David Young
Technical Subject Areas
1. Subject – Weather Services.
2. Introduction – The weather strongly affects whether or not a pilot decides to make a
flight or not. However, looking outside to figure out the weather is not good enough.
The ICAO and the WMO have created standardized weather services that, when looked
at together, can give the pilot a full picture of what the weather is doing and what it will
do in the future. Knowing what each of these weather services provide and where to get
them will help you to become a safer, more competent pilot.
3. Outline –
a. Explain the necessity of a good preflight briefing.
b. Discuss sources that contain weather information.
i. 1-800-wx-brief, Duat.com, adds.aviationweather.noaa.gov, FSS.
c. Discuss overall weather-picture sources.
i. Explain what TIBS, PATWAS, TWEB, FAs, and Weather Channel provide.
d. Discuss how to find out weather information at an airport.
i. Discuss what a METAR is.
1. Explain how to read it.
2. Explain how long it is good for.
ii. Discuss what a TAF is.
1. Explain how to read it.
2. Explain how long it is good for.
iii. Discuss airport weather advisory services.
1. Explain what ATIS, ASOS, and AWOS provide.
2. Give an example of an ATIS broadcast.
e. Discuss the different types of weather reports and forecasts.
i. Explain what PIREPs, SDs, WWs, WAs, WSs, WSTs, CWAs, FDs, and ACs
provide.
f. Discuss the different weather charts.
i. Explain what Surface Analysis Charts, Weather Depiction Charts, Radar
Summary Charts, Significant Weather Prognostic Charts, Composite
Moisture Stability Charts, and Constant Pressure Analysis Charts
provide.
g. Discuss in-flight weather advisory services.
i. Explain what EFAS and HIWAS provide.
4. Contents –
a. Weather affects the way our aircraft handles and the kind of stresses we put on
our aircraft. Knowing what the weather is doing will help us understand what we
could be getting ourselves into by taking a flight.
Young 2, III-B
i. Doing a thorough preflight weather briefing will ensure that you will have
the most up-to-date weather information along your route of flight.
ii. This can help you anticipate what may encounter enroute.
b. There are a lot of different sources for weather briefings, but there are a few that
stand out: 1-800-wx-brief, Duat.com, and adds.aviationweather.noaa.gov, and
FSS.
i. 1-800-wx-brief – a phone service that briefs you on weather and NOTAMs
as well as a service that allows you to file and close flight plans.
1. When using it, simply stay on the line and choose what you would
like on the phone-menu.
2. If talking to a real-life briefer, tell them as specifically as possible
what you would like to know, and they will help you out.
ii. Duat.com – a website that can give you all the pertinent weather and
NOTAMS along your route of flight, as well as a website that allows you
to file and close flight plans.
1. This site is very useful for seeing weather graphics as well as
textual descriptions of the weather.
iii. Adds.aviationweather.noaa.gov – a great resource for visual and textual
representations of aviation weather.
iv. Flight Service Station (FSS) – an in-flight service that briefs you on
weather and NOTAMS as well as a service that allows you to file, open,
and close flight plans.
1. Find the nearest FSS frequency and tune the frequency(s) into your
radio(s).
a. Be sure that on your initial call-up, you tell them what
frequency(s) you are transmitting and receiving over.
2. Use it the same way you would 1-800-wx-brief.
For overall weather information:
c. Telephone Information Briefing Service (TIBS) – provides a continuous telephone
recording of meteorological and/or aeronautical information.
i. Each TIBS will contain area or route briefings, airspace procedures,
special announcements, METARs, TAFs, and winds/temperatures aloft
forecasts.
ii. You may call 1-800-wx-brief for TIBS.
d. Pilot’s Automatic Telephone Weather Answering Service (PATWAS) – a
recorded telephone local forecast (usually within a 50 NM radius).
e. Transcribed Weather Enroute Broadcast (TWEB) – provides continuous
aeronautical and meteorological information on L/MF and VOR facilities.
