Exploitation of Ensemble Output (and other operationally cool stuff) at NCEP HPC Peter C. Manousos NCEP HPC Science & Operations Officer

Goals of Presentation Show how ensemble output is exploited at HPC Briefly –Sneak in an intro on NCEP and HPC –Provide a short term roadmap for the NCEP modeling system –Introduce downscaling techniques employed at HPC Answer questions

NWS CONSTRUCT OF OPERATIONAL OFFICES CWSUs and Regional Headquarters not depicted WFOs RFCs

HPC PRODUCTS AND SERVICES QPF –5 Day QPF –Excessive Rainfall –Probabilistic Snow/Ice –Compile National Flood Outlook Fronts/pressures –Surface Analysis & Daily Wx Map –12h - Day 7 Forecasts –General Weather through 48h –Day 3-7 Max/Min/24h PoP (gridded) –Tropical guidance (to Day 7) Model diagnostics International Desk Experimental products HPC also provides Emergency & Special Products and Services

Ensemble Exploitation

Static Reference Nominally derived ensemble parameters (means, spreads, clusters, etc.) Serve as reference to quantify pattern evolution uncertainty and assist in pattern evolution preference

Automated Guidance Automated ensemble products highlighting areas most likely to exceed critical thresholds

Starting Point Forecaster selected blends to generate starting point grids

Targeted PDF Application Generation of probabilities by applying (centering) ensemble spread on manually generated deterministic forecast (winter weather, QPF, Medium Range)

QPF Confidence Interval Max/Min QPF derived from HPC QPF and Characteristic uncertainty of current pattern

Model Info

NWS Modeling System - Short Term Road Map CCS – Central Computing System –New System being installed/tested –Slated to be operational Jan 07 – all CPU resources already earmarked for use GFS – Global Forecast System –T384/64L resolution, T190 after 180 hrs –No planned increases in resolution – conversion to hybrid sigma/p coordinate system, tweaks to init schemes and physics packages planned after CCS upgrade NAM – North American Mesoscale Model –WRF core run at 12km/60L res, non hydrostatic, sigma/p coordinate system –No short term planned increases to model res, tweaks to init schemes and physics packages intended after CCS upgrade GEFS – Global Ensemble Forecast System –14 members run at T126/L28 4x/day –Increase to 20 members and L64 after CCS upgrade –NAEFS will also increase to 16 CMC + 20 GEFS = 36 members after CCS upgrade SREF – Short Range Ensemble Forecast System –21 members run at approx 34km horiz res 4 cycles per day (posted to 40km res grib files) »10 Eta members, 5 RSM, 6 WRF –Intention to convert all members to WRF after CCS upgrade

Monthly Synergy Meetings Informal meeting with –EMC, NCO, MMB, NCEP Service Centers, WFOs Near term model development and super computer/comm systems plans provided Users can anticipate and accommodate changes Highlights posted to web and ed to “allsoos list”

Downscaling to 5km

5km PRISM data is applied to 380 point forecasts to generate 5km forecast grid 5km Gridded MOS is being tested to replace PRISM data

NDFD D5 Max T HPC

QPF related grids can be downscaled via PRISM as well Impact of downscaling on QPF related grids only occurs where significant gradients in terrain exist

Questions ??? x 7307

How do we get 5km detail from just 380 points ??? 5km PRISM data is used as a starting point Difference between HPC and PRISM data taken at all HPC forecast points (380) A “difference grid” (HPC – PRISM) is generated –Results in a 5km grid with little detail “Difference grid” is then added on top of the PRISM data

Gotcha’s with mean/spread for QPF QPF “mean” can be misleading if output from individual members do not overlap each other