NEXRAD v. on-board Radar

[Dave Siciliano]

Larry Olsen took some pics in his Baron recently showing what the NEXRAD display was showing v. the on-board radar. Shows how late the NEXRAD can be pretty graphically. Also, the NEXRAD is composit; meaning you don't know at what altitude the severest portion of storm is; where radar can slice and dice to isolate it: tilt can show different altitudes and the left right scan puts that on the scope.

Sorry for the fromat. Didn't know how to edit the AvSig extras out. Oops, how do I attach an html file? Attachment won't take it.

Dave

 

[Areeda]

Oops, how do I attach an html file? Attachment won't take it.

If it's on the web probably best to link to it. Otherwise you'd need to get the html file and all the images it refers to (probably).

It seems Nexrad and on-board Radar have different puproses for me. Nexrad if you want/can avoid the storm or land, Radar if you want to penetrate it. I'm a wuss, Nexrad works for my flying.

Joe

 

[Dave Siciliano]

I don't want to link it and do to that board what some folks did to us! I have the html file, but this program won't let me uplink it. It also needs to be edited and Paint and Adobe wouldn't take the file.

Dave

 

[Dave Siciliano]

Trying again to bring up the pics

 

[TMetzinger]

NExrad is supposed to be strategic, and be used to avoid getting close to convective activity.

I've found that the radar carried on light aircraft is generally only useful for tactical "where will I not die in the next 5 minute" decisions - the antenna and transmitted power are just too small. I once saw a comparison of two radar pictures taken of the same storm from practically the same location and altitude - one was on a seneca and the other was on a boeing. The Seneca radar showed an area of dark green with nothing behind it, while the boeing showed the same area of dark green with a monster cell about 5 miles behind it.

I've fllown near enough weather now to state that I have no desire to go tactical with storms, and if someone wants me to fly a mission that requires that kind of flying, they're gonna have to provide me with equipment that's up to the challenge.

I realize that this attitude will likely keep me out of the "freight dog hall of fame", but I'll still be alive to visit it.

 

[Witmo]

The radar picture is obviously boresighted to the nose or perhaps oriented to the track of the aircraft. The NEXRAD picture is North-Up. Without knowing the scale for the radar display or its heading, it's difficult to compare the two pictures meaningfully, at least it is for me.

 

[Witmo]

Oops. I see the track line on the NEXRAD photo now. It makes more sense to me.

 

[Dave Siciliano]

There are many points to be made, and a lot of folks don't understand them.

NEXRAD: First off, the weather display may not be current. XM can have from 5 minute to much longer intervals. Thus, if there is a fast moving storm, or if new cells are building quickly, what you're looking at may be old data. The cell could have moved and new cells could have formed. Also, this is what's called a composite display: the strongest return in that location shis shown. Things may be much different at your altitude.

RADAR: Yes, there are times radar units on small planes may be attenuated (which is what happened in the cite above of a large plane system v. smaller), but larger plane radar can also be attenuated--just ask any of the guys flying the large commercial stuff. For smaller systems, flying between cells and finding tops and bottoms, the on-board radar can be very beneficial. Just last week I climbed through a system departing Dallas. Green and yeller on both the radar and NEXRAD. The radar clearly showed where current convective activity was: it was clear the NEXRAD was a little behind. By using the tilt function on radar, I could determine where the tops were (of the convective activity) and where I'd break out. It was very accurate on my trip. If there was class 4 and up stuff, I probably wouldn't have gone.

Best,

Dave

 

[falcon1]

I have noticed that the XM weather radar usually makes weather appear lot worse than it actually is. I think that this is because the XM picture is made up of many different radar sites. I think that XM is great to see where you should deviate to early on. Airborne radar is best when close to the storm. I have noticed that the cloud tops feature on storms is pretty accurate. If tops are not displayed at 350 you are usually clearing everything. Together these are a great tool. I would be careful using XM alone, unless you plan to clear the storm by many miles.