Young 3, III-B
i. This contains weather information in route format. For example, a TWEB
from the Chicago area to Moline airport is as follows: 217 TWEB 240214
KCHI – KMLI.
=
ALL HGTS AGL EXC TOPS.
P6SM SCT100 SCT250 .
1. This should be read as “TWEB number 217 from the Chicago-land
area to Moline, IL, all heights in AGL except for cloud tops,
visibility is greater than 6 statute miles, scattered cloud layers at
10,000 ft AGL and 25,000 ft AGL.
ii. You can access TWEBs through VOR facilities or through the internet
(adds.aviationweather.noaa.gov has TWEBs).
f. Area Forecast (FA) – provides a forecast of visual meteorological conditions
(VMC), clouds, and general weather conditions over an area the size of several
states.
i. FAs are issued three times a day by the Aviation Weather Center (AWC)
for each of the six areas of the contiguous 48 states.
ii. There are four parts to an FA: Communications and Product Header,
Precautionary Statements, Synopsis, and VFR Clouds and Weather.
1. Communications and Product Header – identifies the office for
which the FA is issued, the date and time of issuance, the product
name, the valid times, and the states and/or areas covered by the
FA.
2. Precautionary Statements – always provides the same precautions
to you in to help you understand specifically what is meant in the
FA.
a. You are referred to AIRMET Sierra for IFR conditions and
mountain obscurations.
b. All indicated thunderstorms contain severe or greater
turbulence, severe icing, low-level wind shear, and IFR
conditions.
c. Non-MSL heights are denoted by AGL or CIG.
3. Synopsis – a brief summary of the location and movement of
fronts, pressure systems, and other circulation features for an 18hour period.
a. References to low ceilings and/or visibilities, strong winds,
or any other phenomena the forecaster considers useful
may also be included.
4. VFR Clouds and Weather (VFR CLDS/WX) – contains a 12-hour
specific forecast, followed by a 6-hour categorical outlook giving a
total forecast period of 18 hours.
a. The breakdown is usually by states or geographical areas
i.e. eastern Illinois or New England.
Young 4, III-B
b. The specific forecast section gives a general description of
clouds and weather which cover an area greater than 3,000
square miles and are significant to VFR flight operations.
c. Surface visibility and obstructions to vision are included
when the forecast visibility is 3 to 5 statute miles.
d. Precipitation, thunderstorms, and sustained winds of 20 kts
or more are always included when forecasted.
e. Occasional (OCNL) is used when there is greater than a
50% probability of a phenomenon, but for less than ½ the
forecast period.
iii. Amended Area Forecasts are issued as needed, and their first line will
always contain “AMD.”
g. Weather Channel – a TV channel and website (weather.com) that provides
general weather conditions that are useful to the general public.
i. The radar maps that the Weather Channel provides may prove helpful to
help you understand the big picture i.e. where is the precipitation/how
severe it is.
For weather information at an airport:
h. Aviation Routine Weather Report (METAR) – contains information at a specified
location. Such information includes: temperature, dew point, wind, precipitation,
amount of precipitation, cloud cover and heights, visibility, barometric pressure,
and weather in the vicinity.
i. METARs are usually issued every hour, approximately 55 minutes past
the hour.
1. They are made with information collected at approximately 30
minutes past the hour.
ii. There are two types of METARs: special and routine.
1. Special (speci) – METAR issued when there is a significant
deterioration or improvement in airport weather conditions. They
are issued between two scheduled METARs.
2. Routine – METAR issued at the normal issuance times.
iii. An example of a METAR is as follows: METAR KCMI 051853Z 04011KT
1/2SM VCTS SN FZFG BKN003 OVC010 M02/M02 A3006 RMK AO2
TSB40 SLP176 P0002 T10171017=.
1. This is broken into several sections separated by spaces (except for
the temperature and dew point, which are separated by a “/”).
