Aviation Weather Radar and Satellite: NEXRAD, IR, and Visible Imagery Explained for Pilots

Nathan Hodell
Aug 27, 2025
9 min read

Updated: May 3

Weather radar and satellite imagery are two of the most powerful tools pilots have for understanding what's happening in the atmosphere. They're complementary — radar tells you where precipitation is right now and how intense it is, while satellite shows the broader cloud structure even where there's no precipitation. Most pilots use both products every flight without really understanding what each is showing them, what the colors mean, the limitations of each, or which one to trust when they disagree.

This post covers both products in practical depth: how NEXRAD weather radar works, what dBZ values mean, the difference between base and composite reflectivity, satellite imagery types (visible, IR, water vapor), the limitations of each, and how to use them together for safer flight planning.

Study this full length lesson (video, podcast, flashcards, and quiz) here: Full Length Lesson >

The Modern Reality: From Radar Summary Chart to NEXRAD

Older pilots may remember the legacy Radar Summary Chart — a static, hand-prepared product that summarized radar conditions across the country every hour or so. The FAA discontinued this product in 2017 along with several other legacy weather products.

What replaced it: NEXRAD (Next Generation Radar) — the network of 160+ Doppler weather radars across the United States, plus their derivative products. NEXRAD provides:

Real-time radar imagery (updated every 4-10 minutes)
Multiple data products from each site
Mosaic products combining all radars
Velocity data showing wind and rotation
Algorithm-derived storm tracking and severe weather alerts

For modern pilots, "weather radar" almost always means NEXRAD or NEXRAD-derived products available through aviationweather.gov, EFB apps, datalink weather, or other sources.

How NEXRAD Weather Radar Works

NEXRAD is a Doppler radar that emits pulses of microwave energy and analyzes the reflected signal. The radar can determine:

Reflectivity: How much of the signal is reflected back, indicating the size and density of precipitation. Larger raindrops, snow, and especially hail reflect more strongly.
Velocity (Doppler): The speed at which precipitation is moving toward or away from the radar. This reveals wind patterns, including rotating storms (mesocyclones) and microbursts.
Spectrum width: The variability in motion within a radar pixel, indicating turbulence.
Polarization (dual-pol): Modern NEXRAD radars use dual-polarization technology, sending out both horizontal and vertical pulses. This allows differentiation between rain, snow, hail, ice, and even non-meteorological returns like birds and insects.

Coverage:

Each radar has approximately 230 NM range
Data reduces in resolution at greater distances
Beam height increases with distance from radar (a precipitation echo 100 NM from the radar is at higher altitude than one 25 NM away)
Some areas have limited coverage between radars or in mountainous terrain

Reflectivity: What the Colors Mean

Radar reflectivity is measured in dBZ (decibels of Z), a logarithmic scale. The higher the dBZ value, the more intense the precipitation:

dBZ Range	Intensity	Description	Color (typical)
< 0 dBZ	Very weak	Clear air return, dust	None typically shown
0-19 dBZ	Light	Light drizzle, snow flurries	Light blue/green
20-29 dBZ	Light	Light rain, light snow	Green
30-39 dBZ	Moderate	Moderate rain	Yellow
40-49 dBZ	Heavy	Heavy rain, possible thunderstorm	Orange/red
50-59 dBZ	Very heavy	Severe thunderstorm, possible hail	Red/pink
60+ dBZ	Extreme	Large hail likely	Pink/purple/magenta

The intensity scale matters for aviation:

30 dBZ — moderate rain, no significant hazard
40 dBZ — entering thunderstorm territory, expect turbulence
50 dBZ — significant thunderstorm, severe turbulence, hail possible
60+ dBZ — severe thunderstorm with large hail very likely; absolute avoidance required

Color schemes vary — some apps use traditional red/orange/yellow/green, others use blue→pink→magenta progressions. The dBZ values are standardized, but the specific color shown depends on the product or app.

Base vs. Composite Reflectivity

Two important radar products differ in what they show:

Base Reflectivity:

Shows the radar return at a specific elevation angle (typically 0.5° tilt)
Shows what's at a specific altitude near the surface
Better for low-level storm structure
Less prone to overstating storm intensity

Composite Reflectivity:

Shows the maximum reflectivity from any elevation in the column
Tells you the most intense precipitation anywhere from surface to top
Better for identifying severe thunderstorms with high cores
Can show high-altitude precipitation that's evaporating before reaching the surface

Which to use:

For most pilots, composite reflectivity is more useful — it shows the worst conditions in the column
Some EFB apps show both options
Datalink weather typically shows composite reflectivity

Echo Tops

Echo tops show the highest altitude at which the radar detects precipitation. This indicates how vertically developed a storm is.

