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What’s New at NCEP? An Update on the What’s New at NCEP? An Update on the HPC Winter Weather Desk and Recent HPC Winter Weather Desk and Recent
Changes to the NCEP Model SuiteChanges to the NCEP Model Suite
Michael J. BrennanScience and Operations Officer
Hydrometeorological Prediction Center
9th Northeast Regional Operational Workshop8 November 2007
OutlineOutline
• HPC Winter Weather Desk– 2006–2007 Verification– What’s new for 2007–2008
• NCEP Model Upgrades– SREF– NAEFS– Hi-Res Window
• New Uncertainty Guidance
HPC Winter Weather DeskHPC Winter Weather DeskOverviewOverview
• Internal deterministic 24-h snow/sleet and freezing rain accumulation graphics for days 1–3
– PRISM-adjusted for Intermountain West
• Public products of 24-h exceedance probabilities for:
– Snow/Sleet: 4,8,12 in.
– Freezing Rain: 0.25 in.
– Probabilities computed from deterministic forecast and model spread
• Track forecasts for sfc. lows associated w/ significant winter weather
• Heavy Snow and Ice Discussion (QPFHSD)
HPC Winter Weather DeskHPC Winter Weather Desk2006–2007 Verification – Snow/Sleet2006–2007 Verification – Snow/Sleet
D1
D2
D3
HPC adjustments show largest improvement over model guidance for snow > 12”
HPC Winter Weather DeskHPC Winter Weather Desk2006–2007 Verification – Freezing Rain2006–2007 Verification – Freezing Rain
Day 2
Day 3
HPC Adjustments show most improvement for FZRA amounts
<0.10”
D1
D2
D3
HPC Winter Weather DeskHPC Winter Weather Desk2006–2007 Verification2006–2007 Verification
Snow-Liquid Ratio
00.5
11.5
22.5
33.5
44.5
5
36 60 84
Climatology
QPF*13
Caribou
Roebber
QPF*10
15 Oct 2006 – 1 May 2007 GFS Root Mean Square Errors
Forecast Hour (from 00Z or 12Z)
•Roebber method had lowest RMSE for computation with GFS model
•10:1 ratio second lowest RMSE at all lead times
HPC Winter Weather DeskHPC Winter Weather Desk2006–2007 Verification2006–2007 Verification
Low Tracks (Associated with “significant winter weather” only)
•HPC low track forecast RMSE ranges from 85 nm at F12 to 140 nm at F72
•HPC shows most improvement over GFS and NAM after 36 h
•Best guidance at most times is GFS/NAM blend
•SREF Mean also performs well (best at F12 and F72)
HPC Winter Weather DeskHPC Winter Weather DeskNew for 2007–2008 New for 2007–2008
• Grid spacing of non-PRISM-adjusted snow/ice grids decreased from 40 km to 20 km
• QPF from Canadian model now available in winter weather precipitation blender
• Addition of ECMWF pending receipt of 6-h QPF
• CoCoRAHS snow data will be used in verification
HPC Winter Weather DeskHPC Winter Weather DeskNew for 2007–2008 New for 2007–2008
• Based on 2006-2007 verification, HPC Snow-Liquid Ratio will be equal blend of:– 10:1 ratio– Roebber method computed from NAM– Roebber method computed from GFS – Climatological SLR
• Computed every 6-h through forecast period• Maps on internal WWD webpage show resultant 6-h SLR values
NCEP Model Suite ChangesNCEP Model Suite Changes
Hi-Res Window (HRW) UpgradeHi-Res Window (HRW) Upgrade• Code upgraded to official public
version of WRF distributed by NCAR • WRF-NMM:
– Decreased horizontal grid spacing from 5.2 km to 4.0 km
– Added local NCEP changes made to NAM
• WRF-ARW:– Decrease horizontal grid spacing from
5.8 km to 5.1 km
• No CP scheme used• Generate new post-processed fields:
– Simulated GOES satellite fields– Improved simulated radar reflectivity
• Available through TOC and ftpprd• Limited fields available on NCEP
models website
Black dots represent water points in model
(Chesapeake Bay)
12 km 4 km
HRW “Large” DomainsHRW “Large” Domains
East-Central CONUS
West-Central CONUS
Alaska
Large Domain Schedule:
00/12Z: East-Central CONUS
06Z: West-Central CONUS
