Many aircraft manufacturers now include data link weather services with new electronic flight display (EFD) systems. EFDs give a pilot access to many of the data link weather services available.

Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 1. Information page
Products available to a pilot on the display pictured in Figure 1 are listed as follows. The letters in parentheses indicate the soft key to press in order to access the data.
  • Graphical NEXRAD data (NEXRAD)
  • Graphical METAR data (METAR)
  • Textual METAR data
  • Textual terminal aerodrome forecasts (TAF)
  • City forecast data
  • Graphical wind data (WIND)
  • Graphical echo tops (ECHO T,,,OPS)
  • Graphical cloud tops (CLD TOPS)
  • Graphical lightning strikes (LTNG)
  • Graphical storm cell movement (CELL MOV)
  • NEXRAD radar coverage (information displayed with the NEXRAD data)
  • Surface analysis to include city forecasts (SFC)
  • County warnings (COUNTY)
  • Freezing levels (FRZ LVL)
  • Hurricane track (CYCLONE)
  • Temporary flight restrictions (TFR)

Pilots must be familiar with any EFD or MFD used and the data link weather products available on the display.

Weather Products Age and Expiration

The information displayed using a data link weather link is near real time but should not be thought of as instantaneous, up-to-date information. Each type of weather display is stamped with the age information on the MFD. The time is referenced from Zulu when the information was assembled at the ground station. The age should not be assumed to be the time when the FIS received the information from the data link.Two types of weather are displayed on the screen: “current” weather and forecast data. Current information is displayed by an age while the forecast data has a data stamp in the form of “__ / __ __ : __.” [Figure 2]

Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 2. List of weather products and the expiration times of each

The Next Generation Weather Radar System (NEXRAD)

The NEXRAD system is comprised of a series of 159 Weather Surveillance Radar–1988 Doppler (WSR-88D) sites situated throughout the United States, as well as selected overseas sites. The NEXRAD system is a joint venture between the United States Department of Commerce (DOC), the United States DOD, as well as the United States Department of Transportation (DOT). The individual agencies that have control over the system are the NWS, Air Force Weather Agency (AFWA) and the FAA. [Figure 3]

Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 3. NEXRAD radar display
NEXRAD data for up to a 2,000 mile range can be displayed. It is important to realize that the radar image is not real time and can be up to 5 minutes old. The NTSB has reported on 2 fatal accidents where in-cockpit NEXRAD mosaic imagery was available to pilots operating near quickly-developing and fast-moving convective weather. In one of these accidents, the images were from 6 to 8 minutes old. In some cases, NEXRAD data can age significantly by the time the mosaic image is created. In some extreme latency cases, the actual age of the oldest NEXRAD data in the mosaic can exceed the age indication in the cockpit by 15 to 20 minutes. Even small-time differences between the age indicator and actual conditions can be important for safety of flight, especially when considering fast-moving weather hazards, quickly developing weather scenarios, and/or fast-moving aircraft. At no time should the images be used as storm penetrating radar nor to navigate through a line of storms. The images display should only be used as a reference.NEXRAD radar is mutually exclusive of Topographic (TOPO), TERRAIN and STORMSCOPE. When NEXRAD is turned on, TOPO, TERRAIN, and STORMSCOPE are turned off because the colors used to display intensities are very similar.

Lightning information is available to assist when NEXRAD is enabled. This presents a more comprehensive picture of the weather in the surrounding area.In addition to utilizing the soft keys to activate the NEXRAD display, the pilot also has the option of setting the desired range. It is possible to zoom in on a specific area of the display in order to gain a more detailed picture of the radar display. [Figure 4]

Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 4. NEXRAD radar display (500 mile range). The individual color gradients can be easily discerned and interpreted via the legend in the upper right corner of the screen. Additional information can be gained by pressing the LEGEND soft key, which displays the legend page

What Can Pilots Do?

Remember that the in-cockpit NEXRAD display depicts where the weather WAS, not where it IS. The age indicator does not show the age of the actual weather conditions, but rather the age of the mosaic image. The actual weather conditions could be up to 15 to 20 minutes OLDER than the age indicated on the display. You should consider this potential delay when using in-cockpit NEXRAD capabilities, as the movement and/or intensification of weather could adversely affect safety of flight.

  • Understand that the common perception of a “5-minute latency” with radar data is not always correct.
  • Get your preflight weather briefing! Having in-cockpit weather capabilities does not circumvent the need for a complete weather briefing before takeoff.
  • Use all appropriate sources of weather information to make in-flight decisions.
  • Let your fellow pilots know about the limitations of in-cockpit NEXRAD.

NEXRAD Abnormalities

Although NEXRAD is a compilation of stations across the country, there can be abnormalities associated with the system. Some of the abnormalities are listed below.

