6-1 CHAPTER 6. AVIATION WEATHER TOOLS Aviation w eather tools are Web-based applications that incorporate multiple weather products into a Web-based interactive display. Chapter 6 will describe two tools, the helicopter emergency medical services (HEMS) Tool and the Flight Path Tool. Both of these tools can be found on the Aviation Weather Center’s (AWC) website at https://www.aviationweather.gov.
Phraseology Change.
The term Emergency Medical Service/Helicopter (EMS/H) or HEMS is obsolete. It has been replaced with helicopter air ambulance (HAA). Refer to AC 135-14, Helicopter Air Ambulance Operations, for terminology changes associated with this name change At the moment, there will be no change to the HEMS Tool phraseology. HAA operators should use the HEMS Tool developed by University Corporation for Atmospheric Research (UCAR) Foundation/National Center for Atmospheric Research (NCAR) and operated by AWC as they always have until a new tool or tool name has been developed.
6.1 Helicopter Emergency Medical Services (HEMS) Tool.
The HEMS Tool is specifically designed to display weather conditions for short-distance and low-altitude flights that are common for emergency first responders. HAA operators are extremely sensitive to changing and/or adverse weather conditions and need weather information presented for non-weather experts quickly and effectively. To meet this need, the Flight Path Tool on the AWC’s website was adapted and simplified to display high-resolution grids of critical weather parameters, particularly cloud ceiling and surface visibility. Using a highly interactive and intuitive tool that focuses on small, localized regions, HAA operators gain critical weather awareness to make all their flights safe for crews and patients.
6.1.1 Availability.
The HEMS Tool is continuously updated and available through the AWC’s website at https://www.aviationweather.gov/hemst.
6.1.2 Content.
The HEMS Tool can overlay multiple grids of various weather parameters, as well as NWS textual weather observations and forecasts including: ceiling, visibility, flight category, winds, relative humidity, temperature, icing, satellite, radar (base and Composite Reflectivity), Airmen’s Meteorological Information (AIRMET) and significant meteorological information (SIGMET), Aviation Routine Weather Reports (METAR), Terminal Aerodrome Forecasts (TAF), Pilot Weather Reports (PIREP), NWS hazards, and Center Weather Advisories (CWA). Some gridded products
(e.g., temperature, relative humidity, winds, and icing) are three-dimensional (3-D).
Other gridded products are two-dimensional (2-D) and may represent a “composite” of a 3-D weather phenomenon or a surface weather variable, such as horizontal visibility. The tool also displays relevant NWS textual weather observations and forecasts needed for aviation. These data are either points of observed or forecast weather, often at airports, or regions of hazardous weather represented by 2-D polygons.
6-2 The default displays the most recent analysis of flight category; colored flight category dots are selected airports, radar loops, SIGMETs, and recent PIREPs. The map can be panned in any direction and zoomed by using the “+/-” buttons or the mouse scroll wheel.
All 3-D data are interpolated to above ground level (AGL) altitudes and can be sliced horizontally on 1,000-foot intervals up to 5,000 feet (ft). All data can be animated from 6 hours before to 6 hours after the current time.
6.1.2.1 Visibility and F light Category.
Three products are available for the ceiling and visibility analysis (CVA) (see paragraph 4.2.1). The ceiling, visibility, and flight category weather products originate from the CVA product, which is a gridded analysis of ceiling and visibility based on surface observations and satellite imagery, and is updated approximately every 5 minutes. The ceiling and visibility are used together to classify the flight category as visual flight rules (VFR), Marginal Visual Flight Rules (MVFR), instrument flight rules (IFR), and low instrument flight rules (LIFR). Due to limitations of the observations, the grid cells are approximately 5 kilometers (km) apart at best. In data 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. Analyses of these fields are not available if the time slider is moved into the future. Figure 6-1, HEMS Ceiling with Flight Category Overlay—Example, Figure 6-2, HEMS Visibility with Flight Category Overlay—Example, and Figure 6-3, HEMS Flight Category with Flight Category Overlay—Example, are exam ples of the different overlays.
