MANAIR Manual of Standards and Procedures for Aviation Forecasts: appendix C


Appendix C: Graphic Area Forecast (GFA)—Supplement to Chapter 4

C.1 GFA domain names

GFA domains. See long description below.

Description of image

Geographical map of the 7 GFACN domains in Canada including the on-request area (part of GFSCN37). Each domain is displayed in a different colour and is identified by its name. The identifier and full name of each domain are listed in a table below the image. The 7 graphic area forecast domains are GFACN31, GFACN32, GFACN33, GFACN46, GFACN35, GFACN36, GFACN37.

Legend:

GFACN31: Pacific region

GFACN32: Prairie region

GFACN33: Ontario Quebec region

GFACN34: Atlantic region

GFACN35: Yukon-Northwest territories region

GFACN36: Nunavut region

GFACN37: Arctic region

C.2 Examples of GFA content

Synoptic features. See long description below.

Description of image

Graphical depictions of synoptic features used in graphic area forecasts. Contains 15 images in colour, each identified by name: low/tropical depression, high, warm front, cold front, stationary front, trowal, trough, upper warm front, upper cold front, upper stationary front, upper trough, speed and direction, tropical cyclones (storm, hurricane, post).

Synoptic features continued. See long description below.

Description of image

Graphical depictions of synoptic features used in graphic area forecasts. Contains 17 images in colour, each identified in categories. Cloud and restriction to visibility includes images for organized cloud area and area of obstruction to vision. Surface wind and low level jet show images for surface wind and low level jet. Continuous precipitation shows images for rain/drizzle/snow, and freezing rain/freezing drizzle/ice pellets. Intermittent precipitation or showers show images for rain/drizzle/snow, and freezing rain/freezing drizzle/ice pellets. Icing shows images for moderate and severe icing. Turbulence shows images for moderate low level turbulence, severe low level turbulence, moderate higher level turbulence, and severe higher level turbulence. Three images along the bottom are to depict freezing level, volcano and radioactive release.

C.3 Guidelines for GFA correction

GFA correction Detailed guidelines
Any unforecast weather phenomena not requiring an AIRMET (i.e. below AIRMET criteria threshold) or any other unforecast weather phenomena that, according to the forecaster, should be depicted in the GFA

Widespread area of BKN or OVC cloud with height of the base between 1000 and 5000 feet AGL

Widespread area affected by the reduction of visibility between 3 and 6SM, including the weather phenomenon causing the reduction in visibility

Widespread mean surface wind speed between 20 KT and 30 KT, or peak wind gust of 30 KT or more

Forecast phenomena (in the GFA chart) that fail to occur Removal of forecast weather phenomena in the GFA chart that are no longer occurring or no longer expected to occur
A significant error was made in a GFA chart A significant error is one which, if uncorrected, would result in an erroneous interpretation of the GFA and create a potential hazard to aviation

C.4 Examples of GFA

Example (1): GFACN33 T0+0 hr clouds and weather panel

GFACN33 T+0 clouds and weather. See long description below.

Description of image

Large pane displays surface isobars and synoptic features with full description of the clouds and weather. Smaller top pane to the right contains title of the chart: GFACN33 CWAO region Ontario - Quebec Clouds and Weather Nuages et Temps Issued at/Émis à 29/05/2012 1131Z VLD 29/05/2012 1200Z. Centre pane displays legend (symbol for thunderstorm, symbol for ice pellet, symbol for freezing rain, symbol for freezing drizzle), scale bar for the map and three default statements: HGTS ASL UNLESS NOTED. CB TCU AND ACC IMPLY SIG TURB AND ICG. CB IMPLIES LLWS. Bottom pane displays comments pertaining to content of the map.

Example (2): GFACN33 T0+0 hr icing and turbulence panel

GFA33_ICG+TURB. See long description below.

Description of image

Large pane displays the synoptic features and full description of icing, turbulence and freezing levels. Smaller top pane on the rights contains title of the chart: GFACN33 CWAO region Ontario - Quebec ICG TURB & FZLVL Issued at/Émis à 29/05/2012 1132Z VLD 29/05/2012 1200Z. Centre pane displays legend, scale bar for the map and three default statements: HGTS ASL UNLESS NOTED. CB TCU AND ACC IMPLY SIG TURB AND ICG. CB IMPLIES LLWS.

Example (3): GFACN31 T0+12 hr clouds and weather panel

GFACN31_CWAO. See long description below.

Description of image

Large pane displays surface isobars and the synoptic features with a full description of the clouds and weather. To the right side in the smaller top pane is title of the chart: GFACN31 CWAO Pacific region Region du Pacifique Clouds and Weather Nuages et temps Issued at/Émis à 09/03/2012 2331Z VLD 10/03/2012 1200Z. Centre pane displays legend (symbol for thunderstorm, symbol for ice pellet, symbol for freezing rain, symbol for freezing drizzle), scale bar for map and the three default statements: HGTS ASL UNLESS NOTED. CB TCU AND ACC IMPLY SIG TURB AND ICG. CB IMPLIES LLWS. Bottom pane displays comments pertaining to map and the IFR outlook statement.

Example (4): GFACN31 T0+12 hr icing and turb panel

GFA31_ICG+TURB. See long description below.

Description of image

Large pane displays synoptic features and full description of icing, turbulence and freezing levels. Smaller top pane on right contains title of chart: GFACN31 CWAO Pacific region Region du Pacifique ICG TURB & FZLVL Issued At/Émis à 09/03/2012 2332Z VLD 10/03/2012 1200Z. Centre pane displays legend (symbol for moderate icing, symbol severe icing, symbol for moderate turbulence, symbol for severe turbulence), scale bar for map and three default statements: HGTS ASL UNLESS NOTED. CB TCU AND ACC IMPLY SIG TURB AND ICG. CB IMPLIES LLWS. Bottom pane displays comments pertaining to map.

Example (5): Corrected GFACN33 T0+12 hr clouds and weather panel

2012053018_GFACN33_cldwx_012. See long description below.

Description of image

Corrected GFACN33 T+12 clouds and weather panel. Large pane displays surface isobars and synoptic features with full description of the clouds and weather. Smaller top pane on right contains title of chart: GFACN33 CWAO CCA region Ontario - Quebec Clouds and Weather Nuages et Temps Issued at/Émis à 31/05/2012 1801Z VLD 31/05/2012 0600Z. Centre pane displays legend (symbol for thunderstorm, symbol for ice pellet, symbol for freezing rain, symbol for freezing drizzle), scale bar for map and three default statements: HGTS ASL UNLESS NOTED. CB TCU AND ACC IMPLY SIG TURB AND ICG. CB IMPLIES LLWS. Bottom pane displays comments pertaining to map and a statement on the correction made to the chart.

Example (6): Corrected GFACN34 T0+12 hr icing and turb panel

2012040500_GFACN34_turbc_012. See long description below.

Description of image

Large pane displaying synoptic features and full description of icing, turbulence and freezing levels. Smaller top pane to the right contains title of the chart: GFACN34 CWAO Atlantic region Region de l'Atlantique ICG TURB & FZLVL Issued at/Émis à 05/04/2012 0031Z VLD 05/04/2012 1200Z. The centre pane displays the legend (symbol for moderate icing, symbol for severe icing, symbol for moderate turbulence, symbol for severe turbulence), scale bar for the map and three default statements: HGTS ASL UNLESS NOTED. CB TCU AND ACC IMPLY SIG TURB AND ICG. CB IMPLIES LLWS. Bottom pane displays comments pertaining to the content of the map and a statement on the correction made to the chart.

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