I have been using 1800WXBRIEF.com and Aviation Weather Center for years since they don’t require a paid subscription. But according to the CFIs at the school I just started flying with, these are not considered legal weather briefings. 

Answer: The question asked begs another one: Legal to whom? 

FAA regulations, notably FAR 91.103, require pilots to obtain weather reports and forecasts. However, according to an FAA spokesperson, “the FAA does not prefer one weather source over another, nor do we define a ‘legal weather briefing.’ It is up to the pilot in command (PIC) to use a weather source that best suits their needs and allows them to meet the preflight planning requirements.“

That being said, there are some CFIs and flight schools that advocate paid subscriptions, such as ForeFlight, and free discreet login services, such as 1800WXBRIEF, because in addition to providing information, they also allow the pilot to file a flight plan. They also require an account, which means it’s easier to prove the pilot obtained a weather briefing prior to the flight because there will be a record of the login.

The latter is often one of the first things the National Transportation Safety Board checks when it investigates an accident or incident.

At the very least, a pilot should check TAFs, METARs, winds aloft, and NOTAMs prior to a flight. It is distressing how many pilots and pilots in training believe that listening to the ATIS/ASOS/AWOS at the airport or along their route constitutes a weather briefing. They don’t. 

Nor does looking out the window at the FBO. Any more than “pretty good” is a PIREP. 

The post Is There an Official Weather Briefing? appeared first on FLYING Magazine.

Answer: During the warm season, convective weather has a huge impact on the National Airspace System (NAS). As the amount of usable airspace diminishes on any given day, this ultimately engenders delays in the system. A departure within busy airspace usually means a delay. In the worst-case scenario, ground stops may be levied depending on route of flight and destination airport. Nevertheless, forecasters at the Aviation Weather Center (AWC) are busy at work issuing advisories to warn pilots of these dangerous convective areas.  

A single-cell, pulse-type thunderstorm is normally easy to spot in the distance and maneuver around while in flight. In this situation, a deviation around such a cell does not eat into your fuel reserves. However, when thunderstorms become embedded, severe, or dense in coverage within an area or along a line, they are considered a significant en route hazard to aviation. This often requires you to plan a more circuitous route, which means carrying extra fuel than if you flew a direct route. It is in this case that an AWC forecaster will issue a convective SIGMET (WST) to “protect” this airspace. 

When you hear “convective SIGMET” during your preflight briefing, don’t think of it as a forecast for thunderstorms. Instead, think of it as a “NOWcast” of organized convection that may be highly challenging or dangerous to penetrate. These active thunderstorms must meet specific criteria before a convective SIGMET is issued. Areas of widely scattered thunderstorms, such as shown in the XM-delivered satellite radar image below, are generally easy to see and avoid while in flight and often do not meet convective SIGMET criteria.

Nevertheless, on any particular eight-hour shift a single forecaster at the AWC’s convective SIGMET desk looks at all of the convective activity occurring throughout the conterminous U.S. on a continual basis. On an active convective weather day, they are likely the busiest forecaster on the planet. This forecaster is given the responsibility to subjectively determine if an area or line of convection represents a significant hazard to aviation using these minimum criteria:

• A line of thunderstorms is at least 60 miles long with thunderstorms affecting at least 40 percent of its length.
• An area of active thunderstorms is affecting at least 3,000 square miles covering at least 40 percent of the area concerned and exhibiting a very strong radar reflectivity intensity or a significant satellite or lightning signature.
• Embedded or severe thunderstorm(s) are expected to occur for more than 30 minutes during the valid period regardless of the size of the area. 

For reference, 3,000 square miles represents about 60 percent of the size of the state of Connecticut.

Will an advisory be issued as soon as the convection meets one or more of these criteria? Possibly. A special convective SIGMET may be issued when any of the following criteria are occurring or, in the judgment of a forecaster, expected to occur for more than 30 minutes of the valid period:

• Tornadoes, hail greater than or equal to three-quarters of an inch in diameter, or wind gusts greater than or equal to 50 knots are reported.
• Indications of rapidly changing conditions, if in a forecaster’s judgment they are not sufficiently described in existing convective SIGMETs.