  • Ground clutter
  • Strobes and spurious radar data
  • Sun strobes, when the radar antenna points directly at the sun
  • Interference from buildings or mountains that may cause shadows
  • Military aircraft that deploy metallic dust and may reflect the radar signature

NEXRAD Limitations

In addition to the abnormalities listed, the NEXRAD system does have some specific limitations.

Base Reflectivity

The NEXRAD base reflectivity does not provide adequate information from which to determine cloud layers or type of precipitation with respect to hail versus rain. Therefore, a pilot may mistake rain for hail.

In addition, the base reflectivity is sampled at the minimum antenna elevation angle. With this minimum angle, an individual site cannot depict high altitude storms directly over the station. This leaves an area of null coverage if an adjacent site does not also cover the affected area.

Resolution Display

The resolution of the displayed data poses additional concerns when the range is decreased. The minimum resolution for NEXRAD returns is 1.24 miles. This means that when the display range is zoomed in to approximately ten miles, the individual square return boxes are more prevalent. Each square indicates the strongest display return within that 1.24 mile square area.


AIRMET/SIGMET information is available for the displayed viewing range on the MFD. Some displays are capable of displaying weather information for a 2,000 mile range. AIRMETS/SIGMETS are displayed by dashed lines on the map. [Figure 5]

Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 5. The AIRMET information box instructs the pilot to press the ENTER button soft key (ENT) to gain additional information on the selected area of weather. Once the ENTER soft key (ENT) is depressed, the specific textual information is displayed on the right side of the screen
The legend box denotes the various colors used to depict the AIRMETs, such as icing, turbulence, IFR weather, mountain obscuration, and surface winds. [Figure 6] The great advantage of the graphically displayed AIRMET/SIGMET boundary box is the pilot can see the extent of the area that the advisory covers. The pilot does not need to manually plot the points to determine the full extent of the coverage area.
Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 6. SIGMET/AIRMET legend display

Graphical METARs

METARs can be displayed on the MFD. Each reporting station that has a METAR/TAF available is depicted by a flag from the center of the airport symbol. Each flag is color coded to depict the type of weather that is currently reported at that station. A legend is available to assist users in determining what each flag color represents. [Figure 7]

Electronic Flight Displays (EFD) /Multi-Function Display (MFD) Weather
Figure 7. Graphical METAR legend display
The graphical METAR display shows all available reporting stations within the set viewing range. By setting the range knob up to a 2,000 mile range, pilots can pan around the display map to check the current conditions of various airports along the route of flight.By understanding what each colored flag indicates, a pilot can quickly determine where weather patterns display marginal weather, IFR, or areas of VFR. These flags make it easy to determine weather at a specific airport should the need arise to divert from the intended airport of landing.

Data Link Weather

Pilots now have the capability of receiving continuously updated weather across the entire country at any altitude. No longer are pilots restricted by radio range or geographic isolations, such as mountains or valleys.

In addition, pilots no longer have to request specific information from weather briefing personnel directly. When the weather becomes questionable, radio congestion often increases, delaying the timely exchange of valuable inflight weather updates for a pilot’s specific route of flight. Flight Service Station (FSS) personnel can communicate with only one pilot at a time, which leaves other pilots waiting and flying in uncertain weather conditions. Data link weather provides the pilot with a powerful resource for enhanced situational awareness at any time. Due to continuous data link broadcasts, pilots can obtain a weather briefing by looking at a display screen. Pilots have a choice between FAA-certified devices or portable receivers as a source of weather data.

Data Link Weather Products

Flight Information Service- Broadcast (FIS-B)

Flight Information Service–Broadcast (FIS-B) is a ground broadcast service provided through the Automatic Dependent Surveillance–Broadcast (ADS-B) Services network over the 978 MHz UAT data link. The FAA FIS-B system provides pilots and flight crews of properly-equipped aircraft with a flightdeck display of certain aviation weather and aeronautical information which are listed below.

  • Aviation Routine Weather Reports (METARs)
  • Special Aviation Reports (SPECIs)
  • Terminal Area Forecasts (TAFs) and their amendments
  • NEXRAD (regional and CONUS) precipitation maps
  • Notice to Airmen (NOTAM) Distant and Flight Data Center
  • Airmen’s Meteorological Conditions (AIRMET)
  • Significant Meteorological Conditions (SIGMET) and Convective SIGMET
  • Status of Special Use Airspace (SUA)
  • Temporary Flight Restrictions (TFRs)
  • Winds and Temperatures Aloft.
  • Pilot Reports (PIREPS)
  • TIS-B service status

The weather products provided by FIS-B are for information only. Therefore, these products do notmeet the safety and regulatory requirements of official weather products. The weather products displayed on FIS-B should not be used as primary weather products (i.e., aviation weather to meet operational and safety requirements). Each aircraft system is different and some of the data that is rendered can be up to 20 or 30 minutes old and not current. Pilots should consult the individual equipment manuals for specific delay times.