Prognostic Charts

High-Level Significant Weather Prognostic Chart:

• HLSWPC is a day 1 forecast of significant weather in the conterminous United States
• Provides information from 24,000' to 60,000'
• Covers much of the Northern Hemisphere and a limited portion of the Southern Hemisphere
• Each section covers a specific area and areas sometimes overlap
• Conditions routinely appearing on the chart are jet streams, cumulonimbus clouds, turbulence, and Tropopause heights
• Surface fronts are included to add perspective
• Sometimes tropical cyclones, squall lines, volcanic eruption sites, sandstorms, and dust storms will appear

Surface Pressure Systems:

• Depict pressure centers, troughs and on selected panels, isobars
  • High and Lows identified by "Hs" and "Ls" respectively
• Pressure troughs are identified by long dashed lines labeled "TROF"
• Isobars are drawn as solid lines to portray pressure patterns
• Isobars are drawn in 8 millibar (mb) intervals instead of 4 mb to provide a less sensitive analysis
• Occasionally, nonstandard isobars will be drawn using 4 mb intervals to highlight patterns with weak pressure gradients
• Nonstandard isobars are drawn as dashed lines

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Fronts:

• Surface fronts are depicted on each panel
• Formats used are the standard symbols and three-digit characterization code used on the surface chart

Type of Front:

Intensity of Front:

Character of Front:

Precipitation:

• Solid lines enclose precipitation areas
• Symbols specify the forums and types of precipitation
• A mix is indicated by the use of two pertinent symbols separated by a slash
• Areas of continuous precipitation is shaded as well as precipitation covering more than half of the area
• A bold dashed line is used to separate precipitation with contrasting characteristics
• A dashed line would be used to separate an area of similar characteristics (snow and rain)

Jet Streams:

• Jet streams with a maximum speed of more than 80 knots are identified by bold lines
• Arrowheads indicate the orientation of each jet stream
• Double hatched lines identified changes in wind speed
• Speed indicators are drawn at 20-knot intervals and begin with 100 knots
• Standard wind symbol (shaft, pennants, and barbs) is placed at each pertinent position to identify velocity
• The altitude in hundreds of feet prefaced with "FL" is placed adjacent to each wind symbol

Cumulonimbus Clouds:

• Cumulonimbus clouds (CBs) are thunderstorm clouds
• Enclosed by scalloped lines
• Isolated or scattered CBs (one-half or less coverage) which are not embedded are not depicted
• Identified with CB and altitude
• Isolated (ISOL)
• Occasional (OCNL)
• Frequent (FRQ)
• Bases that extended below 24,000 are encoded "XXX" (High-Level)
• Thunderstorms imply hazards including turbulence and hail

Tropopause:

• Plotted in hundreds of feet
• Heights enclosed by rectangles
• Centers of high and low heights are identified with "H" and "L" respectively with their heights and enclosed by polygons

Weather Flying Categories:

• Ceiling and visibility determine the category
• VFR - Visual Flight Rules
• MVFR - Marginal Visual Flight Rules
• IFR - Instrument Flight Rules
• IFR areas are enclosed by solid lines
• MVFR areas are enclosed by scalloped lines
• All other areas are VFR

Freezing Levels:

• Depicted by a zigzag line labeled as "SFC" for surface
• Freezing levels aloft are depicted by thin, short dashed lines
• Lines are drawn at 4,000' intervals (80 = 8,000')
• Lines are discontinued where they intersect corresponding altitudes of the Rocky Mountains
• Areas with multiple freezing levels have lines drawn to the highest freezing level

Turbulence:

• Areas of moderate or greater turbulence are enclosed by bold, long dashed lines
• Turbulence intensities are identified by symbols
• The vertical extent of turbulence layers are specified by top and base heights
• Areas of thunderstorms do not include indications of turbulence because it is implied
• Added emphasis is included if the turbulence is from the surface to 24,000' or above, having thunderstorms covering more than half of the area
• Intensity symbols and layer altitudes appear within or adjacent to the forecast area
• Heights are pressure altitude
• Bases that extended below 24,000 are encoded "XXX" (High-Level)

Tropical Cyclones:

• Positions of hurricanes, typhoons and tropical storms are depicted
• Hurricanes use standard symbol while typhoons are shaded
• When pertinent the name of each storm is positioned adjacent to the symbol

Squall Lines:

• Severe squall lines are lines of CBs with 5/8 coverage or greater
• Identified by long dashed lines separated by a V

Volcanic Eruption Sites:

• Identified by a trapezoidal symbol
• Dot at the base indicates latitude and longitude of volcano
• Name, latitude, and longitude are noted adjacent
• Reference SIGMETs for more information

Sand and Dust Storms:

• Areas of widespread sandstorms and dust storms are labeled by an S
• The S with an arrow depicts areas of widespread sandstorms or dust storms
• The S without an arrow depicts severe sandstorm or dust haze

Conclusion:

• For more information, a paper copy of Aviation Weather Services: FAA Advisory Circular 00-45H, Change 1&2 (FAA Handbooks series) [Amazon] is available for purchase
  • A digital copy of Advisory Circular (00-45), Aviation Weather Services is available from the FAA's website
• Still looking for something? Continue searching:

References:

• Federal Aviation Administration (FAA-H-8083-28) Aviation Weather Handbook
• Federal Aviation Administration - Pilot/Controller Glossary
• Advisory Circular (00-45) Aviation Weather Services (8.1) Short-Range Surface Prognostic (PROG) Charts
• CFI Notebook.net - Atmosphere