![[PICS] A320 flies into hailstorm](/iconimages/safety/pics-a320-flies-into-hailstorm_ltr.gif)
[PICS] A320 flies into hailstorm
[PICS] A320 flies into hailstorm
06-10-2024, 08:03 AM
#3
Prime Minister/Moderator
Joined APC: Jan 2006
Position: Engines Turn Or People Swim
Posts: 39,992
IIRC one type of radar found on some 320's seems prone to not detected hail very well.
But hail doesn't show up great on radar anyway, unless it happens to be wet. And hail can blow out of tops and fall quite a ways downwind of the cell. So it's not always as simple as turning the radar on. Modern radars have predictive functions.
But hail doesn't show up great on radar anyway, unless it happens to be wet. And hail can blow out of tops and fall quite a ways downwind of the cell. So it's not always as simple as turning the radar on. Modern radars have predictive functions.
06-10-2024, 08:31 AM
#4
Disinterested Third Party
Joined APC: Jun 2012
Posts: 6,254
I don't see the original poster's post, because she's on my ignore list, in part due to a habit of mindlessly posting links without any contibuting commentary, along with an idiotic caroon thumb-down. I wouldn't be surprised if this is just such another post.
It's very possible to fly into hail and not see it on radar. Hail, and frozen precip, often has little or no reflectivity, which is why we avoid thunderstorms by the margin that we do; hail shafts are frequently not under the storm, but outside it, and those shafts, if not acquired visually, may be entirely invisible to radar. Frozen precipitation does not have the same reflectivity as liquid precip. Large hail has high Dbz returns (greater reflectivity), and the scale of reflectivity varies proportionately to size: large ice particles have a much higher visibility than small ones. Dry hail or dry snow has roughly three percent of the reflectivity of water.
Radar use is not taught like it used to be. The level of ignorance I have seen over many years when it comes to radar is staggering, given it's importance in the cockpit. Critical elements such as basic understanding of tilt, range, reflectivity, interpretation of returns, predictive windshear, various modes and features, etc, are very often lacking. Flight manuals and other documents provide very little guidance, and often what little is given, is given little attention.
In a former life, my mission was atmospheric research. Specifically, thunderstorm research, which involved, by and large, flying back and forth through thunderstorms with a turbojet airplane covered in sensor packages and gathering data. While a unique, educational experience, my chief takeaway from that experience was simple: I don't want to fly through another thunderstorm again. Of course, none of us should. That said, one absolutely must know what one can, and cannot see on radar, and one must undestand that absence of a return does not mean the absence of precipitation, convective activity, turbulence, hail, windshear, etc, for numerous reasons.
Relectivity increases as one approaches the freezing level, but below the freezing level, especially with smaller particles, and decreases above it, with major caveats. One big one is where the maximum icing occurs; it's not at the freezing level, but typically closer to -15C. The freezing level, so far as a target range for reflectivity, isn't just at 0C or 32F, but is a variable band; the greater the convective activity, the wider (taller vertically) the potential band. This means considerable liquid precip may be above it, and frozen precip below it. We hail and snow have similar reflectivity as liquid water, close to the freezing level, and at varying points within that band, and less, away from it. Wait hail and snow reflect quite well; dry hail and dry snow do not.
The worst turbulence (and upset) I experienced was working a level 6 cell, and was outside the airborne radar return of the cell. I was investigating upshear on the upwind side of the cell (rising convectivity) and getting particulate samples and measuring precip and temperatures. I had passed out of the visible precip on the display, which was largely magenta, with a narrow yellow and narrow green band defining the outide of the cell. I was primarily interested in the green and yellow areas, and at the time, at night, was in the black, indicating no precip. I made a left turn back toward the cell and prior to reaching it, hit upshears that we estimated at 12,000+ fpm, from below. I got a shaker, pusher, and a hard slam that broke my headset, one of my headsets loaned to a sensor operator, and stripped the CD drive out of my personal computer, which was in a padded case, and stowed. It was violent. We ended up falling out inverted, from which I recovered and flew away from the cell. This is notable here, becasue there was nothing reflective in front of us, and the cell was well to my left at the time. I was not painting what hit us on radar; it approached from below at a high vertical rate. The same thing can occur from above, as it can with hail ejected from a cell, some distance from the cell.
