Radar

[Matt Young]

A question about something that I guess I just didn't get enough info on
during my instrument training. What exactly are you looking for when
looking at a radar image. Are you trying to avoid all returns? Is an
area of just green ok? Any other things in particular to look for?

[Peter R.]

Matt Young ) wrote:

> A question about something that I guess I just didn't get enough info on
> during my instrument training. What exactly are you looking for when
> looking at a radar image. Are you trying to avoid all returns? Is an
> area of just green ok? Any other things in particular to look for?

Don't rely on color, as different vendors of radar data might color code
the returns differently. Instead, you ought to rely on the intensity
level, which is represented by the different colors on a color radar
product. Refer to the radar key to know what color each intensity
level is.

Rod Machado wrote a pretty good AOPA Pilot article about this very thing
about a year and a half ago. He discussed the relationship between
intensity level and the probability of severe to destructive turbulence.

As there is a small probability of destructive turbulence in level three
returns, with this probability significantly increasing in each of the
higher levels, Machado stated that one should avoid level three and
higher to avoid the probability of destructive turbulence.

--
Peter

[Bob Gardner]

I think that Capt Dave Gwinn, the airborne radar guru, has a web site. I
don't know the URL, but I'll bet you could google it up.

Bob Gardner

"Matt Young" > wrote in message
ink.net...
>A question about something that I guess I just didn't get enough info on
>during my instrument training. What exactly are you looking for when
>looking at a radar image. Are you trying to avoid all returns? Is an area
>of just green ok? Any other things in particular to look for?

[Mike Rapoport]

Where did you come up with this? All airborn weather radar systems have
the same color vs. intensity scale. For example red is always 40dbz.

Mike
MU-2


"Peter R." > wrote in message
...
> Matt Young ) wrote:
>
>> A question about something that I guess I just didn't get enough info on
>> during my instrument training. What exactly are you looking for when
>> looking at a radar image. Are you trying to avoid all returns? Is an
>> area of just green ok? Any other things in particular to look for?
>
> Don't rely on color, as different vendors of radar data might color code
> the returns differently. Instead, you ought to rely on the intensity
> level, which is represented by the different colors on a color radar
> product. Refer to the radar key to know what color each intensity
> level is.
>
> Rod Machado wrote a pretty good AOPA Pilot article about this very thing
> about a year and a half ago. He discussed the relationship between
> intensity level and the probability of severe to destructive turbulence.
>
> As there is a small probability of destructive turbulence in level three
> returns, with this probability significantly increasing in each of the
> higher levels, Machado stated that one should avoid level three and
> higher to avoid the probability of destructive turbulence.
>
> --
> Peter
>
>
>
>
>

[Peter R.]

Mike Rapoport ) wrote:

> Where did you come up with this? All airborn weather radar systems have
> the same color vs. intensity scale. For example red is always 40dbz.

Mike, I interpreted his post as referring to ground-based radar
products. I guess I made a leap of assumption that since the OP was
newly instrument rated, he was referring to pre-flight, not in-flight
radar interpretation.

But perhaps he is flying behind in-flight radar system? It would be
helpful if he posted a follow-up.

Oh, and BTW, I obviously know nothing about active radar in the cockpit.
I have WSI's downlinked Nexrad in the Bonanza, but even within this
product line WSI uses slightly different colors to represent different
intensities depending on the display (MX20 versus laptop screen, etc).


--
Peter

[Mike Rapoport]

Weather Radar is the same as vision in another part of the spectrum. It has
certain resolution and can penetrate a certain distance into obscuring
conditions. The beam reflects off all surfaces (except the stuff stealth
aircraft are made of presumably). The value of radar is that there is a
very high corralation between the reflectivity of water droplets and
turbulence. Large droplets are formed from vertical motion.and large
droplets reflect radar much better than small ones (that is why most clouds
appear transparent to radar.). More vertical motion larger drops. You have
undoubtedly experienced the difference in drop sizes from thunderstorms vs.
stratiform rain. To evaluate a target, you first have to determine that you
are not looking at a ground return which you do by knowing your altitude,
beam width and antenna tilt setting. Generally you avoid all radar targets
containing red (40dbz) returns. You avoid the whole target, not just the
red part. I usually avoid yellow too. Even green targets are fairly bumpy
and full of ice at cruise altitudes (above FL180). Green at lower altiudes
can be smooth. There are various shapes that are associated with hail and
tornados but most people avoid all thunderstorms. The irregular targets are
just avoided by a greater distance.

