Lesson 2-4
Weather Forecasting
Lesson Overview
The history of weather forecasting
 The types of instruments used in weather
forecasting
 The various types of communication methods
used to provide weather information
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Chapter 2, Lesson 4
The First Aviation Weather
Forecast -- 1918
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Weather forecasts done by US Weather Bureau
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Now called NOAA’s National Weather Service
Early meteorologists used primitive methods
Attached instruments to kites and tethered balloons
 Only data on temperature and wind direction
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First reports were used by pilots carrying mail
between New York and Chicago
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Mostly only provided local conditions -- not forecasts
Weather Reports Address
Safety Issues
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By 1920, half of airmail service pilots died on the job
Congress passed Air Commerce Act on 20 May 1926
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Directed US Weather Bureau to0 make air travel safer
Focus on safety also boosted commercial passenger business
Today U.S. has one of world’s most advanced aviation
weather forecasting systems
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Produces 4 million aviation
weather forecasts each year
Courtesy of USAF
Air Force Weather Agency
Army set up its first military weather service in 1917
 AFWA partners with NOAA’s National Weather
Service to improve weather science
 AFWA provides worldwide coverage today
 Since WWII, AFWA has provided hurricane
reconnaissance
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The Types of Instruments Used
in Weather Forecasting—Surface
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4 types of observations:
Surface
 Upper Air
 Radar
 Satellite
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Surface observations are generally in an
area within a 5-mile radius from an airport
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Data collected on wind, visibility, pressure,
temperature, dew point, sky conditions (cloud
cover
Instruments Used to Study
Surface Weather
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Thermometers -- Temperature
Barometers -- Pressure
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Aneroids -- flexible metal bellows that respond to changes in
atmospheric pressure
Psychrometer -- Relative Humidity
Anemometer -- Wind Speed
Surface Weather -- ASOS
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Automated Surface Observing System
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Joint program of NWS, FAA, and DoD
Our main surface weather observing network
Provides surface observations non-stop, every minute, 24
hours a day, 365 days a year
Computer-generated voice broadcasts
Can also provide broadcasts in print and over-the-phone
Limitations – can’t report weather:
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Over the horizon
Above 12,000 feet
Tornadoes
Freezing Drizzle
Snow Depth
Chapter 2, Lesson 4
Upper Air
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More challenging than surface observations
Data collected in two ways:
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1. Radiosondes
 Small instruments suspended from weather balloons
 Collect data such as air temperature, pressure, wind speed, and
wind direction
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2. Pilots
 Only real-time source of information regarding
turbulence, icing, and cloud heights
 Some aircraft also equipped with instruments that
can report weather data to dispatchers on the ground
VIDEO
Weather Balloon
Radiosonde
Radar
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An instrument that sends out and receives radio
waves (invisible electromagnetic waves)
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Reflectivity is the strength of a returned signal—to gauge a
storm’s intensity
On moving and fixed objects, radar can identify:
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Distance
Strength
Direction
Speed
Four Types of Radar
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1. Doppler—common name : WSR-88D NEXRAD
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Two modes of operation: Clear Air and Precipitation
More than 160 Doppler radars are scattered throughout the
United States and overseas
 Max Range of each radar is 250 miles
 Data is converted into brightly colored maps giving info
on distance, strength and velocity of weather fronts
 Can provide info on tornados to 13 minutes in advance
Run by the US Department of Commerce, DoD, and DOT
The heart of the Doppler operation is the Radar Operations
Center in Norman, Oklahoma
Doppler Radar
Four Types of Radar
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2. FAA terminal Doppler -- found at major airports
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Provides severe weather alerts and warnings to air traffic
controllers
Warns pilots of wind shear, gust fronts. Amd heavy
precipitation near airports (for takeoff and landing)
3. FAA airport surveillance
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Main purpose is to detect aircraft
Air Traffic Controllers also use it to know location and
strength of precipitation so they can divert aircraft around
severe weather
Four Types of Radar
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4. Aircraft airborne radar -- flown on aircraft
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Radar can spot a big thunderstorm as well as detect light
rainfall
Can also tell how big a storm is
VIDEO
Using Airborne Radar
Satellites
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The Geostationary Operational Environmental
Satellite (GOES)
Launched in 1975 by NASA for NOAA
Currently 4 satellites operate in geostationary orbits
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Satellites remain over the same part of the earth all the time
Used to track:
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Thunderstorms
Tornados
Fog
Mud Slides
Dust Storms, volcanoes, wild fires
GOES
Satellites
VIDEO
GOES-R Satellite
Satellite Weather Products
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SIGMETs (Significant Meteorological Information