Nice pictures. Really lets people know whats going on.

 

[flyingcheesehead]

Re: NEXRAD v. nothing

I'm beginning to think a 396 should be in my future. After my flight to STE last week where some unforecast junk popped up, and remembering a cancellation where having NEXRAD would have probably allowed us to go... I just like to have as much information as possible.

Of course, bad information is usually worse than no information, and information you can't interpret or use correctly can be dangerous as well.

So, for those folks who've had NEXRAD and/or radar aboard, what guidelines would you have for an IR newbie like myself as to how to use the information available? Or will I be asking for trouble by having NEXRAD at all?

 

[Dave Siciliano]

Kent:

NEXRAD is great as far as seeing the big picture; giving you a heads up the coast is clear or there are issues ahead. The 396 has a lot more information that is also helpful.

Radar is closer in. Once you're going to deal with weather issues, keeps you out of the bad stuff and provides other useful info.

Dave

 

[gismo]

Re: NEXRAD v. nothing

I'm beginning to think a 396 should be in my future. After my flight to STE last week where some unforecast junk popped up, and remembering a cancellation where having NEXRAD would have probably allowed us to go... I just like to have as much information as possible.

Of course, bad information is usually worse than no information, and information you can't interpret or use correctly can be dangerous as well.

So, for those folks who've had NEXRAD and/or radar aboard, what guidelines would you have for an IR newbie like myself as to how to use the information available? Or will I be asking for trouble by having NEXRAD at all?

Just consider that NEXRAD ala 396 is good at showing you where the precip was 2-10 minutes ago. It also can loop so if you belive the past is a good predictor of the future then you can forecast (guess) what things will look like at any particular point along your route when you get to that point. Even on board radar only shows what the precip looks like right now (at least within the last several seconds) and it's no guarantee of how it will change over the 3-5 minutes it takes for you airplane to cover the next 10 miles (which is what you really want to know). IOW even if my onboard radar showed a 20 mile wide precip free area 10 miles ahead of me in an area of developing wx, the unstable moisture laden air in that location might pop into a cell I'd rather not be near at the exact moment I become centered under it. We tend to think of TRW as relatively constant storms that move without giving much consideration to how they begin and grow.

IMO the best theoretical way to look at downlinked NEXRAD is by making some kind of estimate about how much room you need to give the weather it shows in order to avoid getting caught up in it and then plan to avoid the projected (guessed) location of any weather you see by that much.

In practical terms NEXRAD provides these benefits:

1) A believable answer to the question "Is there serious wx ahead of me"?

2) The ability to make small course changes far enough from an area of convective activity to avoid it by a large margin without adding many miles to your trip.

3) Good information on which way to turn to avoid the precip that's ahead.

4) Similarly good information about your options for retreat if the stuff ahead is or becomes unpassable.

With the onboard radar I'm fairly comfortable threading through a broken line of TRW as long as I can find a low return gap at least as big across my path as the length of my path through the line and a minimum of 5-10 miles wide depending on the speed of cell movement and growth over the last several minutes (20-30 miles if the TRW is severe). With NEXRAD I know that the cell locations can be off by as much as the cells can move in 10-15 minutes which can be as far as 15 miles or so. If you add a 15-20 mile buffer to the onboard separation minimums the gap you need could be as much as 30-40 miles and that's more room than you usually see in any well developed line so in reality you will probalby have to make an end run on the line or wait out the passage with NEXRAD in many cases where penetration would work with onboard radar.

OTOH, when the cells are scattered instead of in long lines NEXRAD should be quite sufficient to avoid them and it would probably allow you to remain visual most of the time as well.

 

[wsuffa]

The one other tool you get with Nexrad on the bigger, uglier cells is the SCIT marker that shows direction and speed of the cell. It is no guarantee, of course, because it's estimated on historical data, but they have shown to be pretty accurate.

I don't know if those markers show up on the 396, but they do show up on WxWorx as used on a tablet computer.

