13

Wind "CALM" means a wind speed less than 0.5m/s (1 kt) according to ICAO Annex 3, Appendix 3: 4.1.5.2 In local routine and special reports and in METAR and SPECI: ... d) when a wind speed of less than 0.5m/s (1 kt) is reported, it shall be indicated as calm; Before Amendment 75 of ICAO Annex 3 this read: d) when a wind speed of less than 2 ...


13

Red/blue for pressure is in no relation to surface temperature. Storms develop where the pressure is very low. Red being associated with danger is a good color choice for low pressure. Storms are created when a center of low pressure develops with a system of high pressure surrounding it. Low pressure is also associated with decreased aircraft ...


10

The aircraft they're flying is an Lockheed WP-3D Orion, not a jet- the NOAA doesn't fly its Gulfstream IVs into the storm, as I've noted elsewhere. There is always a risk associated with piloting an aircraft through weather that pilots are usually told to avoid. But they have been doing it for decades, so, with proper training and planning, it appears that ...


8

In the troposphere, air at altitude is colder than air at ground level. But surprisingly, air at altitude at the poles can be warmer than air at altitude at the equator. From the wiki article on troposphere (I added the bullet points): The troposphere is heated from below by latent heat, longwave radiation, and sensible heat. Surplus heating and vertical ...


8

There are actually multiple different answers depending on the specific type of altimeter system and what standard applies. The stand-alone altimeters in older aircraft and small GA aircraft (panel mounted "steam gauge") are certificated to SAE AS392C, Altimeter, Pressure Actuated Sensitive Type. The specified scale range is "at least 28.1 - 30.99 inches ...


8

Yes, it is possible for a METAR to contain both VRB and G. VRB10G25KT is valid. The reason it rarely happens is because, as wind speed increases, major variations in wind directions tend to disappear.


7

As other answers say, yes, this is valid. It appears approximately 150K times in our database of 85 million METARs[1]. This database is built from data provided by NOAA and covers roughly 16 months.[2] Here are several real examples from February 2019. KBML 011110Z AUTO VRB06G18KT 7SM OVC029 M16/M22 A3007 RMK AO2 T11611217 KSZY 011115Z AUTO VRB06G11KT 10SM ...


6

The red color is universally associated with evil, suffering, blood, fire... Low pressures are associated with rain, storms, even with hurricanes and tornados... High pressures are associated with stable weather, sun, blue skies, absence of wind... Hence, it's no wonder that low pressure is indicated in red, and high pressure in blue... Socialist-minded ...


5

Image source Turbulence is merely the measure of Reynolds number of a fluid at rest or motion ( (turbulence occurs when fluid is in motion) let's say you light up a cigarette and when the smoke is at the tip of cigarette you see it flows upwards uniformly and this is because the fluid is in laminar flow and as it expands into its vicinity it becomes ...


5

They don't. Since all aircraft in an area are (or at least should be) having roughly the same error, the errors cancel out and there is no practical effect on vertical separation. Falsely low readings result in more terrain or obstacle clearance than needed, so that's not a problem either. Falsely high readings do potentially create a problem, but the ...


5

The October 2018 issue of AOPA's "Flight Training" magazine provided the following illustration and comments. A 24mph updraft will form ~1/4" hail, while a 98mph updraft will form 4" hail. Down drafts are usually about 1/2 the speed of the updraft (due to a larger outer core area). When a pilot encounters a downdraft, expect an updraft twice the speed to ...


5

The temperature decreases at approximately 3.57 degree Fahrenheit per 1000', the adiabatic lapse rate, until hitting the tropopause, the boundary between the troposphere (lower altitudes) and the stratosphere. At that point the temps flatten out. The lapse rate is pretty constant everywhere, so yes, it should be colder at higher latitudes for the same ...


5

PROB40 is targeted only on the immediate TEMPO group. If there are several PROB/TEMPOs both keywords must be repeated every time. Also, PROB is never associated with BECMG or FM groups, which indicate permanent change.


5

The airplanes do not cruise at a certain altitude, but at a certain pressure level. That could be an irrelevant nitpick if the temperature did not directly affect the pressure as a function of altitude. But it does (through the hydrostatic equilibrium). In colder areas the air is heavier and flight levels are lower as can be seen in maps of geopotential ...


4

To elaborate on a previous answer, large changes in wind direction on short timescales tend to be caused by thermal updrafts passing through the area, tending to "suck" the wind toward their centers. When the overall windspeed is high, the (relatively) small changes in wind velocity (speed and direction) caused by this phenomenon tend to be dwarfed by the ...