However, special issuances are not the norm, especially when there is a lot of convective activity to capture. In most cases, a convective SIGMET is not issued until the convection has persisted and met the aforementioned criteria for at least 30 minutes. Given that these advisories are routinely issued at 55 minutes past the hour, any convection that has not met the criteria by 25 minutes past the hour may not be included in the routine issuance. Consequently, there are times where a dangerous line or area of developing thunderstorms could be present without the protection of a convective SIGMET. All convective SIGMETs will have a valid time of no more than two hours from the time of issuance.

• READ MORE: Surviving Thunderstorms: Cut Your Risk

Last but not least, these convective SIGMETs are often coordinated by an AWC forecaster with meteorologists at the various Center Weather Service Units (CWSUs) located throughout the country at the various Air Route Traffic Control Centers (ARTCCs). At times, a meteorologist at the CWSUs may issue a Center Weather Advisory (CWA) when building cells are approaching convective SIGMET criteria. The goal is not to duplicate advisories when possible and provide the best guidance for pilots.

The post What Is the Criteria for Issuing a Convective SIGMET? appeared first on FLYING Magazine.

But wait, is vertical visibility even a legitimate visibility? Actually, it’s a bit of a misnomer and not a true measure of visibility in the traditional sense. Vertical visibility is a close cousin to ceiling. That is, it represents the distance in feet a person can see vertically from the surface of the Earth into an obscuring phenomenon, or what is called an indefinite ceiling. What isn’t obvious is how vertical visibility is determined, and how this is different from a definite ceiling.

It’s arguable that an indefinite ceiling is perhaps the most misunderstood phenomenon reported in a routine (METAR) or special surface (SPECI) observation. Forecasters will add vertical visibility in a terminal aerodrome forecast (TAF) as illustrated in the image below for Bradford Regional Airport (KBFD) in Pennsylvania. Whether this occurs in a METAR or TAF, vertical visibility is coded as “VV” followed by a three-digit height in hundreds of feet above the ground level. For example, you may see “VV002,” which is a vertical visibility of 200 feet. While a definite ceiling can be broken or overcast, a vertical visibility always implies the sky is completely covered. Let’s explore the difference between a definite and indefinite ceiling and the operational considerations.

Automated Observations

In the early days, human weather observers used to employ what were called “pilot balloons” to estimate the ceiling height. Essentially the balloon was launched by the observer and, given the balloon’s known rate of ascent, they watched the balloon enter the base of the clouds and measured the time it took using a stopwatch to determine the ceiling height. Then new technology emerged called a rotating beam ceilometer that measured the height of clouds. While it was more effective than launching a balloon, this method was phased out around 1990 and replaced with the laser beam ceilometer, the technology still widely used today.

The task of walking outside and assessing the height of clouds is generally a thing of the past given that this technology is incorporated into the automated surface observing system (ASOS) or automated weather observing system (AWOS) present at many airports throughout the U.S. The trained observer simply logs in to the ASOS (or AWOS) and makes their observation based on the data gathered and reported by the automated system. Then the observation is edited and augmented by the observer as necessary. Depending on the airport, this process may be completely automated.

In all honesty, making an estimate of the height of the cloud base isn’t the difficult part. What’s difficult is to provide a representative description of the amount of cloud coverage (e.g., few, scattered, broken, or overcast) in the airport’s terminal area. A laser beam that points straight up may easily miss a scattered or broken cloud deck. To alleviate this issue, the automated systems process the data over a given amount of time since clouds are generally moving through the sensor array area. It was found that a 30-minute time period provided a representative and responsive observation similar to that created by a trained observer. The most recent 10 minutes of sky cover and ceiling height are double weighted using a harmonic mean. (A harmonic mean is used in the visibility and sky cover algorithms rather than an arithmetic mean because it is more responsive to rapidly changing conditions such as decreasing visibility or increasing sky coverage/lower ceiling conditions.) In the end, the goal is to provide an observation representative of the airport’s terminal area, which is the area within 5 sm from the center of the airport’s runway complex. Visibility, wind, pressure, temperature, etc., all have their own harmonic means accordingly.

