Categorical Amendment Criteria (CAC)

FAQ SessionAviation Services BranchNovember, 2009

CAC and AvnFPS

CAC is not intended to be a “best practice” program, rather a beginning point.

In fact, there can be no such thing as a “best practice” when it comes to serving our customers. If we say we can do no better, we will never progress.

CAC Methodology

Employs the following important concepts:Tailors Ceiling and Visibility to meet specific airport requirementsGroups Ceiling and Visibility together into categories to match FAA RegulationsTEMPO groups checked immediately against METARS to notify forecasters of resulting customer impacts

Standard TAF Amendment Criteria

CAC Breaks Down The Wall!

Why CAC ?

To provide our customers with a more responsive product tailored to their regulatory needsTo allow forecasters to use AvnFPS as a Decision Tool, rather than an alert monitor

CAC and AvnFPS

CAC Q and A Session

Question

Programs that tracked TAFs and observations have always been “alert monitors”. This is what folks are used to. How does this software change what forecasters are used to as a decision tool?

Answer

Whether AvnFPS is used as an alert monitor or a decision tool is entirely up to the user and forecasting philosophy they employ.

The NWS advocates that AvnFPS be used as a decision tool rather than an alert monitor.

Answer

That is to say, there should be a focus on proactive rather than reactive amendments.

Furthermore, decisions to amend the TAF should not be made on AvnFPS notifications alone, but rather from the forecaster’s assessment of the meteorological conditions and customer impacts.

Answer

There are many training opportunities that explain this methodology (e.g. DLAC course and CAC modules).

The changes to AvnFPS due to CAC are merely to readjust amendment criteria to focus more on thresholds that our customers use. It also has the added benefit of reducing amendment workload as well.

Question

Is this program encouraging forecasters to chase observations?

Answer

There is currently no feature or recommendations in AvnFPS that encourages a forecaster to "chase" observations.

AvnFPS merely compares one set of data to another set of data for informational purposes. There are many other forms of data important to the decision making process to amend a TAF.

Answer

To "chase" observations because of AvnFPS notification colors requires a forecasting philosophy that is NOT encouraged by the NWS.

Training opportunities such as DLAC course and CAC modules explain the NWS philosophy on amendments to TAFs.

Impact of Chasing Observations

18Z TAF P6SM SCT025 BKN0501854Z 10SM FEW025 SCT090 BKN1401937Z 10SM SCT019 BKN027 BKN0311954Z 10SM SCT019 BKN026 BKN03820Z AMD P6SM BKN025

22Z P6SM SCT025 BKN0502007Z 10SM FEW021 SCT028 BKN0382054Z 10SM –RA FEW018 BKN041 BKN04721Z AMD P6SM SCT025 BKN040

22Z P6SM SCT025 BKN0502138Z 10SM SCT018 BKN026 OVC0312154Z 10SM FEW018 BKN024 OVC1102203Z 10SM FEW021 BKN046 OVC110

Question

Is there a potential problem that alerts will result in the “crying wolf syndrome” and forecasters will begin to ignore the notifications?

Answer

No. Notifications are generated only when there is a mismatch between the METAR and TAF.

In fact, the “crying wolf syndrome” has been fixed by CAC. Standard versions of AvnFPS alert the forecaster to an individual element of ceiling or visibility, regardless of the true impact to the customer.

Example

TAF: 1/4SM FG OVC001METAR: 1/4SM FG OVC001SPECI: 1/4SM FG OVC002

Standard AvnFPS: Yellow CIG notificationCAC AvnFPS: Light Green CAT notification

This is “crying wolf” as the impact to the customer with respect to the TAF remains unchanged.

Question

The prevailing group in the TAF and the METAR are matching. There is a TEMPO forecast in a lower category, so why is AvnFPS lighting up in the Category (CAT) box?

TAF: 5SM BR OVC015 TEMPO 3SM BRMETAR: 5SM BR OVC015

Answer

The FAA Office of Chief Counsel interprets Federal Aviation Regulations to mean that the worst weather conditions forecast used to control flight movement is the controlling factor.

TAF: 5SM BR OVC015 TEMPO 3SM BRMETAR: 5SM BR OVC015

Answer

These interpretations make the remarks portion of a forecast as operationally significant as the main body of the forecast.

Therefore, AvnFPS will notify the forecaster immediately in the CAT box whenever the lowest forecast condition is not being met, regardless if it is in the prevailing or TEMPO group.

Question

Is it the role of CAC to force folks to rethink their TEMPO monitoring or should that be left to sound training?

Answer

It is the role of sound training, CAC merely reinforces the training.

Question

Should CAC monitoring only apply to high impact airports, where forecasts can significantly impact operations and cause economic impacts?

Should CAC monitoring only be used at smaller airports?

Should AvnFPS be upgraded to allow CAC monitoring on a TAF by TAF basis to reduce impact to forecasters’ workload and allow them to focus on airports where more than limited general aviation traffic exists?

Answer

No. Airports are all a part of the National Airspace System (NAS). As such each one can be used as an alternate for any other in inclement weather.

General Aviation customers use smaller airports more frequently than large hubs. They too are our customers whom we support. In addition, Search and Rescue and Medical flights utilize any available airport to support their specific mission needs

CAC and AvnFPS

AvnFPS Notifications

CAT Color Codes and the Forecaster

Light Green: In category situational awareness: - Only one element in category OR - Tempo being verified by remark in observation, OR a remark may indicate an upcoming change

CAT Color Codes and the Forecaster

Yellow – One category difference: - Usually associated with MVFR increasing to VFR, or

decreasing to IFR - As a result, customer impacts need to be realized

by looking at the text message

CAT Color Codes and the Forecaster

Yellow – One category difference: - Can be caused by a small mismatch in either

ceiling or visibility - TPO situational awareness alert can aid in a

decision to amend when warranted

CAT Color Codes and the Forecaster

Orange – Two category difference: - Caused by forecast timing errors or a marginal spread

between a predominant and TEMPO forecast - Associated weather can be hard to define, or rapidly

changing as is the case with showers or thunderstorms

CAT Color Codes and the Forecaster

Red – Three category difference: - Caused by forecast timing errors or a wide spread between

a predominant and TEMPO forecast - Associated weather is usually hard to define, or rapidly

changing as is the case with showers or thunderstorms

CAT Color Codes and the Forecaster

Purple – CAT A: - The lowest condition of ceiling and visibility that is

most often the hardest to define - Caused by large synoptic or small micro-scale

situation - Weather can be highly variable = good use of

TEMPO

CAT Color Codes and the Forecaster

Purple – CAT A: - Purple to Green CAT notifications OK with TEMPO

forecast - TPO situational awareness color codes will provide

timing notifications to aid in decision to amend

TPO Color Codes and the Forecaster

Yellow – TEMPO forecast has not verified in at least one hour

- TEMPO event may be ending or have not developed as anticipated

- Decision to AMD to remove, or refine timing may be appropriate

TPO Color Codes and the Forecaster

Orange – TEMPO forecast has not verified for half of the forecast period

- TEMPO event is over, or not developing - Decision to AMD to remove, or refine timing is

appropriate to relieve impact on customer

Categorical Amendment Criteria (CAC)

Questions or Comments ?