Raising the Forecast Bar: Can the Forecast Community Keep Up With Rising Expectations? “Where America’s Climate, Weather and Ocean Services Begin” Dr. Louis W. Uccellini Director, National Centers for Environmental Prediction St. Louis AMS Chapter St. Louis, MO October 5, 2005

2 Outline Recent Examples of Forecast Successes –May 2003 Tornado Outbreak –2004 – 2005 Hurricane Seasons –Winter Weather Upcoming Advancements for NWS Winter Weather “Desk” – collaborative forecasts Future Considerations –Advancing probabilistic forecasts

3 May 2003 Tornado Outbreak Predicted 5 days in advance Consistent forecast for major outbreak from day to day Warning process captured most tornado occurrences Media provides wide praise for NWS, including “the models”

4 May 2003 Outbreak Sequence DateAllF2-F5F4-F5Fatalities May May 4* May May May May May May May Total Major Outbreak Days are Shaded Red !

5 72 hr forecast of 500 mb hgt/vort 72 hr forecast of 850 mb hgt/winds valid May 4, 2003 Tornado Outbreak Forecasts valid 00Z May 5, 2003

6 Forecasts valid 00Z May 5, hr Eta forecast of slp/dew pt 72 hr Eta forecast of CAPE

7 4 May 2003 – Forecast Refinement Hazards Assessment: 30 April Observed Tornado Fcst: 4 May Morning Severe Thunderstorm Fcst: 2 May Day 3

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9 NHC Atlantic 72 hr Track Forecast Errors Advances Related To USWRP

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12 Katrina’s cone of uncertainty approximately 24 hours before landfall over Florida

13 Ophelia September 6 – 17, 2005

14 Winter (East Coast) DateMedium RangeShort RangeReaction March day forecastRecord warning: 30 hr in advance Headlines! Jan day forecast30 hr warning lead time great Jan hr warning lead time savaged “surprised” Dec 2000Up to 7 day cyclone forecast hr lead time for watch/ warning Wash. DC to NYC Mixed No snow – DC Snow in NYC March 2001Up to 6 day cyclone forecast hr lead time for watch/ warning savaged - off by 100 to 200 km

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16 February 28 th 2005 Event

17 February 28, 2005 Event 48 hr prob of >4”24 hr prob of >4” 24 hr storm track 24 hr snowfall

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19 Public Perception: Have we taken a step back? ?Public more in tune with medium-range prediction ?Increased reliability at longer ranges, even for the rare snowstorm ?Public expectations have increased! They expect more exactness! ?Yet the uncertainties in snow forecasting are large – lends itself to a more probabilistic approach ?When we miss details in short-term, and it does not snow; disappointment turns to anger!

20 Bottom Line Deterministic forecasting is not healthy!

21 The Challenge ?Increase accuracy – short to medium range ?Convey uncertainty

22 The Goal ?Move from the “subjective” model-to- model comparison to the use of a more objective ensemble prediction ?For the NWS – provide a “unified” forecast based on a collaborative approach

23 NWS Winter Weather Desk ?Goals of 4 year experiment from : ?Improve Winter Weather Services to the public through coordination of the winter weather watches/warnings with National guidance products ?Test short range ensemble for their applications to winter weather forecasting ?Motivation: ?Jan 24-25, 2000; December 30, 2000: March 4-6, 2001 ?WWD “operational” September 15, 2004 for season

24 NWS Winter Weather Desk ?Time line: Sep 15 – April 1 ?Participants ?NCEP HPC ?Provide SREF based Winter Wx guidance ?Coordinate with WFOs (Chat Room Technology) ?WFOs ?All CONUS WFOs ?Use guidance from NCEP to produce coordinated Winter Storm Watches/Warnings ?Products: ?24 h probability (low, moderate, high) of meeting/exceeding 4”, 8”, 12” snow, 0.25” freezing rain (for day 1, 2, 3) ?72h Low tracks graphic and discussion

25 HPC Winter Weather Desk New Products for Public –Experimental Low Track Internal –Experimentation with 2 snow liquid ratio (SLR) algorithms (Cobb, Roebber) in addition to Baxter’s Climo SLR –Graphics depicting hi res grids of snow accumulation for the intermountain region Derived from HPC QPF run through Mountain Mapper and converted to snow via Snow Liquid Ratio algorithm 40km HPC Snow grid downscaled to 5km using PRISM data –SREF derived Winter Weather Impact Graphics

26 NOMINAL

27 NEW

28 New Experimental WW Impact Graphics Societal Impact of Winter Events defined by more than just accumulation –Duration, Timing, Intensity Conveyance of impact could be achieved through SREF derived probability graphics highlighting these attributes Distributed internally for evaluation by WFOs and NCEP Verification and evaluation will be performed during the season If results are favorable products will be available publicly next season Examples….

29 SNOWFALL RATE >=1”/hr

30 SFC VIS <= ¼ mile

31 PROBABILITY EVENT DURATION >= 12 HOURS

32 PROBABILITY EVENT DURATION >= 24 HOURS

33 New Experimental WW Impact Graphics Examples Probability of 1” or more Snow accumulation on asphalt Probability of 1” or more Snow accumulation on grass

34 Short Range Ensemble Forecast ?15 members twice per day ?87 hrs from 9 and 21Z ?Resolution ?Eta 32 km/60L ?RSM 45km/28L ?Domain expanded to include Alaska-216 and Hawaii- 243 in addition to CONUS-212 (all km) ?BUFR output generated for all 15 members ? 0.25” prcp

35 SREF to WRF Ensemble 1 st Quarter FY06 (Nov) 21 members twice per day 6 members added (3 WRF-NMM, 3 WRF-ARW) No change to resolution No change to domains Evaluation phase in planning stage

36 Summary Forecast community is now recognized for predicting major weather events Expectations are outpacing our ability to improve In the face of rising expectations, we have to embrace a more probabilistic approach based on ensemble models and be able to communicate the uncertainty

37 Appendix

UPGRADES ATLANTIC TRACK VERIFICATIONS GAIN: ~20% GFS ~15% GFDL GAIN: ~20% GFS ~15% GFDL

39 December 22, 2004 Event

40 December 22 Event 48 hr prob of >8”24 hr prob of >8” 24 hr storm track 24 hr snowfall