2. These sections are: type of METAR, airport identifier, date and
time of issuance, wind direction and speed (in knots), prevailing
Young 5, III-B
visibility (in statue miles), weather in the vicinity, precipitation,
cloud coverage and height (in hundreds of feet AGL),
temperature/dew point (in degrees Celsius), altimeter setting (in
inches of mercury), and remarks.
a. The remarks section is broken into the type of precipitation
sensor, when severe weather began, the amount of
precipitation, and the exact temperature/dew point.
b. The above METAR should be read as follows: routine
METAR for Champaign, issued on the 5th day at 1853
Zulu, winds out of 040 at 11 kts, ½ statute mile visibility,
thunderstorms in the vicinity, freezing fog, broken cloud
layer at 300 ft AGL, overcast cloud layer at 1,000 ft AGL,
temperature minus 2º C, dew point minus 2º C, altimeter
setting 30.06 “ Hg, remarks automatic precipitation
discriminator is being used, thunderstorms began at 40
minutes past the hour, sea level pressure is 1017.6
millibars, .02 inches of liquid precipitation in the past hour,
the temperature is minus (as indicated by the 1 being the
first number) 1.7º C, and the dew point is minus 1.7º C.
i. Terminal Aerodrome Forecast (TAF) – a concise statement of the expected
meteorological conditions within a 5-statue mile radius from the center of an
airport’s runway complex during a 24-hour time period.
i. They are routinely issued every 6 hours.
ii. They use the same weather code as found in METARs.
iii. There are four different forecast groups in a TAF: from, becoming,
temporary, and probability. Appended to each of these forecasts groups
will be the times when the forecast becomes valid, or in the case of
probability, the probability (in percent) of the following weather
occurring.
1. From (FM) – used when rapid and significant changes, usually
occurring in less than one hour, in prevailing conditions is
expected.
2. Becoming (BECMG) – used when a gradual change in conditions
is expected over a period not to exceed two hours. It occurs at an
unspecified time during the forecast.
3. Temporary (TEMPO) – used for temporary fluctuations of wind,
visibility, weather, or sky condition that are expected to last for
generally less than an hour at a time, and expected to occur during
less than half the time period.
Young 6, III-B
4. Probability (PROB) – used when the occurrence of thunderstorms
or precipitation is in the 30% to less than 40% or 40% to less than
50% range, respectively.
iv. An example of a TAF is as follows:
KCMI 111140Z 111212 13012KT P6SM BKN100 WS020/35035KT TEMPO
1214 5SM BR
FM1500 16015G25KT P6SM SCT040 BKN250
FM0000 14012KT P6SM BKN080 OVC150 PROB40 0004 3SM TSRA
BKN030CB
FM0400 14008KT P6SM SCT040 OVC080 TEMPO 0408 3SM TSRA
OVC030CB BECMG 0810 32007KT
1. The above should be read as follows: TAF at Champaign issued
on the 11th day at 1140Z, valid from 1200 Zulu on the 11th to 1200
Zulu tomorrow, visibility is plus 6 statute miles (forecasts will
NEVER forecast anything greater than 6 SM. Instead, they just
say “P6SM.”), broken cloud layer at 10,000ft AGL, wind shearing
up to and including 2,000 ft AGL out of 350º at 35 kts, temporarily
5 statute mile visibility with mist (“BR”) at 1214 Zulu.
2. From 1500 Zulu: winds out of 160º at 15 kts gusting to 25 kts,
visibility is greater than 6 statute miles, scattered cloud layer at
4,000 ft AGL, and broken cloud layer at 25,000 ft AGL.
3. From 0000 Zulu: winds out of 140º at 12 kts, visibility greater
than 6 statute miles, broken cloud layer at 8,000 ft AGL, overcast
cloud layer at 15,000 ft AGL, 40% probability that at 0004 Zulu
there will be 3 statute mile visibility with thunderstorms and rain
with a broken cloud layer of cumulonimbus clouds at 3,000 ft
AGL.