In our everyday experience, we know that many cloud decks observed from the ground have a very well-defined base. For an untrained observer, it might not be a simple task to determine their height. However, it’s easy to pick out where the base of the cloud starts. Even in these cases, the cloud decks may vary in height and multiple cloud layers may exist. Visually, that may be more difficult to discern for the untrained eye, but automated systems do a reasonable job making that observation. In a convective scenario, it is not unusual to see multiple scattered and broken cloud heights. For example, at the West Michigan Regional Airport (KBIV) the following was observed:

KBIV 122353Z AUTO 08011KT 4SM RA BR FEW011 SCT048 OVC065 19/18 A2972

This observation includes three definite cloud layers, which are a telltale sign that a convective environment is in place even before the first lightning strike.

Nuts and Bolts

An ASOS continuously scans the sky. To determine the height(s) of the clouds, the backscatter returns from the ceilometer are put into three different bins. When there’s a “cloud hit,” the system identifies a well-defined and sharp signature pattern that you’d expect with the sensor striking the cloud base. Essentially this means most of the hits are aggregated around a particular height above the ground. Such a sharp signature is then incorporated into the 30-minute sky cover and cloud height harmonic average, and a new observation is born.

On the other hand, a “no hit” is recorded when there isn’t an ample amount of backscatter received, usually because there are no clouds below 12,600 feet agl over the sensor. Note that the ASOS (and AWOS) is designed only to detect clouds below 12,600 feet above the ground, although a trained observer can and does report higher clouds. Lastly, if the backscatter does not provide that sharp signature around a particular height, an “unknown hit” is recorded. It is this unknown hit that leads us down the path to an indefinite ceiling or vertical visibility.

Haze, Mist, and Fog, Oh, My!

So, isn’t an indefinite ceiling the same thing as a ground fog event? Not necessarily. Stratus is the most common cloud associated with low ceilings and reduced visibility. Stratus clouds are composed of extremely small water droplets or ice crystals (during the cold season) suspended in the air and may be touching the surface, so to speak. An observer along a coastal region or on the side of a mountain would likely just call this plain old fog. This is certainly understandable, since we grew up calling this kind of situation foggy.

Fog, however, is thought to be more of an obstruction to visibility from a surface observing standpoint. To understand the recording of obscurations, here’s how the ASOS automatically determines what to report. Once each minute, the obscuration algorithm checks the reported visibility. When the visibility drops below 7 sm, the current dew point depression (temperature-dew point spread) is checked to distinguish between fog (FG), mist (BR), and haze (HZ). If the dew point depression is less than or equal to 4 degrees Fahrenheit (~2 degrees Celsius), then FG or BR will be reported. Visibility will then be used to further differentiate between FG and BR.

Whenever the visibility is below five-eighth sm, FG is reported regardless of the “cloud” that produces it. So fog isn’t really about a cloud or ceiling as much as it is about visibility. Therefore, stratus and fog frequently exist together. In many cases, there is no real line of distinction between the fog and stratus; rather, one gradually merges into the other. Flight visibility may approach zero when flying in stratus clouds. Stratus over land tends to be lowest during night and early morning, dissipating by late morning or early afternoon. Low stratus clouds often occur when moist air mixes with a colder air mass or in any situation where temperature-dewpoint spread is small.

• READ MORE: Decoding the Weather

Moisture-Rich Environment

Essentially, an indefinite ceiling means there is something obscuring your view of the cloud base. When you look up, you won’t be able to see a well-defined cloud base like you would on a day where the sky isn’t obscured. According to the ASOS User’s Guide, “these ‘unknown hits’ are primarily caused by precipitation and fog that mask the base of the clouds.” The laser beam bounces off moisture at various heights, making it impossible to process this as a definite cloud hit. Instead, the ASOS identifies these unknown hits as a vertical visibility abbreviated as “VV” in the resulting routine or special observation.

Given the broad moisture field near the surface that scatters the laser beam signal, indefinite ceilings are guaranteed to be paired with low visibility situations. You are not going to see a surface visibility of 10 miles paired with a VV of 200 feet. Usually this means a low or very low IFR flight category anytime there’s an indefinite ceiling. Also keep in mind that an indefinite ceiling in a terminal forecast will result in a low visibility forecast.

