WAFS Grids Jesse Sparks Aviation Weather Center Kansas

WAFS Grids Jesse Sparks Aviation Weather Center Kansas City, MO

World Area Forecast System • Established by ICAO and WMO – Improve the quality and consistency of en route guidance provided for international aircraft operations • 2 World Area Forecast Centers • WAFC Washington (AWC, EMC, NWSTG) • WAFC London (Exeter, UK) – Each operates its own satellite-based broadcast system to distribute global weather data to airports all over the world – Work in duplicate in a case of failure – Provide each other backup • Issue upper air significant weather forecasts to support global Flight Operations

World Area Forecast System – High Level SIGWX (FL 630 -250) • 4 times daily • 24 -hour forecast • 16 -17 hour lead time – Mid Level SIGWX (FL 450 -100) • 4 times daily • 24 -hour forecast • 16 hour lead time – Format • BUFR • PNG

WAFS High Level SIGWX 00 z, 06 z, 12 z, 18 z • • • Thunderstorms/CB Tropical Cyclones Mod/Sev CAT Tropopause Heights Jetstreams (80 kt and above depicted) Jet Depth Volcanic Eruptions Widespread Sand/Dust storms Release of Radioactive Materials

WAFS Mid Level SIGWX 00 z, 06 z, 12 z, 18 z • • • Thunderstorms/CB Tropical Cyclones Mod/Sev Turb (CAT or IC) Mod/Sev Icing Tropopause Heights Jetstreams (80 kt and above depicted) Jet Depth Volcanic Eruptions Widespread Sand/Dust storms Release of Radioactive Materials

WAFS High Level SIGWX Pacific Chart • Collaborators – – – – – London WEG HFO BOM TAMC KIWI GUM AAWU ZAN

Use of SIGWX Forecasts • Used directly by airline dispatchers for flight planning and weather briefing before departure, and by flight crew members during flight – Pre-Flight Information Bulletin – International Flight Documentation • Pre-flight air traffic routing decision-making • Recommended use for flights from 3 hours before to 3 hours after SIGWX validity

WAFS Gridded Forecasts • Model-derived global forecasts – Washington (GFS) – London (UKMET) • 3 -hour time intervals – T+6, 9, 12, 15, 18, 21, 24, 27, 30, 33, and 36 hours • Recommended use 1 hour 30 minutes before • and after each time step Automatically updates and cancels the corresponding forecast issued six hours earlier

WAFS Gridded Forecasts • Base fields (existing – GRIB-1) – – – Upper-air wind Upper-air temperature Direction, speed, and flight level of max wind Humidity data Geopotential altitude • Derived fields (new - GRIB-2) – – – Clear Air Turbulence (CAT) In-Cloud Turbulence (IC TURB) Icing Cumulonimbus (CB) extent CB top/base

New WAFS Grids CAT IC Turb ICE CB Extent CB Tops/ Bases Algorithm Ellrod (VWS 50 h. Pa Layer × Deformation) Brunt Vasalia Frequency ( ∂θe/∂z × Gravity ÷ θe ) FIP (Cloudy areas with supercooled water) 3 -hr Convective PCPN rate CB Min/max pressure converted to std height Levels 150, 200, 250, 300, 400 h. Pa 300, 400, 500, 600, 700, 850 h. Pa > FL 240 300 h. Pa deep TOPS (min) BASES (max) Max/Avg Interpolate (GFS 0. 3° to WAFS 1. 25°) ± 70 km (h) ± 50 h. Pa (v) ± 70 km (h) (Avg only) Linear Nearest Neighbor

WAFS CAT Valid 12 z May 11

WAFS CB Valid 00 z May 11

WAFS Grids - Advantages • Increased temporal resolution – Valid for operations at all time scales (T+6 through T+36) in 3 -hourly increments – Extends forecast for later portions of long-haul flights – All forecasts updated every 6 hours • Users don’t have to use “old data” for short-haul flights • Users don’t have to “combine” model runs for long-haul flights

WAFS Grids - Advantages • Increased consistency – Common forecast algorithms minimizes differences between WAFC London and WAFC Washington – Eliminates model run-to-run inconsistencies • Available sooner than current SIGWX – Part of WAFC global model output – 3 hours prior to current SIGWX

WAFS Grids - Advantages • Greater detail – CB • Grids contain all convective clouds • SIGWX contains only significant areas of ISOL/OCNL EMBD or FRQ CB – TURB • Grids contain all TURB: CAT, IC TURB, Convective • SIGWX contains only areas of jet stream CAT and IC for only ICAO area NAT (Mid-level SIGWX)

WAFS Grids - Advantages • Greater detail – ICE • Grids contain all icing potential for the entire globe • SIGWX contains only non-convective icing for only ICAO area NAT (Mid-level SIGWX) – Level-specific information for gridded ICE and TURB forecasts • For a “general” global forecast, the forecaster SIGWX cannot compete with WAFS Gridded forecasts

WAFS Grids - Timeline • By November 2013 – Transition WAFS grids from GRIB-1 to GRIB-2 format – WAFS product vendors transition from BUFR format to GRIB-2 format on WAFC workstation – WAFCs make available web-based WAFS grids – Test/verify/refine WAFS gridded forecasts – Eliminate forecaster-produced WAFS SIGWX

WAFS Grids - Timeline Now – Sept 2009 WAFCs develop and test WAFS grids in GRIB-2 form Now – Dec 2009 • WAFCs develop and test WAFS web-based Sept 2009 – Nov 2011 Develop software for displaying WAFS grids in GRIB-2 on WAFC workstation Dec 2009 WAFCs make available web-based WAFS grids (experimental) Nov 2010 WAFS grids become operational; co-exist with SIGWX Nov 2011 – Nov 2013 WAFC workstations upgraded to accept GRIB-2 Nov 2013 Cessation of WAFS SIGWX and WAFS grids in GRIB-1 grids from GRIB-2 data • Verification studies of web-based products

WAFS Grids - Demo • http: //aviationweather. gov/testbed/globalgrids/