To start assessing the weather, you will need to acquire the relevant information. One of the best places to find the current and forecasted data is the internet. There are hundreds of weather focused websites that cover everything from the jet stream, isobars, winds aloft, surface winds etc. There are even pages that focus their weather forecasts specifically for glider pilots, giving you information, that you can’t get anywhere else. The problem with the internet is that there is so much information it is hard to know exactly what to get and where to find it. Your instructor or local pilots will be able to tell you what websites to check for the area you plan to be flying in. 

Aside from the internet you may also use Flight Weather Service which is a public service designed for small plane pilots, but is suitable for us as well. You will talk to a flight briefer who has access to a great deal of information and can help you generate a concise report in a few minutes. They may also tell you if there are any airspace restrictions or advisories such as closures due to fire, or military operations. The number (1-800-WX-BRIEF) is toll free anywhere in the United States and your call will be routed to the nearest flight service station. The flight briefers are accustomed to talking to professional pilots, so when you call it’s a good idea to have written down exactly what you want to ask. You will also need to give them your last name as your pilot identification. 

Weather band radio (NOAA) is good for getting updates on localized surface conditions and active advisories. This is a good source for current information, but it is not very useful for forecasting. A 2-meter radio is usually capable of picking up the NOAA station. Local instructors should have the frequency for your station. 

Local weather stations will have general weather information and forecasts, but you will want more detailed and up to the minute data. The Weather Channel is usually of little use - “It will be sunny and warm in California” is not detailed enough. 

Some of the most commonly used websites for wind and weather information are: 

- www.nws.noaa.gov 

- www.weather.gov

- www.wunderground.com 

- www.windy.com

- www.weather.com

- www.xcskies.com - This site is a paid site specifically for pilots. The information can be overwhelming, so look at it closely with someone who has a subscription to decide if it is something you are willing to spend money on. 

Now that smartphones have become so commonplace, there are more and more apps coming out every day that provide wind readings and forecasts, site specific weather info, frontal maps, storm info, and the list goes on. Most will offer real time data from local weather stations - these are usually your best indication of the current conditions. Some apps to look at include:

- Wunderground 

- Windy - there are two apps with this name and both are good.

- WindAlert 

- Storm - NOAA Weather

- Windfinder 

- The Weather Channel

- SailFlow 
 

At some point you may have stood on top of a hill and felt a breeze lightly gusting up a hill. Sometimes strong, sometimes completely still. This is caused by the sun heating the ground, which heats the air above it. That air tends to flow up hill and is called anabatic flow. 

As the heating decreases toward the end of the day, so will the anabatic flow. Once the sun is sufficiently low and no longer provides enough heating, the upper colder air will begin to flow down hill. This is called catabatic flow. This flow will start in shaded areas first so you want to watch these areas for a change in wind direction.

 

The surface pressure is related to the isobars and high vs. low pressure systems. The barometric pressure will have an effect on the stability of the day. High pressure days are generally more stable and usually sunny but may also result in sharper thermal edges. Low pressure days are less stable and may have cumulous clouds and tend to have smoother edged thermals. High pressure systems descend in a clockwise rotation. Low pressure systems ascend counter-clockwise. The barometric pressure trend will help you determine whether a weather system is arriving, leaving, or sitting over you. 

The barometric pressure for a day is not a “deal breaker” for flying. It is merely another data point which will help you determine what the day will be like. The standardized pressure is 29.92. If you note that it is at 30.10 you can expect sharper thermals.
 

Isobars are lines on a weather map that connect areas of equal barometric pressure. They are read very much the same way you would read the altitude lines on a TOPO map. Lines that are spaced far apart or “loose” indicate a shallow pressure gradient from one area to another with light or no wind. Wind generally tends to move along isobar lines from high pressure zones to low pressure zones. Lines that are very close together or “compressed” indicate a steep pressure gradient and may indicate higher winds as the pressure tries to equalize. If there are more than 2 isobars in your state (about the size of Wa.) they are compressed.
 

In the northern hemisphere, the jet stream acts as a boundary between northern latitude polar air, and mid latitude warm air. The jet stream can be described as a river of air moving West to East somewhere around 30,000 ft. It is in a constant state of fluctuation in speed, latitude, and altitude. During the summer months the jet stream tends to migrate north and reside mostly in Canada or along the border between Canada and the United States. A dip in the jet stream can be an indicator of an approaching cold front and the possibility for unstable weather or high winds. As the jet stream moves South into your area, you will notice the upper level air temperatures start to drop. This can decrease the overall stability of the region. If the jet stream is significantly North of your area, you don’t need to be concerned with it. If it is over your region or south of you, keep in mind that the weather conditions will likely be unstable and may change rapidly.
 