Typical hail fall rates range from 25 mph to 40 mph vertically, up to 100 mph for larger hail. At the lower speeds, always tempered by the convective activity in which they're rising or falling (cumulative values as air rises or falls), that equates to about 2,000 fpm at the low end to 9000 fpm at the higher end. What I saw with the updrafts was about 12,000 fpm, and was only moisture and rising air. Frozen precip could approach at high velocity, along with vertical current or shear, leading to both damage and upset, and can occur outside of a cell, and some distance from the cell. Hail can occur within up to 20 miles of a cell. That's well to keep in mind (especially when considering winds through that cell at altitude and the surface; if you're downwind of that cell, it may look clear, but damaging hail can still occur well away from the cell, as can lightning.
It's very possible to fly into hail and not see it on radar. Hail, and frozen precip, often has little or no reflectivity, which is why we avoid thunderstorms by the margin that we do; hail shafts are frequently not under the storm, but outside it, and those shafts, if not acquired visually, may be entirely invisible to radar. Frozen precipitation does not have the same reflectivity as liquid precip. Large hail has high Dbz returns (greater reflectivity), and the scale of reflectivity varies proportionately to size: large ice particles have a much higher visibility than small ones. Dry hail or dry snow has roughly three percent of the reflectivity of water.
Radar use is not taught like it used to be. The level of ignorance I have seen over many years when it comes to radar is staggering, given it's importance in the cockpit. Critical elements such as basic understanding of tilt, range, reflectivity, interpretation of returns, predictive windshear, various modes and features, etc, are very often lacking. Flight manuals and other documents provide very little guidance, and often what little is given, is given little attention.
In a former life, my mission was atmospheric research. Specifically, thunderstorm research, which involved, by and large, flying back and forth through thunderstorms with a turbojet airplane covered in sensor packages and gathering data. While a unique, educational experience, my chief takeaway from that experience was simple: I don't want to fly through another thunderstorm again. Of course, none of us should. That said, one absolutely must know what one can, and cannot see on radar, and one must undestand that absence of a return does not mean the absence of precipitation, convective activity, turbulence, hail, windshear, etc, for numerous reasons.
Relectivity increases as one approaches the freezing level, but below the freezing level, especially with smaller particles, and decreases above it, with major caveats. One big one is where the maximum icing occurs; it's not at the freezing level, but typically closer to -15C. The freezing level, so far as a target range for reflectivity, isn't just at 0C or 32F, but is a variable band; the greater the convective activity, the wider (taller vertically) the potential band. This means considerable liquid precip may be above it, and frozen precip below it. We hail and snow have similar reflectivity as liquid water, close to the freezing level, and at varying points within that band, and less, away from it. Wait hail and snow reflect quite well; dry hail and dry snow do not.
The worst turbulence (and upset) I experienced was working a level 6 cell, and was outside the airborne radar return of the cell. I was investigating upshear on the upwind side of the cell (rising convectivity) and getting particulate samples and measuring precip and temperatures. I had passed out of the visible precip on the display, which was largely magenta, with a narrow yellow and narrow green band defining the outide of the cell. I was primarily interested in the green and yellow areas, and at the time, at night, was in the black, indicating no precip. I made a left turn back toward the cell and prior to reaching it, hit upshears that we estimated at 12,000+ fpm, from below. I got a shaker, pusher, and a hard slam that broke my headset, one of my headsets loaned to a sensor operator, and stripped the CD drive out of my personal computer, which was in a padded case, and stowed. It was violent. We ended up falling out inverted, from which I recovered and flew away from the cell. This is notable here, becasue there was nothing reflective in front of us, and the cell was well to my left at the time. I was not painting what hit us on radar; it approached from below at a high vertical rate. The same thing can occur from above, as it can with hail ejected from a cell, some distance from the cell.
