CHAPTER 2

Chapter 24
Section 24.1 METAR

METAR
Roughly translated from the French as Aviation Routine Weather Report
On July 1 1996 the METAR format was adopted for global standardization
Provides common frame of reference for international flights

METAR
2 Types:
METAR comes out hourly from H+45 to the top of the hour
SPECI which is non routine and comes out when special conditions exist… see table 24-2

Types of Observations
Manual Observation
Done by a human
Automated Observation
Automated surface observing system (ASOS)
Automated Weather Observing System (AWOS)
Augmented Observation
Human oversight, including tower personnel
AUTO is not used when the wx dude gets involved

METAR
Type of Report
Station ID
Date/Time
Modifier
Wind
Visibility

Weather
Sky condition
Temp/Dew point
Altimeter
Remarks

METAR DECODED
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO

TYPE OF REPORT
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO

SPECI KMWH 282021Z 00000KT 2SM BR OVC009 01/M01 A3076 RMK AO2 CIG 003V011 T00111011
Designates if it is a METAR or SPECI

ICAO IDENTIFIER
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
ICAO identifier, K = continental U.S.

DATE AND TIME
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
30 = day of the month, 1456Z indicates time the report was issued in Zulu

MODIFIER
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
AUTO will be absent if the report is taken by or augmented by a human.

MODIFIER
METAR KSMP 301456Z COR VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
COR will be present if a corrected report has been sent out.

WIND
METAR KSMP 301456Z AUTO 09026KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
The first three digits are direction, last two or three digits are velocity in knots. Direction is True and which way it is FROM

WIND
METAR KSMP 301456Z AUTO 08012G25KT 040V120 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Wind gust is a rapid speed change of 10kts or more.
To be reported as variable, direction must vary 60˚ or more and speed greater than 6kts. If speed is less than 6, then VRB will be reported.

WIND
METAR KSMP 301456Z AUTO 00000KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
If calm, then it will be reported as 00000KT

VISIBILITY
METAR KSMP 301456Z AUTO VRB06KT M1/4SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Automated stations use an M to indicate “less than”

VISIBILITY
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Visibility is reported in Statue Miles.
P6SM means visibility greater than 6 statue miles.

RVR
METAR KSMP 301456Z AUTO VRB06KT 1/2SM R32R/3000V4500FT SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
R denotes the group, 32R the runway, 3000V4500FT the visual range 3000 variable to 4500.

RVR
METAR KSMP 301456Z AUTO VRB06KT 1/2SM R32R/M0600FT SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
RVR is coded from 600’ to 6000’. P or M indicates Above or Below those limits (R32R/M0600FT)

PRESENT WX GROUP
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Intensity qualifiers: (-) = light, none = ( )
moderate, (+) = heavy.
Weather is inside a 5 mile radius.
VC for 5-10 mile radius.
See table 3-2 for descriptors.
BR is vis 5/8 to 6 miles, FG is less than 5/8.

PRESENT WX GROUP
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Descriptor qualifiers MI=shallow, PR=partial, BC=patches, DR=low drifting, BL=blowing, SH=showers, TS=t-storm, FZ=freezing.

PRESENT WX GROUP
METAR KSMP 301456Z AUTO VRB06KT 1/2SM TSB05E45 VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Thunderstorm began 5 min after the hour and ended 45 min after the hour.

PRESENT WX GROUP

SKY CONDITION
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
OVC = overcast, BKN = broken, SCT = scattered, FEW = few, SKC = from a human, CLR = from a machine at or below 12,000. OVC020 clouds are 2000 AGL. See table 3-3.

SKY CONDITION
Height is reported in AGL
Cloud type may be reported TCU, CB, ACC
VV = Vertical Visibility, VV001
Ceiling is broken or overcast
If the sky is obscured VV is the ceiling
Sky is broken into 8ths Table 3-3

Sky Cover
The abbreviation CLR will be used at automated stations when no layers at or below 12,000 feet are reported
The abbreviation SKC will be used at manual stations when no layers are reported.
Any layer amount less than 1/8 is reported as FEW.