It takes some practice, but using Nexrad as a strategic tool and watching the trends, together with something like a stormscope for tactical, you can reach a better level of confidence. Still, give a strong cell a pretty wide berth.

YMMV.

 

[PoAdeleted5]

deleted.

 

[flyingcheesehead]

NEXRAD is great as far as seeing the big picture; giving you a heads up the coast is clear or there are issues ahead. The 396 has a lot more information that is also helpful.

Radar is closer in. Once you're going to deal with weather issues, keeps you out of the bad stuff and provides other useful info.

Dave,

That sums it up very nicely. Thanks! When are you going to be in WI next?

 

[flyingcheesehead]

Re: NEXRAD v. nothing

so in reality you will probalby have to make an end run on the line or wait out the passage with NEXRAD in many cases where penetration would work with onboard radar.

That's not bad at all, really. I don't think I'm quite ready to go penetrating lines anyway. I'll at least wait until I get my permanent, spiffy Wright Brothers plastic pilot certificate.

The 2-10 minute delay sure beats the heck out of the delay between calling flight service (insert preflight, startup, fairly lengthy pre-takeoff checks, plus actually getting up in the air here) and getting to the weather!

Now if only I could trade a slice of that car I just bought for the 396! $2500 is a lot of money for something that's not going to get that much use in the grand scheme of things. My $2500 top-of-the-line laptop usually gets several hours a day in, the 396 would be useful maybe once a month on average and it's sure to be superseded by something even newer and better soon. Ugh.

 

[Dave Siciliano]

Dave,

That sums it up very nicely. Thanks! When are you going to be in WI next?

Kent:

I'm shooting for Memorial Day weekend, but not sure yet.

Dave

 

[gismo]

The one other tool you get with Nexrad on the bigger, uglier cells is the SCIT marker that shows direction and speed of the cell. It is no guarantee, of course, because it's estimated on historical data, but they have shown to be pretty accurate.

I don't know if those markers show up on the 396, but they do show up on WxWorx as used on a tablet computer.

It takes some practice, but using Nexrad as a strategic tool and watching the trends, together with something like a stormscope for tactical, you can reach a better level of confidence. Still, give a strong cell a pretty wide berth.

YMMV.

The 396 shows the cell information but my Avidyne does not, regardless of which level of XM wx service I sign up for. The other thing you do get on either display lightning (part of the more expensive monthly plan) which is another good tool for detecting and avoiding TRW. I don't know the latency of that info though.

 

[gismo]

Re: NEXRAD v. nothing

That's not bad at all, really. I don't think I'm quite ready to go penetrating lines anyway. I'll at least wait until I get my permanent, spiffy Wright Brothers plastic pilot certificate.

The 2-10 minute delay sure beats the heck out of the delay between calling flight service (insert preflight, startup, fairly lengthy pre-takeoff checks, plus actually getting up in the air here) and getting to the weather!

Now if only I could trade a slice of that car I just bought for the 396! $2500 is a lot of money for something that's not going to get that much use in the grand scheme of things. My $2500 top-of-the-line laptop usually gets several hours a day in, the 396 would be useful maybe once a month on average and it's sure to be superseded by something even newer and better soon. Ugh.

Well, unless your newly purchased (Saab?) has a GPS map display, you could use the 396 in the car and in any case it might prove useful in your truck. In the truck I'd think the wx might be handy as well.

Just trying to help you justify spending some more dough.

 

[wsuffa]

The 396 shows the cell information but my Avidyne does not, regardless of which level of XM wx service I sign up for. The other thing you do get on either display lightning (part of the more expensive monthly plan) which is another good tool for detecting and avoiding TRW. I don't know the latency of that info though.