Typical hail fall rates range from 25 mph to 40 mph vertically, up to 100 mph for larger hail. At the lower speeds, always tempered by the convective activity in which they're rising or falling (cumulative values as air rises or falls), that equates to about 2,000 fpm at the low end to 9000 fpm at the higher end. What I saw with the updrafts was about 12,000 fpm, and was only moisture and rising air. Frozen precip could approach at high velocity, along with vertical current or shear, leading to both damage and upset, and can occur outside of a cell, and some distance from the cell. Hail can occur within up to 20 miles of a cell. That's well to keep in mind (especially when considering winds through that cell at altitude and the surface; if you're downwind of that cell, it may look clear, but damaging hail can still occur well away from the cell, as can lightning.
06-10-2024, 11:15 AM
#5
Gets Weekends Off
Joined APC: Mar 2014
Posts: 3,221
I don't see the original poster's post, because she's on my ignore list, in part due to a habit of mindlessly posting links without any contibuting commentary, along with an idiotic caroon thumb-down. I wouldn't be surprised if this is just such another post.
It's very possible to fly into hail and not see it on radar. Hail, and frozen precip, often has little or no reflectivity, which is why we avoid thunderstorms by the margin that we do; hail shafts are frequently not under the storm, but outside it, and those shafts, if not acquired visually, may be entirely invisible to radar. Frozen precipitation does not have the same reflectivity as liquid precip. Large hail has high Dbz returns (greater reflectivity), and the scale of reflectivity varies proportionately to size: large ice particles have a much higher visibility than small ones. Dry hail or dry snow has roughly three percent of the reflectivity of water.
Radar use is not taught like it used to be. The level of ignorance I have seen over many years when it comes to radar is staggering, given it's importance in the cockpit. Critical elements such as basic understanding of tilt, range, reflectivity, interpretation of returns, predictive windshear, various modes and features, etc, are very often lacking. Flight manuals and other documents provide very little guidance, and often what little is given, is given little attention.
In a former life, my mission was atmospheric research. Specifically, thunderstorm research, which involved, by and large, flying back and forth through thunderstorms with a turbojet airplane covered in sensor packages and gathering data. While a unique, educational experience, my chief takeaway from that experience was simple: I don't want to fly through another thunderstorm again. Of course, none of us should. That said, one absolutely must know what one can, and cannot see on radar, and one must undestand that absence of a return does not mean the absence of precipitation, convective activity, turbulence, hail, windshear, etc, for numerous reasons.
Relectivity increases as one approaches the freezing level, but below the freezing level, especially with smaller particles, and decreases above it, with major caveats. One big one is where the maximum icing occurs; it's not at the freezing level, but typically closer to -15C. The freezing level, so far as a target range for reflectivity, isn't just at 0C or 32F, but is a variable band; the greater the convective activity, the wider (taller vertically) the potential band. This means considerable liquid precip may be above it, and frozen precip below it. We hail and snow have similar reflectivity as liquid water, close to the freezing level, and at varying points within that band, and less, away from it. Wait hail and snow reflect quite well; dry hail and dry snow do not.
The worst turbulence (and upset) I experienced was working a level 6 cell, and was outside the airborne radar return of the cell. I was investigating upshear on the upwind side of the cell (rising convectivity) and getting particulate samples and measuring precip and temperatures. I had passed out of the visible precip on the display, which was largely magenta, with a narrow yellow and narrow green band defining the outide of the cell. I was primarily interested in the green and yellow areas, and at the time, at night, was in the black, indicating no precip. I made a left turn back toward the cell and prior to reaching it, hit upshears that we estimated at 12,000+ fpm, from below. I got a shaker, pusher, and a hard slam that broke my headset, one of my headsets loaned to a sensor operator, and stripped the CD drive out of my personal computer, which was in a padded case, and stowed. It was violent. We ended up falling out inverted, from which I recovered and flew away from the cell. This is notable here, becasue there was nothing reflective in front of us, and the cell was well to my left at the time. I was not painting what hit us on radar; it approached from below at a high vertical rate. The same thing can occur from above, as it can with hail ejected from a cell, some distance from the cell.