SKY CONDITION CODING

TEMPERATURE/DEW POINT
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Temperature/Dew Point in Celsius
M = Minus

ALTIMETER
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Altimeter setting measured in inches of Hg 30.19

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Remarks are used to clarify the conditions specified in the body of the report. Checkout pg 3-18

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
AO2 = Precip discriminator, A01=No Precip discriminator
PK WND = Highest wind speed since the last METAR in direction, speed and time (PK WND 20032/15)
WSHFT = Wind shift and the time. If due to frontal passage then FROPA is entered (WSHFT 30 FROPA)
TWR VIS = Vis given by the tower (TWR VIS 1 1/2)
VIS 1/2V2 = Variable visibility
VIS NE 2 1/2 = Sector visibility
VIS 2 1/2 RWY 14L = Vis at a second location
OCNL LTGICCG NW, FRQ LTG VC, or LTG DSNT W

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Sea Level Pressure 1025.8 Add a 10 or a 9 whichever will bring the number closest to 1000
REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Pecip amount 8/100ths of an inch

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
6 hour precip amount. 6 is the group indicator, the following 4 digits the amount
.20 inches of precip
2.17 inches would code out to 60217

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T00221028 58004 TSNO $
Temperature Plus 2.2°C Dew Point Minus 2.8°C 1=minus, 0=plus
$ means maintenance is needed

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 TSNO
Pressure tendency 8=steady or increasing then decreasing by 0.04 hectopascals

REMARKS
METAR KSMP 301456Z AUTO VRB06KT 1/2SM SN FZFG VV001 M02/M03 A3019 RMK AO2 SLP258 P0008 60020 T10221028 58004 SHRAB05E15SHSNB20E55 TSNO
Rain showers began 0005 and ended 0015 then snow showers began 0020 and ended 0055

AWOS, ASOS, AMOS
Automated wx
Provides minute by minute wx data
Stations are strategically located in the runway complex
Uses same technique as humans do for pressure, temp, dew point, wind, and precip accumulation
For sky condition uses fixed location time averaging technique
Humans use fixed time spatial averaging technique

AWOS, ASOS, AMOS
4 MODES
1. Full time operation
2. Full time operation with local notams
3. Full time operation with manual augmentation and local notams
4. Manual operation
Broadcasts ground to air and telephone

AWOS, ASOS, AMOS
Ceiling and sky cover
Visibility
Temp dew point
Wind direction, speed and gusts
Altimeter setting
Remarks, density altitude, variable vis, variable wind direction
AMOS only gives info when asked by net.

Chapter 24
24.5 PIREPS/AIREPS

Aircraft Obs and Reports
There are 3 kinds
Pilot weather reports (PIREP)
Routine and urgent
Aircraft reports (AIREP)
Routine and urgent
Volcanic Activity Reports (VAR)
For aircraft encounters with ash and/or sulfur dioxide

AIREP
These can be reported by the pilot or by sensors onboard the aircraft
The AIREP format is used world wide
Automated equipment installed in commercial aircraft automatically make reports to ground stations
The PIREP format is a U.S. thing

PIREPS
The only means of getting:
1. Cloud tops
2. Icing
3. Turbulence
4. Layers
5. In-flight vis
They are available on the AviationWx.gov site

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
ICAO location Identifier

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Type of Report UA = Routine report, UUA = Urgent report (pg 3-32 for details)

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Location = MWH 070º radial, 15 NM out. OV YKM = directly over nav aid

PIREP
MWH UA /OV MWH070015-EAT250010 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Route description = from the MWH 070 rad at 15 NM to the EAT 250 rad at 10 NM

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Time report was taken in Zulu.

