Aviation Weather Pronostic Charts

Prognostic Charts portray forecasts of positions and characteristics of pressure patterns, fronts, and precipitation at specific times.

Introduction

Introduction
  • Found at http://aviationweather.gov/adds/progs/
  • Portray forecasts of selected weather conditions at specific times
  • The chart is an extension of the day 1 U.S. LLSWPC issued from the same observed data base time
  • Displays forecast positions and characteristics of pressure patterns, fronts, and precipitation
  • The 36 and 48-Hour Prognostic Chart is a day 2 forecast of general weather for the conterminous United States

Aviation Weather Prognostic Charts

Aviation Weather Prognostic Charts
  • Aviation Weather Prognostic Charts
    Aviation Weather Prognostic Charts
  • Aviation Weather Prognostic Charts provide relatively long-term weather forecasts on a large scale to enable future flight planning

Issuance & Validity

Issuance & Validity
  • Issued four times daily (00Z, 06Z, 12Z, 18Z)
  • Valid for the time specified (12, 24, 36, 48 hrs)
  • Data is forecasted
  • Information is insufficient for flight planning
  • An effective overview of observed and prognostic charts allow the many essential details to fit into place and have continuity

Low-Level Significant Weather Prognostic Chart

Low-Level Significant Weather Prognostic Chart
  • LLSWPC in a day 1 forecast of significant weather in the conterminous United States
  • Provides information from the surface to FL240 (400 mbs)
  • Altitudes from the surface to 17,999 are referenced using MSL altitudes
  • Altitudes from 18,000' to FL240 are referenced using pressure altitude
  • Provided in two forecasts, 12 and 24 hours in 4 panels
  • Two top panels depict the 12 and 24 hour produced at the Aviation Weather Center (AWC) in Kansas City, Missouri
  • Two lower panels depict the 12 and 24 hour produced at the Hydro meteorological Prediction Center (HPC) in Camp Springs, Maryland

High-Level Significant Weather Prognostic Chart

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

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
  • Prognostic Chart Symbols
    Prognostic Chart Symbols 2
  • Prognostic Chart Symbols
    Prognostic Chart Symbols 2
  • Prognostic Chart Symbols
    Prognostic Chart Symbols 1
  • Prognostic Chart Symbols
    Prognostic Chart Symbols 1

Fronts

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:

    Code
    Descriptions
    0
    Quasi-stationary at surface
    2
    Warm front at surface
    4
    Cold front at surface
    6
    Occlusion
    7
    Instability line

  • Intensity of Front:

    Code
    Descriptions
    0
    No specification
    1
    Weak, decreasing
    2
    Weak, little, or no change
    3
    Weak, increasing
    4
    Moderate, decreasing
    5
    Moderate, little, or no change
    6
    Moderate, increasing
    7
    Strong, decreasing
    8
    Strong, little, or no change
    9
    Strong, increasing

  • Character of Front:

    Code:
    Descriptions:
    0
    No specification
    5
    Forming or existence expected
    6
    Quasi-stationary
    7
    With waves
    8
    Diffuse

     

Precipitation

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
  • 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
  • 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

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

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

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

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

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

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

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

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

Conclusion

References

References