AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 1 June 26, 2007 EVALUATION OF THE NCEP WRF NMM AND ARW MODELS FOR SOME RECENT HIGH-IMPACT WEATHER EVENTS Ed Szoke 1,2, Steve Koch 2, Dave Barjenbruch 3, and Doug Wesley 4 2 NOAA/Earth Systems Research Laboratory Global Systems Division 1 Joint collaboration with the Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO 3 NOAA National Weather Service, Boulder, Colorado 4 Cooperative Program for Operational Meteorology, Education and Training (COMET), Boulder, Colorado

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 2 June 26, 2007 Overview At the last WAF/NWP Conference in D.C. (August/2005) there was a session with talks on the DWFE (DTC Winter Forecast Experiment) and the high-resolution models run during DWFE During that session Nelson Seaman announced that NCEP would begin to routinely run hi-res windows for the ARW and NMM at ~5 km horizontal grid resolution, in part because of the DWFE experience Since late 2005 these runs have been made in real-time and posted to the web Purpose of this talk Examine the hi-res models for some recent winter high-impact events Compare to the operational models (NAM and GFS) Focus on precipitation forecasts Do the hi-res models offer improved guidance to the forecaster for these events? In this talk will focus on the big pre-Christmas 2006 blizzard in Colorado

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 3 June 26, 2007 Coverage and initialization times for the high-resolution window runs

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 4 June 26, 2007 Run out to: 84 h 240 h 48 h

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 5 June 26, 2007 Headlines on Thursday 21 December 2006 (Denver Post)

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 6 June 26, 2007 Headlines on Friday 22 December 2006 (Denver Post)

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 7 June 26, 2007 Boulder Daily Camera headline on Thursday 21 December. For some, a 15 min commute turned into 2+ hours. Others were stranded...

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 8 June 26, 2007 Midday 20 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 9 June 26, 2007 Late in the day 20 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 10 June 26, 2007 The next morning ” total

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 11 June 26, 2007 This storm was followed by another foot+ storm the next week...scene by 30 Dec 06

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 12 June 26, 2007 The focus today will be on the first storm...snow totals: max 50” in the foothills west of Fort Collins, ~20-24” Denver city

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 13 June 26, 2007 Statistics Terrain is a big player in modulating snowfall...

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 14 June 26, 2007 Estimated precipitation totals from the NOHRSC. Max totals for 24 h ending: 0600 UTC/21 Dec = ” 0600 UTC/22 Dec = ” totals ~ 2-2.8” For comparison with model forecasts need precipitation totals. Most of the snow fell from 1200 UTC/20 Dec to 1200 UTC/21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 15 June 26, 2007 Note the minimum downstream of the Cheyenne Ridge of ” Agrees pretty much with the Boulder NWS estimated total precip using many volunteer and official reports

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 16 June 26, 2007 This was a high-impact event for areas well-beyond Northeast Colorado Watches and warnings as of 0000 UTC 20 December

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 17 June 26, mb analysis: 1200 UTC/18 Dec 2006

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 18 June 26, mb analysis: 1200 UTC/19 Dec 2006

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 19 June 26, mb analysis: 1200 UTC/20 Dec 2006

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 20 June 26, mb analysis: 0000 UTC/21 Dec 2006

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 21 June 26, 2007 Statistics Time 1: 1200 UTC 18 Dec GFS 48-h 700 mb forecast valid 1200 UTC/20 Dec Elongated upper-low with nw flow along Front Range.

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 22 June 26, 2007 Similar to GFS 18 Dec 06/1200 UTC NAM 48 h 700 mb valid 1200 UTC 20 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 23 June 26, 2007 Also an elongated low, but more N to NNE flow along the Front Range 18 Dec 06/1200 UTC WRF/ARW 48 h 700 mb valid 1200 UTC 20 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 24 June 26, 2007 flow is even more NE at ~10 kts with hint of secondary low 18 Dec 06/1200 UTC WRF/NMM 48 h 700 mb valid 1200 UTC 20 Dec Big picture is similar to the GFS and NAM... but along the Front Range

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 25 June 26, 2007 Much more circular 700 mb low is what verifies Verifying 700 mb analysis at 20 Dec 06/1200 UTC

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 26 June 26, 2007 Deep upslope just above 700 mb. 20 Dec 06/1200 UTC Denver sounding

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 27 June 26, 2007 Results in lots of snow wrapping into Colorado UTC/20 Dec radar.