 Can cover areas of at least 3000 square miles
 Provides data on weather that reduces visibility
to less than 3 miles
Severe and extreme turbulence
 Severe icing
 Widespread dust or sandstorms
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Chapter 2, Lesson 4
Satellite Weather Products
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AIRMETs (Airman’s Meterological Information)
 Weather advisories issued to modify earlier
forecasts and reports
 Especially vital to pilots of smaller aircraft or pilots
with limited experience
 Does not cover severe weather events like
SIGMETS
 Reports include:
Moderate icing and turbulence
 Winds of 30 knots or more
 Ceilings of less than 1,000 feet
 Visibility less than 3 miles
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VIDEO
NASA’s A-TRAIN
Weather Outlets
Purpose: Get the latest weather data to pilots
 Who: FAA, NOAA, NWS, Private Groups
 Outlets:
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AFSS: Automated Flight Service Station
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Main source for preflight weather reports
Briefing available 24 hours by phone
Tailors info for pilot’s route, type of aircraft, type of
flight (VFR or IFR), altitude, etc
Can also provide in-flight weather data
Weather Outlets
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Outlets (continued):
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TIBS: Transcribed Information Briefing Service
Briefings are prerecorded, quick rundown of weather
 Includes special announcement
 Does not replace fuller pre-flight briefings
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EFAS: En Route Flight Advisory Service
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Also called “Flight Watch”
Used once the pilot is airborne
One of best sources for current weather along a route
Limitation: Not available 24 hours a day
Weather Outlets
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Outlets (continued):
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HIWAS: Hazardous Inflight Weather Advisory Service
Broadcasts bad weather alerts 24 hours a day
 Broadcasts are just summaries
 Pilots would use other services if they want more
detailed info
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Types of Briefings
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Standard
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Most complete report used before departure
Provides an overall weather picture
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Adverse conditions; airport closings
Recommendation regarding VFR or IFR
Fronts and other major weather systems in area
Ceilings, winds, temperatures
Enroute weather forecasts
Destination weather at time of landing
NOTAMS: Notices to Airmen => airport closings and
restricted flight space (e.g., around DC area)
VIDEO
Standard Pilot
Weather Brief
Types of Briefings
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Abbreviated
Shortened version of the standard
 Used to update a standard brief you already have
 Add one or two weather items you don’t yet have
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Outlook
At least 6 hours in advance of your planned
departure time
 Can influence route, altitude, departure time, etc
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Current Weather Reports
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METARs: Aviation Routine Weather Reports
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PIREPs: Pilot Weather Reports
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Hourly reports of current surface weather
Wind direction and speed, visibility, strength and
location of precipitation and funnel clouds
Current upper air conditions such as icing
RAREPs: Radar Weather Reports
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Also known as SDs (Storm Detections)
Current readings of precip and thunderstorms
Forecast Weather Reports
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TAFs: Terminal Aerodrome Forecasts
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FAS: Area Forecasts
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Give picture of clouds, general weather, and visual
conditions over large area (several states)
SIGMETs and AIRMETs
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—cover a five-mile radius around airports
See earlier slides
FDs: Winds and Temperature Aloft Forecasts
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Predict winds and temperatures for specific spots
based on upper air readings from radiosondes
Weather Charts
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Surface analysis chart:
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Assesses current surface weather
Shows areas of high and low pressure, fronts, temps, dew
points, wind directions/speed, visual obstructions
Weather Charts
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Radar summary chart:
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Marks precipitation cells only; published every hour
Marks areas of severe weather (tornadoes, thunderstorms)
with heavy dashed lines
Weather Charts
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Significant weather prognostic charts:
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Forecast weather—does not provide current weather
Predicts turbulence, freezing levels, and IFR weather
Standard Uniform
Altimeter Setting
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How does an altimeter work?
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It’s a simple barometer set to convert to pressure
reading to the atmospheric altitude
Average sea-level pressure is 29.92
 Above 18,000 feet, all planes set altimeter to
have sea-level pressure at 29.92
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This ensures aircraft will know what altitude they
are in relation to other aircraft
 What would happen if an aircraft used something
different than 29.92, say 28.86 when they took off?
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Atmospheric Pressure and
Temperature Table
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Atmospheric Pressure Table
Next….
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Done – weather forecasting
Next – the effects of weather on
aircraft
Chapter 2, Lesson 4
Courtesy of AP Photo.