Typical hail fall rates range from 25 mph to 40 mph vertically, up to 100 mph for larger hail. At the lower speeds, always tempered by the convective activity in which they're rising or falling (cumulative values as air rises or falls), that equates to about 2,000 fpm at the low end to 9000 fpm at the higher end. What I saw with the updrafts was about 12,000 fpm, and was only moisture and rising air. Frozen precip could approach at high velocity, along with vertical current or shear, leading to both damage and upset, and can occur outside of a cell, and some distance from the cell. Hail can occur within up to 20 miles of a cell. That's well to keep in mind (especially when considering winds through that cell at altitude and the surface; if you're downwind of that cell, it may look clear, but damaging hail can still occur well away from the cell, as can lightning.
It's very possible to fly into hail and not see it on radar. Hail, and frozen precip, often has little or no reflectivity, which is why we avoid thunderstorms by the margin that we do; hail shafts are frequently not under the storm, but outside it, and those shafts, if not acquired visually, may be entirely invisible to radar. Frozen precipitation does not have the same reflectivity as liquid precip. Large hail has high Dbz returns (greater reflectivity), and the scale of reflectivity varies proportionately to size: large ice particles have a much higher visibility than small ones. Dry hail or dry snow has roughly three percent of the reflectivity of water.
Radar use is not taught like it used to be. The level of ignorance I have seen over many years when it comes to radar is staggering, given it's importance in the cockpit. Critical elements such as basic understanding of tilt, range, reflectivity, interpretation of returns, predictive windshear, various modes and features, etc, are very often lacking. Flight manuals and other documents provide very little guidance, and often what little is given, is given little attention.
In a former life, my mission was atmospheric research. Specifically, thunderstorm research, which involved, by and large, flying back and forth through thunderstorms with a turbojet airplane covered in sensor packages and gathering data. While a unique, educational experience, my chief takeaway from that experience was simple: I don't want to fly through another thunderstorm again. Of course, none of us should. That said, one absolutely must know what one can, and cannot see on radar, and one must undestand that absence of a return does not mean the absence of precipitation, convective activity, turbulence, hail, windshear, etc, for numerous reasons.
Relectivity increases as one approaches the freezing level, but below the freezing level, especially with smaller particles, and decreases above it, with major caveats. One big one is where the maximum icing occurs; it's not at the freezing level, but typically closer to -15C. The freezing level, so far as a target range for reflectivity, isn't just at 0C or 32F, but is a variable band; the greater the convective activity, the wider (taller vertically) the potential band. This means considerable liquid precip may be above it, and frozen precip below it. We hail and snow have similar reflectivity as liquid water, close to the freezing level, and at varying points within that band, and less, away from it. Wait hail and snow reflect quite well; dry hail and dry snow do not.
The worst turbulence (and upset) I experienced was working a level 6 cell, and was outside the airborne radar return of the cell. I was investigating upshear on the upwind side of the cell (rising convectivity) and getting particulate samples and measuring precip and temperatures. I had passed out of the visible precip on the display, which was largely magenta, with a narrow yellow and narrow green band defining the outide of the cell. I was primarily interested in the green and yellow areas, and at the time, at night, was in the black, indicating no precip. I made a left turn back toward the cell and prior to reaching it, hit upshears that we estimated at 12,000+ fpm, from below. I got a shaker, pusher, and a hard slam that broke my headset, one of my headsets loaned to a sensor operator, and stripped the CD drive out of my personal computer, which was in a padded case, and stowed. It was violent. We ended up falling out inverted, from which I recovered and flew away from the cell. This is notable here, becasue there was nothing reflective in front of us, and the cell was well to my left at the time. I was not painting what hit us on radar; it approached from below at a high vertical rate. The same thing can occur from above, as it can with hail ejected from a cell, some distance from the cell.
