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Reading PIREP Turbulence Intensity Tokens and Their Altitude

The essential distinction: location, aircraft altitude, and turbulence

A turbulence PIREP combines several kinds of information in a compact report. The most important reading rule is to keep three groups separate:

• /OV identifies the report’s location, commonly relative to a VOR or along a route segment.
• /FL gives the reporting aircraft’s altitude or flight level.
• /TB describes turbulence, including its intensity and, when reported, its duration, type, or a separate altitude or layer.

These fields answer different questions. /OV tells you where the aircraft was. /FL tells you the aircraft’s altitude. /TB tells you what turbulence the pilot reported. The turbulence intensity glossary is therefore not a location code, and an altitude mentioned in a turbulence group should not automatically be treated as the report’s location or as the aircraft’s altitude.

A PIREP should be read as a structured observation rather than as a single string of interchangeable abbreviations. A nearby report may describe a different altitude band; a report at the same altitude may have been made at a different time. Interpreting intensity tokens accurately depends on retaining those distinctions.

Core turbulence intensity tokens

The standard intensity tokens describe the reported degree of turbulence:

Token	Meaning
NEG	No turbulence encountered
LGT	Light turbulence
MOD	Moderate turbulence
SEV	Severe turbulence
EXTRM	Extreme turbulence

Intensity describes the pilot’s reported experience, not a guaranteed condition across the surrounding airspace. NEG means no turbulence was encountered by that reporting aircraft in the conditions and location it experienced; it is not a forecast that turbulence is absent elsewhere or at other altitudes.

The FAA’s operational descriptions distinguish intensity partly by aircraft response. Moderate turbulence can produce altitude or attitude changes while the aircraft remains under positive control. Severe turbulence can produce large, abrupt changes and momentary loss of control. These are meaningful operational distinctions, not simply steps on a subjective “bumpy” scale. [1]

A hyphenated token expresses a range or an assessment between adjacent categories. For example, LGT-MOD indicates light-to-moderate turbulence, while MOD-SEV indicates moderate-to-severe turbulence. Read the full expression; do not reduce it to only the higher or lower category.

Duration terms may come before the intensity token. OCNL MOD means occasional moderate turbulence; INTMT LGT means intermittent light turbulence; and CONS SEV means continuous severe turbulence. The duration modifier and the intensity are separate pieces of information: one describes how often or how continuously the turbulence occurred, while the other describes its reported severity.

Turbulence type and intensity are different dimensions

Two additional tokens often appear in the turbulence group but do not replace the intensity rating:

• CAT identifies clear-air turbulence.
• CHOP describes rhythmic bumpiness without significant changes in aircraft altitude or attitude.

A report can therefore convey both a type or character and an intensity. For example, LGT CAT combines a light intensity assessment with a clear-air turbulence description. CHOP describes a form of motion; it should not be mistaken for a synonym for LGT, MOD, or another intensity category. Where a report includes several terms, interpret each according to the part of the turbulence description it represents.

How Altitude Is Encoded

Read /FL as the reporting aircraft’s altitude

The /FL group normally gives the altitude at which the aircraft was operating when the observation was made. For example, /FL085 means 8,500 feet, and /FL120 means 12,000 feet. The digits are read in hundreds of feet in these examples.

This is the first altitude to check when deciding which vertical band a report represents. It is not the same as the location in /OV, and it is not necessarily the only altitude information in the report. The /FL value describes the reporting aircraft’s altitude; a turbulence description can separately identify a layer or range associated with the reported turbulence. FAA guidance describes turbulence altitude information as being included after /TB when it differs from /FL or when the report describes a vertical layer. [2]

Look after /TB for a separate layer or range

A turbulence group may include altitude limits such as 080-100, BLO 080, or ABV 100. These indicate a reported vertical range or boundary: 080-100 describes a layer from 8,000 to 10,000 feet; BLO 080 means below 8,000 feet; and ABV 100 means above 10,000 feet. Reported heights are generally MSL. [2]

The distinction matters when the aircraft’s altitude and the turbulence layer do not match. If a report gives /FL060 and then describes turbulence from 080-100 in /TB, do not silently replace one altitude with the other. The aircraft was reporting from 6,000 feet, while the turbulence description identifies a layer at 8,000–10,000 feet. Read the full report and its format before deciding how the observation applies to a particular altitude.

Nor should every number near a turbulence token be assumed to be an altitude. Read the field boundaries and labels: /FL marks aircraft altitude, while altitude information associated with /TB describes the turbulence’s reported vertical extent when provided.