Basically it comes down to the fact that anything that lifts huge amounts of
water miles into the atmosphere contains a lot of vertical shear and
therefore turbulence.

There are several books on the subject, I like Archie Trammels stuff, Dave
Gwinn's book and Severe Weather Flying by Newton. There was a great deal on
AvWeb a couple of years ago where you got Trammels video course, Severe
Weather Flying and Buck's Weather Flying for around $125 along with a
discount for his live course.

Mike
MU-2


"Matt Young" > wrote in message
ink.net...
>A question about something that I guess I just didn't get enough info on
>during my instrument training. What exactly are you looking for when
>looking at a radar image. Are you trying to avoid all returns? Is an area
>of just green ok? Any other things in particular to look for?

[Mike Rapoport]

Fair enough! I assumed that he was talking about airborn radar. It is
interesting how personal experience colors our interpretation of the same
statement!

Mike
MU-2

"Peter R." > wrote in message
...
> Mike Rapoport ) wrote:
>
>> Where did you come up with this? All airborn weather radar systems have
>> the same color vs. intensity scale. For example red is always 40dbz.
>
> Mike, I interpreted his post as referring to ground-based radar
> products. I guess I made a leap of assumption that since the OP was
> newly instrument rated, he was referring to pre-flight, not in-flight
> radar interpretation.
>
> But perhaps he is flying behind in-flight radar system? It would be
> helpful if he posted a follow-up.
>
> Oh, and BTW, I obviously know nothing about active radar in the cockpit.
> I have WSI's downlinked Nexrad in the Bonanza, but even within this
> product line WSI uses slightly different colors to represent different
> intensities depending on the display (MX20 versus laptop screen, etc).
>
>
> --
> Peter
>
>
>
>
>

[Nick Coleman]

Mike Rapoport wrote:

> Fair enough!

I've always thought that was an Australian expression (personal
experience colours our etc ;). Made me do a double take.

--
Nick

[Matt Young]

I was referring to ground based radar, things I can look at before
leaving. No radar in my skyhawk.

Peter R. wrote:
> Mike Rapoport ) wrote:
>
>
>>Where did you come up with this? All airborn weather radar systems have
>>the same color vs. intensity scale. For example red is always 40dbz.
>
>
> Mike, I interpreted his post as referring to ground-based radar
> products. I guess I made a leap of assumption that since the OP was
> newly instrument rated, he was referring to pre-flight, not in-flight
> radar interpretation.
>
> But perhaps he is flying behind in-flight radar system? It would be
> helpful if he posted a follow-up.
>
> Oh, and BTW, I obviously know nothing about active radar in the cockpit.
> I have WSI's downlinked Nexrad in the Bonanza, but even within this
> product line WSI uses slightly different colors to represent different
> intensities depending on the display (MX20 versus laptop screen, etc).
>
>

[Stan Gosnell]

Matt Young > wrote in news:0i0fd.6540$KJ6.2254
@newsread1.news.pas.earthlink.net:

> I was referring to ground based radar, things I can look at before
> leaving. No radar in my skyhawk.

I have to say it's hit or miss. I've flown through areas that ground radar
had painted yellow and some red, and never saw a drop of rain, not any
turbulence. I've also seen some heavy rain that hadn't been on the TV
earlier. I've seen heavy precip shown over the place where I was sitting, on
the ground, and not a drop of rain had fallen all day. Look at radar
presentations with a jaundiced eye, and take them with a lot of salt, to mix
some metaphors. Read pireps, and ask the FSS briefer what has been going on.

--
Regards,

Stan

[Peter R.]

Mike Rapoport ) wrote:

> Fair enough! I assumed that he was talking about airborn radar. It is
> interesting how personal experience colors our interpretation of the same
> statement!

Someday I hope to be able to interpret as you do. :)

--
Peter

[Nathan Young]

On Fri, 22 Oct 2004 15:37:18 GMT, Matt Young >
wrote:

>A question about something that I guess I just didn't get enough info on
>during my instrument training. What exactly are you looking for when
>looking at a radar image. Are you trying to avoid all returns? Is an
>area of just green ok? Any other things in particular to look for?