Typical hail fall rates range from 25 mph to 40 mph vertically, up to 100 mph for larger hail. At the lower speeds, always tempered by the convective activity in which they're rising or falling (cumulative values as air rises or falls), that equates to about 2,000 fpm at the low end to 9000 fpm at the higher end. What I saw with the updrafts was about 12,000 fpm, and was only moisture and rising air. Frozen precip could approach at high velocity, along with vertical current or shear, leading to both damage and upset, and can occur outside of a cell, and some distance from the cell. Hail can occur within up to 20 miles of a cell. That's well to keep in mind (especially when considering winds through that cell at altitude and the surface; if you're downwind of that cell, it may look clear, but damaging hail can still occur well away from the cell, as can lightning.
My airline has had a few hail incidents but from what I can tell, every single one of them was because they flew through the storm, not alongside it. I'd imagine if one stays a couple miles upwind of the storm, hail risk is essentially nil?
I feel like many times the auto radar sets tend to overpaint storms. While I agree one should avoid anything convective at all times, we all know that isn't necessarily possible and some times you really need to know the difference between "dangerous" convective" and building/collapsing convective. Many times this overpainting results in flying approaches through what look like severe convective but mild conditions, leading to a "boy cries wolf" mentality.
06-10-2024, 11:43 AM
#6
Disinterested Third Party
Joined APC: Jun 2012
Posts: 6,254
Hail is reflective, but size and wetness or consistency make a very big difference. Dry hail, like snow, is about 3% of the reflective value of liquid water; the level at which it is found also makes a difference. Size of the hail makes a difference, as does the amount. Further, where you're scanning makes a difference, as does the type of radar, gain and calibration, range, etc.
Archie Trammel's courses were very good, albeit very dry, and while some of the data is dated, much of it still applies.
Setting the calibration at zero doesn't actually tell you where the beam is going, regardless of altitude. There are mathematical formulas regarding antenna size and beam width and distance, but a really easy practice, once you get up to cruise altitude, is to put the bottom of your beam at 80 miles; that draws a line from your radar to the ground at 80 miles, and anything that penetrates that plane ends up visible (or potentially visible, depending on reflectivity and return) to you. Obviously, a towering cumulus that does not rise to your altitude, may penetrate that line closer to the 80 mile range, but as you draw closer, a lower thunderstorm or towering cumulus (having enough moisture to be reflective) will eventually fall beneath the beam and disappear. This is to say, as you draw closer to targets which may not be a threat to you (as you'll be well above them), the targets gros smaller and disappear as they disappear below your beam. Targets which remain, inside the 80 mile range, you should consider in your planning for deviations or avoidance, and if they remain once inside the 40nm ring, are players. Anything closer than that should be given careful consideration.
That said, zero doesn't tell you much; zero in one airplane won't be the same as zero in another; those are simply reference numbers that may have some relative meaning to pitch and horizon and so forth, but not in every airplane, and not in all circumstances. You need to tilt up and down and place your beam where you want it, rather than setting the tilt to a number. That's a very common mistake, to simply set a number. A very common mistake is to try to deduct the degrees of pitch, on the radar, and think that's zero; it's not. For me, in most equipment, at cruise or once above 18-25,000, look at resting the bottom of the beam (when you start painting ground clutter) at eighty miles. Some try to set it out to farther ranges, and the return energy isn't that reliable or great at longer distances. Some features like turbulence detection operate at much shorter ranges, typically 40 nm, and rely on doppler motion of moisture (so can't see clear air turbulence, etc).
The gain feature varies by system in use; some use an auto or calibrated position as the norm. Moving away from this may increase, or decrease gain, depending on the radar set in use. The only way to tell is to read the manual; many manuals aren't clear on that, but you can tell by adjusting the gain. If you see colors go away, you're decreasing sensitivity, and if colors change and increase up the scale, you're increasing sensitivity. Most units won't let you turn the sensitivity down so far as to miss critical weather, and if you turn it until the colors switch to one level lower (eg, green goes to black, yellow to green, etc), you've dropped it 10 dbz. Most of the time, run it in CAL or auto, as your particular unit may specify.
