11/14/16 Aviation Weather Services AC 00-45H 3-65 Table 3-8. AAWU Surface Observations Flying Categories and Criteria FLYING CATEGORY CEILING (feet) VISIBILITY (miles) VFR (black) Greater than 3,000 feet Greater than 5 miles MVFR (blue) 1,000 to 3,000 feet 3 to 5 miles IFR (red) Less than 1,000 feet Less than 3 miles
3.6.1.2.2 Station Plot.
METAR elements are plotted for each station in the form of a station plot (see Figure 3-41, Surface Observations—Aviationweather.gov METAR Static Display Example).
Figure 3-37. AAWU Surface Observation Plot Legend
3.6.1.2.3 Sky Cover.
The sky cover symbol is plotted at the station location and is filled according to the summation total of the sky condition element from the METAR report.
For example, if the METAR sky condition element was SCT030 BKN060 OVC090, the sky cover would be overcast and have a completely filled circle.
3.6.1.2.4 Station Identifier (STNID).
The four-letter ICAO station identifier is entered to the upper right of the station.
3.6.1.2.5 Wind.
Wind is plotted the same as the NWS surface analysis charts.
3.6.1.2.6 Temperature (TMP deg F).
Temperature in degrees Fahrenheit is plotted to the upper left of the sky cover symbol.
3.6.1.2.7 Visibility (VIS).
Visibility in statute miles is plotted to the left of the sky cover symbol.
Decimals are used to represent tenths of miles, when necessary.
3.6.1.2.8 Dewpoint Temperature (DEWPT deg F).
Dewpoint temperature, in degrees Fahrenheit, is plotted to the lower left of the sky cover symbol.
11/14/16 Aviation Weather Services AC 00-45H 3-66
3.6.1.2.9 Ceiling (CIG).
Ceiling is the height from the base of the lowest layer aloft covering more than one-half of the sky. Additionally, vertical visibility into a total surface-based obscuration is defined as a ceiling. For a METAR report, the first broken (BKN) or overcast (OVC) layer is the ceiling. For example, if the METAR sky condition element is SCT030 BKN060 OVC090, the ceiling is 6,000 ft.
For a total surface-based obscuration, no ceiling is plotted and the METAR must be consulted.
If the sky cover is clear, few, or scattered, no ceiling is plotted.
The ceiling is plotted to the lower right of the station circle. Ceilings are reported as hundreds of feet AGL. If no ceiling is present, the code 999 will be plotted.
3.6.1.2.10 Present Weather (WX).
Present weather symbols are entered to the left of the station. Note that the older Surface Aviation Observation (SAO) code is used instead of surface analysis chart symbols or the modern METAR code.
11/14/16 Aviation Weather Services AC 00-45H 3-67 Table 3-9. AAWU Surface Observation Precipitation Symbols Symbol Meaning T Thunderstorm R Rain RW Rain Shower L Drizzle ZR Freezing Rain ZL Freezing Drizzle A Hail IP Ice Pellets IPW Ice Pellet Showers S Snow SW Snow Showers SP Snow Pellets SG Snow Grains IC Ice Crystals
11/14/16 Aviation Weather Services AC 00-45H 3-68 Table 3-10. AAWU Surface Observation Obstruction to Visibility Symbols Symbol Meaning BD Blowing Dust BN Blowing Sand BS Blowing Snow BY Blowing Spray D Dust F Fog GF Ground Fog H Haze IF Ice Fog K Smoke Table 3-11. AAWU Surface Observation Precipitation Intensity Symbols Symbol Meaning
- Light (No symbol) Moderate + Heavy
3.6.1.3 Use.
AAWU Surface Observations provide an overview of weather flying categories and other adverse weather conditions for the valid time shown on the graphic display. This product often does not completely represent the en route conditions because of terrain variations and the possibility of weather occurring between reporting stations. This product should be used in addition to the latest METAR/SPECIs, PIREPs, and radar and satellite imagery for a complete look at the latest flying conditions.
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3.6.2 METARs on Aviationweather.gov.
3.6.2.1 Issuance.
Surface observations (METAR and SPECI) are provided on http://www.aviationweather.gov in several formats. The formats range from traditional text (referred to as the raw format) to different types of map displays. The two types of map displays are interactive (see Figure 3-38, Surface Observations-Aviationweather.gov METAR Interactive Display Example) and static (see Figure 3-41).
3.6.2.1.1 Interactive Display.
The interactive display includes zoom and pan. Increasing the zoom allows more METARs to be displayed.
Figure 3-38. Surface Observations-Aviationweather.gov METAR Interactive Display Example
ADDS METARS INFO 1ETAR Display at valid at 0129 UTC 17 Apr 2015 permalinI 997 CW NZ 025 52 PART 182 006 ITM r5845 Map: Plot Options: Data Options: Overlays:
OLight All • Temp aWind Alt Latest • Time • Highways Dark • Vis •Wx •Cover Ceil Decoded • Top Jetroutes
•Simple None Dew aWgst DId OTAF •ARTCC/FIR Bounds Data layers:
Satellite Data density
•Radar Metric OHover (1 • Scale Temp 26966--Alt W×- Vis-O.! KRFD~~-Id -Ceil Wind @Calm 15knt 060knt FIt Cat: •MVFR • IFRO LIFR Dew- Windbarb 3-69
11/14/16 Aviation Weather Services AC 00-45H 3-70 “Plot Options” allows users to choose the weather elements displayed
(e.g., view only ceilings and visibilities). The following parameters can be displayed using a station plot model (see Figure 3-39, Interactive Display Station Plot Example):
Figure 3-39. Interactive Display Station Plot Example
• Temp: Temperature in Fahrenheit. Celsius is also available, if metric is selected.
• Alt: Atmospheric pressure reduced to MSL.
o Where expressed in inches of mercury (Hg) or altimeter setting, the value is expressed in hundredths of an inch where the leading 2 or 3 is omitted (e.g., 982 would be 29.82 in, 025 would be 30.25 in). When trying to determine whether to add a 2 or 3, use the number that will give you a value closest to 30.00 in.
o Where expressed in millibars, the value is expressed in tenths of a millibar with the leading 9 or 10 omitted (e.g., 998 would be 999.8 mb, 164 would be 1,016.4 mb). When trying to determine whether to add a 9 or 10, use the number that will give you a value closest to 1,000 mb.
• Ceil: Cloud ceiling in hundreds of feet (BKN, OVC, and OVX only).
• Id: The four-letter ICAO identifier for the airport.
• Windbarb: The stick points in the direction the winds are coming from.
Wind speed is in knots. Red represents wind gusts.
• Dew: Dewpoint in Fahrenheit. Celsius is also available, if metric is selected.
• Vis: Visibility in miles. Kilometers (km), if metric is selected. Visibility value on the chart may not represent actual value reported in the METAR or SPECI, and may be fractionally lower than shown. (e.g., 2 ½ in the METAR is shown as 3 on the surface plot) (see Table 3-12, Rounding of Actual METAR Visibility Values for Depiction on Aviationweather.gov/AWC METAR Display).
• Wx: Weather symbol (see Appendix F, Area Forecasts (FA)—Continental United States (CONUS) and Hawaii) representing current weather.
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• Sky: Cloud cover symbol (see Figure 3-40, Station Plot Sky Symbols) is plotted in the center. The amount the circle is filled represents the amount of cloud cover. The color of the circle represents one of the following weather categories (see Table 3-13, Station Plot Weather Categories):
o Green: VFR, o Blue: MVFR, o Red: IFR, or o Purple: Low instrument flight rules (LIFR).
A click on the station circle displays the raw METAR in a separate text window. When the Hover option is selected, the raw METAR text window appears by merely placing the cursor over the station circle. If the Decoded option is set, the METAR appears in plain language instead of METAR code.
If the TAF option is set, the latest Terminal Aerodrome Forecast (TAF) will be appended to the information in the text window.
Table 3-12. Rounding of Actual METAR Visibility Values for Depiction on Aviationweather.gov/AWC METAR Display Visibility Reported in METAR Visibility, as depicted on surface plot 0, 1/16, 1/8, 3/16, 1/4, 3/8 0.3 ½ 0.5 ¾ 0.8 1 ½, 1 ¾, 2 2 ½, 3 3
11/14/16 Aviation Weather Services AC 00-45H 3-72 Table 3-13. Station Plot Weather Categories Category* Color Ceiling Visibility LIFR (Low IFR) Magenta Below 500 feet AGL and/or Less than 1 mile IFR Red 500 to below 1,000 feet AGL and/or 1 mile to less than miles 3 MVFR (Marginal VFR) Blue 1,000 to 3,000 feet AGL and/or 3 to 5 miles VFR Green Greater than 3,000 feet AGL and Greater than 5 miles *These categories are not flight rules and should not be confused with the flight rules provided in Part 91, including those for Basic VFR Weather Minimums. Rather, these categories were created for weather charts as a means to visually enhance the products.
