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What does a Prognostic chart display?
Include the latest surface analysis with 12, 24, 36, 48 hour forecast
What is a surface analysis chart?
- Depicts pressure centers, front,s and barometric pressure lines
- Observed weather, the chart represents past history, and is not a forecast
What does next generation radar (NEXRAD) provide?
- Precipitation levels
- The radar energy is measured in dbz- decibels
- Displays areas of tornadoes, hail, wind shear, and microburst
What is a "hook echo?"
- NEXRAD does not directly observe tornadic circulation
- It displays a "hook echo" an echo that is considered an inactive tornado in the shape of a hook
What are NEXRAD characteristics of hail?
- Intense cores between 2-5 NM
- Very reflective values 55 dbz.
- Thunderstorms with strong updrafts, extensive vertical height, high liquid water content, large cloud drop sizes
How are microburst detected on NEXRAD?
- The density gradient of the descending air
- Particulate matter contained inside
- May not be detected beyond 20 NM
What does infrared (IR) satellite imagery provide?
Temperature differences between the cloud tops and the ground, as well as temperature gradations of cloud tops over the surface of the earth.
What does visible satellite imagery provide?
- Displays clouds and the earth reflecting sunlight back to the satellite sensors
- Used to determine the presence of clouds and type of clouds from shape and texture
On winds and temperature aloft chart, what does 9900 indicate?
winds are light and variable
On winds and temperature aloft chart, what does 7409 indicate?
- Subtract 50 from direction, add 100 to wind speed
- 240 at 109 knots
In what conditions would wind and temperature be left out of the wind and temperature aloft chart?
- Wind information is never forecasted for altitudes within 1500' of the surface
- Temperature information is never forecast within 2500' of the surface
- Temperature information is never forecast for the 3000' level
Describe a Aviation Severe Weather Watch Bulletin.
- Contain WW in the heading
- Issued on the progress of severe weather
- Times are local
What are Aviation Severe Weather Watch Bulletins issued for?
- Funnel clouds or tornadoes
- Severe thunderstorms, defined by frequent lightning and one or more of the following:
- Wind ≥ 50 knots
- Hail ≥ 3/4"
What is included in the body of a aviation severe weather watch?
- area of coverage
- effective time
- expected type of severe weather
- mean wind vector
- amplifying remarks deemed necessary
What is a severe weather forecast alert?
- a preliminary message issued to alert users that a severe weather watch bulletin (WW) is being issued
- Advise of significant weather that is potentially hazardous to all aircraft
- Valid up to 4 hours
- Covering an area of at least 3000 square miles
What are SIGMETs issued for?
- Severe or extreme non-convective turbulence, CAT not associated with thunderstorms
- Severe icing not associated with thunderstorms
- Widespread dust storms or sandstorms, lowering surface and/or visibilities to less than 3 miles
- Volcanic eruption and ash clouds
What is the first issuance of a SIGMET called?
Urgent SIGMET (UWS)
What is a convective SIGMET?
- Are issued only for thunderstorms and related convective phenomena over the conterminous US
- Valid for 4 hours
What weather would be issued a convective SIGMET (WST)?
- Lasting longer than 30 minutes:
- Line of thunderstorms
- Embedded thunderstorms
- Thunderstorm areas greater ≥ thunderstorm intensity of ≥ 4 with an area coverage of 40% or more
- Hail ≥ 3/4" and/or wind gust ≥ 50 knots
For a WST, a line of thunderstorms defined as?
Being at least 60 miles long with thunderstorms affecting at least 40% of its length
For a WST, embedded thunderstorms are defined as?
- occurring within and obscured by haze, stratiform clouds, or precipitation from stratiform clouds
- Visual or radar detection of the thunderstorm could be difficult or impossible
What is an AIRMET?
- Advises of weather other than convective activity but indicates conditions at intensities lower than those that trigger SIGMET
- Conditions must affect an area of at least 3000 square miles
- Wide spread IFR conditions affecting over 50% of the area or for extensive mountain obscuration
- Ceilings < 1000', visibility < 3 miles
Moderate turbulence or for sustained surface winds of 30 knots or more
For moderate icing or freezing level data
When is ATC required to solicit PIREPS?
- Whenever the following conditions are forecast:
- Ceilings ≤ 5000'
- Visibility ≤ 5 miles
- Thunderstorm related phenomena
- Light icing or greater
- Moderate turbulence or greater
- Wind shear
When are pilots required to submit a PIREP?
- In-flight when requested
- When unusual or unforecast weather conditions are encountered
- When weather conditions on an IFR approach differ from the latest observation
- When a missed approach is executed due to weather
- When wind shear is encountered on departure or arrival
- When volcanic activity is observed
- When hazardous activity is encountered
- When large concentrations of bird or wildlife are observed near the airport/airfield
What is a DD form 175-1?
- Flight weather briefing
- Prepared and used by local weather office to brief pilots on weather conditions both locally and along planned route of flight
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