Reading echo tops:

Typically displayed in flight levels (FL250 = 25,000 feet)
Higher tops indicate stronger updrafts
Tops above FL400 indicate severe thunderstorm potential
Tops above FL500 indicate exceptionally strong storms

For pilots:

Tops to FL500+ in summer thunderstorms are common in central U.S.
Tops far above your cruise altitude don't necessarily mean you're safe — turbulence and hail can extend laterally from high-topped storms
Anvil-level cirrus can extend hundreds of miles from the parent storm

Velocity (Doppler) Products

Doppler velocity products show motion toward or away from the radar:

Toward the radar (incoming): Typically shown in green Away from the radar (outgoing): Typically shown in red

What pilots can identify from velocity products:

Mesocyclone signature: A "couplet" of inbound and outbound velocities indicates rotation — a possible tornadic storm.
Microburst signature: Strong outbound velocities at low levels indicate a microburst — extreme wind shear.
Wind direction and speed: Areas of consistent inbound or outbound velocities indicate the wind direction at that altitude.

Practical use:

Velocity products are mainly meteorologist tools
Some EFB apps show simplified velocity overlays
Storm-based motion arrows derived from velocity are commonly displayed

Limitations of Weather Radar

Radar doesn't show clouds without precipitation:

Thin cirrus, scattered cumulus, fog — invisible to radar
VFR ceiling problems may not show on radar
Always combine with satellite and METARs

Beam blockage and ground clutter:

Mountains can block radar beams (poor coverage in some valleys)
Buildings near the radar can cause artifacts
Birds and insects can produce false returns
Wind farms can produce significant clutter

Beam height issues:

The radar beam rises with distance
A storm 200 NM from the radar may have its base above the lowest beam scan
Light precipitation may not be detected at long range

Datalink delay:

Free FIS-B weather (ADS-B) has 5-15 minute delay
XM Weather has approximately 2-5 minute delay
A storm shown as "moderate" on delayed data may have intensified to "severe" by the time you're near it
Use datalink to AVOID storms, never to PENETRATE them

Attenuation:

A storm can absorb radar energy, hiding storms behind it
Strong thunderstorms can create "radar shadows"
Always cross-reference with multiple radars

Satellite Imagery: Three Main Types

Weather satellites provide imagery in three primary forms, each useful for different purposes:

Visible Imagery:

Shows reflected sunlight from clouds and surfaces
Looks like a black-and-white photograph from space
Daytime only (no useful image at night)
Best resolution and detail
Shows cloud texture and structure

What pilots can see:

Cloud coverage and type
Snow cover (similar to clouds visually)
Smoke plumes from fires
Frontal structure
Convective storm structure

Limitations:

Useless at night
Cannot distinguish between thick low clouds and snow
Provides no information about cloud-top temperature

Infrared (IR) Imagery:

Measures the heat (infrared radiation) emitted by clouds
Available 24/7
Cold clouds appear as bright/white; warm surfaces appear dark
Cloud-top temperature indicates altitude (colder = higher)

What IR imagery shows:

Cloud-top heights (colder = higher tops)
Severe thunderstorms (very cold tops)
Frontal cloud systems
Tropical systems
Day or night usability

Color enhancement: Most modern IR imagery uses color enhancement to make cloud-top temperatures more visible:

Black/dark gray — Earth surface and low warm clouds
Light gray — Mid-level clouds
White — Cold cloud tops
Yellow → Orange → Red → Pink — Increasingly cold (higher) cloud tops
Pink/Magenta — Extremely cold tops, thunderstorms

Water Vapor Imagery:

Shows water vapor in the upper atmosphere
Useful for identifying jet streams, dry slots, troughs
Mostly meteorologist tool but increasingly available in apps

Reading Satellite Imagery

Visible imagery cues:

Bright white — Thick clouds (cumulonimbus, deep stratus)
Light gray — Thinner clouds
Dark gray — Earth surface (no clouds)
Sharp edges — Convective tops with strong vertical development
Smooth, layered — Stratus or stratocumulus
Lumpy, rounded — Cumulus development
Comma-shaped — Mature low pressure system
Spiral patterns — Tropical or extratropical cyclone
Linear features — Frontal cloud bands

IR imagery cues:

Color intensity — Cloud-top temperature/altitude
Yellow areas — Mid-level clouds (typically 15,000-25,000 ft)
Red/orange — High clouds (25,000-35,000 ft)
Pink/magenta — Very cold cloud tops, severe storms
Smooth temperature gradient — Stratiform layer
Sharp temperature gradients — Convective storm boundaries

Animation:

Looping (animating) satellite images shows movement over time. This reveals:

Storm system speed
Cloud development or dissipation
Rotation around pressure systems
Frontal movement

Most modern weather products allow looping. A 2-3 hour animation gives a clear picture of system trajectories.

