceiling (visibility) forecasts. 10

11. DATA AVAILABLE LAMP has a long archive Two warm seasons of HRRR data were available (April-September, 2013, 2014) – 8 months used for development – 4 months used for independent verification April 2013, August 2013, June 2014, September 2014 Previous work used 1 season of cool season data (not reported here) 11

12. REEP USED FOR PRODUCING MELD (REGRESSION ESTIMATION OF EVENT PROBABILITIES) REEP predictors for ceiling (visibility): – LAMP Probability of each of 7 (6) categories at the 1552 LAMP stations Probabilities better than categorical values as predictors – HRRR forecasts in binary form, total of 12 (11), interpolated to the LAMP stations Small spots removed/coalesced before making binaries – Observations (obs) in binary form, total of 15 (15) at the LAMP stations REEP predictands in binary form, total of 24 (16) categories at the LAMP stations (ground truth) – More definition than original LAMP Generalized development—All points grouped together 12

13. REEP PREDICTOR SELECTION Forward selection of predictors – > 0.5% reduction of variance cutoff for any projection for any predictand category For ceiling (visibility) 15 (14) predictors were selected: – All 7 (6) LAMP probabilities – 5 (3 ) HRRR binaries – 3 (5 ) Obs binaries 13

14. REEP EQUATIONS REEP produces 24 X 25 = 600 (16 X 25 = 400) equations, one for each of 24 (16) categories of ceiling (visibility) for each of the 25 projections. – Each equation has the same predictors, except that the LAMP and HRRR forecasts match the predictand projections. – The same-cycle HRRR is not available in time to be used, so the 1-h old forecast is used. – Beyond 14 hours, the 14-h HRRR is continued for all predictand projections. 14

15. VERIFICATION ON INDEPENDENT DATA Primary performance metrics – Threat score for < categories – Bias for categories 15

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24. IMPLEMENTATION STRATEGY Development was done at points Implementation was done on the 2.5-km NDFD grid – Analyze LAMP probabilities to the grid – Analyze obs to the grid – Apply the HRRR forecasts on the grid – Apply the REEP equations at each gridpoint Other implementation strategies possible 24

25. LAMP/HRRR MELD CEILING HEIGHT FORECAST FOR APRIL 11, 2013, 7-H PROJECTION FROM 1200 UTC 25

26. LAMP CEILING HEIGHT FORECAST, 7-H PROJECTION FROM APRIL 11, 2013, 1200 UTC 26

27. HRRR CEILING HEIGHT FORECAST FOR APRIL 11, 2013, 8-H PROJECTION FROM 1100 UTC 27

28. CONCLUSIONS The Meld of LAMP and HRRR for one cycle (start time) has produced ceiling and visibility forecasts generally superior to LAMP and especially to HRRR. It is MDL’s intention to implement a LAMP/HRRR Meld built on the work shown here with possible improvements. 28

29. REFERENCE Glahn, B., A. D. Schnapp, and J.-S. Im, 2015: The LAMP and HRRR ceiling height and visibility meld. MDL Office Note 15-1. Meteorological Development Laboratory, National Weather Service, NOAA., U.S. Department of Commerce, 28 pp. Can be found at: http://www.nws.noaa.gov/mdl/lamp/publications/ lamp_hrrr_office_note_ON_15-1_7_31_15_final.pdf The general LAMP web site URL: http://www.nws.noaa.gov/mdl/lamp/index.shtml http://www.nws.noaa.gov/mdl/lamp/index.shtml 29