3

All these clouds signal an approaching warm front and potentially a storm. Warmer, moisture laden air rides over the top of cooler air, forming visible clouds while the ground level front is still many miles away. Cirrus clouds are composed of ice crystals and form at very high altitudes. They are the first of the approaching clouds. Cirrostratus form as ...


3

Jet streams are influenced by the horizontal temperature gradient between two air masses which creates what is called a "thermal wind component", which when supplemented by the actual wind movement, creates the local acceleration of wind running along the top of the frontal boundary into a jet (above 90kt), and which is always nestled into the warm air side, ...


3

A microburst is generally an intense down draft while wind shear can occur in any direction. It might be safe to say that a microburst is windshear but not all windshear is a microburst. From your linked pages A microburst is intense small-scale downdraft produced by a thunderstorm or rain shower. and Windshear is any rapid change in wind direction ...


3

Usually, when we translate TAFs we use the word expect. So, in this case, we expect the visibility to drop from 600m to 150m. So when planning a flight you would use 150m. Also, I find it odd how the time format is different to what I am used to. At my local airport, this is the TEMPO in the TAF. TEMPO 0302/0307 6000 SHRA SCT030TCU So this would translate....


3

TEMPO means that there were be fluctuations in the weather in the time period specified, lasting as long as 50% of the time range specified. TEMPO 0406 0150 FG VV001 means that in the period between 04:00 and 06:00 UTC the visibility will at some point go down to 150 in heavy fog, and it could last up to an hour in total. One thing I would point out is that ...


3

The BECMG group in a TAF describes a gradual change which will take place over a prolonged period of time, but will be the prevailing weather once that change is complete. The time period described in the TAF is the beginning and ending hour during which the gradual change is forecast to be in progress. At the end of the described time the change is expected ...


2

This NOAA newsletter lists a number of specific ways that PIREPs are used by meteorologists: To "assess the strength and position of the jet stream" For thunderstorm and snow level forecasting For forecast discussions of regional weather phenomena, like "downslope wind storms in the lee of the Sierra Nevada" To "determine the likelihood of clouds thinning ...


2

For the purpose of aircraft limitations, it's TAT for the upper limit of +10C. SAT for the lower limit of -40C. Generally once you are going faster (in the RJ, above 230kts) you only need to have cowls on for all visible moisture conditions, and wings only need to be on if actual icing is happening or indicated. Ice can form on cowls from the temperature ...


2

"From high to low, look out below." Pilots use this mnemonic to remember that when flying from high pressure into low pressure, the altimeter will read higher than actual altitude, which can be dangerous. (also true from high temperature into low temperature). I don't know if it was by design, but I've always associated the red low pressure with danger, ...


2

Boeing provides some decent notes on this in their powerpoint which you can find in full here. Their sections on pilot reports and the summary section have some good notes for identifying ice crystals in flight/clouds/fog Pilots have reported rain, sometimes ‘heavy rain’ on the windscreen, Sometimes at impossibly cold temperatures. This is believed ...


2

The pressure ranges for altimeters in the United States are set forth in a technical standing order. For example TSO-C10b in turn references SAE standard AS392C, which indicates the following performance parameters: Type I : range to 35,000 feet Type II: range to 50,000 feet Both adjustable from 28.1 to 30.99 inHg. These parameters have regulatory ...


2

There are many websites and apps that do this for you already. The website SkyVector will show colored dots that indicate what the airport status is. There is also a ForeFlight app that will show colored dots on their maps. I am not endorsing any products, simply pointing out tools that accomplish what you are asking. All these companies use information ...


2

There are two altimeter reading questions here, what happens when: flying towards the cold front (third paragraph) flying into the cold front (headline) According to this University of Illinois web article following things happen: Flying towards a cold front (or in the article the front is approaching you, but it makes no difference): pressure drops ...


1

Percentages of pollutants will not have a significant effect on earth as compared with temperature and pressure. However, on a planet like Mars, with a CO2 atmosphere, the density difference may be significant enough to effect lift calculations. Maybe NASA could go with a twisted Prandtl biplane using a high altitude electric motor and prop. They have ...


1

From a practical sense, remember: From high to low, look out below. If your barometric pressure and/or your temperature goes down (either/or), your altimeter will read a higher indicate value than the actual MSL true value. You will be at a lower altitude than you think. Ex. Check the Pressure and Density Altitudes at an airport reporting METARs over time....


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