I fly a PA28-180 equipped with WxWorx Nexrad. My experience has been:

light green = little/no rain (might be virga)
dk green = solid rain, but still not too heavy, certainly ok for IFR
flight
yellow = strong rain. Strong enough that I will only fly through it
if it is a small return.
orange = deviation
red = no way
purple = no way

I have not flown through orange, red, or purple intensities, and do
not intend to do so.

-Nathan

[John R. Copeland]

Mike, add special emphasis to the reading of the Z-scale numbers.
The NOAA radar depiction sets their lowest color level (cyan)
at -24 to -28 dBZ when no storms are shown on the presentation,
but when storms are present, the same color is +5 to +10 dBZ.
That's why a casual look at the radar can mislead the unwary
to mistake wet clouds for a rainstorm. The dBZ numbers rule.
---JRC---

"Mike Rapoport" > wrote in message =
k.net...
> Weather Radar is the same as vision in another part of the spectrum. =
It has=20
> certain resolution and can penetrate a certain distance into obscuring =

> conditions. The beam reflects off all surfaces (except the stuff =
stealth=20
> aircraft are made of presumably). The value of radar is that there is =
a=20
> very high corralation between the reflectivity of water droplets and=20
> turbulence. Large droplets are formed from vertical motion.and large=20
> droplets reflect radar much better than small ones (that is why most =
clouds=20
> appear transparent to radar.). More vertical motion larger drops. =
You have=20
> undoubtedly experienced the difference in drop sizes from =
thunderstorms vs.=20
> stratiform rain. To evaluate a target, you first have to determine =
that you=20
> are not looking at a ground return which you do by knowing your =
altitude,=20
> beam width and antenna tilt setting. Generally you avoid all radar =
targets=20
> containing red (40dbz) returns. You avoid the whole target, not just =
the=20
> red part. I usually avoid yellow too. Even green targets are fairly =
bumpy=20
> and full of ice at cruise altitudes (above FL180). Green at lower =
altiudes=20
> can be smooth. There are various shapes that are associated with hail =
and=20
> tornados but most people avoid all thunderstorms. The irregular =
targets are=20
> just avoided by a greater distance.
>=20
> Basically it comes down to the fact that anything that lifts huge =
amounts of=20
> water miles into the atmosphere contains a lot of vertical shear and=20
> therefore turbulence.
>=20
> There are several books on the subject, I like Archie Trammels stuff, =
Dave=20
> Gwinn's book and Severe Weather Flying by Newton. There was a great =
deal on=20
> AvWeb a couple of years ago where you got Trammels video course, =
Severe=20
> Weather Flying and Buck's Weather Flying for around $125 along with a=20
> discount for his live course.
>=20
> Mike
> MU-2
>=20
>=20
> "Matt Young" > wrote in message=20
> ink.net...
>>A question about something that I guess I just didn't get enough info =
on=20
>>during my instrument training. What exactly are you looking for when=20
>>looking at a radar image. Are you trying to avoid all returns? Is an =
area=20
>>of just green ok? Any other things in particular to look for?=20
>=20
>

[Peter R.]

John R. Copeland ) wrote:

> Mike, add special emphasis to the reading of the Z-scale numbers.
> The NOAA radar depiction sets their lowest color level (cyan)
> at -24 to -28 dBZ when no storms are shown on the presentation,
> but when storms are present, the same color is +5 to +10 dBZ.
> That's why a casual look at the radar can mislead the unwary
> to mistake wet clouds for a rainstorm. The dBZ numbers rule.

I got burned by the sensitivity of the Nexrad display last March. I was
flying down to Wings Field (north of Philly, PA) from central NY when
radar depicted what looked like a line of t-storms approaching mid-PA.

After seeing this on the ADDs weather site, I was going to cancel but
instead decided to call Flight Service for a briefing. It was then that
I learned the red radar returns were from snow, not heavy liquid precip.
The briefer had told me that most likely the radar was more sensitive
than it would have been during the summer, which made the returns look
much stronger than they were.

Had I seen the key, I would have determined this myself.

--
Peter