4. From 0400 Zulu: winds out of 140º at 8 kts, visibility greater than
6 statute miles, scattered cloud layer at 4,000 ft AGL, overcast
cloud layer at 8,000 ft AGL, temporarily 3 statute mile visibility
and thunderstorms and rain and overcast cloud layer of
cumulonimbus clouds at 3,000 ft AGL at 0408 Zulu, becoming
winds out of 320º at 7 kts at 0810 Zulu.
j. Automatic Terminal Information Service (ATIS) – continuous recorded broadcast
of weather information, active runways, available approaches, and NOTAMs.
i. Pilots generally tune into ATIS before arriving at an airport to get a feel
for conditions at the airport before they arrive.
ii. ATIS broadcasts are updated hourly (usually 55 minutes past the hour) or
as needed (if weather or runways/approaches available changes).
1. Each broadcast is given a phonetic letter designation (i.e. “Delta”)
to help pilots know which broadcast is most recent.
Young 7, III-B
iii. ATIS is available on very high frequency (VHF) radio frequencies, and
they are listed in the AFD (for the airports that have ATIS as not all do),
on sectionals, and on approach plates.
iv. An example of an ATIS broadcast is as follows: “Champaign Willard
Airport information X-Ray, time one three five five Zulu, wind two seven
zero at eight, gusting one five, visibility seven miles, one thousand one
hundred scattered, two thousand five hundred broken, temperature one
five, dew point ten, altimeter two niner niner four. ILS 32R approach in
use, landing and departing three two right, three two left, advise on initial
contact, you have X-Ray.”
1. Decoding an ATIS broadcast is pretty simple. All that is required
is that you put the numbers together i.e. one five becomes 15.
k. Automated Surface Observing System (ASOS) – similar to ATIS, but it consists of
an automated system that updates weather information at an airport, hourly.
l. Automated Weather Observing System (AWOS) – similar to ASOS, but it
generally provides less information than ASOS can provide (check the AIM for a
side-by-side comparison).
i. The AWOS broadcasts are updated about every twenty minutes.
Weather reports and forecasts:
m. Pilot Report (PIREP) – a report made by a pilot that gives the actual weather
conditions in flight.
i. They are only issued when a pilot makes a report.
ii. There are two types of PIREPS: urgent and routine.
1. Urgent (UUA) – contains severe weather reports such as tornadoes,
severe to extreme turbulence, severe icing, hail, volcanic ash, low
level wind shear, etc…
2. Routine (UA) – contains weather phenomenon that are not as
severe as those listed above.
iii. An example of a PIREP is as follows: UA /OV CMI090045/TM
1600/FL100/TP C172/SK BKN024-TOP032/TA M12/IC LGT-MOD RIME
055-080.
1. PIREPS contain the following information, in this order: type of
PIREP (UUA/UA), location (/OV), time (/TM), altitude (/FL),
aircraft type (/TP), sky cover (/SK), flight visibility and weather
(/WX), temperature (/TA), wind (/WV), turbulence (/TB), icing
(/IC), and remarks (/RM).
2. This should be read as “routine PIREP 45 miles east of Champaign
VOR, at 1600 Zulu at 10,000 ft MSL, type of aircraft is a Cessna
Young 8, III-B
172, broken cloud layer beginning at 2,400 ft MSL and with tops at
3,200 ft MSL. Outside air temperature is minus 12º C, light to
moderate rime icing is reported between 5,500 and 8,000 ft MSL.”
iv. PIREPs are available on DUATs, adds.aviationweather.noaa.gov, 1-800wx-brief, and FSS.
v. To file a PIREP, find the frequency of the FSS nearest to you, and give
them as much information as you can list above in (1).
n. Radar Weather Report (SD) – includes type, intensity, and location of the very
tops of precipitation.
i. These tops are called “echo tops,” and they are the upper-most altitude
that precipitation is falling from.
ii. In all honesty, it is easier to look at a radar summary chart to help you
visualize the information contained in a SD, but it important that you
know how to read an SD in case you don’t have access to such tools.
iii. An example of an SD is as follows: ILX 1135 AREA 4TRW+9/100
130/75 50W C2425 MT310 at 45/47 AUTO.
