Safety Recommendation A-14-014

-From Bryan Bedford, Administrator: The FAA, in coordination with the NWS, ensured that the new Memorandum of Understanding enables the NWS to assume the recommended responsibilities identified in Safety Recommendations A-14-17 and A-14-18. Turbulence by mountain wave activity was integrated into the Graphical Airman’s Meteorological Information (G-AIRMET) advisories beginning April 30, 2026. The NWS’s Service Change Notice 26-17, Updated: Implementation of Mountain Wave Turbulence to the Graphical AIRMETs, is available at the following website:

https://www.weather.gov/media/notification/pdf_2026/scn26- 17_Updated_Mountain_Wave_Turbulence_aaa.pdf

The G-AIRMET retired the text AIRMET back in January 2025. It is available at the following website:

https://aviationweather.gov/gfa/#gairmet

I believe the FAA has effectively addressed the safety issues identified in Safety Recommendations A-14-13 through A-14-15 and consider our actions complete.

We note that the text Airman’s Meteorological Information’s (AIRMET’s) retirement has been delayed and, as a result, work to include the MWA in the standalone graphical AIRMET (G-AIRMET) is expected to be completed by January 2025.

During a June 7, 2022, meeting of staff from the NWS, FAA, and the National Transportation Safety Board (NTSB), we explained that the intent of this recommendation is to identify turbulence—not all activity—caused by mountain waves. Although we believe your plan to include the MWA information in the G-AIRMET is responsive to this recommendation, we reiterate that we are only interested in capturing MWA and associated features that cause turbulence. Pending completion of that action, Safety Recommendation A-14-14 remains classified OPEN-- ACCEPTABLE RESPONSE.

-From Kathryn B. Thomson, Deputy Administrator: The Federal Aviation Administration continues to work with the NWS to address these recommendations. The MWA remains scheduled for inclusion in the standalone G AIRMET graphical Airmen’s Meteorological Information (G-AIRMET); however, due to delays in the retirement of the text AIRMET, the target date for inclusion is now January 2025.

I will keep the Board informed of our progress with Safety Recommendations A-14-14 and -15 and anticipate providing an update by September 30, 2024.

We note that the NWS is planning to include terminology for describing MWA as part of an update to the graphical-airmen’s meteorological information notices (G-AIRMETs), which is a primary aviation weather product that is currently included in the preflight weather briefing package. Pending implementation of the updated G-AIRMET and any necessary revisions to the interagency agreement, Safety Recommendations A-14-14 and -15 remain classified OPEN-- ACCEPTABLE RESPONSE.

From Billy Nolen, Acting Administrator, Federal Aviation Administration: This is our final response to Safety Recommendation A-14-13, further response to Safety Recommendations A-14-14 and -15, and supplements our previous letters.The FAA incorrectly stated that it added “turbulence caused by mountains” to Airmen’s Meteorological Information Notices (AIRMET) in our January 21, 2020, letter. The FAA clarified with the NWS that this phrase would not be added due to the continued development of graphical AIRMETs (G-AIRMETs), which will eventually replace AIRMETs. G-AIRMETS will include the appropriate MWA weather data, and issuance is projected to begin in April 2023.

I believe that the FAA has effectively addressed Safety Recommendation A-14-13, and I consider our actions complete. I will keep the Board informed of our progress with Safety Recommendations A-14-14 and -15 and anticipate providing an update by September 30, 2023.

You reported that the NWS Western Region Center Weather Service Units (CWSUs) now issue center weather advisories (CWAs) for MWA. You also reported that the NWS now includes the terminology “turbulence caused by mountains” in airmen’s meteorological information notices (AIRMETs) and in significant meteorological information notices (SIGMETs) if MWA is suspected to be the cause of the aviation weather hazard. We are aware, however, that this language has, in fact, not been added to AIRMETs.

Although the actions that you reported are responsive to this recommendation, we were not able to confirm that they have all been implemented. The NWS confirmed that “DUE TO MTN WV ACT” is included in SIGMETs when issued for mountain waves; however, not for AIRMETs. The NWS reported that it does not have the same flexibility with AIRMETs, which include no cause statement when issued for moderate turbulence. In addition, the NWS said that the additional verbiage cannot be added at this time because the NWS is required to abide by character limitations on certain lines of text in the product, and changing this requirement would require your agency’s involvement and approval.

Pending confirmation from you that the recommended language has also been included in AIRMETs, Safety Recommendation A-14-14 remains classified OPEN--ACCEPTABLE RESPONSE.

-From Steve Dickson, Administrator: In response to Safety Recommendation A-14-18. the NWS Aviation Weather Center implemented version 3 of Graphical Turbulence Guidance (GTG), which includes clear air and mountain wave turbulence. The NWS Western Region Center Weather Service Units (CWSU) now issue Center Weather Advisories (CWA) for MWA. These CWA for MWA are consistent with severe turbulence criteria, and represent a consistent measure that can be used to forecast all mountain wave activity for all mountains throughout the National Airspace System.

