Welcome Guest. Sign in or Signup

4 Answers

Significant Weather Prognostic Charts

Asked by: 6231 views ,
Commercial Pilot, Flight Instructor, General Aviation, Instrument Rating, Light Sport Aircraft, Private Pilot, Student Pilot

I have the following questions on Significant Weather Prognostic Charts: 1) What does the valid time mean? If a chart shows a valid time of 18Z, does it mean the chart is valid till 18Z or it is valid for 12/24 hours from 18Z? Does the same apply to other charts such as a TAF for example? 2)Why are the tops of moderate/greater turbulence shown and not the base? 3) Why does it contour the height of the highest freezing level in 4000 ft increments and not the lowest?

Ace Any FAA Written Test!
Actual FAA Questions / Free Lifetime Updates
The best explanations in the business
Fast, efficient study.
Pass Your Checkride With Confidence!
FAA Practical Test prep that reflects actual checkrides.
Any checkride: Airplane, Helicopter, Glider, etc.
Written and maintained by actual pilot examiners and master CFIs.
The World's Most Trusted eLogbook
Be Organized, Current, Professional, and Safe.
Highly customizable - for student pilots through pros.
Free Transition Service for users of other eLogs.
Our sincere thanks to pilots such as yourself who support AskACFI while helping themselves by using the awesome PC, Mac, iPhone/iPad, and Android aviation apps of our sponsors.

4 Answers



  1. Lucas on Oct 15, 2014

    Here is a video on the FAA questions on the Prog Chart. Maybe it can help answer some of your questions

    http://youtu.be/7D6T7D4mojY

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  2. psequeira on Oct 21, 2014

    Thank you Lucas

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  3. psequeira on Oct 22, 2014

    I still did not find my answer through the video Lucas

    0 Votes Thumb up 0 Votes Thumb down 0 Votes



  4. Lucas on Oct 29, 2014

    The valid time in a Prog Chart is when the forecast starts so it would be a 12 hour forecast starting at 18Z.

    A TAF displays both the issue time and valid time:
    KEWR 291121Z 2912/3018
    For Newark issued the 29 of October at 1121 Zulu and valid from the 29th at 12Z to the 30th at 18Z.

    The bases of the turbulence are also shown at times the number on top shows the TOPs and the number underneath shows the BASEs of the turbulence.

    for the freezing levels take a look at this:

    The surface freezing level is depicted by a zigzag line and labeled “SFC.” The surface freezing level separates above-freezing from below-freezing temperatures at the Earth’s surface. Freezing levels aloft are depicted by thin, short dashed lines. Lines are drawn at 4,000-foot intervals beginning at 4,000 feet and labeled in hundreds of feet. For example, “80” identifies the 8,000-foot contour. Freezing level heights are referenced to MSL. The lines are discontinued where they intersect corresponding altitudes of the Rocky Mountains. The freezing level values for locations between lines is determined by linear interpolation. For example, the freezing level midway between the 4,000 and 8,000 foot lines is 6,000
    feet. Areas with forecast multiple freezing levels have lines drawn to the highest freezing level. For example, with freezing levels forecast at 2,000, 6,000, and 8,000 feet, the analysis is drawn to the 8,000 foot value. Notice that not all freezing levels are identified with a multiple freezing level event.
    Information about the 2,000- and 6,000-foot freezing levels in this example would not be displayed. Surface-based multiple freezing levels are located over areas which have below-freezing temperatures at the surface and above-freezing temperatures within at least one layer aloft. Freezing rain and freezing drizzle (freezing precipitation) are associated with surface-based multiple freezing levels. The 11-5 intersection of the surface freezing level line and freezing level contours encloses an area with surface based multiple freezing levels.

    Cheers

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes


Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.