11/14/16 Aviation Weather Services AC 00-45H 6-10
6.1.2.6 Data Overlays.
The HEMS Tool allows the user to select multiple fields to be overlaid on the grids including: METARs/TAFs, Flight Category, PIREPs, Windbarbs, SIGMETs and G-AIRMETs (Graphical Airmen’s Meteorological Information), CWAs, and NWS hazards. These fields may be selected on or off in the drop-down Overlays menu. Figure 6-11, HEMS Data Overlays with Text METAR—Example, is an example.
6.1.2.6.1 METARs/TAFs.
The METAR observations plotted using the standard station model where temperature, dewpoint, winds, altimeter setting, weather, ceiling, and visibility are displayed around the station location.
The data plotted comes from the latest available observation, including Special Weather Reports (SPECI). The stations displayed follow a progressive priority scheme that will show more stations depending on how far the user zooms in. This density can be changed through the Configuration menu. If the time slider is moved into the past, the nearest observation before the listed time is displayed. If the slider is moved into the future, the TAF for that station is shown. It should be noted there are fewer TAF stations than available METAR sites. More configuration options are available, including parameters displayed, scale factor of graphic, and whether the TAF is included in the pop-up display.
6.1.2.6.2 Flight Category.
This displays only the flight conditions at a particular airport as a colored dot.
The flight category display uses the same priority filter system as the METAR plots, but the density is much higher.
6.1.2.6.3 PIREPs.
This displays turbulence and icing PIREPs. The default is to show only PIREPs reported in the last 90 minutes, and only those below 12,500 ft. These options can be changed in the Configuration menu.
11/14/16 Aviation Weather Services AC 00-45H 6-11
6.1.2.6.4 SIGMETs.
This displays the current valid SIGMETs. This will show both domestic and international SIGMETs. Individual SIGMET types can be toggled on and off through the configuration menu. SIGMETs can be distinguished by their red outline and red labels.
6.1.2.6.5 G-AIRMET.
This displays the current valid G-AIRMETs. This will show all G-AIRMET types, which can be cluttered. Each type can be toggled on and off through the Configuration menu.
6.1.2.6.6 Center Weather Advisories (CWA).
This displays the CWA issued by the Center Weather Service Units (CWSU) at each air route traffic control center (ARTCC). CWAs can be distinguished by the black outline and black labels.
6.1.2.6.7 NWS Hazards.
This displays all current warnings, watches, and advisories. The Configuration menu will allow the user to select “Warnings” which will only show tornado, severe thunderstorm, blizzard, winter storm, and ice storm warnings.
6.1.2.6.8 Windbarbs.
This displays windbarbs from the RAP model based on the height selected through one of the weather displays (CVA, Icing and RAP temperature, relative humidity (RH), and wind speed). If the user selects temperature at 2,000 ft AGL, the display would also show the winds at 2,000 ft AGL. The windbarbs are filtered based on zoom level. As the display is zoomed in, more windbarbs will show.
11/14/16 Aviation Weather Services AC 00-45H 6-12 Figure 6-11. HEMS Data Overlays with Text METAR—Example
Note: Text information from these fields can be accessed by clicking on the station or in the polygon, or by selecting “hover” in the Configure menu and scrolling the mouse over the area of interest.
Data can be customized in the Configure menu (see Figure 6-12, Configure Menu—Example). The user can select the type of background map; the level of transparency for the weather overlays; the types of SIGMETs, G-AIRMETs, PIREPs, and NWS hazards they wish to view; the preferred satellite view; and the density of observations.