In general, the higher the vertical visibility, the better the surface visibility. Therefore, a vertical visibility of 200 feet (VV002) is usually met with a visibility of one-half sm. Furthermore, a vertical visibility of 700 feet (VV007) will likely be associated with a visibility between 1 and 2 sm. While rare, you may even see a fairly high vertical visibility over 1,000 feet (e.g., VV012). In this case, the surface visibility may be over 3 sm. The really bad stuff, however, occurs with a visibility of one quarter sm (or even “M1/4 SM” denoting less than that) and a vertical visibility of zero feet (VV000) as illustrated in the image below for Bradford Regional Airport. This very low indefinite ceiling is not all that common unless you are stationed on the summit of Mount Washington in New Hampshire, where this low vertical visibility happens quite often throughout the year. It also occurs fairly often at airports along West Coast regions of the U.S., especially during their “May gray” or “June gloom” time frame.

As mentioned earlier, fog and precipitation are the two primary reasons the base of the cloud deck is obscured. Therefore, it’s common to see vertical visibility reported when light rain, drizzle, or even snow is falling from the cloud base.

Precipitation or not, it’s generally rare to see a single station reporting an indefinite ceiling. Most of the time, you will see indefinite ceiling reports embedded in a widespread area of low or very low IFR conditions, especially at coastal airports. Although airports such as Nantucket Memorial Airport (KACK) in Massachusetts can be reporting a low indefinite ceiling, at stations farther inland near Cape Cod the sky can be clear or nearly so.

It’s important to note that conditions producing an indefinite ceiling often take longer to improve. Normally there will be a transition from an indefinite to definite ceiling once the moisture begins to mix out with the help of the sun. However, the visibility may still be quite low for the next few hours. Keep this in mind when flight planning to an airport reporting an indefinite ceiling.

Operational Significance

From a practical standpoint, you should treat an observation or forecast for a vertical visibility the same as you’d treat a definite ceiling. Given the nature of conditions that produce an indefinite ceiling, you can expect a longer transition as you depart into such a ceiling under IFR. It’s easy to get spatial disorientation because of the gradual change.

An indefinite ceiling restricts the pilot’s flight (air-to-ground) visibility. Therefore, an instrument approach may be a bit more challenging even after you drop below the reported ceiling height because of the reduced visibility. Most importantly, a circle-to-land approach with an indefinite ceiling will make it quite difficult to keep the runway in sight, especially at night. And, as a final consideration, with an indefinite ceiling, don’t be surprised to see runway visual range also pop up in the observation for airports with such equipment.

This feature first appeared in the October 2023/Issue 942 of FLYING’s print edition.

The post Here’s the Lowdown on ‘Vertical Visibility’ appeared first on FLYING Magazine.

• READ MORE: NOAA Changing Weather Site

Overview

A majority of the weather data will appear on the graphical forecasts for aviation (GFA) webpage. This is the heart and soul of the new site. Here’s a brief description of the purpose of this page as posted in the GFA help on aviationweather.gov.  

“The GFA webpage is intended to provide the necessary aviation weather information to give users a complete picture of the weather that may impact flight in the United States (including Alaska & Hawaii), Gulf of Mexico, the Caribbean, and portions of the Atlantic and Pacific Oceans. The webpage includes observational data, forecasts, and warnings that can be viewed from 18 hours in the past to 18 hours in the future. Hourly model data and forecasts, including information on clouds, flight category, precipitation, icing, turbulence, wind, and graphical output from the National Weather Service’s National Digital Forecast Data (NDFD), are available.”

What’s a Progressive Web App?

Let’s begin with the good news. Like my website, EZWxBrief, the Aviation Weather Center (AWC) decided to build its website  as a progressive web app (PWA). The aviationweather.gov legacy site was very clumsy and nearly impossible to use on a mobile device such as an iPhone. Developing this as a PWA offers a very responsive design, and that means it works reasonably well on those smaller hand-held devices in both portrait and landscape orientations. 

No, you won’t find this “app” in the App Store or Google Play Store. Instead, you should install the PWA on your device to have the best user experience. Not to worry, it literally takes just a few seconds and applies to any device, not just handhelds. 

Here’s the installation process. Simply open a browser that supports a PWA such as Chrome, Safari, or Brave and enter “https://aviationweather.gov” into the browser’s address bar. On your hand-held device, locate the “Share” icon (sometimes called a “Bookmark” or “Send to” icon). This is an icon that’s shaped like a square with an upward pointing arrow in the center. Please note that not all browsers support progressive web apps. A tap on that icon and you have finished step one of three to install the app. 

