The “categorical outlook” is a very general description of ceiling and visibility conditions contained in the Area Forecast. How can we use this extremely broad description to make a good go / no-go decision?
FIRST … THE TERMS
The categorical outlook describes cloud ceiling and visibility requirements in one of four ways:
- VFR. “Visual flight rules,” more accurately “visual meteorological conditions (VMC)” means that cloud ceilings are greater than 3000 feet (above ground level, or AGL) and visibility is greater than 5 miles.
- MVFR. “Marginal VFR” describes weather with ceiling 1000 to 3000 feet AGL and/or visibility 3 to 5 miles.
- IFR. “Instrument flight rules” denotes a ceiling 500 to (but not equaling) 1000 feet AGL and/or visibility 1 to less than 3 miles.
- LIFR. “Low IFR” warns of a ceiling less than 500 feet AGL and/or visibility less than 1 mile.
INTO THE LINGO
MVFR, IFR and LIFR will be amended with the cause of the restriction. The contraction CIG attached to the categorical outlook means that cloud ceiling height warrants the less-than-VFR description.
EXAMPLE — MVFR CIG.
METAR/TAF codes like RA (rain), SN (snow), F (fog), FU (smoke) or HZ (haze) are added when the restriction relates to that phenomenon.
EXAMPLE — IFR RA.
When both ceiling and visibility meet categorical definitions both codes will be used.
EXAMPLE — LIFR CIG HZ.
Any time the wind or wind gusts will be expected to be 25 knots or more the code WIND is added.
EXAMPLE — VFR WIND.
As always, there are some “tricks” to interpreting and using the categorical outlook:
- As part of the Area Forecast (FA), the categorical outlook does not describe conditions as they actually exist, but instead as they are expected to form or continue into the forecast period.
Translation: The farther the time of your flight from the issue of the FA, the less accurate it may be.
- Also, since the FA covers wide geographic areas, the categorical outlook may not accurately describe conditions at any one point or along a particular route within that area.
Translation: Weather may be locally better or worse than the categorical outlook describes.
REAL WORLD EXAMPLE: I live in a valley between the Smoky Mountains and the Cumberland Plateau in eastern Tennessee. The categorical outlook here often describes IFR conditions when actual IFR is limited to mountain ridges or river bottoms, with wide-open VFR in between.
- All weather forecasts derive at least in part from localized observations at weather reporting points, usually airports. More and more observations are made by automation, which “average” conditions and may sometimes misidentify areas of mainly cloudy or clear sky.
Translation: A categorical outlook from automated observations may not accurately reflect conditions at places between or distant from reporting points.
- A cloud “ceiling” indicates the height (AGL) of the bases of the lowest cloud layer identified as either “broken” or “overcast” (except a “thin overcast” [where the sun or moon is visible through the clouds], which is not a “ceiling“).
Translation: Scattered cloud layers or areas with “few” clouds are not identified in the categorical outlook.
- Hazardous flying weather — especially thunderstorms — often exist when ceilings and / or visibilities still exceed 3000 feet and five miles.
Translation: Dangerous wind shear and locally low ceilings and / or visibilities may accompany a storm in an area where the categorical outlook remains VFR or MVFR.
- “MVFR” conditions, although potentially hazardous, still allow VFR flight operations, especially in uncontrolled (Class G) airspace.
Danger: Know your limits — just because it’s legal doesn’t mean it’s smart.
CATEGORICAL OUTLOOK FLYING
Q: How can we use the categorical outlook, then?
A: Use the categorical outlook to make a preliminary go / no-go decision before takeoff. Then personally evaluate conditions to update your go / no-go planning en route.
STRATEGY Try this decision matrix:
Of course surrounding area weather, possible icing or embedded thunderstorms, single-engine vs. multiengine airplane, and other factors may affect your categorical outlook decision-making matrix.
Before takeoff, look at the categorical outlook from the forecasts. Translate current observed (METAR) weather into categorical terms also, then using current and forecast weather apply the decision-making matrix to make a preliminary go / no-go decision.
En route, continually observe actual weather conditions and evaluate them in terms of categorical outlook. Listen “ahead” of your route of flight (AWOS / ASOS, ATIS, Flight Watch or other weather sources) and define those conditions in categorical terms. Then make in-flight go / no-go (continue flight as planned/change altitude or route or land early) decisions using your personal categorical outlook decision-making matrix. This lets you compensate for inaccurate or not forecast ceilings and visibilities.
BOTTOM LINE: Obtaining weather information isn’t as critical a skill as learning what to do with the information once you get it. Most weather-related accidents happen when pilots initiate flight into known, poor conditions, or continue flight into deteriorating conditions. Using the categorical outlook and an outlook-based decision-making matrix is one way to improve your safety and flexibility in flight.