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Flight level = 37,000 feet. FL040 = 4,000 feet MSL

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Aircraft Type TP UNKN means type is unknown

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Sky cover = Overcast with bases at 4,000 tops at 8,000

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Flight Visibility in statute miles. FV99SM = visibility unrestricted See table 3-7 for restrictions to vis

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Temperature in ºC, M = minus

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Wind direction in mag velocity in knots = 320º at 52 kts

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Turbulence can be classified as Light, Moderate, Severe, and Extreme (Table 3-8)

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /IC LGT RIME /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Icing intensities trace, light, moderate, severe and type rime, clear, mixed. (Table 3-9)

PIREP
MWH UA /OV MWH070015 /TM 1448 /FL370 /TP B757 /SK OVC040-TOP080 /WX FV50SM /TA M58 /WV 32052KT /TB SMOOTH WITH OCSNL MOD CHOP /RM MOUNTAIN WAVE +/- 20K…LAST 30 MILES
Remarks clarify items in the body of the report. LLWS, TORNADO, TS, LTGIC (in cloud), LTGCC, LTGCG, LTGCA (cloud to air)

PIREP

PIREPS
All altitudes are MSL unless otherwise noted
Distance for visibility is in statute miles
Distance for everything else is in nautical miles
Time is in Zulu

Chapter 24
Section 24.6 Radar

Weather Surveillance Radar
WSR-88D
Weather Surveillance Radar – 1988 Doppler
AKA NEXRAD
Consists of 160 (01/24) radar installations
Observation times are not standard
Nor are they linked to other radar sites
So good for the time listed

Modes of Operation
Clear Air Mode
Most sensitive
Slowest rotation rate
Images update every 10 minutes
Precipitation Mode
Less sensitive
Faster rotation rate
Images update every 4 to 6 minutes

Echo Intensities
Colors represent echo intensities in dBZ
Scale goes from -30 (least) to 75 (most)
Check table 4-1 for ATC terminology based on echoes
Values below 15 dBZ are usually just clouds but may be dust, insects, pollen ect.
This means values above 15dBZ are probably precip, although may be virga
Snowfall intensity is not show by the table
Usually the higher the return the heavier the snowfall rate

Radar Mosaics
Multiple radar images combined
These may be base or composite
Skyvector.com has my favorite

Composite Reflectivity
Radar scans through multiple elevations
Gives a more complete vertical picture
When compared to the base reflectivity you can get an idea of the structure of the precip
Aircraft radar uses composite reflectivity

Base Reflectivity
Radar is aimed about half a degree above the horizon (0.5°)
Short range to 124 NM
Long range out to 248 NM

Base Reflectivity
Useful for:
Finding precip probably reaching the ground
The intensity of precip
Coverage of precip
When looped, movement of precip

Base Reflectivity
For stratiform precip look for:
Widespread coverage
Weak reflectivity
39 dBZs or less
Slow change when looped
For cumulus precip look for:
Small cells
Strong reflectivity
High dBZs
Can be fast moving and or dissipating

Base vs Composite Reflectivity
Especially useful for cumuliform cloud structures.
Allows you to develop a vertical picture of intensities

Radar Coded Message
The RCM replaced the RAREP, ROB, SD
Updated every 30 min
Based on the composite reflectivity
Includes the max echo top for each site
Can show errors when precip is far away

New Stuff
Product update to 5 min
Mosaicked Composite Reflectivity
Dual Polarization Radar
Better at determining what the precip is
Including Graupel (snow pellets) and
Hail

Terminal Doppler Weather Radar
Used for detection of
Wind shear (microbursts)
Precipitation
Winds aloft
There are 47 TDWR stations at bigger airports

Terminal Doppler Weather Radar
TDWR vs WSR-88D
Resolution is higher
TDWR 150 meters (500’) within 135 km (72NM) and 300 m (1000’) beyond 135 km
WSR-88D 250 m (820’)and 1 km (.5NM) for surveillance data
Beam width
TDWR .55 degrees
WSR-88D .95 degrees

Terminal Doppler Weather Radar
Normally the radar runs in monitor mode (VCP 90) until
A region of 20 dBZ echoes located within 24.3 NM from the associated airport with a nominal areal extent of 1.3 NM and an altitude of at least 1.3 NM AGL, or
The radar detects windshear or a microburst.
At which point the radar shifts into hazardous mode (VCP80) to achieve higher rates of data