I've compared the lightning on the WxWorx to the Stormscope. The Stormscope wins hands-down. I don't even turn on the strikes page on the XM WX most of the time, other than occasionally to check if a distant cell is showing strikes. It is far less accurate than the NexRad display.

https://thunderstorm.vaisala.com/tux/jsp/explorer/explorer.jsp#

 

[flyingcheesehead]

Re: NEXRAD v. nothing

Well, unless your newly purchased (Saab?) has a GPS map display, you could use the 396 in the car and in any case it might prove useful in your truck. In the truck I'd think the wx might be handy as well.

Just trying to help you justify spending some more dough.

Haha... I don't need any help with that!

The new car (Volvo... And did you know that there is a Volvo Aero division?) doesn't have the navigation system. I suppose I could use the 396 in the car, but I usually know where I'm going anyway.

In the truck, I have a Garmin Street Pilot 2620 which has a hard drive and can store street-level maps for the entire US and the more populated parts of Canada. It also has a touch screen and a remote, which is nice as I can stay in a better seating position and keep my second hand close to the wheel just in case.

The problem with the 396 in the truck is that I'd have to keep using a laptop to load new maps onto it. The reason I bought the 2620 to begin with is because I knew if I had to keep hooking it up to a laptop I'd end up not using it as much as I should to get my money's worth.

I've been hoping for something that could do both navigation and XM weather, and Garmin came out with the Street Pilot 2730 (same form factor as my 2620) and the Street Pilot 7600 (7" screen, otherwise it seems to be the same) which have XM traffic and weather (and radio) available.

Unfortunately, the $15/mo XM weather subscription does not get you NEXRAD or really anything useful - You get the happy "sun peeking over the cloud" type of icons all over the screen. Yuck.

I certainly would like weather in the truck too... Maybe I'll have to keep using the 2620 for nav and the 396 for weather. I'll need to add some more power plugs to the truck too I guess! (Already have a 3-way up front: Sirius, iPod, and GPS; I already swap things out to plug my phone in too!)

We'll see what Garmin has at OSH this year...

 

[flyingcheesehead]

I'm shooting for Memorial Day weekend, but not sure yet.

I sure hope we can hook up this time! I'm supposed to be at KLWC (KS) on the 28th for a wedding reception (well, OK, from what I hear it'll be more akin to a "kegger" ) but I should hopefully be around the rest of the weekend.

 

[Dave Siciliano]

I sure hope we can hook up this time! I'm supposed to be at KLWC (KS) on the 28th for a wedding reception (well, OK, from what I hear it'll be more akin to a "kegger" ) but I should hopefully be around the rest of the weekend.

As it gets closer, I'll let you know. The Baron is going in for annual; so, I may be in the A-36.

Dave

 

[flyingcheesehead]

As it gets closer, I'll let you know. The Baron is going in for annual; so, I may be in the A-36.

You getting it back soon? Cool!

Have you ever been to The Hitching Post right near C47? If so, what's it like?

 

[gismo]

As it gets closer, I'll let you know. The Baron is going in for annual; so, I may be in the A-36.

Dave

FWIW, I expect to be in Michigan over the holiday weekend. Anyone for lunch at Mackinac Is (or somewhere else in the LP)?

 

[Dave Siciliano]

You getting it back soon? Cool!

Have you ever been to The Hitching Post right near C47? If so, what's it like?

It's supposed to be ready. Hope so, the Baron will be in annual.

Hitching Post is O.K. Nothing special to me, but O.K.

Dave

 

[flyingcheesehead]

Hitching Post is O.K. Nothing special to me, but O.K.

It's special only because it's within walking distance of an airport.

I'll have to give it a try sooner or later.

 

[Dave Siciliano]

It's special only because it's within walking distance of an airport.

I'll have to give it a try sooner or later.

Yes it is Kent. Portage also has a pretty good, reasonable taxi service it you want to go somewhere else. I've never waited more than ten or 15 minutes for them. There are a couple places I'd rather go, by Hitching Post is convienent to the airport. There's a steak house south of downtown that is good there, and Dinos is also within a couple miles--also average, but flexible hours.

Dave