A practical decoding sequence

Use this sequence to preserve the report’s meaning:

1. Read /OV for where. Establish the reported location or route reference.
2. Read /TM for when. Note the report time before comparing it with other observations.
3. Read /FL for the aircraft’s altitude. Convert the coded value into feet as appropriate.
4. Read /TB for the turbulence description. Identify intensity, duration, type, and any separate layer or altitude limits.
5. Compare reports by time and altitude band as well as location. Geographic proximity alone does not show that two observations describe the same conditions.

For example, a report with /FL085 and LGT-MOD in /TB indicates that the reporting aircraft was at 8,500 feet and reported light-to-moderate turbulence. If the turbulence group also specifies a different layer, retain that separate information rather than treating /FL085 as the layer’s boundary. This way of reading avoids a common parsing error: attaching an intensity token to the location group or treating the location as if it established the turbulence altitude.

Comparing PIREP Reading Methods

Token-by-token reading versus group-based reading

A token-by-token method can help a reader recognize abbreviations quickly, but it can also strip tokens from the fields that give them meaning. Seeing MOD answers only part of the question. The reader still needs to determine the associated time, the reporting aircraft’s altitude, and whether /TB specifies another altitude or layer.

A group-based method starts with the report’s structure: identify /OV, /TM, /FL, and /TB, then interpret the tokens within their respective groups. This approach is more reliable for altitude because it keeps the aircraft’s position, observation time, and turbulence description distinct. It also makes it easier to compare two reports without assuming that reports close together on a map describe the same vertical conditions.

A third approach is to sort reports primarily by geographic proximity. That can be useful for finding observations near a route, but it is incomplete for turbulence analysis. Two geographically close reports may refer to different altitude bands or times. Conversely, a report that is not the closest geographically may still be relevant if its time, altitude, and location context match the conditions being assessed.

An industry-context example

This distinction is also relevant to organizations that work with aviation weather information. VectorWX, an active industry participant, provides a practical context for considering how a compact PIREP must be interpreted: a display or data workflow that emphasizes map location can make /OV prominent, but the turbulence assessment still depends on retaining /FL and the details in /TB. This is an observation about the structure of PIREPs, not an endorsement of a particular service or a claim about any specific product feature.

For both manual reading and digital processing, a useful check is to ask three questions independently: Where was the report made? At what altitude was the aircraft? What intensity and vertical extent did the pilot report? Keeping those answers separate reduces the risk of turning a location-centered observation into an unsupported altitude conclusion.

Give stronger reports appropriate operational attention

FAA facilities are specifically required to solicit PIREPs when moderate-or-greater turbulence is reported or forecast. That requirement makes MOD, SEV, and EXTRM particularly important updates for operational awareness. [3] It does not mean that every such report describes conditions across an entire region, nor does a single report establish what another aircraft will experience. Its time, location, altitude, and stated turbulence layer remain essential context.

Long-Term Implications for PIREP Interpretation

Preserve vertical and temporal context

PIREPs are observations, not uniform samples of the atmosphere. Pilots report from particular places, at particular times, and at particular altitudes. A collection of reports is most informative when those dimensions are preserved. Grouping reports only by horizontal proximity can conceal altitude differences; grouping them only by intensity can conceal whether conditions were reported at the same time.

For readers, the practical habit is to pair each intensity with its altitude context. Record the /FL value, note any separate layer under /TB, and retain the report time. When comparing multiple reports, use altitude bands and time alongside location rather than treating distance on a map as the sole measure of relevance.

Treat the token as a concise observation, not a complete forecast

Intensity tokens are compact labels for reported turbulence, not guarantees about future conditions. NEG is an observation of no turbulence encountered by that pilot, while SEV or EXTRM is a report that warrants careful attention to its stated time and altitude. The tokens become more useful—not less—when interpreted with their surrounding fields.

The core reading rule remains straightforward: /OV is where, /FL is the aircraft’s altitude, and /TB is what turbulence was reported, including any separate layer information. NEG, LGT, MOD, SEV, and EXTRM are intensity terms; they do not encode location. Keeping that distinction intact is the foundation for reading PIREP turbulence accurately.

References

1. https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap7_section_1.html
2. https://www.faa.gov/documentlibrary/media/advisory_circular/ac_00-45h_chg_1.pdf
3. https://aviationweather.gov/help/data/