Using Radar and Satellite Together

The two products complement each other:

Where radar shows nothing but satellite shows clouds:

Likely VFR but with reduced visibility
Possible IFR with stratus/fog
Could indicate non-precipitating cloud layers
Check METARs for actual conditions

Where both show activity:

Radar shows precipitation with intensity
Satellite shows the larger cloud structure
Radar tells you where to avoid; satellite shows the system context

Where radar shows precipitation but satellite shows little:

Possibly virga (precipitation evaporating before reaching ground)
Could be precipitation under thin cloud cover
Verify with METARs and PIREPs

Where satellite shows high cold tops but radar is moderate:

Cumulonimbus development with high anvil
Storm intensity may be increasing
Even moderate radar return with high tops indicates significant storm

The integrated picture:

Use satellite for big-picture pattern (frontal positions, storm systems)
Use radar for tactical avoidance (where exactly are storms now)
Cross-reference both with METARs and TAFs
Verify against PIREPs for actual conditions

Practical Flight Planning Use

Pre-flight:

Check satellite for overall weather pattern
Check radar for current precipitation/storm activity
Loop both to see motion and trends
Identify storms moving toward your route
Identify cloud coverage at departure and destination

During flight:

Use datalink weather (FIS-B, XM) for real-time updates
Monitor storm movement and development
Use radar to plan deviations
Use satellite to anticipate cloud cover ahead

Decision-making:

40+ dBZ areas = avoid by 20 NM minimum
50+ dBZ areas = avoid by 50 NM minimum
High echo tops (FL400+) = severe storm, expand avoidance
Pink/magenta IR satellite = significant convective activity
Use trends to anticipate developing storms

Sources for Radar and Satellite Imagery

Pre-flight:

aviationweather.gov — official FAA aviation weather products
weather.gov — National Weather Service
1800wxbrief.com — graphical briefings include radar/satellite
College of DuPage Weather Lab and other educational sites
ForeFlight, Garmin Pilot, FltPlan Go — EFB apps with comprehensive imagery

In-flight:

ADS-B FIS-B (free with ADS-B In) — radar mosaic, METAR, TAF, AIRMETs/SIGMETs
XM Weather (subscription) — radar mosaic with shorter delay
Cellular data via iPad/EFB (when in coverage)
Aircraft datalink systems

Limitations and Cautions

Datalink weather delay:

ADS-B FIS-B: 5-15 minute delay typical
XM Weather: 2-5 minute delay
Storm conditions can change significantly during this delay
Use datalink to AVOID storms, never to PENETRATE
Always assume conditions ahead may be worse than displayed

Pixel size limitations:

Each radar pixel covers approximately 1 NM
Small intense storms may be averaged with surrounding clear air
Storm peaks may not be fully represented

Tilting and beam height:

Distant radar returns may be from higher altitudes than the surface
A 230 NM-distant storm shown at 50 dBZ may actually be at 30,000 feet, possibly less intense at lower altitudes

Composite reflectivity caveats:

Shows the worst in the entire column
A 40 dBZ composite return might be entirely above your cruise altitude
Cross-reference with echo tops and base reflectivity

On the Written Test and Checkride

Radar and satellite products appear consistently on tests and oral exams. The most commonly tested topics:

Difference between radar and satellite imagery
Limitations of weather radar
dBZ scale interpretation
Echo tops
Visible vs. IR satellite imagery
Use of NEXRAD products
Datalink weather delays and use

Quick Reference

Radar (NEXRAD):

Updated every 4-10 minutes
Shows precipitation only (not clouds without precipitation)
230 NM range per site
Available via aviationweather.gov, EFB apps, datalink
Limitations: ground clutter, beam blockage, attenuation, datalink delay

dBZ Scale:

dBZ	Intensity	Pilot Action
20-29	Light	Note, monitor
30-39	Moderate	Plan deviation if convective
40-49	Heavy	Avoid 20 NM
50+	Severe	Avoid 50 NM
60+	Extreme	Hail likely; absolute avoidance

Satellite:

Visible: Daylight only, shows reflected light, best resolution
IR: 24/7, shows cloud-top temperature
Water Vapor: Shows upper-level moisture/dry slots

Combining:

Satellite for pattern recognition
Radar for storm tactical avoidance
METARs for actual surface conditions
PIREPs for actual flight conditions
All four for complete picture

Datalink delays:

ADS-B FIS-B: 5-15 min
XM Weather: 2-5 min
Use to AVOID, not to PENETRATE

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Author: Nathan Hodell

CFI, CFII, MEI, ATP, Creator and CEO

Nathan is an aviation enthusiast with thousands of hours of flying and dual instruction over the past 15+ years. Through his aviation career he has been able to earn his ATP, fly as an airline pilot, own/operate flight schools, and create and host wifiCFI.