By default, the HEMS Tool displays the most recent analysis of flight category colored distinctly for VFR, MVFR, IFR, and LIFR. The classifications (see Table 6-1, Flight Categories) are defined by certain cloud base ceilings and surface visibility values.
Table 6-1. Flight Categories
Figure 6-1. HEMS Ceiling with Flight Category Overlay-Example Helicopter Emergency Medical Services Tool INFO Feedback Weather Overlays View Configure 1555 UTC 7 May 2015 _ Satellite
• Radar Chevenge
• None
• Flight Category
• Ceiling
• Visibility Icing Severity >> Icing Probability >> Temperature >> Rel Humidity >> Wind speed >>
OKLAROMA MEXICO
CRAMENTO 100 ml Ceiling o RAP Windbarb at 1000 AGL SIGMET CWA GAIRMET OrbH FIt Cat: •MVFR • IFR • LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: LGT If MOD (I SEV Obscure 0' 500' 1000' 3000' Note: Ceilings above 3,000 ft are transparent.
Figure 6-2. HEMS Visibility with Flight Category Overlay-Example Helicopter Emergency Medical Services Tool INFO Feedback Weather Overlays View Configure 1555 UTC 7 May 2015
- Satellite
- Radar Che
- None
• Flight Category
• Ceiling.
• Visibility Icing Severity >> Icing ProDaDIty >> Temperature >> Rel Humidity >> Wind speed >>
OKLAROMA окі пота City MEXICO Source: Ess gubbock
SACRAMENJO 100 mi Visibility RAP Windbarb at 1000 A.
SIGMET CWA GAIRMET urbHt PabLo LEWS stend Dang the LER FIt Cat: •MVFR • IFR • LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: L LGT / MOD (p) SEV Note: Visibilities above 5 miles (mi) are transparent.
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6-4 Figure 6-3. HEMS Flight Category with Flight Category Overlay—Example
Note: The flight category is colored for MVFR, IFR, and LIFR. The VFR areas are transparent. Yellow is used instead of red for coloring because it’s more difficult to distinguish between red and magenta on the image backgrounds.
6.1.2.2 Radar.
The HEMS Tool uses the Multi-Radar/Multi-System (MRMS) mosaic produced by NWS. The radar image combines more than 140 radars from around the country into a single image. Additional post-processing is performed to remove some ground clutter and Anomalous Propagation (AP).
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 image used in HEMS is the lowest reflectivity scan from the nearest radar. This is a 1 km image for the continental United States (CONUS). Like the satellite images, the radar mosaic is sliced up and put into the tile cache to provide the maximum resolution and optimal transmission bandwidth. The tile cache is only updated every 10 minutes (MRMS data is available every 2 minutes).
The HE MS display (see Figure 6-4, HEMS Radar Display—Example) incorporates the latest radar image plus the previous four into a loop of radar data s howing the progression of precipitation echoes. By moving the time
slider into the past, the radar loop will always show the latest five images ending in the time shown in the slider box.
Figure 6-4. HEMS Radar Display-Example Helicopter Emergency Medical Services Tool INFO Feedback Weather Overlays View Configure 1557 UTC 7 May 2015
• Radar - Satellite 3 Cheyenne NEBRASK
• None
• Flight Category
• Ceiling
• Visibility.
Icing Severity >> Icing Probability COLORADO KANSAS Rel Humidity >> Wind speed >>
N D STATE
COLOR, IDO Santa Fe OKLAHOMA Albuquerque Oklahoma City er
NEW MEXICO 100 km RAMENTO 100 mil RAP Windbarb at 1000'AGL
SIGMET CWA GAIRMET FIt Cat: •MVFR • IFR • LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: LJ LGT (/ MOD H SEV
6.1.2.3 Satellite.
The HEMS Tool uses a global satellite mosaic constructed from the five geostationary satellites plus the appropriate polar global imagery. The resulting image is created every 30 minutes from the available imagery.
