Instrument Insights Part 11 of 12

Weather on the Fly

November 1, 1998

In-flight briefing options

The last time you checked the weather, the flight service station briefer mentioned that a front was heading for your proposed route of flight. It shouldn't affect you, the briefer said, hinting strongly that low clouds and visibilities will move in hours after you've landed.

But something's changed. What began as a nice VFR flight has obviously deteriorated. What looked like haze in the distance turned out to be cloud layers that you'll encounter in the next few miles. Will you be able to continue the flight under VFR? Have ceilings and visibilities gone to pot at your destination? Will thunderstorms pop up before you even get there? If so, where will you go to find decent weather?

Questions like these can be answered by using several sources. All a savvy pilot — instrument-rated or not — needs to do is tune in a few pertinent frequencies, ask the right questions, listen up, and execute a plan of action for dealing with any adverse weather.

The next time you're cruising along and wondering about the weather, consider consulting the following:

  • En route flight advisory service (EFAS). Better known as flight watch, this service can be called up on 122.0 MHz, anywhere in the United States. This frequency is intended for use by aircraft flying below 17,500 feet msl. Discrete high-altitude flight watch frequencies have also been established for airplanes flying between 18,000 and 45,000 feet msl. The flight watch service areas, the locations of their remote communications outlets, and high-altitude flight watch frequencies can be found on the inside back covers of the Airport/Facility Directories.

    Please bear in mind that, depending on your location, more than one flight watch facility may be in radio range. When calling up flight watch, try to call up the correct facility for your location. However, if you can't recall or look up the correct flight watch facility, don't worry about it too much. You can always make your callup sound something like this: "Any flight watch, this is N7236W, near Anytown VOR, over." This way, you've given flight watch specialists a good idea of where you are.

    Flight watch is intended for weather updates only. Don't tie up a flight watch frequency with a request for a full route briefing (the briefer probably will remind you of this and deny you a full-blown briefing, anyway). Instead, use flight watch to keep track of such things as the surface conditions at your destination, learn of any pilot weather reports along your route, and follow the progress of any fronts or convective activity that may be coming your way. Flight watch information is also a great way to verify or disprove the forecasts that you've heard during a preflight briefing. So, think of flight watch as an early warning system. Flight watch is a great source of current radar information, too. Flight watch specialists have access to some of the latest-generation weather radar imagery.
  • Flight service station (FSS) frequencies. Let's say that you want a full route briefing while en route. Flight watch is no good for that, but there is an alternative. For prolonged sessions with a flight service station briefer, you can call up FSSs on their published frequencies. These can be found above VOR frequency identification boxes on aeronautical charts. Often, these frequencies are either 122.2, 122.4, or 122.6 MHz — although other frequency designations are certainly possible.

    Again, remember that flight service specialists talk and listen on many different frequencies, and that some of those simplex frequencies are co-located with VOR frequencies. It helps immensely if you mention the frequency that you're broadcasting and/or listening to. Good examples of these helpful callups might sound like, "Leesburg Radio, this is N7236W, on 122.6," for a multiplex callup, or "Leesburg Radio, this is N7236W, listening on Gordonsville VOR," for a simplex callup (one where you talk on one communications frequency, and listen on a VOR frequency — a handy technique if you have a single navcom).
  • HIWAS (Hazardous inflight weather advisory service). HIWAS is a continuous broadcast of inflight weather advisories, carried over selected VOR frequencies. You simply tune in a VOR with HIWAS (identified by a small, solid square within the VOR's frequency identification box), select your VOR's identification mode, turn up the receiver volume, and listen in.

    Convective sigmets, sigmets, center weather advisories, severe weather forecast alerts, airmets, and urgent pireps are all broadcast on HIWAS. As soon as one of the above statements is issued and/or updated and recorded, it's immediately broadcast on HIWAS. Then it starts to run, over and over. This makes it easy to copy information, because if you didn't get the message the first time around it will soon be repeated.

    HIWAS broadcasts may be dated, so pay attention to the time they were recorded.

    Keep this firmly in mind: In areas where HIWAS is commisioned, air route traffic control centers (ARTCC), tower facilities, and flight service stations will not broadcast inflight weather advisories. They'll simply mention over their frequencies that an advisory has been published, and ask you to tune in to HIWAS for details.
  • Flight following. Even though you may not be flying on an IFR flight plan, there is a way to stay abreast of weather and traffic information. By calling up an ARTCC frequency and asking for VFR flight following, you can receive the same type of inflight information as other airplanes — on IFR flight plans — on the frequency. In areas not served by HIWAS, center weather advisories, sigmets, and other weather statements will be broadcast over center frequencies, and often it's possible to ask controllers for the weather ahead. ATC radar cannot contour precipitation echoes all that well, but controllers can pass along any weather reports or pireps from aircraft ahead of you. It's even possible to obtain updated weather for your destination. Just remember that flight following for VFR aircraft is granted on a workload-permitting basis. If the traffic is dense, or adverse weather covers your route, controllers may deny you flight following. Of course, if the weather is that bad, you probably should be on an IFR flight plan anyway.
  • ASOS/AWOS. Tuning in to ASOS (automated surface observation system) and AWOS (automated weather observing system) frequencies is a great way to keep up with the surface weather. These frequencies are published in the Airport/Facility Directory, and also appear on sectional charts, instrument approach plates, and other airport information publications — such as AOPA's Airport Directory.

    Although automated weather observing systems have some flaws, they are valuable as tools for obtaining up-to-date surface conditions. Listening in as you fly along, it's possible to learn of surface winds (these reports are very accurate); density altitudes (also very reliable); and ceiling, cloud cover, and visibilities (somewhat less reliable, but extremely useful as trend indicators) at airports on or near your flight path.
  • TWEB (Transcribed weather broadcasts). Another inflight weather source, TWEBs are becoming rare. TWEB information is broadcast over certain VOR and NDB frequencies (look for a small "T" in the navaid box) and often includes route-specific surface weather reports and forecasts. Up to five reporting stations' weather observations can be included in a TWEB. Winds aloft, sigmets, and airmets may also be recorded. As fast overviews, TWEBs are great — particularly if they cover the routes that you usually fly. They can also be accessed via telephone in some locations; TWEB phone numbers are published in the FSS and National Weather Service Telephone Numbers section of the Airport/Facility Directory.

Whether flying under VFR or IFR, the services we've discussed here show that there's plenty of inflight help available when it comes to weather updates. It can be lonely and scary when adverse weather crops up during your flight. Checking in with flight watch, flight service, HIWAS, ASOSs and AWOSs, TWEBs, and using flight following can give you the information and confidence that you need to formulate escape strategies — and preserve your wits. And that goes for instrument- as well as noninstrument-rated pilots.


E-mail the author at tom.horne@aopa.org.