Figure 3-40. Station Plot Sky Symbols
Automated stations report “CLR” when clouds may exist above 12,000 ft, so a square is used to represent this uncertainty, whereas an unfilled circle is used for “SKC”, when a human reports the sky is completely clear overhead. The abbreviation “OVX” is unofficial, but AWC uses it to indicate the sky is obscured, which is the case when a METAR reports vertical visibility and no cloud information. “Miss” means the sky condition is missing.
3.6.2.1.2 Static Display.
Static display products are provided on the AWC’s Web site for 19 select regions plus the CONUS. Each product is updated every 5 minutes using the latest METAR or SPECI information. The Web page automatically refresh every 15 minutes.
The static display has fewer features than the interactive display. Primarily, the static display does not provide ceiling height. Also, the static display does not have the functionality to display separately the raw METAR or TAF, or change units to metric.
11/14/16 Aviation Weather Services AC 00-45H Figure 3-41. Surface Observations-Aviationweather.gov METAR Static Display Example B0 852 AR da ita at 1550 UTO 2015 $11 40_002 ad by ADDE
• VER (Viaual Flight Rulea)| • MVER (Marginal VER] • IFR (Instrument Flight Rules) • LIFR LOW_JEBY Figure 3-42. Static Display Station Plot Example Temp Windbarb WX - Alt 021 Vis - 1 Id Dew Station plot descriptions are:
• Temp: Temperature in Fahrenheit (F).
• Windbarb: The windbarb. The stick points in the direction the winds are coming from.
3-73
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• Alt: Last three digits of the altimeter setting in inches of mercury. For example, 032 represents 30.32 in Hg.
• Id: The last three letters of the ICAO identifier for the airport.
• Dew: The dewpoint temperature in Fahrenheit.
• Vis: The visibility in statute miles.
• Wx: Weather symbol (see Appendix F) representing current weather.
• Sky: The cloud cover symbol is plotted in the center. The amount the circle is filled represents the amount of cloud cover. The color of the circle represents one of the following weather categories:
o Green: VFR, o Blue: MVFR, o Red: IFR, or o Purple: LIFR.
3.6.2.2 Use.
Graphical depictions of surface observations, both interactive and static display, provide an overview of weather flying categories and other adverse weather conditions for the valid time shown on the graphic display.
3.7 Aviation Weather Cameras.
3.7.1 FAA Aviation Weather Cameras.
The FAA’s Aviation Weather Camera network (see Figure 3-43, Map of FAA’s Aviation Weather Camera Network in Alaska) consists of more than 220 camera facilities in Alaska. Each site has up to four cameras. The direction of each camera (see Figure 3-44, Sectional Chart Depicting Shungnak (SHG), Alaska Camera Orientations) is provided with reference to a Sectional Chart. A clear day image (see Figure 3-45, “Clear Day” Image from Aviation Weather Camera Image at Shungnak (SHG), Alaska) is provided for reference and comparison with the latest image (see Figure 3-46, Aviation Weather Camera Image at Shungnak (SHG), Alaska).
3.7.2 Issuance.
Camera images are available on the FAA’s Aviation Weather Camera Web site. Images are generally updated every 10 minutes. The time of the last update is indicated on each image. Actual site conditions may differ from displayed images due to a variety of reasons (e.g., rapidly changing weather conditions, image update frequency, optical distortion).
11/14/16 Aviation Weather Services AC 00-45H 3-75 Figure 3-43. Map of FAA’s Aviation Weather Camera Network in Alaska
Figure 3-44. Sectional Chart Depicting Shungnak (SHG), Alaska Camera Orientations
11/14/16 Aviation Weather Services AC 00-45H 3-76 Figure 3-45. “Clear Day” Image from Aviation Weather Camera Image at Shungnak (SHG), Alaska
Figure 3-46. Aviation Weather Camera Image at Shungnak (SHG), Alaska
3.7.3 Use.
The images should only be used for flight planning and to improve situational awareness (SA). They are not to be used to comply with regulatory requirements (e.g., to determine weather minimums for IFR flight).