Study guide
5.3 Significant Weather Prognostic Charts (SIGWX)
FAA Aircraft Dispatcher Certificate ADX
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1 Chapter 1: Regulations, Certification & Operational Control
1.1 Part 65 Subpart C: Certification, Eligibility & Currency 1.2 Operational Control & Dispatcher-PIC Joint Responsibility 1.3 Domestic, Flag & Supplemental Operations Framework 1.4 Dispatch Release Elements, Signatures & Recordkeeping 1.5 Regulations, Manuals, Crew Qualifications, and Source Control
2 Chapter 2: Atmospheric Physics, Pressure Systems & Fronts
2.1 Atmospheric Structure, Standard Atmosphere & Altimetry 2.2 Air Masses, Frontal Systems & Frontogenesis 2.3 Atmospheric Stability, Lapse Rates & Cloud Formation 2.4 Earth Motion, Regional Weather, Local Winds, and Water Phase Changes
3 Chapter 3: Aviation Weather Hazards & Severe Weather Avoidance
3.1 Structural and Induction Icing: Types, Accretion & Operations 3.2 Thunderstorms, Squall Lines, Microbursts & Low-Level Windshear 3.3 Clear Air Turbulence (CAT), Mountain Waves & Jet Streams 3.4 Low Ceilings, Fog Types & Visibility Restrictions 3.5 Hurricanes, Typhoons, Tornadoes, and Tropical Dispatch Hazards
4 Chapter 4: Weather Observations, Forecasts & Advisories Decoding
4.1 METAR and SPECI Surface Observations: Decoding & Operations 4.2 Terminal Aerodrome Forecasts (TAF): Groups & Timing 4.3 Pilot Weather Reports (PIREP): Coding, Severity & Urgent Alerts 4.4 In-Flight Advisories: AIRMETs, SIGMETs & Convective SIGMETs 4.5 Weather Collection, NWS Facilities, GFA, and EWINS
5 Chapter 5: Aviation Weather Charts & Upper-Air Analysis
5.1 Surface Analysis & Radar Summary Charts 5.2 Constant Pressure Analysis & Winds Aloft (FB) 5.3 Significant Weather Prognostic Charts (SIGWX) 5.4 Satellite Imagery, Moisture-Stability Analysis, and Forecast Integration
6 Chapter 6: Air Navigation, Airspace Architecture & Route Structure
6.1 National Airspace System: Classes, Rules & Special Use 6.2 Ground-Based Navigation Aids & Standard Service Volumes 6.3 Area Navigation (RNAV), GNSS/GPS, PBN & RNP Fundamentals 6.4 En Route Airways, SIDs, STARs & Chart Interpretation 6.5 Earth Coordinates, UTC, Chart Projections, and Flight Instruments 6.6 North Atlantic, Pacific, RVSM, and Global Navigation Differences
7 Chapter 7: Instrument Approaches, Minimums & Airport Operations
7.1 Precision Approach Systems: ILS Categories & Tolerances 7.2 Non-Precision Approaches, RNAV & Decision Minimums (MDA/DA) 7.3 Takeoff Minimums, Lower-Than-Standard & Takeoff Alternates 7.4 Holding Procedures: Patterns, Speed Limits & Timing
8 Chapter 8: Subsonic Aerodynamics & Jet Aircraft Performance
8.1 Subsonic Jet Aerodynamics: Lift, Drag & Flight Regimes 8.2 High-Altitude Flight: Mach Number, Buffet & Coffin Corner 8.3 Transport Turbine Engines: Thrust, Specific Fuel & Bleed Air
9 Chapter 9: Transport Category Takeoff & Landing Runway Analysis
9.1 Takeoff Performance Speeds & Balanced Field Concept 9.2 Takeoff Climb Segments & Obstacle Clearance Gradients 9.3 Landing Performance: Field Lengths, 60% Rule & Contamination
10 Chapter 10: En Route Performance, Driftdown Profiles & ETOPS Operations
10.1 One/Two-Engine-Inoperative En Route Net Profiles & Driftdown 10.2 Extended-Range Operations (ETOPS): Philosophy & Regulations 10.3 ETOPS En Route Alternates: Adequate vs. Suitable & Critical Fuel
11 Chapter 11: Aircraft Weight & Balance, Center of Gravity, and Loading
11.1 Transport Aircraft Structural Weight Limits: Definitions & Rules 11.2 Center of Gravity Computations: Datum, Arm, Moment & Index 11.3 Mean Aerodynamic Chord (%MAC) Computations & Stability 11.4 Payload-Range Analysis, Zero Fuel Weight Tradeoffs & Loading
12 Chapter 12: Destination Alternate Airport Selection & Weather Rules
12.1 Destination Alternate Selection: 91.169 & Part 121 1-2-3 Rule 12.2 Flag & Supplemental Operations Destination Alternate Rules 12.3 Derived Alternate Minimums: 1-Nav and 2-Nav Facility Rules
13 Chapter 13: Part 121 Fuel Planning, Reserves & En Route Re-Release
13.1 Part 121 Domestic Fuel Requirements: Reserves & Calculations 13.2 Part 121 Flag Fuel Requirements: 10% Reserve & Island Rules 13.3 Supplemental Fuel Requirements & Holding Fuel Management 13.4 Redispatch and En Route Re-release Procedures