Hail risk isn't nil near a storm; upwind is better than downwind, but depending on the updrafts and the angle at which the hail is ejected from the storm, hail may fall upwind. Remember that the winds aren't necessarily the same at every level. The top of the storm may have an anvil leaning to one side like a beret, indicating the wind blowing in that direction, and hail up there may travel with the wind, but hail may not exit there; it could exit any number of places, as there aren't just vertical shears in the cell, but horizontal ones; those can move or eject hail laterally mid-cloud, out the side, front or back. We see a towering cumulus or thunderstorm, and it apears to blow with the wind, but that's not at all what's happening. Wind blows through the cell, and the cell is constantly forming and collapsing. The upwind or upshear side is constantly building into the cell and the downwind or downshear is constantly collapsing; that can happen on more than one side and in fact does, and in more than one place, and may not always be visible. The wind isn't blowing the storm, but blowing through it, and that horizontal motion can carry hail out in multiple places and levels. It affects veritcal winds or shears differently at different points in the convective cell; the vertical velocities are cumulative as air rises, so air rising at 1,000 fpm meets another parcel that is rising at 1,000 fpm, and the colum develops 2,000 fpm or better, depending on temperature, shear, and other factors. How a horizontal gust or wind blowing through that vertical column will affect the column depends on the velocity of the column, how it affects the horizontal shear, the size of droplets or particles in the vertical column, and so on. Just like cars colliding in an intersection, the big one wins, to varying degrees. Horizontal wind blowing through a cell may eject hail, or alter it's progression up or down. Hil can come from above, or below.
This is especialy true when overflying cells; hail can be ejected with considerable force from a cell, into the air above the cell, where one may meet hail and ice, as well as liquid precipitation. I flew with a gentleman who encountered severe damage to his leading edges and engine inlets upon encountering vertical hail from below, over a storm, in South America (I wasn't on board when it occurred). The leading edges were flattened like it ran into a wall, and mangled. He happened to discover the highest/coldest liquid water at the time on that same flight, as he picked up ice. It was -40C.
I am neither an atmospheric scientist (amateur or otherwise) nor meteorologist; my casual observations, as previously noted, can best be summed up as "avoid thunderstorms." I hope to not transit one again.
Honeywell notes that deviations are made in some oceanic areas not for weather, but instead of islands painted on radar that are mistaken for weather. That may be attributed in most cases to misunderstanding of operation of radar. That said, while one could call it boy-who-cries-wolf syndrome, I'd much rather deviate conservatively, than fly into a place I ought not. It's a bit like a missed approach or go-around; the most conservative call of the day wins.
Archie Trammel's courses were very good, albeit very dry, and while some of the data is dated, much of it still applies.
Setting the calibration at zero doesn't actually tell you where the beam is going, regardless of altitude. There are mathematical formulas regarding antenna size and beam width and distance, but a really easy practice, once you get up to cruise altitude, is to put the bottom of your beam at 80 miles; that draws a line from your radar to the ground at 80 miles, and anything that penetrates that plane ends up visible (or potentially visible, depending on reflectivity and return) to you. Obviously, a towering cumulus that does not rise to your altitude, may penetrate that line closer to the 80 mile range, but as you draw closer, a lower thunderstorm or towering cumulus (having enough moisture to be reflective) will eventually fall beneath the beam and disappear. This is to say, as you draw closer to targets which may not be a threat to you (as you'll be well above them), the targets gros smaller and disappear as they disappear below your beam. Targets which remain, inside the 80 mile range, you should consider in your planning for deviations or avoidance, and if they remain once inside the 40nm ring, are players. Anything closer than that should be given careful consideration.