The Board's letter, dated September 16, 2014, requested adding, "turbulence caused by mountains" to existing NWS notices such as Significant Meteorological Information Notices (SIGMET), Airmen's Meteorological Information Notices (AIRMET), and CWA will satisfy this safety recommendation. The FAA coordinated with the NWS to add the terminology "turbulence caused by mountains" to AJRMETs and SIGMETs, where mountain wave activity is suspected as the cause of aviation weather hazards.

These actions, in combination with the implementation of the GTG and issuance of CW A for MW A, complete our action to provide a primary aviation weather product specifically addressing aviation weather hazards caused by MWA.

We note that you plan to add “turbulence caused by mountains” to significant meteorological information (SIGMET) advisories where mountain wave activity is suspected as the cause of aviation weather hazards, to address severe turbulence aloft caused by mountain wave activity. Although SIGMETs can advise on severe turbulence at all altitudes, and their size is often tailored to focus on relatively small regions of interest (as compared to most airmen’s meteorological information [AIRMET] advisories), we are concerned that SIGMETs are rarely issued to identify hazards less than 3,000 square miles in size.

NWS instruction 10-811 allows small advisories to be issued if the hazard is deemed to “have a significant impact on the safety of aircraft operations”; however, NWS instruction 10-811 does not allow SIGMET issuance for significantly strong surface wind (for example, downslope wind storms) or low-level wind shear (for example, rotors), both of which may be produced by mountain wave activity. Therefore, we do not believe that identifying these hazards simply as “turbulence caused by mountains” will satisfy the intent of this recommendation, which is to convey to pilots information on particular hazards resulting from mountain wave activity.

We believe that adding “turbulence caused by mountains” to AIRMETs would be valuable, particularly in AIRMETs that address low-level wind shear and strong surface gusts. However, significant mountain wave activity should be identified in a product such as a SIGMET and/or a center weather advisory (CWA), which are both intended to advise of severe turbulence applicable to all aircraft types.

Although you did not indicate any plans to use CWAs as vehicles for delivering advisory information on hazards associated with mountain wave activity, we are aware of efforts by some NWS Center Weather Service Units (who issue CWAs) to locate areas prone to mountain wave activity and establish a consistent measure for forecasting mountain waves and associated turbulence aloft, downslope winds, and rotors. We believe that a consistent measure, such as the one being developed by NWS Center Weather Service Units, is essential for forecasting all mountain wave activity throughout the national airspace and to satisfy the intent of this recommendation.

Accordingly, pending completion of the actions described above, Safety Recommendation A-14-14 remains classified OPEN—ACCEPTABLE RESPONSE.

-From Michael P. Huerta, Administrator: An enhanced Graphical Turbulence Guidance product that forecasts turbulence from the surface to l 0,000 feet, including turbulence caused by mountain waves, will be ready for operational use by the end of2015. In addition, the FAA is working with the NWS to add the terminology "turbulence caused by mountains" to existing Airmen's Meteorological Information (AIRMETs) and Significant Meteorological Information (SIGMETs), where mountain wave activity is suspected as the cause of aviation weather hazards.

I will keep the Board informed of the FAA's progress on this safety recommendation and update the Board by November 2016.

We note that you will work with the NWS to produce and disseminate turbulence forecasts, warnings, and advisories, including those related to mountain wave activity. We further note that you plan to release the Graphical Turbulence Guidance?Mountain Wave (GTG MW). Although GTG-MW will provide more timely and accurate turbulence forecasts, it is not directly applicable to this recommendation because it is a supplemental, not a primary, product; it is a potentially useful tool for preflight planning, but is not usable by airplanes in the air. In fact, taking the action in this recommendation is simpler than developing the GTG-MW.

Just adding “turbulence caused by mountains” to existing NWS notices?such as significant meteorological information notices (SIGMETs), airmen’s meteorological information notices (AIRMETs), and center weather advisories (CWAs)?will satisfy this recommendation. Pending completion of that action, Safety Recommendation A-14-14 is classified OPEN—ACCEPTABLE RESPONSE.

-From Michael P. Huerta, Administrator: The FAA will work with the NWS to determine the most effective way to produce and disseminate turbulence forecasts, warnings, and advisories, including those related to turbulence caused by MW A. The FAA's Aviation Weather Research Program plans to release Graphical Turbulence Guidance - Mountain Wave (GTG-MW), a new capability, in the near future. GTG-MW will provide more timely and accurate turbulence forecast guidance from the surface to flight level 450 including turbulence caused specifically by mountain waves. Currently GTG-MW is expected to be available for flight planning purposes from the NWS's Aviation Digital Data Service Web portal.