Thunderstorms can throw out intense gust fronts with winds that exceed 40 Mph so if there is a possibility of thunderstorms in your area it is best not to launch. These "gust fronts" are caused by cool air flowing out from the base of a thunderstorm, and sometimes form a long, horizontal, arc-shaped cloud just in front of the thunderstorm. The arrival of the gust front is often the best sign that a thunderstorm is arriving. Rain and lightning usually follow the gust front. If conditions are favorable for thunderstorm development, the gust front of one thunderstorm can actually act as a "cold wedge" and push up the warmer air in front of it, leading to the birth of yet another thunderhead. 

It may be difficult to identify thunderstorms in unstable skies. Two common indicators are: 

1. Mammatus clouds: Pouch-shaped clouds hanging down from a higher cloud layer. These pouch clouds look like dozens of gray or black half- basketballs suspended from the cloud layer above. Pouch clouds are only formed as a result of thunderstorm activity. If they're in the distance and not approaching, the thunderstorm that produced them is probably not a problem. If they're large and approaching, prepare to get hit by a storm. 

2. A sudden change in the direction and strength of the wind and a sharp drop in temperature.

 

Most fronts are preceded by a variety of higher altitude cloud types. Those types of clouds can be used by pilots to determine what the macro level weather pattern may suggest for the coming hours or days. 

Mare’s tails: Thin, white to light-gray streamer clouds high in the sky (cirrus clouds). Iso- lated mare's tails aren't a strong portent of bad weather to come, but dense and wide- spread mare's tails can indicate the approach of a front from as far as 24 to 48 hours away. 

Cirrostratus: Uniform, featureless, white or gray clouds at high altitude covering most or all of the sky. These clouds usually mean that a significant amount of moisture is moving into the area. They aren't spectacular, but they are important. Monitor the sky for a change in the weather. 

Halos: Rings of light around the sun or moon caused by light refracted through high altitude ice crystals. The old adage about halos preceding storms by 24 to 48 hours generally holds true in the wetter regions of the United States, but sometimes in drier climates halos can pass with no ill weather side effects. 

Altostratus: Gray, water-droplet clouds at medium altitude. A solid coverage of these gunmetal-gray clouds usually precedes major weather systems by less than ten hours. 

Nimbostratus: A layer of dark clouds with noticeable blurring below the cloud bases. These clouds bring rain or snow, and in the warmer months can develop into thunder- storms. Typically associated with the arrival of a front. The weather is likely to stay bad for 24 hours. 

 

Most of the time our best indicator for the status of the atmosphere is the presence or absence of clouds. There are many different types of clouds and this information is by no means complete. For the purpose of serving you best as a beginner paragliding pilot, there are some cloud types that you will see often - some are good signs for flying, others are not. 

Cumulus 

These clouds are a thermal pilot’s best friend - they almost always are accompanied by consistent lifting air, or as you will hear many times in your piloting career: a thermal. 

Cumulus clouds technically are formed when a parcel of air laden with moisture, rises to the dew point. At the dew point, a cumulous cloud forms. If the thermal doesn’t rise as high as the dew point, no cloud forms. In essence, cumulous clouds mark the tops of thermals. Small cumulous clouds, that look like cotton balls, can be very friendly and indicate good lift. When the lift becomes stronger, the cloud may start to become taller than it is wide. These "Cumulus Congestus” clouds should be avoided at all costs. They resemble Marge Simpson's hairdo. The lift under them may be very strong and you may not be able to escape. Not only is flying in clouds illegal, but they may also be very turbulent inside, and you have no horizon reference. You should be aware of the risks of flying in thermic conditions before launching into a sky of cumulus clouds. Mountains can help generate Cumulus clouds by providing the source for rising air or thermals. This is why mountain weather tends to be less stable than flatland weather. If cumulous clouds are the only clouds in the sky by mid- to late afternoon, there probably isn't much risk of thunderstorms developing. When these clouds become taller than they are wide, they become cumulus congestus and the chance of thunderstorms rises greatly. 

