Severe Weather Storm
The National Transportation Safety Board (NTSB) doesn’t think pilots are getting all the information or the best information to make decisions during preflight or while in flight when they go to the typical aviation weather sources, specifically the Aviation Weather Center or the Flight Service. Technically the Aviation Weather Center’s web page is not an official source of weather information for preflight planning. In order to have a documented weather briefing from an approved source you need to get your weather through a flight service station briefing or a DUAT or DUATS weather briefing. But, guess where they get their weather information, from the Aviation Weather Center and the National Weather Service.
There are non-aviation related weather products produced by the National Weather Service (NWS) that are not normally addressed when agencies provide pilot weather briefings.
The NTSB cites accidents where the aviation weather provided to pilots during preflight planning did not paint as clear a picture of the forecast weather as other products available from the National Weather Service. In a recent NTSB Safety Recommendation to the FAA the NTSB said they are “concerned that although weather hazards are identifiable by NWS meteorologists, routinely issued aviation weather products may not alert the aviation community to the presence or full severity of these hazards”.
Here are some examples from the NTSB letter:
“On January 17, 2010, a Cessna 182R collided with mountainous terrain 9 miles northwest of Corvallis, Oregon, resulting in two fatalities. While several NWS aviation weather products were issued for wind for the state of Oregon that day, the NWS Weather Forecasting Office in Portland, Oregon, had issued a nonaviation-specific high wind warning for wind much higher than that forecast in the aviation weather products. On November 10, 2011, a Eurocopter EC130B4 helicopter collided with mountainous terrain near Pukoo on the island of Molokai, Hawaii, resulting in five fatalities. While NWS aviation weather products for wind and turbulence had been issued, two NWS nonaviation-specific weather products advised of wind magnitudes 13 to 15 knots higher than what had been advised in the aviation weather products.On May 24, 2012, a Gulfstream American AA-5A impacted terrain about 40 miles northeast of Lakeview, Oregon, resulting in one fatality. While NWS aviation weather products advised of broken ceilings, rain showers, and moderate turbulence, an NWS nonaviation-specific weather product advised of wintry conditions and significant wind gusts.On March 3, 2013, a Mooney M20E impacted terrain after departing Angel Fire Airport, Angel Fire, New Mexico, resulting in four fatalities. At the time of the accident, there was a substantial crosswind to the runway with a sustained wind of 33knots and gusts to 47 knots; however, an NWS aviation weather product only advised of wind gusts to 25 knots, while two NWS nonaviation-specific weather products discussed stronger wind gusts.”
One source of aviation weather information that is not widely disseminated is weather advisories produced by NWS forecasters located in each air route traffic control center called Center Weather Service Units (CWSUs)
Another weather hazard the NTSB feels is not getting enough emphasis or dissemination is mountain wave activity (MWA). Pilots will often get forecasts of turbulence with no mention of mountain wave and just as importantly you can have smooth air with strong mountain wave activity present. I’ve had this happen to me on two occasions, once VFR and once IFR, and in both cases the downdrafts exceeded the aircraft’s capability to maintain altitude. In each case I allowed enough altitude for the possibility and was able to safely transit the area. The first was a VFR flight from San Diego to Lake Havasu. The winds were out of the west and although the air was smooth the down drafts on the leeward side of mountain ridges were very strong. I maintained full power at VY and watched the aircraft descend at 500 feet per minute as I flew through the down drafts. It occurred over the valleys to the east of the mountains so the altitude I had to clear the mountains allowed me to ride it out. The second was an IFR flight from Phoenix to San Diego. I intentionally went the southern route through Yuma and Imperial as the downdrafts and turbulence around Julian VORTAC are notorious when the winds are strong and have caused many accidents. I heard others on center frequency working to maintain altitude. I made sure I was well above the minimum enroute altitude (MEA) as well as the clouds as I approached the mountains east of San Diego. At first I was able to maintain altitude but fighting the head winds and down drafts I was making a huge 40 knots of ground speed. Because it is a mountain wave activity you progress through down drafts and up drafts. Eventually, I got to one down draft where I couldn’t maintain altitude and I let center know. He cleared me for a 2,000 foot altitude block and I was able to regain lost altitude each time I encountered an up draft. I went through two cycles of that before I got to the windward side of the mountains and no longer had trouble maintaining altitude but I stayed high as long as I could before starting the descent to get through the cloud layer and land.
Currently neither the NWS nor the Aviation Weather Center are not required to provide advisories when mountain wave activity is present so your only clue may be strong winds over the mountains, listening to the radio on flight following to hear how others are doing and, possibly, PIREPS if pilots report mountain wave. Two air traffic control centers, Denver and Salt Lake, provide weather warnings about mountain wave activity in their weather products.
To address these problems the NTSB recommends the FAA ensure that preflight weather briefings include any products created by the NWS and that the NWS include mountain wave activity in aviation weather products. The NTSB also recommends that weather information produced by air traffic control center weather service units be included in the information that is briefed to pilots.
What can you do in the mean time? Well maybe watching the Weather Channel and local media forecasts in addition to getting the required aviation forecasts can help give you a better picture of the situation and isn’t such a silly idea after all. If what you are hearing from non-aviation sources differs greatly from what you are getting from flight service or DUAT/DUATS you should consider using the more extreme of the two values. Also, now that ADS-B IN weather information is available in the cockpit at reasonable prices, you can keep up with the weather information in flight. You no longer have to rely solely on the stale information you got during your preflight briefing.
ADS-B Weather Display
The entire recommendation letter from the NTSB to the FAA is available at: