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Estimating TS Cell Height

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Estimating TS Cell Height

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Old 10th Jul 2018, 15:57
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Estimating TS Cell Height

We are required to teach a method for estimating thunderstorm cell height using the weather radar. The method IMHO is more inaccurate than simply looking out the window if in daylight.

[gnd return at distance = to height in feet, move up 10 degrees to establish perpendicular beam position, find cell, examine chicken entrails, x .20 % equal cell height....)

Do any other carriers still teach this? Is so why? (I am trying to make a case to delete this from our program)
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Old 10th Jul 2018, 17:32
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Originally Posted by CaptainMongo View Post
We are required to teach a method for estimating thunderstorm cell height using the weather radar. The method IMHO is more inaccurate than simply looking out the window if in daylight.

[gnd return at distance = to height in feet, move up 10 degrees to establish perpendicular beam position, find cell, examine chicken entrails, x .20 % equal cell height....)

Do any other carriers still teach this? Is so why? (I am trying to make a case to delete this from our program)

What I don't like about the radar tilt formula for estimating cell heights is that it only sees the top of the radar return.
You can plan on getting your butt severely kicked in the turbulent cloud tops above the highest radar return that don't show on radar.[/left]
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Old 10th Jul 2018, 20:14
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Originally Posted by dweeks View Post
What I don't like about the radar tilt formula for estimating cell heights is that it only sees the top of the radar return.
You can plan on getting your butt severely kicked in the turbulent cloud tops above the highest radar return that don't show on radar.
You would probably want to add around 6000ft to the radar tops (hint from a forecaster I worked with] And remember radar does not see hail which can be a considerable distance from the cell you do see on radar.
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Old 11th Jul 2018, 12:24
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Originally Posted by dweeks View Post
What I don't like about the radar tilt formula for estimating cell heights is that it only sees the top of the radar return.
You can plan on getting your butt severely kicked in the turbulent cloud tops above the highest radar return that don't show on radar.

Our formula is to add 20 percent to the outcome. As an exercise to understand the operation of the weather radar, I can see it has some value. Beam width, the importance of tilt management (most of our control heads don’t have auto tilt) I teach it because I must, but I advocate against its use operationally.
    • Parallel beam position, estimating cell height
    • EVALUATING CELL HEIGHT
      • Useful only for determining the relative severity of storm
      • Should not be used to attempt overflight in IMC.
      • Radar height is not the storm height, due to low reflectivity in the cell tops. Assume the actual storm top is at least 20% above the measured radar top. Severe turbulence can exist well above the actual top.
      • Tilt - Adjust to parallel beam position
        • Adjust the tilt to paint the ground stripe at a range equal to current AGL altitude
        • (e.g., flying at FL 370 over sea-level terrain, paint it at 37 NM; at FL 370 over Denver, paint it at approximately 32 NM):
        • Increase tilt 10 degrees from previous step
    • Determine cell height
      • Increases tilt until echo disappears.
      • Distance to echo x 100 x degrees of tilt change =
        • Radar height of storm above current flight level
      • e.g., an echo at 40 NM disappears with a 4 tilt increase: 40 x 100 x 4= radar top, which is at least 16,000 feet above current flight level; actual top is 120% of 16,000 feet or at least 19,200 feet above current flight level).
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Old 12th Jul 2018, 04:11
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I wasn't taught this on the line (wouldn't rely too much on it either on line flights for the reasons given above regarding accuracy) but A320 FCTM has this formula for "assessment of vertical expansion of a storm cell": Height (ft) = distance (NM) x tilt (degrees) x 100
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Old 12th Jul 2018, 04:35
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Originally Posted by CaptainMongo View Post
We are required to teach a method for estimating thunderstorm cell height using the weather radar. The method IMHO is more inaccurate than simply looking out the window if in daylight.

[gnd return at distance = to height in feet, move up 10 degrees to establish perpendicular beam position, find cell, examine chicken entrails, x .20 % equal cell height....)