11/14/16 Aviation Weather Services AC 00-45H Figure 6-12. Configure Menu-Example Helicopter Emergency Medical Services Tool INFO Feedback Weather Overlays View Configure 1619 UTC 7 May 2015 239 KAKS Map >> Satellite >> Radar >> Weather >> METAR/TAF >> Parameters visible:
rignt cat e- All • Temp Wind Alt PIREP >> • Vis • Wx Cover • Ceil SIGMETS >> None Dew Wgst Id G-AIRMET >> Density: 0 Scale: 1 Hazards >>
• Hover • Decoded METAR • Include TAF 100 mi 28 | KTCS SIGMET CWA GAIRMET BurbHi Purbl FIt Cat: OMVFRO IFROLIFR PIREP Turb: ALGT A MOD A SEV PIREP Ice: LJ LGT MOD I SEV
6.1.2.7 ESRI Basemaps and Overlays.
The HEMS Tool has high-resolution basemaps for the entire United States (U.S.). More detail is revealed as the user zooms in. The user can select their preferred Environmental Systems Research Institute (ESRI) basemap through the HEMS Configure menu. Options include Terrain, Road, or Satellite, and the user can select a light, dark, or simple map background. The default basemap is the ESRI Terrain view.
Map overlays include highways, roads, counties, top jet routes, ARTCC boundaries, Navigation Aids (NAVAID), airports, and runways. These can be toggled on or off in the Overlays menu.
6.1.3 Strengths and Limitations.
6.1.3.1 HEMS Strengths.
1. One-stop shop for multiple data fields.
2. Focused on low-altitude flights common to HEMS.
3. Simplified display for non-meteorologist users.
4. Available 24/7.
6.1.3.2 HEMS Limitations.
1. Due to limitations of the observations, the ceiling, visibility, and flight category grid cells are approximately 5 km apart. In data 6-13
11/14/16 Aviation Weather Services AC 00-45H 6-14 sparse regions, the best possible estimate of ceiling and visibility is assumed from the nearest surrounding data and may not represent the actual conditions at a specific point.
Due to limitations of the radar, such as blockage by mountains, spacing of radar locations and over processing of clutter and AP, there may be precipitation when radar data does not detect or show a complete weather picture. The most commonly seen example is very shallow clouds with light precipitation, like freezing drizzle or snow. An excellent Web site with more information concerning radar technology and limitations is found at the NWS JetStream-Online School for Weather, under Radar Frequently Asked Questions (FAQ).
In regions of steep terrain, AGL altitudes may have significant deviations from actual height above terrain, given the limiting factor of grid cell size, which is approximately 13 km, and the resolution of the topography in the model.
6.1.4 Use.
The HEMS Tool has been specially designed to meet the needs of emergency first responders flying short-distance, low-altitude flight routes. This tool is not designed for General Aviation (GA) or commercial flights and does not constitute an official weather brief.
6.2 Flight Path Tool.
6.2.1 Description.
Flight Path Tool is a comprehensive, interactive, geographical display that brings together the weather products available on the AWC’s Web site. It runs as a desktop application on your computer for maximum performance. The Flight Path Tool can overlay multiple fields of interest, such as:
• Icing forecasts at 1-hour intervals from the surface through flight level (FL) 450 (probability, severity, and Supercooled Large Drops (SLB)).
• Turbulence forecasts at 1-hour intervals at altitudes from 10,000 ft mean sea level (MSL) to FL 450.
• Winds, relative humidity, temperature, and forecasts at 1-hour intervals from the surface through FL450.
• METARs and graphical depictions of flight categories.
• TAFs.
• AIRMETs and G-AIRMETs.
• SIGMETs and the graphical representation of the area covered by SIGMETs (includes Convective SIGMETs).
• PIREPs and the graphical representation of PIREPs.
11/14/16 Aviation Weather Services AC 00-45H 6-15 All 3-D data can be sliced horizontally at selected FLs at 1,000-foot intervals or vertically along a user-designated flight path. All gridded data can be animated in time.
The Flight Path Tool lets you zoom in to identified regions of the globe, however, data availability is limited to mostly METARs and TAFs.
6.2.2 Access.
The Flight Path Tool is available on http://www.aviationweather.gov and runs as a standalone Java application.
