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Leidos Flight Service has a website that allows you to view current and forecast weather and file flight plans. One of the things that I recently noticed is that it has detailed legends for the three most useful charts. The legends are useful for understand the charts and also for taking Knowledge Tests. Radar Summary […]

NASA Earth Observatory

Wow. I like the note on BWI—no significant weather observed at this time.

Checking out the hurricanes on Earth Wind Map I happened to notice two lows in the Pacific.

In general, icing is any deposit of ice forming on an object. It is one of the major weather hazards to aviation. Icing is a cumulative hazard. The longer an aircraft collects icing, the worse the hazard becomes. Supercooled Water Freezing is a complex process. Pure water suspended in the air does not freeze until […]

A thunderstorm is a local storm, invariably produced by a cumulonimbus cloud, and always accompanied by lightning and thunder, usually with strong gusts of wind, heavy rain, and sometimes with hail. Thunderstorm cell formation requires three ingredients: sufficient water vapor, unstable air, and a lifting mechanism (see Figure 19-1).Sufficient water vapor (commonly measured using dewpoint) […]

AC 00-6B: Aviation Weather Air Masses An air mass is a large body of air with generally uniform temperature and humidity. The area from which an air mass originates is called a source region. Air mass source regions range from extensive snow-covered polar areas to deserts to tropical oceans. The United States is not a […]

Vertical Motion and Cloud Formation A cloud is a visible aggregate of minute water droplets and/or ice particles in the atmosphere above the Earth’s surface. Fog differs from cloud only in that the base of fog is at the Earth’s surface while clouds are above the surface. Clouds form in the atmosphere as a result […]

Weather is not a capricious act of nature, but rather the atmosphere’s response to unequal rates of radiational heating and cooling across the surface of the Earth and within its atmosphere. Troposphere. The troposphere begins at the Earth’s surface and extends up to about 11 kilometers (36,000 feet) high. The vertical depth of the troposphere […]

I don’t think that any of the FAA books cover El Niños, but as flyers, we should be aware of their impact. The drought in California from 2012-2016 was primarily caused by the weather pattern associated with the lack of an El Niño, a La Niña, as well as the effects of global climate change. […]

One of the sample questions for the Instrument Rating is: A generally recommended practice for autopilot usage during cruise flight in icing conditions is   A) keeping the autopilot engaged while monitoring the system.   B) periodically disengaging the autopilot and hand flying the airplane.   C) periodically disengaging and immediately reengaging the altitude hold function. This is […]

Icing can occur any time there is visible moisture and the temperature is between +02 and −10 degrees Celsius. As shown in the videos, icing can accumulate gradually or suddenly, with catastrophic effects. The FAA has put out a lot of information on icing—including an entire chapter in AC 00-6b Aviation Weather. The WINGS program […]

The meteorologists and designers at Weather Underground teamed up to bring you the science behind some of the most spectacular weather phenomena in a simple and artistic way.

Atmospheric rivers are a welcome event in Southern California. This is what the charts looked like on January 12, 2017 at the end of a week of heavy precipitation. This article on the Earth Observatory site explains how they form and has an animation from satellite-based measurements from January 7 to January 10, 2017. As […]

It is surprisingly difficult to find documentation on the FAA and NOAA websites that explicitly state wind direction as either true or magnetic. Everyone knows that the wind direction in local reports, ATIS and automated weather are reported with reference to magnetic north. “Long-lines” reports, METARs, TAFs, Winds Aloft, etc. are given with reference to […]

NASA and NOAA have several aircraft that fly right into the eye of a hurricane to gather data so that forecasters can plot its course. Here’s the track of one of them on October 7th.

Weather fronts are as familiar as rain. For those who live outside of Earth’s tropics, the movement of warm and cold masses of air creates the weather, and when the two clash, it often rains. Understanding what happens when cold and warm air meet (cold and warm fronts) has given meteorologists the ability to predict […]

Mammatus are most often associated with the anvil cloud that extends from a cumulonimbus, but may also be found under altocumulus, altostratus, stratocumulus, and cirrus clouds, as well as volcanic ash clouds. In the United States, sky gazers may be most familiar with the very distinct and more common cumulonimbus mammatus. When occurring in cumulonimbus, […]

Patrick Smith has an interesting post about icing, how it affects the airplane and the airlines, and a bit about accidents due to icing. Snow will not stick to an airplane during flight. Ice, however, is another story. Owing to aerodynamic forces, it tends to adhere to the thinner, lower-profile areas, and not to larger […]

There’s a huge storm in the east right now. Here’s the METAR and TAF for LaGuardia. Update: Here’s a picture from space of the snow on the ground, Output produced by METARs form (0456 UTC 27 December 2010) found at http://aviationweather.gov/adds/metars/index.php KLGA 270451Z 33031G40KT 1/4SM R04/2000V2800FT SN BLSN VV001 M04/M07 A2915 RMK AO2 PK WND […]

On a recent November morning, around 8:30, I went over to the airport to practice slow flight with our new vortex generators. Since I was there I wiped the dew and bugs off of the Cherokee. We’d had some rain so the dew was pretty thick. While I was wiping the dew off of the […]

fractus /ˈfræktəs/ Adjective

This spectacular image of sunset on the Indian Ocean was taken by astronauts aboard the International Space Station (ISS). The image presents an edge-on, or limb view, of the Earth’s atmosphere as seen from orbit. Read more at NASA. NASA has another view highlighting polar mesospheric clouds which occur near the boundary between the mesosphere […]

Click on the image below to see a stunning slideshow and explanation of the origins of noctilucent clouds. NASA sent a satellite into orbit to study these clouds and has a site with photos and details on how they are changing over time. NOAA has a page of links to sites featuring noctilucent clouds and […]

