Understanding Weather

Understanding Weather

Many books have been written about weather, especially aeronautical weather. That's because weather impacts flyers. If there's a thunderstorm brewing and you need to get to work you'd probably drive there. As a VFR pilot you'd never think of flying near a thunderstorm.

The FAA's Pilot's Handbook of Aeronautical Knowledge includes information about weather to help you pass your knowledge and practical tests as well as teach you how weather affects flying. To be a private pilot you don't need to become a meteorologist. However, you do want to know how weather works for you and against you when flying.

FAR 91 outlines basic VFR weather minimums, telling you the minimum conditions in which you can fly as a student and private pilot. Smart pilots (that includes you!) have personal minimums that are higher, especially when first learning to fly. Private pilots should have personal weather minimums that are greater than those required by FAR 91.

In addition, you should be able to read weather maps and understand meteorological reports that the FAA and National Weather Service (NWS) provide to pilots. Fortunately, most of the maps and reports include a legend to help you decipher them. Some practice will help, so refer to the Pilot's Handbook of Aeronautical Knowledge and similar publications for more specifics.

Unfortunately, the knowledge test will ask you questions about teletype weather codes that aren't frequently used anymore. Even so, you have to learn them to pass the test. To help, I recommend aftermarket training material and other educational aids written specifically to help you pass the knowledge and practical tests. Pay special attention to Direct User Access Terminal Service (DUATS) reports and how to get weather briefings from FAA flight service stations (FSS) because you will use them more than the old teletype services.

You also can call up an FAA automated flight service station (AFSS) for a personal weather briefing or you can listen to the Pilot's Automatic Telephone Weather Answering System (PATWAS). (Don't you just love all these acronyms?) It's PATWAS that gives you a recorded weather briefing for the area within 50 miles of the FSS. The telephone number for any AFSS is 1-800-WXBRIEF.

Another useful type of weather report is called the PIREP, short for pilot weather report. These are observations from real pilots flying in specific locations and speaking to the needs of other pilots. Of course, a PIREP from a Northwest Airlines pilot at 35,000 feet isn't much use to you at 3,500 feet in your Piper Cub. Fortunately, the reports indicate who is reporting, when, what the pilot is flying, and what the pilot saw.

Here's a short summary of how weather impacts flying. First, air moves because it gets heated up by the sun's rays. The heat exchange makes air move from a high pressure system (marked H on weather maps) to low pressure systems (marked L). As the atmosphere moves across the surface of the Earth it can whirl, eddy, or even stop depending on the terrain over which it travels. That's the surface wind. Winds at higher altitudes could be coming from a different direction or at a dissimilar speed.