The NOAA Rapid Update Cycle (RUC) 1-h assimilation cycle WWRP Symposium -- Nowcasting & Very Short Range Forecasting – 8 Sept 2005 – Toulouse, France Stan Benjamin Steve Weygandt John Brown NOAA Forecast Systems Lab – Boulder CO, USA RUC web site - GOAL: Provide high-frequency (1h) mesoscale 3-d analyses and short-range (1-12+h) forecasts for aviation, severe weather, hydrology, …

RUC Hourly Assimilation Cycle Time (UTC) 1-hr fcst Background Fields Analysis Fields 1-hr fcst 1-hr fcst 3DVAR Obs 1-hr fcst 3DVAR Obs 3DVAR Obs 3DVAR Obs 3DVAR Obs 1-hr fcst 1-hr fcst

RUC Hourly Assimilation Cycle + Forecasts > 1h Time (UTC) 9-hr fcst Background Fields Analysis Fields 9-hr fcst 9-hr fcst 3DVAR Obs 9-hr fcst 12-h fcst 12-h fcst 3DVAR Obs 3DVAR Obs 3DVAR Obs 3DVAR Obs Run-time at NCEP for RUC 12h fcst – 17 min

Data type~ NumberFrequency Rawinsonde~85/12h+spec Aircraft /1h NOAA profiler32/1h VAD winds~125/1h PBL profilers25/1h Surface METAR /1h Mesonet~6000/1h Buoy/ship /1h GOES precip water /1h SSM/I precip water /6h GPS precip water~280/1h GOES cloud-drift wind /1h GOES cloud-top (p,T)~10km/1h Radar ref / /lightning 1km  13km /1h RUC Obs Sources - experimental 13km RUC -- As of 6 Sept 05

5 RUC20 Wind forecast Accuracy -Sept-Dec 2002 Verification against rawinsonde data over RUC domain RMS vector difference (forecast vs. obs) RUC is able to use recent obs to improve forecast skill down to 1-h projection for winds (kts) Analysis ~ ‘truth’

6 Application of Digital Filter Initialization (DFI) in RUC Model Critical for 1-h assimilation cycle 45 min forward, 45 min backward – no physics Average over DFI period Applicable for diabatic application, nudging to radar obs during DFI ‘pre-forecast’ Noise in surface pres at 1h forecast is much lower with DFI

7 Vert Coord Hybrid isentropic-sigma – 50 levels Stable clouds, NCAR mixed-phase (cloud Precipitation water, rain water, snow, graupel, ice, ice particle number. concen. Sub-grid Grell-Devenyi ens scheme precipitation (144 members, closure/CIN Land-surfaceRUC LSM - 6-level soil/veg model, 2-layer snow model - Smirnova Rapid Update Cycle Model Current operational RUC: 13-km 9-12-hr fcst

Recent changes to RUC13 3DVAR analysis (among many): 1. Use of surface obs throughout PBL (NCEP Fall 2004) 2. Cloud analysis (GOES, METAR ceiling/vis/curr-wx)

9 PBL-based METAR assimilation -- create additional obs corrections thru PBL Use METAR data through PBL depth from 1h fcst RUC oper analysis 18z 3 Apr 02 IAD x x x x Effect of PBL-based METAR assimilation

10 RUC enhancements: 1.Use of METAR obs through boundary-layer depth (Sept 04) 2.Assimilation of GPS precipitable water observations (RUC13 - ~Jun05) CAPE impact from two RUC enhancements 3h fcst WITH enhancements 3h fcst OPERATIONAL 0000 UTC 21 Apr 2004 Severe reports NWS SPC Norman, OK Tornadoes

11 Use GOES CTP, radar reflectivity, lightning, METAR (clouds,wx,vis) to modify 1h fcst 3-d q* fields Clear/build (change qc, qi, qv) with logical arrays Safeguards for pressure-level assignment problems (marine stratus, convective clouds) Use nationwide mosaic radar data to modify water vapor, hydrometeor fields – in testing, crude Lightning data used as a proxy for radar reflectivity Feedback to cumulus parameterization scheme – bypass convective inhibition via radar/lightning, GOES ECA RUC Cloud Analysis

12 GOES cloud top pressureRadar/lightning data PRES Qv Qc RH Cloudwater, water vapor and relative humidity before ( ) and after (----) GOES Cloud- top pressure adjustment Rainwater, snow, cloud ice and reflectivity before ( ) and after (----) GOES radar/lightning adjustment PRES Qr Qs Qi dBZ

13 IFRLIFR VFR CLR MVFR Sample ceiling analysis impact Ceiling from RUC hydrometeors Analysis WITH cld/wx/ vis obs Analysis NO cld/wx/ vis obs Aviation Flight Rules cloud ceiling height (meters) 1800 UTC 17 Nov 2003 Observations

Data type~ Number 3-d reflectivity dataNSSL mosaicked data NASA Langley experimental GOES cloud products TAMDAR aircraft regional carriers – T/V/RH – lower-mid troposphere 65 aircraft Radar radial wind120 WSR-88D radars GPS zenith wet delay (replacing prec water retrievals) 280, increasing QC’d mesonet data6000, but many not usable due to poor siting and lack of QC monitoring/metadata Experimental or future RUC Obs Sources To be added in next 6 months to experimental 13km RUC

15 Radar reflectivity assimilation - experimental RUC13 init 09z - 3-6h precip Valid UTC 6 Sept 2005 Control – oper RUC Exp RUC13 W/ rad ref assim Obs – 1345 UTC

Sample 3DVAR analysis with radial velocity 500 mb Height/Vorticity * Amarillo, TX Dodge City, KS * * Analysis WITH radial velocity * * Cint = 2 m/s * * Cint = 1 m/s K = 15 wind Vectors and speed 0800 UTC 10 Nov 2004 Dodge City, KS Vr Amarillo, TX Vr * * Analysis difference (WITH radial velocity minus without)

17 Current RUC CONUS domain Planned Rapid Refresh domain Goals: Hourly NWP update in - Alaska - Wider E. Pacific -- Canada - Caribbean Sea Rapid Refresh -replace RUC – km resolution - use WRF model

18 The RUC by 2008, testing in 2006 “Rapid Refresh” Simple  more complex assimilation of radar reflectivity and radial winds Improved use of sat data, GPS, aircraft, surface/mesonet Use of WRF model w/ RUC-like physics Use of NCEP data assimilation (GSI) with RUC-specific enhancements – use of sfc data, cloud analysis North American coverage