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 28 June 26, 2007 Much better 700 mb shape and location of the upper low but flow is still too northerly Time 2: 19 Dec 06/0600 UTC GFS 42-h 700 mb valid 0000 UTC 21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 29 June 26, 2007 Somewhat better flow tho still nw at ~ Denver's location 19 Dec 06/0600 UTC NAM 42 h 700 mb forecast valid 0000 UTC 21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 30 June 26, 2007 Flow is more NNE and strong (30 kts) near Denver 19 Dec 06/0600 UTC WRF/ARW 42 h 700 mb forecast valid 0000 UTC 21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 31 June 26, 2007 Pretty close to the ARW 19 Dec 06/0600 UTC WRF/NMM 42-h 700 mb forecast valid 0000 UTC 21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 32 June 26, 2007 Upper low is deepening in a perfect spot Verifying 700 mb analysis at 21 Dec 06/0000 UTC

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 33 June 26, 2007 Deep northeast flow. Evidence of low level damming with a more nw surface wind. 21 Dec 06/0000 UTC Denver sounding

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 34 June 26, 2007 The more N to NW flow forecast for the Front Range kept precip amounts too low near the foothills/Urban Corridor. 19 Dec 06/0600 UTC GFS 48 h total precipitation ending 0600 UTC 21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 35 June 26, 2007 NAM had better NE flow at least in northern CO so better wrap-around precip, but not far enough south so Denver kept out of the heavy amounts. 19 Dec 06/0600 UTC NAM 48 h total precipitation ending 0600 UTC 21 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 36 June 26, 2007 Not so with the ARW. Denver is located near the “X”, with 2-2.5” predicted just to the nw. Note the minimum of precip in the ” range downstream of the Cheyenne Ridge. Also a good forecast of the heavier precip extending east of Denver near 40 o N. 19 Dec 06/0600 UTC WRF/ARW 48 h total precipitation ending 0600 UTC 21 Dec x min 40 o N

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 37 June 26, 2007 NMM also has great wrap-around precip all the way to Denver, though not as much as the ARW (max amounts in this forecast in the ” range). Also a min downstream of the Cheyenne Ridge but not as dramatic ( ”) as in the ARW forecast. 19 Dec 06/0600 UTC WRF/ARW 48 h total precipitation ending 0600 UTC 21 Dec x x min

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 38 June 26, 2007 Precipitation analysis (repeated)

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 39 June 26, mb forecasts were similar for this final time (~ 6-8 h before the S+ began), so will only show the precipitation forecasts. GFS still having trouble getting the max amounts back into the Front Range but is better, with 1.26” max near Fort Collins. Time 3: 20 Dec 06/0600 UTC GFS 48 h total precipitation ending 0600 UTC 22 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 40 June 26, 2007 NAM is much better. Max is now just over 3”. Also, nicely picks up the min south of the Cheyenne Ridge (of ”) as well as a min south of the Palmer Ridge (near Colorado Springs, similar) Observed amounts in the Springs area were as low as just under 0.5”. 20 Dec 06/0600 UTC NAM 48 h total precipitation ending 0600 UTC 22 Dec

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 41 June 26, 2007 Max amounts now up to the 3-4” range just w-nw of Denver (marked by X). The mins south of the Cheyenne Ridge and the Palmer Divide are similar to those forecast by the NAM. 20 Dec 06/0600 UTC WRF/ARW 48 h total precipitation ending 0600 UTC 22 Dec x

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 42 June 26, 2007 Similar forecast to the ARW, except a little less precip east of Denver. 20 Dec 06/0600 UTC WRF/NMM 48 h total precipitation ending 0600 UTC 22 Dec x

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 43 June 26, 2007 Summary of the big storm Early forecasts ~ 48 h in advance of the storm were similar on the larger scale with an elongated 700 mb low in all the models But the high-resolution runs had more favorable flow near the Front Range...is this a result of the flow modeled at higher resolution interacting with higher resolution terrain? The higher resolution models had better precipitation forecasts sooner than the operational models, with the GFS slowest to come around to having the precipitation wrap into the Front Range. Close to the storm onset the NAM forecast was fairly similar to that from the high resolution models Including being able to capture precipitation minima and maxima that were highly modulated by terrain Forecasts from the ARW and NMM were relatively close...a little more precipitation from the ARW. For this case the precipitation amounts forecast from the high-resolution models were in line with observed totals. More generally, we have noticed a tendency to over predict orographic precipitation, especially with weaker synoptic systems.

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 44 June 26, 2007 Some thoughts on the high-resolution runs The runs were accessible through the web (for the most part). Are they being used? An informal survey of several WFOs suggested they are not used much. Why? Not on AWIPS (also, therefore, cannot input to IFPS) Run only once per day (although depending where you are, like in Colorado, two windows overlap) so model output becomes “old” compared to the six-hourly operational runs Model forecast reflectivity was a very popular product during DWFE, but was not available on the web The future looks better! NCEP plans to make changes: Bigger, CONUS sized windows Run twice daily At 4 km horizontal grid resolution With attempt to get output into AWIPS

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 45 June 26, 2007 Here is an event that was a big bust for the Front Range. 48-h 700 mb forecast from the NAM valid at 1200 UTC 13 April Note the upslope flow in the forecast. Lastly....if the NAM has a really bad forecast, the high-resolution model will also go down

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 46 June 26, mb low verifies farther west and south...no upslope for Denver/Boulder!

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 47 June 26, 2007 As a result most of the precipitation stayed to the south

AMS 22 nd Conference on Weather Analysis and Forecasting/18 th Conference on Numerical Weather Prediction – Park City, Utah 48 June 26, 2007 Somewhat different forecasts for northeastern Colorado, but both models predict too much precipitation too far north (really nothing verified in southeast Wyoming). 48-h total precipitation forecasts from the hi-res models ending at 1200 UTC 31 April ARW NMM