Lenticular clouds form in the lee of mountains. They are associated with extreme turbulence—even as they look very pretty. Below are some examples I’ve been collecting. NASA’s APOD has lots more.  Above Washington  Over Hawaii  Over New Zealand  Nightime over Flagstaff  Cap Cloud and Lenticular Cloud in the Canary Islands They also have a time […]

A temperature inversion occurs when cold air is trapped beneath warmer air. The temperature of the air in the air mass near the ground is colder than the temperature in the air mass above. Inversions often occur when the cold air is trapped in a valley surrounded by high mountains. In the US, LA and […]

Two hurricanes recently hit the Gulf Coast and it’s interesting to see the how the altimeter dropped and wind picked up over the course of a few hours. The code PRESFR means Pressure falling rapidly. I edited out the TNSO, A02, and AUTO so more of the information fits on one line. I have readings […]

METARs and TAFs have been around since before the high-speed internet made data transmission instantaneous (and they are based on Surface Aviation Observation (SAO) and Terminal Forecasts (TF) for current weather conditions before June 1, 1996) so they use a somewhat cryptic method for encoding weather data. However, once you learn how to decode them […]

The FAA knowledge tests have many questions on thunderstorms—the stages, hazards associated with them, and weather products related to them. Stages of a Thunderstorm The best explanation of the stages is found in Advisory Circular 00-6B Aviation Weather. For a thunderstorm to form, the air must have (1) sufficient water vapor, (2) unstable lapse rate, […]

Most FBOs have a computer for checking the weather but I can never remember the addresses for METARs, NOTAMs, and TFRs. This is a list of sites I check before returning. Now that Electronic Flight Bags (EFBs) like ForeFlight and WingsX have weather, NOTAMS, and TFRs built in, this page isn’t as useful as it […]

This post summarizes FAA Advisory Circular AC 00-54 PILOT WINDSHEAR GUIDE issued 11/25/88. I changed the punctuation a bit and left out a lot of the text. Additions are indicated by brackets [ ]. Bold indicates things I’d like to remember. This document uses windshear as a single word—other documents split it into two words—wind […]

The Aviation Safety Network database contains 69 wind-shear accidents, most of which did not result in fatalities. Three accidents—New Orleans in 1975, New York in 1982, and Dallas-Fort Worth crash in 1985—prompted NASA to begin a program to understand and detect wind shear. As a result of the program, wind-shear alert systems have been installed […]

[The Aviation Weather Services book includes a section on Supplementary Products. These are not likely to be of interest to general aviation pilots, but are included here for completness.] Collaborative Convective Forecast Product (CCFP) The Collaborative Convective Forecast Product (CCFP) is a graphical representation of forecast convective occurrence verifying at 2-, 4 -, and 6-hours […]

Short-Range Surface Prognostic (Prog) Charts Short-Range Surface Prognostic (Prog) Charts (Figure 8-1) provide a forecast of surface pressure systems, fronts and precipitation for a 2-day period. The forecast area covers the 48- contiguous states, the coastal waters and portions of adjacent countries. The forecasted conditions are divided into four forecast periods, 12-, 24-, 36-, and […]

Area Forecasts (FA) The NWS issues Area Forecasts (FA) to provide an overview of regional weather conditions that could impact aviation operations in the U.S. and adjacent coastal waters. Area forecasts are issued by the following offices for the following areas: • The Aviation Weather Center (AWC)   o Conterminous U.S. and adjacent coastal waters (CONUS) […]

Significant Meteorological Information (SIGMET) SIGMETs provide aircraft operators and aircrews notice of potentially hazardous en route phenomena such as thunderstorms and hail, turbulence, icing, sand and dust storms, tropical cyclones, and volcanic ash. SIGMET Criteria (Non-Convective) A SIGMET may be issued when any of the following conditions occur or is expected to occur in an […]

Aviation Routine Weather Report (METAR) Aviation Routine Weather Report (METAR) is the primary observation code used in the U. S. to satisfy World Meteorological Organization (WMO) and International Civil Aviation Organization (ICAO) requirements for reporting surface meteorological data. A METAR report includes the airport identifier, time of observation, wind, visibility, runway visual range, present weather […]

There are lots of sources for aviation weather and I cover them in some detail in this post. The National Weather Service publishes weather observations for aviators and publishes most of them at the Standard Briefing page. Most of them are covered in the FAA publication Aviation Weather Services AC 00-45F. The 2007 version of […]

There are lots of questions on the FAA Knowledge Tests about altimeter readings at non-standard temperature and pressure settings. The non-standard pressure questions are fairly intuitive. We all know that pressure decreases as altitude increases. Therefore, if the pressure is lower than what the altimeter expects, the altimeter is fooled into thinking it is higher […]

The knowledge tests have lots of questions of METARs and TAFs and rather than copy this information into every question, I’ve posted it here. AVIATION ROUTINE WEATHER REPORT (METAR) Handbook of Aeronautical Knowledge p 11-4, 11-5, 11-6 An aviation routine weather report, or METAR, is an observation of current surface weather reported in a standard […]

Update 2017-01-04 Many of the links on this page are broken but I’m leaving it up in case you want to track them down. Some of them like the Aviation Weather page have just moved to another location on the site. Others are no longer in existence. Here is a great place to start—the Standard […]

The winds along the Central Coast of California are sometimes strong, but usually onshore so runways are pretty much lined up with the wind. When they vary in direction it is usually because of thermal activity so they are fairly light. In the fall the Santa Ana’s can be very strong and from directions where […]

The Detroit/Pontiac branch of NOAA’s National Weather Service Weather Forecast Office had a glossary of weather terms that you can get through the Internet Archive. It includes common terms that every airman should know like Air Mass Thunderstorm as well as less common terms like Alberta Clipper that apply to certain areas of the country. […]