Terminal Doppler Weather Radar
There are 3 categories of products available
General Products
Base Reflectivity, Base Velocity, Spectrum Width, Vertically Integrated Liquid, and the Velocity Azimuth Display (VAD) Wind Profile.
Precipitation Products
Estimated ground accumulated rainfall
Overlay Products
Detailed info for storm cells
Radar Messages
Information about the radar status and special product data

Chapter 24
Section 24.7 Satellite

GOES-R Series Satellites
GOES (Geostationary Environmental Satellite) sit at 22,000 miles out in geostationary orbit
GOES 16 was Launched in 11/19/2016
GOES-16 observes Earth from the coast of West Africa, to Hawaii, and everything in between.
GOES-17 was launched on 03/01/2018
GOES-17 will cover the west coast of the US and the Pacific to New Zealand
Is the single most important source of wx data

Spider Lightning

SATELLITE PICTURES
1. GOES Geostationary Environmental Satellite
visible imagery depends on height thickness and ability to reflect
infrared is heat radiation (high clouds less heat)
2. POES Polar Orbiter Environmental Satellite
They orbit from 124 to 1,240 miles up
Since they are closer the resolution is better, 5/8 of a mile
Not stationary so it can be several hours before it passes over an area

Satellite
3 different images:
Visible
GeoColor
Infrared
Water vapor

GeoColor
GeoColor is a multispectral product composed of true color (using a simulated green component) during the daytime, and an IR product at night.
During the day, the imagery looks approximately as it would appear when viewed with human eyes from space.
At night, the blue colors represent liquid water clouds such as fog and stratus, while gray to white indicate higher ice clouds, and the city lights come from a static database.

Visible Imagery
The amount of reflected light is referred to as albedo
The band across the top is the albedo in %
Visible imagery has the highest resolution of the 3
It approximates what the eye sees
High thin clouds are grey
Thicker more dense and snow appear whiter

Infrared Imagery
This is a measurement of temperature
The warmer the more energy
The colors are used to enhance readability
Sort of like the colors on the Coors light bottle enhance drinkability

Color IR

Infrared Imagery
Unenhanced decoding
Shades of grey are equated to temp in C
Land is warm
High clouds are cold duh!

Water Vapor
Displays the quantity of water vapor located from about 700mb (10,000 ft) to 200mb (FL390)
No direct relationship between temp on the chart and the temp of the clouds
Most useful for locations and movements of weather systems, jets and thunderstorms
Shades of red are very dry
Shades of blue or green are moist
Available 24 hours a day

Water Vapor Imagery
Displays the quantity of water vapor
Good for locating wx systems, jet and TS
Shades of red indicate very dry conditions
Shades of pink, blue and orange indicate lots of moisture
When used with other wx products it may give an idea of what type of clouds to expect

Using Them Together
Here is a cold winter storm in Jan of 2001
This one storm dumped precip from San Diego to Sandpoint ID
https://aviationweather.gov/gfa/#obs

Chapter 24
Section 24.8 Upper-Air Observations

Radiosonde Observations
A radiosonde is a small instrument package carried aloft by balloon
Measures pressure, temp, wind speed/direction and moisture
Ascends at about 1,000 ft/min
Launched twice daily at 11:00z and 23:00z
Takes about 90 minutes to reach 100,000 feet

Dropwindsonde
Dropped from weather research aircraft
Usually dropped over the ocean where meteorological information is highly lacking
Measures pressure, temperature, moisture, and the vertical distribution of horizontal wind speed and wind direction
They play an important role in improving the forecast of typhoon/hurricane track and intensity.

Chapter 24

Section 24.9 Aviation Weather Cameras

Aviation Camera Network
The Camera Network
https://weathercams.faa.gov/

WS DOT Airport Camera Network
https://wsdot.wa.gov/travel/aviation/airports-list/airport-cameras-map

Visibility Estimation
VEIA – Visibility Estimation through Image Analytics
Uses all views to estimate prevailing visibility
VWOS – Visual Weather Observation System
Has sensors in combo with the cameras that reports winds, cloud height, visibility, present weather, temperature, dewpoint, and pressure
Images updated every 10 minutes