14 Chapter 14: Transport Systems, Pressurization & MEL/CDL Procedures
14.1 Transport Jet Auxiliary Power, Electrical, Hydraulic & Pneumatic Systems 14.2 Cabin Pressurization, Rapid Decompression & Oxygen Requirements 14.3 Master Minimum Equipment List (MMEL), MEL & CDL Procedures 14.4 Flight Controls, Autoflight, Fuel, Oil, Brakes, and Fire Protection
15 Chapter 15: Hazardous Materials, Duty Regulations & Emergency Procedures
15.1 Dangerous Goods Carriage by Air (49 CFR Part 175) & NOTOC 15.2 Dispatcher Duty Limitations, Rest Requirements & Fatigue 15.3 Emergency Authority, Declaration & Diversion Decision-Making 15.4 NTSB Part 830 Accident Reporting & Wreckage Preservation 15.5 Security, Overdue Aircraft, and FAA Emergency Services
16 Chapter 16: Communications, ATC, and Flight Plan Procedures
16.1 Voice, Data Link, Position Reports, and Lost Communications 16.2 ATC Facilities, Separation, ICAO Flight Plans, and Traffic Management
17 Chapter 17: Human Factors and Practical Dispatch Applications
17.1 Dispatch Resource Management, Human Error, and Risk Decisions 17.2 Manual Flight Planning, PIC Briefing, Flight Watch, and Postflight Closeout
5.3 Significant Weather Prognostic Charts (SIGWX)
Key Takeaways Explain This Topic AI
Read the actual SIGWX product’s region, vertical layer, legend, and forecast time; current products are not all identical to legacy figures.
Traditional high-level CB coverage uses ISOL <4/8, OCNL 4/8–6/8, and FRQ >6/8; EMBD concerns cloud/haze concealment.
On traditional high-level charts, XXX can indicate CB bases below the chart’s lower boundary.
A boxed tropopause 450 represents approximately FL450; it does not guarantee turbulence or a safe fixed offset.
Cruise and diversion weather must both be assessed with products covering their actual altitude/time profiles.
Last updated: October 2026
Significant Weather Prognostic Charts
SIGWX products describe forecast significant weather within their displayed vertical, geographic, and time coverage. They support strategic flight planning and briefing; they are not a tactical clearance to penetrate weather or a complete substitute for observations, advisories, radar, satellite, and PIREPs. Read the chart header and legend before applying a memorized symbol to a particular product.
Current products and legacy examination figures
The FAA Aviation Weather Handbook discusses low-level significant-weather progs, WAFS information, and traditional international high-level charts. Traditional high-level charts commonly use FL250–FL630 ; other layers and newer WAFS products have their own coverage and forecast times. Do not claim every current SIGWX product has one universal range or a single 24-hour validity. A legacy examination figure should be interpreted using its actual printed legend and times.
The World Area Forecast System (WAFS) supplies international aviation forecasts through the World Area Forecast Centers. Use the appropriate region and flight phase. A cruise-level chart does not fully cover a diversion descent to an airport, and a surface flight-category depiction does not establish the entire enroute icing or turbulence profile.
Low-level flight categories
Low-level progs can show areas of IFR, MVFR, and VFR conditions, turbulence, and freezing levels within their stated coverage. The standard flight-category thresholds use the worse of ceiling and visibility:
- Category Ceiling and/or visibility relationship
- IFR Ceiling below 1,000 ft and/or visibility below 3 SM, including lower categories where shown
- MVFR Ceiling 1,000–3,000 ft and/or visibility 3–5 SM, when no lower category controls
- VFR Ceiling above 3,000 ft and visibility above 5 SM
A forecast ceiling of 800 feet with visibility 6 SM still supports an IFR category; favorable visibility does not override the lower ceiling. The meteorological category is not itself an airline dispatch minimum. Apply the actual destination, alternate, and operating-rule tests separately.
Cumulonimbus depiction
Traditional high-level charts emphasize cumulonimbus (CB) because of its associated aviation hazards. The FAA handbook describes ISOL as less than four-eighths coverage, OCNL as four-eighths to six-eighths, and FRQ as more than six-eighths. EMBD identifies concealment in cloud layers or haze; night by itself is not the definition of embedded CB.