Next, you’ll be shown the “Share” menu. Scan down that menu using Chrome or Safari and tap on the “Add to Home Screen” selection.

During the third and final step, you’ll be able to name your PWA icon. You are free to change the long default name from “AviationWeather.gov” to AWC or whatever you like. When you’ve chosen the name, tap on the “Add” button in the upper-right corner. This will add an Aviation Weather Center icon to your home screen with the name you chose. Even better, when the Aviation Weather Center makes future updates, they will be available the next time you restart the app. It’s actually easier than installing and updating native apps.

Just like any native app, tap on that home screen icon and the aviationweather.gov site will open up. You’ll notice that it doesn’t have any browser bar or other browser controls, which frees up valuable screen real estate on smaller devices. Essentially, it will have the same look and feel as a native app without the overhead of Apple or Google. 

You can do the same installation on your desktop or laptop computer, but the process is a bit different. Once again, open up your browser and type “https://aviationweather.gov” into the address bar, and you will see an Install button appear at the end of the address bar for any website (and browser) that supports a PWA.

Clicking on the “Install” button will provide the prompt below to install the app.  Once done, you’ll see an Aviation Weather Center icon on your desktop. By the way, you can also always uninstall the app at any time for any of your devices.

One of the issues that is apparent with the site on some hand-held devices is that the app will crash or reset when using a rapid, pinch-and-zoom gesture on the interactive GFA map. This is evidently an issue with Leaflet (the software it uses to render the maps), and the workaround is to avoid any rapid, pinch-and-zoom gestures. Just slow your roll and you’ll be fine.  

Cross Section Tool

To replace the Java Flight Path Tool that required you to download Java onto your computer (Java isn’t permitted on iOS devices), the AWC added a cross-section tool that now runs on any platform. You will see an icon on the right to start this tool. It’s the icon just under the settings icon (cog wheel).

You simply define a route, such as KMCI.KMEM.KAVL (note the periods in between the identifiers), and you can plot this path on the GFA map as a great circle route or view it as a cross section. Currently, the only variables you can plot on the vertical cross section are temperature, wind speed, turbulence, and icing.

Reduction in Static Imagery

The overall new design of the website is radically different from its legacy counterpart. Perhaps the most significant long-term effect is that the AWC decided to terminate the generation of dozens of static images that were available on the legacy site. Many flight planning websites, and even some of the heavyweight EFB apps referenced, scraped many of these images off of the AWC site. Consequently, you may have noticed back in the middle of October that these apps had to scramble to delete those from their own static imagery collections. The imagery collections that were depreciated included: 

• Lowest freezing level forecast from the Rapid Refresh (RAP) model
• TCF, eTCF, ECFP convective forecasts
• RAP/NAM Wind/Temperature graphics
• PIREP plots
• Satellite regional plots

Although you can still find access to prog charts, G-AIRMETs, as well as icing and turbulence static imagery within the decision support imagery page (https://aviationweather.gov/graphics), the AWC has a goal to eventually eliminate all static imagery.

Missed Opportunities

Your opinion  may differ, but I find the user interface for the decision support imagery to be very antiquated and clumsy. Even on large screens, you have to constantly scroll up and down, and it requires an immense amount of button clicks or taps to get what you want. It’s very exhausting and tedious to use. In fairness, that page suggests it was “designed for Center Weather Service Unit meteorologists who build information packages on desktop computers.” Instead, AWC suggests that pilots utilize the interactive map page (https://aviationweather.gov/gfa).

The issue here is that the DSS page gives you a vertical resolution of 2,000 feet for icing and turbulence forecasts. If you use its interactive map, you only get a 3,000-foot or even 6,000-foot vertical resolution despite the fact that the native vertical resolution of the icing and turbulence products is 1,000 feet. It is understandable that browsers have hard limitations, and this was likely a tradeoff to providing something that has a reasonable performance. 

While the Aviation Weather Center removed the regional satellite imagery from the site, it has been incorporated as a separate layer into the graphical forecasts for aviation (GFA) tool. Currently there isn’t a replacement for the color infrared satellite imagery. That is something it will be adding in the future.