1. SDs contain the following information, in this order: location
identifier and time of radar observation (ILX is Lincoln, IL – the
closest station in central IL), the echo pattern (LN for a line,
AREA for a group of echoes of similar type, and CELL for an
isolated echo), coverage, in tenths, of precipitation in the defined
area, type and intensity of weather (- means light, (none) means
moderate, + means heavy, ++ means very heavy, X means intense,
and XX means extreme), azimuth and range in NM from the radar
site of points that define the echo, dimension of the echo, cell
movement, and maximum tops.
2. This should be read as “Lincoln, IL automated SD at 1135 Zulu.
An area of echoes 4/10 coverage, containing thunderstorms and
heavy rain showers. Area is defined by points (from ILX radar
site) at 9 degrees, 100 NM and 130 degrees, 75NM. These points,
plotted on a map and connected with a straight line, define the
center line of the echo pattern. The width of the area is 50 NM (25
NM on either side of the center line). The cells are moving from
240 degrees at 25 kts. Maximum top is at 31,000 ft MSL located at
45 degrees and 47 NM from ILX.”
iv. After the radar identifier, the following words have the following
definitions:
1. PPINE – radar is operating normally but there are no echoes being
detected.
2. PPINA – radar observation is not available.
3. PPIOM – radar is inoperative or out of service.
Young 9, III-B
4. AUTO – automated radar report from WSR-88D.
v. SDs are issued whenever there are echo returns.
vi. SDs are available on Duat.com.
o. Severe Weather Watch Bulletin (WW) – defines areas of possible severe
thunderstorms or tornado activity.
i. Severe thunderstorm watch criteria are expected ¾” hail or larger and/or
wind gusts 50 kts or greater.
ii. Tornado watch describes areas where the threat of tornados exists.
iii. WWs will be announced by ARTCC facilities one time (unless an
emergency exists) unless there is a HIWAS nearby.
iv. WWs are unscheduled and issued as required.
p. AIRMET (WA) – an in-flight advisory of significant weather with intensities
lower than that which are required to issue a SIGMET.
i. AIRMETs issued every 6 hours.
1. Unscheduled updates are issued as necessary.
ii. There are three types of AIRMETs: Sierra, Tango, and Zulu.
1. Sierra (S) – IFR conditions and/or extensive mountain
obscurations exist.
2. Tango (T) – moderate turbulence, sustained surface winds of 30
kts or greater, and/or non-convective low-level wind shear.
3. Zulu (Z) – moderate icing.
iii. You can remember these by remembering T is for Turbulence, Z is for
freeZing, and S is Somehow for IFR.
iv. These can be found on Duat.com, 1-800-wx-brief, and
adds.aviationweather.noaa.gov.
q. SIGMET (WS) – advises of non-convective weather that is potentially hazardous
to all aircraft.
i. SIGMETs are unscheduled products that are valid for four hours.
1. Conditions associated with hurricanes are valid for six hours.
2. Updates are issued as necessary.
ii. SIGMETs are issued for any of the following reasons: severe icing not
associated with thunderstorms, severe or extreme turbulence or clear air
turbulence (CAT) not associated with thunderstorms, dust storms or
sandstorms lowering surface or in-flight visibilities to below three miles,
and volcanic ash.
iii. SIGMETs are announced once (unless it’s an emergency) by ARTCC
facilities unless a HIWAS is nearby.
iv. These can be found on Duat.com, 1-800-wx-brief, and
adds.aviationweather.noaa.gov.