That said, zero doesn't tell you much; zero in one airplane won't be the same as zero in another; those are simply reference numbers that may have some relative meaning to pitch and horizon and so forth, but not in every airplane, and not in all circumstances. You need to tilt up and down and place your beam where you want it, rather than setting the tilt to a number. That's a very common mistake, to simply set a number. A very common mistake is to try to deduct the degrees of pitch, on the radar, and think that's zero; it's not. For me, in most equipment, at cruise or once above 18-25,000, look at resting the bottom of the beam (when you start painting ground clutter) at eighty miles. Some try to set it out to farther ranges, and the return energy isn't that reliable or great at longer distances. Some features like turbulence detection operate at much shorter ranges, typically 40 nm, and rely on doppler motion of moisture (so can't see clear air turbulence, etc).
The gain feature varies by system in use; some use an auto or calibrated position as the norm. Moving away from this may increase, or decrease gain, depending on the radar set in use. The only way to tell is to read the manual; many manuals aren't clear on that, but you can tell by adjusting the gain. If you see colors go away, you're decreasing sensitivity, and if colors change and increase up the scale, you're increasing sensitivity. Most units won't let you turn the sensitivity down so far as to miss critical weather, and if you turn it until the colors switch to one level lower (eg, green goes to black, yellow to green, etc), you've dropped it 10 dbz. Most of the time, run it in CAL or auto, as your particular unit may specify.
Hail risk isn't nil near a storm; upwind is better than downwind, but depending on the updrafts and the angle at which the hail is ejected from the storm, hail may fall upwind. Remember that the winds aren't necessarily the same at every level. The top of the storm may have an anvil leaning to one side like a beret, indicating the wind blowing in that direction, and hail up there may travel with the wind, but hail may not exit there; it could exit any number of places, as there aren't just vertical shears in the cell, but horizontal ones; those can move or eject hail laterally mid-cloud, out the side, front or back. We see a towering cumulus or thunderstorm, and it apears to blow with the wind, but that's not at all what's happening. Wind blows through the cell, and the cell is constantly forming and collapsing. The upwind or upshear side is constantly building into the cell and the downwind or downshear is constantly collapsing; that can happen on more than one side and in fact does, and in more than one place, and may not always be visible. The wind isn't blowing the storm, but blowing through it, and that horizontal motion can carry hail out in multiple places and levels. It affects veritcal winds or shears differently at different points in the convective cell; the vertical velocities are cumulative as air rises, so air rising at 1,000 fpm meets another parcel that is rising at 1,000 fpm, and the colum develops 2,000 fpm or better, depending on temperature, shear, and other factors. How a horizontal gust or wind blowing through that vertical column will affect the column depends on the velocity of the column, how it affects the horizontal shear, the size of droplets or particles in the vertical column, and so on. Just like cars colliding in an intersection, the big one wins, to varying degrees. Horizontal wind blowing through a cell may eject hail, or alter it's progression up or down. Hil can come from above, or below.
This is especialy true when overflying cells; hail can be ejected with considerable force from a cell, into the air above the cell, where one may meet hail and ice, as well as liquid precipitation. I flew with a gentleman who encountered severe damage to his leading edges and engine inlets upon encountering vertical hail from below, over a storm, in South America (I wasn't on board when it occurred). The leading edges were flattened like it ran into a wall, and mangled. He happened to discover the highest/coldest liquid water at the time on that same flight, as he picked up ice. It was -40C.
I am neither an atmospheric scientist (amateur or otherwise) nor meteorologist; my casual observations, as previously noted, can best be summed up as "avoid thunderstorms." I hope to not transit one again.
Honeywell notes that deviations are made in some oceanic areas not for weather, but instead of islands painted on radar that are mistaken for weather. That may be attributed in most cases to misunderstanding of operation of radar. That said, while one could call it boy-who-cries-wolf syndrome, I'd much rather deviate conservatively, than fly into a place I ought not. It's a bit like a missed approach or go-around; the most conservative call of the day wins.