Cumulus Congestus 

Watch these clouds carefully. They are the first stage of thunderstorm growth and can become dangerous in a matter of minutes. Thunderstorms are the most serious type of local weather. Since the sun's heat energy is a major factor in thunderstorm generation, thunderstorms typically occur in the spring and summer. Winter sunshine simply doesn't deliver enough warmth. For thunderstorms to develop, the air needs to be warm, moist, and unstable—typical Spring and Summer conditions. These white or gray clouds with flat bases are taller than they are wide. The earlier in the day that they appear, the greater the probability that they will develop into thunderstorms. Their growth can usually be seen with the naked eye, and the faster they grow the more likely they are to produce a thunderstorm. The air rising underneath them can be very strong and the risk of "cloud suck" rises. 

Since the weather in the United States generally moves West to East, cumulous congestus clouds to your West are much more dangerous than cumulous congestus clouds to your East. This West to East airflow doesn't always hold true - especially in mountain ranges - so try to determine if the clouds are headed toward you so you can make a good decision on which way to fly to get as far away as possible. 

Cumulonimbus 

As the rising tops of a thunderstorm surge into the Jet Stream, the strong upper level winds drive the top of the cloud downwind forming the "anvil" shape of a cumulonimbus. At this stage a thunderstorm is capable of generating violent and unpredictable conditions including rain, hail, sleet, snow, lightning, flooding, gust fronts etc. If you see cumulonimbus clouds in the sky it is probably a good day to do something other than flying. 

Lenticular 

These clouds are smooth contact-lens shaped clouds. They are formed when very fast moving air is forced over a mountain or another air mass and typically form over mountain peaks or over the top of overgrown cumulus or cumulonimbus clouds. These are only formed when the winds aloft are very high. 
 

The winds aloft are calculated from measurements taken at winds aloft reporting stations located throughout each state. For each reported altitude you want to get wind direction, speed and temperature. The reported altitudes are 3,000 ft, 6,000 ft, 9,000 ft, 12,000 ft, 18,000 ft. Our FAA imposed ceiling is 18,000 feet, so there is little need to col- lect data above that level. If you are talking to a flight briefer, you will need to know which altitudes and the time frame you want the information for. If you obtain the data off the internet, you will need to understand the format in which it is presented. If the winds aloft within a few thousand feet of the ground are high, the surface winds may in- crease at some point during the day. You should be absolutely certain they will not in- crease to unsafe levels quickly and unexpectedly. Like the surface winds, if the winds aloft look too strong during the times you want to fly, there is no need to look further into the weather for that day. 

You can fly in higher winds aloft than surface winds, so long as there are no obstacles such as large mountains, or the winds aren’t so strong they threaten to push you into undesirable territory. Generally winds near or above your trim speed are to be avoided. Depending on the thermal strength for the day, winds aloft may “shred” the soft outer edges of the thermals, leaving sharp edged and unpleasant thermal cores. 

When flying in the mountains, keep in mind the altitude and direction of the winds so as not to launch or fly into turbulence (rotor) on the lee side (see Section 8 - The Lee and Rotor). If you you don’t know what the winds aloft are doing, the winds you see at launch may be misleading. This is one of those circumstances where col- lected weather data and visual observation can contradict and fool you into launching in dangerous conditions. 

Some sites, under the right conditions, will do what is called “thermal blocking” where there is enough heat and thermal activity coming off the ground to block out a wind that is blowing from the wrong direction. These can be great conditions, but you should be aware of the prevailing winds aloft, and that the conditions may change quick- ly. At some point during the day, there will no longer be enough heating, or the winds aloft overpower the heat. Conditions can change very quickly, and you should be pre- pared to handle them or be out of the air before they change. 

When collecting winds aloft data be sure to collect the temperatures at the re- ported altitudes. This will help you later when figuring out what the thermal potential for the day will be.
 

Wind is our biggest nemesis and largest determining factor for flying. If it is too windy to launch and land safely during the times you plan to be flying, your weather data collection can end here and you may break out the fishing gear. As an entry level pilot anything over 12 Mph is generally too strong. 

You may obtain surface wind data from flight service, from a nearby airport, or from the internet. Airports often have an automated announcer that will give the current surface winds and the trend over the last few hours. On the internet, wunderground.com or usairnet.com will give you detailed current and forecasted surface wind conditions for your area. Be sure to obtain current and forecasted conditions, so you know what to expect throughout the day. Some days you may be able to fly in the morning knowing that the wind is expected to increase later in the day or vise/versa.