Another deficiency is that the site doesn’t acknowledge when the layer you are viewing is void of data. For example, if you pull up the center weather advisories (CWAs) on the GFA tool, you may get a blank map. Is the map blank because there are no CWAs active, which happens more often than not? Or perhaps it’s because your browser or internet connection is being finicky? The lack of any data or advisories is just as critical as the presence of them. AWC doesn’t provide any acknowledgement or banner to alert you when this occurs.  

If you are looking to travel outside of the U.S., some of the weather guidance on the GFA tool, such as icing and turbulence, stops at the border. While this was also true with the legacy GFA tool, it still represents a shortcoming given that much of this guidance is available over a good portion of Canada and northern Mexico. The National Weather Service (NWS) has a directive that it can’t show forecasts outside of the U.S., especially over Canada and Mexico. Pilots are supposed to go to the respective website/services for those countries to receive that forecast information.

This is inconsistent since some decision support graphics (i.e., static imagery) clearly show forecasts for icing and turbulence in Canada and Mexico. Moreover, if you plot a route from International Falls, Minnesota, to Caribou, Maine (through southern Ontario and Quebec, Canada), the cross-section view shows this guidance.

Finding HEMS

If you are looking for the helicopter emergency medical services (HEMS) tool, it has been integrated into the interactive GFA and rebranded as the GFA-LA tool (with “LA” for “low altitude”). When viewing the GFA, click on the helicopter button in the upper-right part of the map to switch the GFA from general aviation mode into low-altitude mode, which offers expanded capability from the HEMS tool.

Final Thoughts

There’s no doubt that there are winners and losers with this update. I’ve read hundreds of comments on social media posts and other aviation forums that despise the new site and those that simply love it. The biggest advantage is that the site is very responsive on hand-held devices with the occasional glitch that I’m sure will be resolved in time. The dismantling of nearly half of the static imagery is truly a loss and will likely be felt for months, if not years, to come. As a matter of fact, I am in the process of finding replacements of these image collections for my own website, EZWxBrief. 

Lastly, if you are still hanging onto a glimmer of hope that AWC will bring back the legacy site, don’t hold your breath. While there are still some growing pains with this new version, the Aviation Weather Center is fully committed to this new release—so just get used to it. 

The post Aviation Weather Center Website Upgrade—the Good, Bad, and Ugly appeared first on FLYING Magazine.

The new site has a much cleaner appearance than the legacy site from the Aviation Weather Center arm of NOAA. It features more interactive maps, static images to embed in briefing material, and a dark mode.

User Features

The user can select raw data or, with a push of a button, have it presented decoded.

You can select the most recent weather or take a look as far back as 48 hours, and there is a “remember” feature.

Under the weather tab at the top of the page is a drop-down menu for observations and forecasts for ceiling, visibility, precipitation, thunderstorms, temperature, winds, turbulence, and icing. Each item is indicated with text and an icon.

Clicking on the icons calls up an interactive map with a slider that displays a graphic depiction of the forecast conditions.

According to the agency, the upgrade is designed to be adaptable to permit use on mobile devices.

All displays and tools available on the current aviationweather.gov are available on the updated website. In addition, the new website merges the legacy Helicopter Emergency Medical Services (HEMS) tool into the same framework as the Graphical Forecasts for Aviation while keeping its focus on low-altitude flight.

The Aviation Weather site is a free service and does not require a discreet login or user account. This makes it more accessible as a weather tool. However, unlike products that require a discreet login, the user’s interaction with the site is more difficult to verify.

If you can’t wait until Monday, test out the new features here: https://beta.aviationweather.gov.

The post NOAA Changing Weather Site appeared first on FLYING Magazine.

Answer: MOS stands for model output statistics and is pronounced “moss.” MOS has been around since the 1960s and was originally developed to provide aviation meteorologists with guidance to produce useful forecasts to pilots. But over the last decade, MOS has been making its way into the aviator’s toolkit and is offered by a couple of the heavyweight electronic flight bag (EFB) apps. 

So, what does MOS offer? Crazy as it may seem, most pilots really want to know what’s happening at an airport from a weather perspective. Before they depart, they’d like to know what the ceiling or visibility will be like when they reach their destination. Will they get that visual approach or will they need to prepare to fly an instrument approach? Or perhaps they want to find an airport with favorable winds to practice some crosswind landings. 

