# Presentation: 940772

## 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 (FL630-250)
- 4 times daily
- 24-hour forecast
- 16-17 hour lead time
- Mid Level SIGWX (FL450-100)
- 4 times daily
- 24-hour forecast
- 16 hour lead time
- Format
- BUFR
- PNG

## WAFS High Level SIGWX00z, 06z, 12z, 18z

- Thunderstorms/CB
- Tropical Cyclones
- Mod/Sev CAT
- Tropopause Heights
- Jetstreams (80kt and above depicted)
- Jet Depth
- Volcanic Eruptions
- Widespread Sand/Dust storms
- Release of Radioactive Materials

## WAFS Mid Level SIGWX 00z, 06z, 12z, 18z

- Thunderstorms/CB
- Tropical Cyclones
- Mod/Sev Turb (CAT or IC)
- Mod/Sev Icing
- Tropopause Heights
- Jetstreams (80kt 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 50hPa Layer
× Deformation) | Brunt Vasalia
Frequency
( ∂θe/∂z
× Gravity
÷  θe ) | FIP
(Cloudy areas with supercooled water) | 3-hr ConvectivePCPN rate
 | CB
Min/max
 pressure converted to std height |
| Levels | 150, 200, 250, 300, 400 
hPa | 300, 400, 500, 600, 700 hPa | 300, 400, 500, 600, 700, 850 hPa | > FL240
300 hPa deep
 | > FL240
300 hPa deep

TOPS (min)

BASES (max) |
| Max/Avg | ± 70 km (h) | ± 70 km (h)
± 50 hPa (v) | ± 70 km (h)
± 50 hPa (v) | ± 70 km (h)
(Avg only) | ± 70 km (h)
(Avg only) |
| Interpolate
(GFS 0.3° to WAFS 1.25°) | Linear | Linear | Linear | Nearest Neighbor | Nearest Neighbor |

## WAFS CAT

- Valid 12z May 11			Valid 12z May 11

**Notes:**
Obtained image at 19z May 10th

## WAFS CB

- Valid 00z May 11			Valid 00z May 11

**Notes:**
Obtained 19z May 10 for a 00z flight

## 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 grids from GRIB-2 data
Verification studies of web-based products |
| 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 |

## WAFS Grids - Demo

- _[http://](http://aviationweather.gov/testbed/globalgrids/)__[aviationweather.gov/testbed/globalgrids](http://aviationweather.gov/testbed/globalgrids/)__[/](http://aviationweather.gov/testbed/globalgrids/)_