Questions tagged [weather]

Weather means the atmospheric conditions, including wind, temperature and precipitation, in a specific area at a specific time.

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1answer
57 views

Station pressure vs. reported altimeter

I must be missing something big. Page 12-5 of the PHAK tells me that a station at 5,000 feet above sea level would convert its 24.92 pressure reading to 29.92. I understand that this helps to track ...
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3answers
3k views

Why are pressure levels raised on warm days?

As I'm studying for the PPL knowledge exam, I had the following note: Pressure levels are raised on warm days and the indicated altitude is lower than true altitude. (source: AOPA) But I don't quite ...
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What is inflated wind speed?

According to NOAA, inflated wind speed is "the true wind speed (in knots) adjusted to improve forecasts of higher wind speeds. Wind speeds greater than the mean wind speed observed are increased, ...
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2answers
106 views

Best way to forecast density altitude?

Let's say I'm planning a day trip from a low elevation home base to a warm, mountainous location. I wake up early, check the weather, do performance calculations based on current METARs, and decide to ...
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2answers
95 views

Why is the minimum for VFR 1000/3 while there are VFR weather minimums for every single airspace?

It seems like I have a concept error here. I don't understand why "the VFR min is 1000/3" when I think I would need to check in which airspace I am to then check for its respective weather ...
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3answers
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Effect of heat and humidity on take off, descent, climb, and cruise

I am aware of this question, this resource (phak), and this resource that explains the science, but I am looking for a more straightforward answer. I am student pilot and there's a lot of literature ...
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1answer
86 views

What kind of weather conditions would produce turbulence with an intensity of 90 feet per second?

This is the official documentation that we found regarding current commercial airplane design criteria; https://www.law.cornell.edu/cfr/text/14/25.341 It says the criteria for continuous turbulence is ...
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1answer
91 views

Why does the Winds Aloft ‘For Use Time’ start before the ‘Valid Time’?

Why is it that a winds aloft forecast normally has a "valid time" that comes in the middle of the "for use" time range? Why don't they just state the valid time as the beginning of ...
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1answer
72 views

What does Region @TOP mean on the aviationweather.gov website?

When looking at raw METAR data on the aviation weather center, "@TOP" appears in the text box where you can type identifiers. What does TOP mean?
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230 views

Do airliners get substantially different weather briefings from the rest of us?

Southwest Airlines flights were delayed and cancelled this week due to an outage in their third-party weather provider. I understand if they have a streamlined business process for getting weather ...
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112 views

How can I calculate the "stability state" of air from a given set of data?

I would like to know the answer for the above question, it is about how to find whether atmosphere is stable or unstable using DALR (dry adiabatic lapse rate), SALR (saturated adiabatic lapse rate) ...
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1answer
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What is the red barb for in the NOAA weather briefing?

Wind barbs are well-defined symbols, but I noticed in my WX briefing that there are now occasional red barbs in the chart. The red appears on both the 5kt and 10kt barbs, and sometimes for largest ...
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Can gusts be reported as lower than wind speed?

KADS 072350Z 31030G20KT 13SM SKC 24/02 A2980 I’ve never seen a negative gust factor before. Is that a real thing (and if so, what does it mean), or did someone just make a typo?
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106 views

When was the last time the US Standard Atmosphere 1976 was updated?

I imagine due to slight changes in Earth's atmosphere or more accurate instrumentation it's been updated at least once, but also because it's understood to be a less precise model we might not have ...
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1answer
98 views

How to get an accurate time of arrival to the en-route alternate airport during flight planning?

I was thinking about accurate criteria of selecting en-route alternate (ERA) weather from ground (planning stage) especially for ERA 3% contingency flight plan. As we all know we should care about one ...
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1k views

Can I derive the wind speed and direction? [duplicate]

If I know the IAS and GS (with directional components) of an aircraft, can I derive the wind speed and direction? I'm working on an application that simulates the flight of an aircraft. Another ...
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70 views

What are the Requirements for the implimentation of Low Visibility Procedures at an airport?