Images are sliced up and provided through a progressive tile cache to optimize data transmission and image resolution.
Note: A limitation of the satellite imagery is that the European Meteosat imagery is only available every 3 hours; therefore, imagery over Europe and Central Asia may be up to 3 hours old.
There are three types of satellite imagery available in HEMS:
1. Infrared (IR): This is a 10 km image where brighter grays show colder cloud temperatures (see Figure 6-5, HEMS Satellite Imagery-Example).
2. Visible: This is a 5 km image showing visible reflection from clouds and the ground surface. Consequentially, these images will be black at night.
3. Water Vapor: This is a 10 km image where brighter grays show higher areas of water vapor.
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6-6 Figure 6-5. HEMS Satellite Imagery—Example
6.1.2.4 Icing.
The i cing severity product is a 3-D product and provides depictions at specified altitudes AGL at 1,000 ft-intervals up to 5,000 ft. In regions of steep terrain, these 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. The icing severity product (see Figure 6-6, HEMS Icing Severity—Example) combines a multitude of weather observations (e.g., temperature, humidity, satellit e, observed surface weather and pilot reports, radar data) to diagnose areas of expected trace, light, moderate, and heavy icing. Separate overall icing probability (from 5 to 85 percent) (see Figure 6-7, HEMS Icing Probability—Example) i s provided as well.
These products originate from the Current Icing Product (CIP) and Forecast Icing Product (FIP) (see paragraph 5.21.1). These products start with data from the Rapid Refresh (RAP) model, which is run hourly. FIP has forecasts at 1, 2, 3, 6, 9, 12, 15, an d 18 hours. The time slider will use CIP for current and past times and time-adjusted FIP for future times.
Figure 6-6. HEMS Icing Severity-Example Helicopter Emergency Medical Services Tool INFO Feedback Weather Overlays View Configure 2023 UTC 8 May 2015 LSatellte
• None
•Flight Category celling Icing Severity >> OTUOU AGI @2000' AGL Icing Probability @3000' AGL Temperature >> @4000' AGL NOR TH D
•@5000' AGL Rel Humidity >> Wind speed >> OREGON
NEBRASKA Denver af 200 KANSAS ALL 200 mil Icing Severity at 5000 AGL NITED STAT E S RAP Windbarb at 5000'AGL SIGMET FIt Cat: •MVFR • IFR • LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: LJ LGT / MOD (H/ SEV Trace Light Moderate Heavy
HEMS PDD The severity is colored in shades of blue, with the lightest for trace and the darkest for heavy.
Figure 6-7. HEMS Icing Probability- -Example Helicopter Emergency Medical Services Tool INFO Feedbac Weather Overlays Configure 2023 UTC 8 May 2015 Satellite Jone Flight Category ) Ceiling Visibility Icing Severity >> Icing Probability @1000' AGL 02000 ACL Temperature >> OSUOU AGL Rel Humidity >> 04000 AGL
•@5000' AGL Wind speed >>
ORE GOI
NEBRASKA Devel Kansas
ETED STAT ES AL 200 mi Icing Probability at 5000'AGL RAP Windbarb at 5000'AGL
SIGMET CWA GAIRMET FIt Cat: •MVFR • IFR • LIFR PIREP Turb: \ LGT AMOD A SEV PIREP Ice: L LGT (/ MOD ( SEV 15 25 35 45 55 65 75
HEMS PDD The probability is colored in shades starting at blue (5 percent), through yellow (50 percent), to orange (>75 percent).
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6.1.2.5 Temperature, Relative Humidity, and Wind Speed.
