weather charts

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Weather Charts

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Current Weather Products

• Observations– Surface Analysis Charts– Constant Pressure Charts– Weather Depiction Charts– Lifted Index Charts– Radar Summary Charts

• Forecast Charts– Short Range Surface Prognostic Chart– Low level Significant Weather Prognostic Chart

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Surface Analysis Chart

• Shows the “big picture” – helps plan flights around WX• Depicts– Sea level pressure– Position of highs, lows, ridges and troughs– Position of fronts– Position of boundaries– Overview of winds, temperatures and dew points

• Issued every 3 hours• Valid for 6 hours• Available at: http://www.hpc.ncep.noaa.gov/html/sfc2.shtml

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Cold front – Pips show direction of movement

Warm front

stationary front

Data

High - Number adjacent is central pressure

LowSea Level Pressure –4mb interval lines- Line below # is pressure trend

Temp

Dew Point

Wind

Sea Level pressure (first 10 or 9 digits omitted)

or ceiling height

Sky cover – If station symbol is square then automated data was used

Tropical wave

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DUATS Surface Analysis Chart

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Constant Pressure Charts

• Similar to the surface analysis chart but at different pressure levels (altitudes will vary)– 850 MB chart ≈ 5,000’– 700 MB chart ≈ 10,000’– 500 MB chart ≈ 18,000’

• Provides a 3D view of large areas – interpolate between charts

• Data gathered through balloons• Shows winds and temps – can identify jet stream /

freezing risks for example• Charts available at: http://aviationweather.gov/std_brief/

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Constant Pressure Charts

Wind

Level

Issue date/time

X Marks high/low center

Contour line area of = height in meters (850 MB omits 1 before and 700 omits 2 or 3 before – which ever makes the number closer to 3,000 meters) e.g. 309 = 3309 meters or 10,754’ – Look at gradients - wind speed proportional to gradients (close = high winds). Contours can be interpreted in the same manner as isobars on the surface chart (e.g. high altitude=high pressure area)

Some charts also show: isotherms – areas of equal temperature – bold dashed lineisotachs – constant wind speed areas – short fine dashed line with __K

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Historic (FAA) Constant Pressure Chart

Satellite dataBalloon /

Ground station

Airplane observation

Latitude

Temp / Isotherm

Longitude

Temp

Temp – DP spread

Height / pressure altitude

Height change / aircraft type

Wind

Data

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Duats Constant Pressure Chart

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Weather Depiction Chart

• Broad overview of flying conditions – IFR (<3sm vis;1,000’), MVFR (3 to 5sm vis;1k to 3k ceiling), VFR (>5sm vis; >3,000 ceiling)

• Also shows fronts and troughs (except 10 and 23Z)

• Prepared 8 X per day

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Weather Depiction Chart

LegendData

IFR

MVFR

Sky cover

Precipitation / Vis obstructions

AGL cloud height

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Weather depiction Chart Symbols

NB: Symbols are the same as the Surface Analysis Chart

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DUATS Weather Depiction Chart

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Radar Summary Chart

• Aids in preflight planning by identifying general areas and movement of precipitation and/or thunderstorms

• Issued hourly• Shows:– Radar echos– Types of precipitation– Movement of cells– Tops of precipitation– Severe Thunderstorm and Tornado Watch areas– DOES NOT SHOW clouds or fog

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Radar Summary Chart

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Radar Summary Chart

• Individual cell movement is indicated by an arrow with the speed in knots entered as a number at the top of the arrow head.

• Highest echo height in the area is shown above a short line, with the top height displayed.

• Severe weather watch areas are outlined by heavy dashed lines, usually in the form of a large rectangular box.

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NWS Radar Summary Chart

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Nexrad Radar

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Lifted Index Chart

• Provides plot of the lifted index and K index values– Lifted Index

• is a measure of atmospheric stability – it is a comparison of predicted temperature change from the surface (2° saturated or 3° unsaturated) less actual temperature change from the surface to 500mb (18,000 msl +/-)

• Positive LI – colder so stable air• Negative LI – warmer so less stable• Zero LI – neutral stability• Becomes more stable with decreased dew point, decreasing surface

temperature or increasing 500 mb temperature• Severe thunderstorm guide 0 to -2 weak potential; -3 to -5

moderate potential; ≤-6 Strong potentia;

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Lifted Index Chart

– K Index – used mostly by meteorologists • During warm season a large Ki indicates conditions

favorable for thunderstorms• In winter temperature terms completely dominate K

index• Ki < 20 – No chance of thunderstorms• Ki 20 to 25 – Isolated thunderstorms• Ki 26 – 30 – Widely scattered thunderstorms• Ki 31 – 35 – Scattered Thunderstorms• Ki > 35 – Numerous thunderstorms

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Lifted Index Chart

Lifted Index (LI) Severe Potential K-Index *Airmass Thunderstorm Probability

0 to -2 Weak <15 near 0%

15-20 20%

-3 to -5 Moderate 21-25 21-40%

26-30 41-60%

< -6 Strong 31-35 61-80%

36-40 81-90%

>40 near 100%

It is essential to note that an unstable Lifted Index does NOT automatically mean thunderstorms. Look at the synoptic situation and if thunderstorms are expected to develop in the unstable air, this table may be used. * Use caution when applying these values in the western mountainous terrain due to elevation

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Lifted Index Chart

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Short Range Surface Prognostic Chart

• Surface forecast of pressure systems, fronts and precipitation for two day period – 12, 24, 36 and 48 hours

• Uses Surface Analysis chart symbols• Produced 4 x day for 12 and 24 hour periods;

twice per day for 36 and 48 hour periods

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Precipitation

Trough

Shading = >50% coverage; Unshaded precip indicates 30 to 50% coverage

A bold, dashed, grey line is used to separate precipitation within an outlined area with contrasting characteristics

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DUATS Low Level Weather Prognostic Chart

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Low Level Significant Weather Prognostic Chart

• Forecast of aviation weather hazards• Preflight use• 3 versions (High level (FL250-FL630); mid level (FL100-FL450)

and low level (SFC-FL240)) • 12 and 24 hour panels; additional charts for 30, 36 and 48 hours• Depicts

– VFR, MVFR and IFR areas (top panel)– Freezing levels (top panel)– Turbulence (top panel) – Fronts and pressure systems (lower panel)

• Available at: http://aviationweather.gov/products/swl/

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DUATS Severe Weather Outlook

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DUATS Winds Aloft Forecast Chart

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NWC AirMet / Sigmet Charts

Airmet Sierra - IFR

Airmet Tango - Turbulence

Airmet Zulu - Icing

Freezing levels

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Freezing Level Chart

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Icing

SLD (super-cooled large drop - includes freezing drizzle and freezing rain).

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Turbulence

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Infrared Satellite Chart

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Visible Satellite Chart

Night

Day

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