So I was wondering if the RVR at an airport is reported above CAT I conditions for eg 1400 Meters etc but the Visibility is 50 to 100 Meters then would the pilots carry out non instrument approach or ...
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1answer
169 views

Why are the airport pressure values for "altitude" (inHg) and "sea level" (mb) slightly different on the NOAA web sites?

If one looks, for example, at the NOAA web site for Denver International Airport we see (at the time of posting this question) the Pressure/Altimeter is 29.78 inHg, the Pressure/sea level is 1006.1 mb ...
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0answers
57 views

A scenario question regarding meteorology

In the image attached, I’m struggling to find out why the answer is the way it is; maybe is me not being able to visualise it, but some help would be greatly appreciated.
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1answer
85 views

What causes Gusty winds? ( Meteorlogy) [closed]

I was wondering why winds can become gusty. I know that gusty winds tend to be related with frontal passage. Thanks : )
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3answers
136 views

What weather should we expect when temperature and dew point are similar?

What should i expect during my flight planning when i see both temperature and dew point are the same? I understand there will be fog but what else? could it mean icing? any difference between 20/20 ...
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1answer
86 views

Why is cloud base estimation taught in Fahrenheit?

I've seen the formula for estimating cloud base consistently presented using Fahrenheit temperature and dewpoint (for example, see PHAK 12-14; Jeppesen also teaches it this way): $$ \mathrm{cloud\:...
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2answers
137 views

How can I calculate ambient air pressure from flight data?

I am playing around with data collected during a flight. I would like to find out the (real, not ISA) ambient air pressure for each data point, since it is not reported in the spread sheet containing ...
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1answer
103 views

How can air stability be predicted?

After several weeks of being grounded due to low clouds, I was looking forward to the cool air, clear skies, high pressure and light winds that arrived this morning as forecasted. However, there is an ...
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1answer
148 views

What is the difference between the WSUSnn IDs used in convective SIGMETs?

When NOAA issues a convective SIGMET, it falls under one of three bulletin IDs: WSUS31, WSUS32, or WSUS33. Below are three examples from the current forecast. WSUS31: ...
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370 views

What is the difference between mist and haze in terms of relative humidity?

I am an aviation meteorologist and I struggle to distinguish the two of them.
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409 views

Where can I listen online to live VOLMET broadcasts?

Are there sites that stream live VOLMET broadcasts? I need to listen to the format but haven't have the time to put together an amateur radio.
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2answers
7k views

What do pilots landing on aircraft carriers do when the ship is not visible due to weather?

Say an aircraft takes off of a carrier to do a mission somewhere, and upon returning to the carrier the pilot comes to find that a thick layer of fog has formed just above the surface of the water in ...
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2answers
200 views

Does DA/DH refers to ceiling?

If airport is reporting FEW001 or SCT001 and RVR is above 600m, does it means that there will be no LVO because ceiling is defined as more than 4/8 and DA/DH will be more than 100ft because DA/DH is ...
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1answer
59 views

Are AWOS data open for commercial use? [closed]

I 've found out this great website where you can get historical AWOS weather data. I would like to use it for a commercial application but I don't find any data license. Do you know if the AWOS data ...
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1answer
84 views

Where is there an FAA source that states that squall lines are non-frontal?

There's a question in the FAA commercial question bank that indicates that squall lines are nonfrontal, and the reference for the question points to the Aviation Weather Advisory Circular. The word, &...
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4answers
816 views

Can the "G" and "VRB" wind conditions be combined in METARs?

I have never seen the "VRB" (for wind direction variations < 60°; e.g. VRB12003KT) and "G" annotation (for gusts > 10KT wind speed difference; e.g. 12003GT30KT) being combined in a METAR. Until ...
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1answer
62 views

How would a pilot apply the information found on a 500 Millibar Vorticity chart to a flight?

The U.S. Flight Service website has these weather products listed: I have circled the 500 Millibar Vorticity Charts. I've been a pilot for 10+ years and have never heard mention of this chart by ...
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2answers
137 views

Is AMDAR a required system on aircraft?