Temperature (see Figure 6-8, HEMS Temperature-Example), relative humidity (see Figure 6-9, HEMS Relative Humidity-Example), and wind speed data (see Figure 6-10, HEMS Wind Speed with Windbarb-Example) is derived from the AGL grids provided as part of the RAP model output.
Data are presented on 1,000 ft AGL increments to 5,000 ft. These grids are available from the RAP model output every hour and forecasts run 7 hours into the future. If the time slider is moved into the past, the RAP analysis for that hour is shown.
Figure 6-8. HEMS Temperature-Example Helicopter Emergency Medical Services Tool INFO Feedback Weather Overlays View Configure 1605 UTC 7 May 2015
• Satellite
- Radar
• None
• Flight Category.
• Ceiling
• Visibility.
Icing Severity >> Icing Probability >> Temperature >> @1000 AGL Rel Humidity >> • @2000' AGL Wind speed >> • @3000' AGL
• @4000' AGL
• @5000' AGL Source: Esri 500 km 500 mi RAP Temperature at 5000'AGL RAP Windbarb at 5000 AGL
SIGMET CWA FIt Cat: •MVFR • IFR O LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: LJ LGT (/ MOD (p) SEV -40-30-20-10 0 10 30 The temperature data are colored from blues for the coldest temperatures to reds for the warmest. Delineation between light blue and yellow is used to show the freezing level.
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Figure 6-9. HEMS Relative Humidity-Example Helicopter Emergency Medical Services Tool INFO Feedback weather Overlays View Configure 1605 UTC 7 May 2015 .. Satellite Radar O None
• Flight Category
• Ceiling
• Visibility Icing Severity >> Icing Probability >> Temperature >> Rel Humidity >> @1000 AGL Wind speed >> • @2000' AGL
• @3000 AGL
• @4000' AGL
• @5000' AGL Source: Esri 500 km 500 mi RAP Rel humidity at 5000 AGI RAP Wingbarb at 5000 AGL
SIGMET CWA FIt Cat: •MVFR • IFR O LIFR PIREP Turb: ALGT A MOD A SEV PIREP Ice: LJ LGT / MOD H SEV 10 20 30 40 50 60 70 80 90 The humidity data are colored from oranges for very dry, to yellow for 50 percent, to dark green for near 100 percent. Oranges would be more indicative of clear skies while greens would show cloud or low-visibility areas.
Figure 6-10. HEMS Wind Speed with Windbarb-Example Helicopter Emergency Medical Services Tool INFO Feedback weduen Overlays View Configure 1607 UTC 7 May 2015
• Satellite
- Radar O None
- Flight Category
• Ceiling © Visibility..
Icing Severity >> Icing Probability >> Temperature >> Rel Humidity >> › @1000' AGL
• @2000' AGL
• @3000' AGL
• @4000' AGL _ Sourde: Esri 500 500 mi RAP Wind speed at 5000 AGL RAP Wing barb at 1000 AGL FIt Cat: •MVFR • IFRO LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: LJ LGT / MOD (/ SEV 45 60 75 The wind speed data are colored from blues for the lightest winds to light green for stronger winds.
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6.1.2.6 Dat a 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—Ex ample, 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.
T he 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.
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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.
Figure 6-11. HEMS Data Overlays with Text METAR-Example Helicopter Emergency Medical Services Tool INFO Weather Overlays View Configure 1625 UTC 7 May 2015 -A SPER • METAR/TAF
• FItCat 45
• PIREP
• SIGMET
• G-AIRMET
• CWA
- NWS Hazards
• Windbarb
• Highways
• Roads
- Counties IN ACE PR RNO
• Top Jetroutes
• ARTCC Boundaries
- Nav Aids
• Airports Runways
OLORADO
PL A TA OU 'MEX 100 mil 28 || KTCS
SIGMET CWA GAIRMET E FIt Cat: OMVFRO IFRO LIFR PIREP Turb: ALGT AMOD A SEV PIREP Ice: L LGT If MOD | SEV 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.
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