6.2.3 Use.
A tutorial on http://www.aviationweather.gov provides information on effectively using the Flight Path Tool. The following topics are covered:
• How to use the Configuration Manager,
• How to Zoom,
• How to Change the Altitude,
• How to Choose the Data Valid Time,
• How to Choose the Time Range and Animate,
• How to Select Data Types,
• How to Configure Data Layers, and
• How to Create a Flight Path.
11/14/16 Aviation Weather Tools AC 00-45H Appendix A A-1 APPENDIX A. DEFINITION OF COMMON TERMS USED IN EN ROUTE
FORECASTS AND ADVISORIES Table A-1. Definition of Common Terms Used in En Route Forecasts and Advisories (FA, SIGMET, AIRMET, TCA, VAA, ROFOR) Contraction Translation Definition EMBD Embedded Thunderstorms Cumulonimbus or Thunderstorms are embedded haze.
or cumulonimbus (CB) clouds that in cloud layers or concealed by
EXTREME TURB Extreme Turbulence Turbulence in which aircraft is violently tossed about and is practically impossible to control. It cause structural damage.
may FIR Flight Information Region An airspace of defined dimensions within which flight information service and alerting service are provided.
FL Flight Level A surface of constant atmospheric pressure which is related to a specific pressure datum, 1013.2 hectopascals (hPA), and is separated from other such surfaces by specific pressure intervals.
FRQ Frequent Thunderstorms or Cumulonimbus Consisting of elements with little or no separation between adjacent thunderstorms with a maximum spatial coverage greater than 75 percent of the area affected by the phenomena at a fixed time or during the period of validity.
IMC Instrument Meteorological Conditions Ceiling greater than or equal to 500 feet to less than 1,000 feet and/or visibility greater than or equal to 1 to less than 3 miles. LIMC is a sub-category of IMC, thus, IMC conditions are ceiling less than 1,000 feet and/or visibility less than 3 miles.
ISOL Isolated Thunderstorms or Cumulonimbus Consisting of individual features affecting an area with a maximum spatial coverage less than 50 percent of the area affected by the phenomena at a fixed time or during the period of validity.
LINE TS Line (of Thunderstorms) A line of thunderstorms being at least 60 miles long with thunderstorms affecting at least 40 percent of its length.
LIMC Low Instrument Meteorological Conditions Ceiling less than 500 feet and/or visibility less than 1 SM. LIMC is a sub-category of Instrument Meteorological Conditions.
MVMC Marginal Visual Meteorological Conditions Ceiling greater than or equal to 1,000 feet to less than or equal to 3,000 feet and/or visibility greater than or equal to 3 to less than or equal to 5 miles.
11/14/16 Aviation Weather Tools AC 00-45H Appendix A A-2 Contraction Translation Definition MOD ICE Moderate Icing The rate of accumulation is such that even short encounters become potentially hazardous and use of deicing/anti-icing equipment or diversion is necessary.
MOD TURB Moderate Turbulence Turbulence that causes changes in attitude (pitch, roll, yaw) and/or altitude, but the aircraft remains in positive control at all times. It usually causes variations in indicated airspeed.
MT OBSC Mountain Obscuration Conditions over significant portions of mountainous geographical areas are such that pilots in-flight should not expect to maintain visual meteorological conditions or visual contact with mountains or mountain ridges near their route of flight.
OBSC Obscured Thunderstorm or Cumulonimbus Obscured by readily seen haze, smoke, or cloud due to darkness.
or cannot be OCNL Occasional Thunderstorms or Cumulonimbus An area with a maximum spatial coverage between 50 and 75 percent of the area affected by the phenomena at a fixed time of during the period of validity.
SCT Scattered 25 to 50 percent of area affected.
SEV ICE Severe Icing The rate of accumulation is such that normal deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.
SEV TURB Severe Turbulence Turbulence that causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control.