Young 10, III-B
r. Convective SIGMET (WST) – advises of severe convective activity associated
with strong thunderstorms.
i. Three convective SIGMET bulletins are issued every 55 minutes past the
hour: western (w), central (c), and eastern (e).
ii. Each convective SIGMET is valid for 2 hours.
1. Updates are issued as necessary.
iii. The thunderstorms must affect 40% of an area of at least 3,000 square
miles, or if in a line, be at least 60 NM long.
iv. The thunderstorm can also be severe or embedded and affecting an area
for at least 30 minutes.
v. These can be found on Duat.com, 1-800-wx-brief, and
adds.aviationweather.noaa.gov.
s. Central Weather Advisory (CWA) – an aviation warning for use by air crews to
anticipate and avoid adverse weather conditions in the enroute and terminal
environments.
i. Because CWAs are not useful as a flight planning aid, we will not discuss
them.
t. Wind and Temperatures Aloft Forecast (FD) – a forecast for the winds and
temperatures at specified altitudes.
i. As a pilot, it is useful to know what the winds will be doing when you are
at altitude. Knowing what the temperature aloft is helps a pilot avoid icing
in freezing temperatures.
ii. Forecasts are made twice daily at 0000 Zulu and 1200 Zulu.
iii. Be sure to read the time of use for the FD you are looking at.
iv. Find the altitude you want to know the information for, and read the string
of information.
1. For example, if the string says 2726-09, translate this as “winds
270 degrees as 26 kts, temperature is minus 9 degrees Celsius.”
2. 9900+00 means winds light and variable, temperature is 0º C.
3. 850552 means 350 degrees (subtract 50 from 85 whenever the first
two numbers are greater than 36) at 105 kts (add 100 kts to the
number after 85), temperature is minus 52º C.
v. These can be found on Duat.com, 1-800-wx-brief, and
adds.aviationweather.noaa.gov.
u. Convective Outlook (AC) – a national forecast of thunderstorms. There are two
forecasts: day 1 and day 2.
i. These forecasts describe areas in which there is a slight, moderate, or high
risk of severe thunderstorms.
ii. To be a severe thunderstorm, the storm must have at least 50 kts surface
wind or hail with a diameter of at least ¾”, or tornados.
Young 11, III-B
iii. The times of issuance on day 1 are 0600Z, 1300Z, 1630Z, 2000Z, and
0100Z.
iv. The AC is updated at 1730Z on day 2.
v. These can be found on Duat.com, and adds.aviationweather.noaa.gov.
Weather charts:
v. Surface Analysis Chart – a computer-generated chart with frontal analysis.
i. These are the typical frontal charts you may see on the news (refer to
Figure A).
ii. They are transmitted every 3 hours.
iii. They contain surface wind direction and speed, temperature, dew point,
position of fronts, areas of high or low pressure, and obstructions to
vision.
iv. “L” denotes a low pressure center whereas “H” denotes a high pressure
center.
v. Areas of equal pressure are connected by isobars.
vi. Predominant wind as well as sky cover are also denoted by the circle-andbarb symbols.
vii. Troughs, or lines of low pressure, are shown by dotted brown lines.
viii. Ridges, or lines of high pressure, are not depicted.
ix. The surface analysis chart helps us determine the overall picture of fronts
and weather.
x. These can be found on Duat.com and adds.aviationweather.noaa.gov.
w. Weather Depiction Chart – a computer-generated chart composed by METARs.
It contains cloud heights, weather, obstructions to visibility, and current flight
rules (refer to Figure B).
i. It is transmitted at 3-hour intervals, and is valid at the time of the plotted
data.
ii. Use this chart to help you determine the closest VFR conditions along
your route of flight as well as the general height of the clouds along your
route.
iii. These can be found on Duat.com.
x. Radar Summary Chart – a computer-generated graphical display of SDs. It
shows precipitation as well as intensity, coverage, echo top, and cell movements.
i. The more contours a cell has, the more intense it is.