Do any other carriers still teach this? Is so why? (I am trying to make a case to delete this from our program)
[/left]
..Yes, delete it..This method makes no sense, because the top of the CB does not create any return..

..Fly safe,
B-757
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Old 12th Jul 2018, 15:17
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Originally Posted by Escape Path View Post
I wasn't taught this on the line (wouldn't rely too much on it either on line flights for the reasons given above regarding accuracy) but A320 FCTM has this formula for "assessment of vertical expansion of a storm cell": Height (ft) = distance (NM) x tilt (degrees) x 100
I use the same and it's very easy to apply. Formula at first sight looks complicated IMHO but it's actually simple maths. Eg: You set -2 degrees at 40Nm on your ND the center of the beam will be at 2*4 = 8000 feet. All you have to do is to multiple your tilt with your range and add 2 zeros. But if you want to know the cloud top ( assuming there is enough water to appear on the radar) you need to take into consideration the beam width which is about 3 degrees: 3.5 degrees on the WXR-2100 weather radar. So for example if you set your tilt at 3 degrees down, the beam covers actually up to -1.25 degrees down and down to -4.75 degrees.
To be more precise the formula should be: Beam width ( in feet) = (Distance in NM + ''00'') *3.5.

The formula and what I explained above is explained in the ''WXR-2100 Multiscan radar manual.'' Very interesting. If you guys are interested PM me and I can email it to you.
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Old 12th Jul 2018, 15:40
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I thought it's better to just avoid CBs laterally rather to do all this astronaut math, just to end up flying over the top in turbulence, or worse, picking up some ice crystal icing...
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Old 12th Jul 2018, 16:40
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Originally Posted by FlyingStone View Post
I thought it's better to just avoid CBs laterally rather to do all this astronaut math, just to end up flying over the top in turbulence, or worse, picking up some ice crystal icing...
True... On the mini bus it’s praticaly impossible to safely over fly CBs anyway...
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Old 13th Jul 2018, 18:51
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I thought it's better to just avoid CBs laterally rather to do all this astronaut math
True especially in tropics where the tops can be beyond the ceiling of the aircraft. Even if slightly lower you wont get another 5to 7 thousand cushion that is required to overfly safely. But in Europe CB tops can be much lower where they can be overflown.
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Old 13th Jul 2018, 21:04
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Just a pax here (with some GA experience).....

You could learn all you need about CB avoidance flying around Florida (in daylight) at this time of year.

Coming off the Atlantic into KMCO in a 744 at FL390 a couple of weeks ago - as we approached the coast (Canaveral area) we cruised past a CB that was already topping above our level, and you could see it growing as we flew past - a sobering sight and one that showed me why you would never try to outclimb.
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Old 13th Jul 2018, 21:38
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Why would you need to know the top of a cb; to compare with the forecast, interest, etc.

You should be planning how best to avoid the area, never contemplate going over it. If there are red returns, or even a large area of yellow from a radar scan at your level then the avoidance margin should be increased. Red returns indicated a storm above your level, yellow, similar and / or water-ice outflow, both conducive to ice crystal icing - associated with large storms.

Use the radar to assess the shape and extent of the storm and any others around it, which way is it moving, direction of the anvil - avoid going under that. Compare these with the expectation based on the forecast, generate and assess options for action; choose the safest.

Use your time to plan ahead instead of playing with some math formula or rule of thumb.

#1, why not ask why do we need to teach angle / height / range relationships in conjunction with cbs; what bad habits might be formed, negative training.
Just as much learning value in checking altitude / range from coast lines, etc, or angle - range cross track avoidance distance which is of much more value.
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Old 16th Jul 2018, 05:02
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Line check question...

I was the checkee on a line check and the checker tried to impress me with his magic numbers estimating the height of a CB ahead. I looked at him and said I didnt give a f..k about his estimate, were going around it no matter what you say.
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