I was intrigued by the assertion that COVID-19 depressing commercial aviation has lead to lower quality weather forecasting The aircraft observations are a key piece in the jigsaw of national and ...
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1answer
165 views

Does a METAR report variable wind direction in a clockwise direction?

Does the convention for reporting variable wind direction always use a clockwise (nautical) sense? For example, if the wind varies between 340 degrees and 10 degrees, assuming a clockwise sense the ...
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1answer
91 views

Is an area of localized reduced visibility considered to be a cloud?

If there an area containing visible moisture in an otherwise clear sky and that area of visible moisture is transparent is it considered a "thin cloud" or simply a "localized area of reduced ...
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1answer
171 views

What is an approved weather source for flying an instrument approach into an airport with no working ATIS?

What can you use as viable weather information landing at an airport with ATIS inoperative due to the tower being closed after hours? Let's assume the approach secondary weather source is also ...
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2answers
2k views

Who makes the call to start in terrible weather conditions?

I once headed to the airport during a huge thunderstorm with winds above 55 knots and massive rain and some small hail. At the airport, I saw that most flights were delayed or even canceled. To my ...
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2answers
334 views

Are helicopters impacted by fog more than airplanes?

With the crash of Kobe Bryant's helicopter, it seems a lot of focus has been placed on the helicopter flying low in fog (under "special VFR"). However, I've seen several suggestions that the ...
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282 views

How far can the sound of a sonic boom travel? [closed]

Are there conditions or distances from the plane to cloud to the observer in which a sonic boom from a plane is muted?
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2answers
104 views

Why and how do atmospheric properties sometimes vary from the ISA? [closed]

I'm curious as to why sometimes atmospheric properties don't match the ISA's. One reason I am considering is due to calibration discrepancies. By atmospheric properties I mean temperature, Density, ...
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5answers
7k views

Why did my LGA-ORD flight make an S-shaped turn round the time it was passing a storm?

On a recent United UA1709 flight into Chicago (hit by a heavy storm at the time), I felt a noticeable descent, combined with two wide banks around 1 hour before landing. Looking at the flight path, I ...
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1answer
2k views

How do pilots avoid thunderstorms at night over the pacific en route to Australia where there is no radar? And what if a large front develops?

While there is some limited radar on board for pilots, we hear that there is no radar over the ocean which is why flight locations are estimated. As the distance between the United States and ...
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1answer
527 views

What to do if trapped on top VFR?

In the event that, despite his best efforts, a VFR-only pilot has gotten trapped on top of a solid cloud layer, what is(are) the safest course(s) of action? For example, consider a long cross-country ...
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1answer
192 views

How to avoid getting trapped on top VFR?

This question addresses whether it is legal to fly VFR over-the-top. One of the comments mentioned the difference between safety and legality, i.e. doing so may not be safe even if it is legal (in ...
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1answer
9k views

What fomula use for calculating pressure altitude?

I'm having some trouble making my calculations of pressure altitude match those in apps and text books. I'm using the formula from Wikipedia: (29.92 - altimeter setting) * 1000 + airport elevation ...
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1answer
912 views

What is the difference between ACARS and ADS-B?

What is the difference between ACARS and ADS-B? For weather information in-flight or pre-flight which one is used?
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1answer
2k views

Does the coriolis force have an effect on the direction in which an aircraft travels?

Suppose an aircraft is flying from Kenya (which lies on the equator) to UK (which lies in the northern hemisphere). Does the Coriolis force veer the aircraft to the right? Do pilots have to correct ...
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1answer
922 views

Can you continue an ILS approach when weather falls below minimum?

If, after passing the final approach fix, weather deteriorates so that the reported values are now below required minima, is it allowed to continue the approach?
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1answer
155 views

What is the reasoning behind this question about the correct altitude to avoid clear icing?

This question has been killing me for a while and it's an original PPL question: You are approaching to an airmass with a temperature of 6 C at 10000ft. Which altitude should you be in order to avoid ...

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