1. The center of the contours is the most intense.
ii. The echo tops are reported in hundreds of feet MSL.
1. If you see “220,” the maximum tops are at 22,000 ft MSL.
Young 12, III-B
iii. The cells’ movements are determined by an arrow, which will point in the
direction of movement.
1. A number at the end of the arrow is the cell’s speed in knots.
iv. Use this chart to help determine where precipitation, especially intense
precipitation exists, and where it will be moving.
v. These are available on Duat.com and adds.aviationweather.noaa.gov.
y. Significant Weather Prognostic Chart – portrays forecasts of selected weather
conditions at specified valid times.
i. There are two types of Sig. Prog. Charts: U.S. low-level and U.S. highlevel.
1. U.S. low-level – a one day forecast of significant weather from the
surface to FL240 (refer to Figure C).
a. It has two forecast periods: 12 hours and 24 hours.
2. U.S. high-level – a one day forecast of significant weather from
above 24,000 ft to FL600 (refer to Figure D).
a. This covers a large portion of the Northern Hemisphere and
some of the Southern Hemisphere.
b. It gives the heights of cumulonimbus clouds.
i. If the bases are below 24,000 ft, then “XXX” is
used as the base.
ii. These are available on Duat.com and adds.aviationweather.noaa.gov.
z. Composite Moisture Stability Chart – provides information on the stability and
relative humidity of the air throughout the U.S.
i. It is updated twice daily (once at 0000Z and the other at 1200Z).
ii. K Index (KI) – provides the moisture and stability information.
1. Ranges from high positive values to low negative values.
2. A high positive KI implies moist and unstable air (usually bad).
3. A low or negative KI implies dry and stable air (usually good).
iii. Lifted Index (LI) – a measure of the atmospheric stability.
1. It is obtained by hypothetically displacing a parcel of surface air
upward to 500 millibars and evaluating its stability.
2. LI can be positive, negative, or zero.
3. If the LI is positive, it is stable (good).
4. If the LI is negative, it is unstable (bad).
iv. A combination of a high KI and a low LI means conditions for a
thunderstorm.
v. Use this chart to help determine where thunderstorms are and where they
may show up.
vi. These are available on Duat.com.
Young 13, III-B
aa. Constant Pressure Analysis Chart – provides information about the observed
temperature, wind, and temperature/dew point spread at a specified altitude.
i. This information is gathered by weather balloons that are released twice
daily (once at 0000Z and the other at 1200Z).
ii. Isotherms – lines that connect areas of similar temperature.
iii. Use this chart to help determine the wind and temperature aloft.
In-flight weather advisories:
bb. Enroute Flight Advisory Service (EFAS) – an in-flight briefing that may be used
to update your current weather information.
i. It is available for aircraft between 5,000 AGL and 17,500 MSL on 122.0.
ii. It is also known as “Flight Watch.”
iii. Although it is not meant as a complete briefing, it can help a pilot to
understand what the weather will be like ahead of him.
1. This makes EFAS especially useful for longer flights.
cc. Hazardous In-Flight Weather Advisory Service (HIWAS) – a continuous
broadcast of advisories including AWWs, SIGMETS, convective SIGMETS,
CWAs, AIRMETs, and urgent PIREPs.
i. ARTCC will announce a HIWAS update one time.
ii. Otherwise, you may tune into HIWAS over a VOR.
1. Not all VORs have HIWAS. Only those with the little “H” in the
corner are capable of providing HIWAS.
iii. Use HIWAS to help stay informed on possible severe weather along your
route of flight.
5. Evaluation –
a. The student can identify which sources to go to for what information.
b. The student knows how often each service is updated and how to access it.
c. The student can read/interpret each chart or textual description.
6. References –
a. Aviation Weather Services
Young 14, III-B
Figure A
Young 15, III-B
Figure B
Figure C
Young 16, III-B
Figure D