18Z: Alaska
•1 hurricane run cancels ARW runs on large and small domains
•2 or 3 hurricane runs cancel both ARW runs and NMM run on large domain
•4 hurricane runs cancel all runs
•Small domains:
•Hawaii (00/12Z)
•Puerto Rico (06/18Z)
Short Range Ensemble Short Range Ensemble Forecast System (SREF) UpgradeForecast System (SREF) Upgrade
• 21 members– 10 Eta– 6 WRF– 5 RSM
• Bias corrected output for all parameters except QPF
– Same BC methodology used for GEFS/NAEFS
– Decay function weights last 50-60 days most heavily
• 4 new aviation forecast parameters
– Icing– Clear Air Turbulence– Low-Level Ceiling– Flight Restriction
• Parallel evaluation: 2 Oct.• Implementation: 11 Dec.• Bias-corrected SREF output will
eventually replace current output in AWIPS
SREF Mean BC 500-mb hght (magenta)
SREF Mean 500-mb hght (red)
Magnitude of bias correction for 87-h 500-mb height forecast
Short Range Ensemble Short Range Ensemble Forecast System (SREF) UpgradeForecast System (SREF) Upgrade
• Next SREF upgrade – tentatively scheduled for the 3rd quarter of FY08– Upgrade the WRF members to the latest version– Increase the resolution of all members to as close as 32 km as
possible given computational resources– Eta members already running at 32 km
SREF Probability of 24-h QPF > 2” with TS Noel
Experimental HPC/SPC SREF-based Winter Weather Impact Graphics
Real Time Mesoscale Analysis (RTMA)Real Time Mesoscale Analysis (RTMA)
• 5 km NDFD resolution hourly analysis of T, Td, wind, sfc. pres.
• First Guess: downscaled RUC (NAM) as first guess for CONUS (AK, Hi, PR)
• Uses ‘all’ sfc obs within +/- 12 min of analysis time
• Data assimilated with 2-D version of NCEP’s Gridpoint Statistical Interpolation (GSI) analysis scheme
• Available on NDFD page http://www.weather.gov/forecasts/graphical/sectors/
• Used for NAEFS downscaling
2-m T
10-m WND
North American Ensemble Forecast North American Ensemble Forecast System (NAEFS) UpgradeSystem (NAEFS) Upgrade
• Combined NCEP and CMC ensemble system
– 40 members, available twice daily (for now)
• Bias corrected output using same methodology as SREF
• Output includes– Ensemble Mean, Spread, Mode– 10th, 50th (median), and 90th
percentile probabilities– Anomalies compared to
NCEP/NCAR reanalysis
• Downscaled output to 5-km NDFD grid using RTMA
– 2-m T, 10-m wnd, sfc. pres.
• Parallel evaluation: 25 Oct. • Operational implementation:
4 Dec.
NAEFS Ensemble Mean MSLP and Spread 90-h forecast of Noel from 00 UTC 31 Oct
NAEFSNAEFSDownscalingDownscaling
NAEFS Ensemble Mean Bias Corrected 2-m Temperature (F) (1°)NAEFS Ensemble Mean Bias Corrected & Downscaled 2-m Temperature (F) (5km)
NAEFSNAEFSUncertainty InformationUncertainty Information
Mean 10th percentile
90th percentile Median (50th percentile)
HPC Alaska DeskHPC Alaska Desk• Working with EMC to provide additional
uncertainty information medium range guidance for Alaska WFOs– HPC deterministic forecast mode– 10th and 90th percentile probabilities
computed from downscaled NAEFS and adjusted with HPC forecast for Min/Max T & wind speed
9010Mode
• Remaining issues – How to downscale for max/min T occurring at widely varying
times?– Quality of RTMA over Alaska (for downscaling and verification)– Potentially very large spreads for temperature, wind speed – is
10/90 best range?– Desk will begin issuing experimental products in December– Opportunity to try new things – if successful may be transitioned to
CONUS medium range
Looking Ahead...Looking Ahead...
NOAA Center for Weather and Climate Prediction (NCWCP)College Park, Maryland
268,762 ft2 building will be new home for NCEP, NOAA’s Satellite and Information Service, and
Air Resources Laboratory
Scheduled to be complete early 2009
Construction Progress as of 23 October