VMC Visual Meteorological Conditions Ceiling greater than 5 miles.
than 3,000 feet and visibility greater
VOLCANIC
ERUPTION Volcanic Eruption A volcano eruption has occurred when an eruption report is received from a volcano observatory. A volcanic eruption is also considered to have occurred regardless of volcano observatory notification if reported by PIREP, or ground observer, or if remote sensing data indicates that an eruption has occurred based on satellite imagery or WSR-88D radar data or any other reliable sources are identified.
11/14/16 Aviation Weather Tools AC 00-45H Appendix A A-3 Contraction Translation Definition VOLCANIC Volcanic Ash Any ash that can be seen by any one or more of the ASH following: satellite imagery (visible, IR, multi-channel or TOMS), PIREPs, ground observations, radar and VAFTAD (In the event volcanic ash is entrained in clouds, the volcanic ash will be treated as visible using the VAFTAD as guidance).
WDLY SCT Widely Scattered Less than 25 percent of area affected.
WDSPR Widespread 50 percent or greater of the area affected.
11/14/16 Aviation Weather Tools AC 00-45H Appendix B APPENDIX B. STANDARD CONVERSION CHART Figure B-1. Standard Conversion Chart Speed - Distance Temperature Pressure - Altitude Altimeter Setting M/H KTS KM/H °F °c INS. MBS./hPas.
1007 50 INS. MBS./hPas. 100'S 28.5 965 120 FT* 110 -1 80 12 400 • 230 970 90 -170 110 40 13 220 210 100 160 100 14 - 200 190 980 15 - 500 180 29.0 30 - 170 16 160 990 17 • 150 20 18 600 140 130 29.5 - 1000 70 19 120 10 20 - 110 1010 60 700 - 100 21 90 30.0 22
• 80 1020 23 70 800 40 -10 24 • 1030 30 10 25 50 30.5 30 50 26 40 1040 20 40 -20 27 900 30 20 -10 30 28 20
31.0 - 1050 -20 10 10 20 -30 29 10 1000 10 -30 30
- 1060 -40 •-40 31 1050 - -10 M/H KTS KM/H ° F ° C INS. MBS./hPas. 100'S IFT* 31.5 - 1065 * Standard Atmosphere INS. MBS./hPas.
B-1
11/14/16 Aviation Weather Tools AC 00-45H Appendix C APPENDIX C. DENSITY ALTITUDE CALCULATION To determine density altitude:
1. Set the aircraft's altimeter to 29.92 inches of Mercury. The altimeter will indicate pressure altitude.
2. Read the outside air temperature.
3. Mark the intersection of pressure altitude (horizontal) and temperature (vertical) lines on the chart.
4. Read the density altitude from the diagonal lines.
Figure C-1. Density Altitude Computation Chart 20,000
STANDARD ATMOSPHERE + +
- DENSITY ALTITUDE 15,000 15,000 10,000 10,000 5,000 + 5,000 + + - 5,000 →ZERO + -5,000 -50 -40 -30 -20 -1° Temperature °C 0°C 10 20 30 40 50 -50 -40 -20 0°F 20 40 60 80 100 120 Temperature °F C-1
11/14/16 Aviation Weather Tools AC 00-45H Appendix D D-1 APPENDIX D. INTERNET LINKS Table D-1. Selected National Weather Service (NWS) Links
NWS WEB SITE LINKS National Weather Service (NWS) Aviation Digital Data Service (ADDS) Aviation Weather Center (AWC) Storm Prediction Center (SPC) Alaska Aviation Weather Unit (AAWU) Center Weather Service Units (CWSU) Weather Forecast Office (WFO) Weather Forecast Office (WFO) Honolulu, HI –Aviation Products Table D-2. Selected Federal Aviation Administration (FAA) Links FAA Web Site Links Federal Aviation Administration (FAA) Air Traffic Control System Command Center (ATCSCC) Flight Service Operations