06-10-2024, 12:32 PM
#7
Gets Weekends Off
Joined APC: Mar 2014
Posts: 3,221
Hail is reflective, but size and wetness or consistency make a very big difference. Dry hail, like snow, is about 3% of the reflective value of liquid water; the level at which it is found also makes a difference. Size of the hail makes a difference, as does the amount. Further, where you're scanning makes a difference, as does the type of radar, gain and calibration, range, etc.
Archie Trammel's courses were very good, albeit very dry, and while some of the data is dated, much of it still applies.
Setting the calibration at zero doesn't actually tell you where the beam is going, regardless of altitude. There are mathematical formulas regarding antenna size and beam width and distance
Archie Trammel's courses were very good, albeit very dry, and while some of the data is dated, much of it still applies.
Setting the calibration at zero doesn't actually tell you where the beam is going, regardless of altitude. There are mathematical formulas regarding antenna size and beam width and distance
It's my understand that the VIP return levels you see at that target alttitude (25k? 20k?) is what the NOAA VIP levels are based on.
As an example if you are at 10,000 ft, there is a cell 20 miles in front of you, you'd want to tilt up at approximately +5* to center beam at 20,000. That would give you an approximation for its true VIP value.
06-10-2024, 04:30 PM
#8
Disinterested Third Party
Joined APC: Jun 2012
Posts: 6,254
The amount of tilt is entirely dependent on what's needed; again, a fixed number has no meaning. If stabilization is off, or fails, most units default to the long axis of the airplane. In that case, it's pointed to whatever the pitch of the aircraft is. In some units, once stabilized, the unit tries to maintain the same itch relationship with the earth, regardless of the pitch attitude of the aircraft (think Honeywell Primus). This is not the case with all radar systems.
Tilt shouldn't be a one-and-done pitch management system, especially where there's weather. I move the tilt, scan. Some radars do that for you, taking sectional snapshots up and down, of weather. Many don't. How you manage the tilt will depend on the system in use. For some operators, manual tilt is a thing of the past; for many, it's a necessity and in some cases, an art. I prefer to tilt up and down to find weather. You can do the math if you know the true zero of your system, but it doesn't necessarily correspond with a given number of degrees or pitch values. I look up and down for weather. On departure, for example, I'll. be raising the radar up and doing some scanning, not necessarily at a specific value, and I'll be scanning down, too as I climb. Like trees, weather usually starts at the bottom and grows upward, though not always, so I make no assumptions. I look at terrain, too. Partially for orientation, but partially because terrain influences weather.
So far as picking an altitude for a "true" value, the weather coiuld be at any altitude, and the weather is where you find it. What if the storm exists from 20,000' on down, and you're departing the surface? I've seen some severe weather that doesn't extend above 15,000 to 20,000,' but packs plenty of punch. Start at the surface and scan up; see what's there. Far better to go around than to plan to climb over, if able, unless it's fair weather cumulous.
Tilt shouldn't be a one-and-done pitch management system, especially where there's weather. I move the tilt, scan. Some radars do that for you, taking sectional snapshots up and down, of weather. Many don't. How you manage the tilt will depend on the system in use. For some operators, manual tilt is a thing of the past; for many, it's a necessity and in some cases, an art. I prefer to tilt up and down to find weather. You can do the math if you know the true zero of your system, but it doesn't necessarily correspond with a given number of degrees or pitch values. I look up and down for weather. On departure, for example, I'll. be raising the radar up and doing some scanning, not necessarily at a specific value, and I'll be scanning down, too as I climb. Like trees, weather usually starts at the bottom and grows upward, though not always, so I make no assumptions. I look at terrain, too. Partially for orientation, but partially because terrain influences weather.
So far as picking an altitude for a "true" value, the weather coiuld be at any altitude, and the weather is where you find it. What if the storm exists from 20,000' on down, and you're departing the surface? I've seen some severe weather that doesn't extend above 15,000 to 20,000,' but packs plenty of punch. Start at the surface and scan up; see what's there. Far better to go around than to plan to climb over, if able, unless it's fair weather cumulous.
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