There’s nothing special about these requirements, however. One nice aspect about MOS is that it’s available for more than 2,100 civilian and military airports throughout the U.S. and its territories. At the moment, the National Weather Service (NWS) only issues a terminal aerodrome forecast (TAF) for 700 airports in this same region. So, if your departure, destination, or alternate airport does not have a TAF, MOS provides some useful guidance about the expected meteorological conditions significant to aviation at those airports at the time of your departure or arrival. 

Here’s the technical part. Most weather prediction models that you often hear about on the local news, such as the American or European model, don’t automatically produce a point forecast for a specific town or airport for various sensible weather elements, such as ceiling height, visibility, and surface wind. This is where MOS shines. 

MOS combines this “raw” model forecast with geoclimatic data in an attempt to improve upon it using a statistical method. It relates observed weather elements (decades of past observations) to appropriate variables (predictors) via a statistical approach. Because it uses geoclimatic data, MOS is capable of accounting for local effects that cannot be resolved by these models alone. In other words, if the airport is in a valley or on a hilltop or next to a large body of water, MOS is able to account for that local topography. It’s a lot like the old local pilot who has been flying for 50 or more years that can tell you exactly what to expect on the final approach when the winds are coming off of the mountains west of the airport. 

The other important element is that MOS downscales the model data into weather elements important to aviation. This includes, but is not limited to, cloud coverage, ceiling height, prevailing visibility, wind speed and direction, precipitation type, and the probability of precipitation or thunderstorms. 

While MOS does an excellent job most of the time, remember it’s an automated forecast—there’s no human in the loop like a TAF. It should never be used as a wholesale replacement for a forecaster-issued TAF. So it should never be used to replace a TAF from a legal perspective. If the airport has a TAF, that forecast needs to be used to determine if an alternate is required and alternate minimums for instrument flight rules. MOS guidance is best used as a way to fill in the blanks when the official forecasts don’t provide the details necessary. 

• READ MORE: Navigating Smoke

Two of the three existing MOS forecasts are being retired in the next few years. However, the only version of MOS that has made its way into the FAA literature (see the Aviation Weather Handbook/FAA-H-8083-28) is called LAMP, which stands for localized aviation MOS program. It is issued hourly and is being fully supported by the NWS in the foreseeable future. Does this effectively mean that LAMP can be used to make operational decisions about a flight? I’ll let the legal scholars opine on that. Nevertheless, visit https://vlab.noaa.gov/web/mdl/lamp to view the suite of LAMP forecasts.  

MOS has some important limitations you should know about. It cannot forecast multiple cloud layers as you see in a TAF. Except for when the forecast is shown as clear, a single fixed cloud layer is the best MOS can do at this point, and it cannot tell the difference between a definite and indefinite ceiling. MOS also cannot directly forecast showers in the vicinity (VCSH) or fog in the vicinity (VCFG), nor can it forecast precipitation intensity or tell the difference between rain or drizzle. MOS is also unable to predict a variable wind.

The post What Is a MOS Forecast? appeared first on FLYING Magazine.

The industry research company attributes the expected growth in part to global efforts to increase aviation safety and the introduction of new weather forecasting technology with capabilities well beyond those of the aging systems in place at many airports.

Insight says it expects North America to represent the largest share of the aviation weather forecasting system market share in 2022, led by the U.S. According to Insight, the U.S. is home to more airports than any other country—a total of 19,622 airports, of which 5,000 are public-use facilities. The U.S. is also “investing heavily” in upgrading its airports with advanced technology to improve safety and security, the research firm says.

“According to data from several aviation sources in 2018, the FAA announced that the U.S. will be spending [approximately] $70 billion on more than 50 airport construction projects in the next three years,” the Insight report says, noting that the projects are likely to include upgrades in weather forecasting technology.

• READ MORE: ID Your Personal Weather Minimums

The report also cites airport projects in India, South Korea, China, and a number of other developed and developing countries that are expected to drive demand for aviation weather forecasting equipment over the next several years.

The post Researcher Expects Boom in Aviation Weather Forecasting appeared first on FLYING Magazine.