On the traditional high-level product, isolated CB is depicted when embedded in clouds or concealed by haze. A chart that omits an isolated nonembedded cell does not prove that no convection exists. Check the other current products and observations. The CB label implies associated thunderstorm hazards including turbulence, icing, hail, and lightning; do not interpret it as harmless cloud coverage.
Vertical limits and XXX
Read top and base values in the specified flight-level notation. In the traditional FL250–FL630 high-level chart, XXX can identify a CB base extending below the chart's lower boundary. It does not mean that a cloud top automatically exceeds FL630. A hypothetical CB annotation with top 450 and base XXX therefore indicates a top near FL450 and a base below that product's lower boundary; consult the legend and lower-level products for the actual base.
Turbulence areas and other hazard layers also require their proper upper/lower values and severity symbols. A top/base fraction is a chart-notation convenience, not a mathematical quotient that computes severity. Confirm whether an altitude is in flight levels, hundreds of feet, or another unit before comparing with a proposed aircraft profile.
Jet streams and tropopause
Jet axes, flight-level labels, wind barbs/pennants, and associated annotations describe forecast wind structure. A pennant commonly represents 50 knots and a full barb ten knots; read the product legend for all symbols. An annotated layer associated with an 80-knot isotach describes wind structure, not a guarantee that severe CAT exists throughout that layer.
Tropopause heights are commonly shown in boxed values in hundreds of feet on traditional charts. A boxed 450 corresponds to about FL450. A lowered tropopause or sharp change can support a jet/shear assessment, but it does not by itself diagnose turbulence or guarantee a safe altitude a fixed 4,000 feet away. The tropopause is a variable transition region, not an impermeable boundary preventing all overshooting convection.
Other significant phenomena
The actual product may depict volcanic eruption information, tropical cyclones, or other significant hazards. A volcano symbol is a prompt to consult current volcanic-ash advisories, SIGMETs, and dispersion information, not proof that every shaded cloud is ash or that no ash exists elsewhere. Regional tropical products provide center motion and weather information, while surrounding rainbands can extend far outside a center-position annotation.
Interpret each phenomenon with its source, validity, and movement. Forecast polygons cover anticipated weather with uncertainty; the airplane's passage time and altitude must be compared with the forecast, and its diversion profile may cross a different hazard layer. A static screenshot without its timestamp is not adequate evidence for a current operational decision.
Worked cruise and diversion check
A fictional flight plans FL350 through a forecast turbulence layer FL310–FL390. The dispatcher examines a lateral reroute and alternate cruise levels using current turbulence guidance, PIREPs, aircraft limits, ATC availability, and fuel. Do not prescribe FL320 as automatically clear when it lies inside the stated layer. A proposed lower route must also clear terrain and remain within approved performance and weather limits.
Now evaluate an engine-out or decompression diversion. The applicable approved profile may descend through cloud and icing below the main high-level chart. Add the relevant lower-level products, ETOPS alternate forecast window where applicable, and actual field/approach information. A suitable cruise corridor does not automatically make every diversion safe.
Briefing and continued assessment
Explain the chosen route, the significant chart features, assumptions, uncertainty, and the source/time for updates. Provide safety information under § 121.601 and reassess after changes in aircraft status, route, ETA, or weather. Use the chart as one part of a coherent operational weather analysis. The practical-test objective is an authorized, defensible flight and contingency plan, not recital of chart symbols without applying them.
Surface Prognoses and Depiction Across Time
A surface analysis represents an observed/analyzed past or current state; a surface prognostic chart forecasts a future state. Read issue time, valid time, region, legend, and units before applying either. A forecast pressure center and fronts help estimate where a low, cold front, or precipitation zone will be when the flight reaches that area. Compare consecutive valid times rather than treating one picture as stationary weather. Tight isobar spacing supports a pressure-gradient/wind assessment, but friction, terrain, and local circulation affect the actual runway wind.
For a hypothetical evening arrival, an earlier analysis has the cold front west of the destination while the arrival-valid surface prognosis places it east of the field. The dispatcher anticipates a possible frontal wind shift and post-frontal temperature change, then checks the destination TAF, observations, and runway performance rather than declaring a specific wind or ceiling from frontal position alone. If successive forecasts disagree about timing, preserve alternate and fuel options that address that uncertainty.
Traditional weather-depiction charts emphasize observed ceiling/visibility categories; contemporary GFA flight-category layers offer a related operational view with their own observed/forecast timing. Neither product is a blanket dispatch authorization. Surface pressure/precipitation prognoses and lower-level flight-category forecasts complement high-level SIGWX: they inform takeoff, destination, and alternate conditions that a cruise-layer chart cannot show. For an engine-out diversion, match each product to the diversion’s actual altitude and possible landing time.
Official References
Source check: 2026-10-12 . 2026 FAA Aviation Weather Handbook . For operational use, apply current issued authorizations and the assigned aircraft’s approved data.