May 27, 2009

Summer time

I just watched the annual Memorial Day fireworks in Manchester, so summer is officially here. The weather has moved in...


What you see out the window above looks like this on the screen below...

Happy Birthday to the MD80 First Officer who took these last week over Florida. No wonder the shuttle couldn't land.

Till next time...



Frank Van Haste said...


Yes, summer is here, along with the advent of CB, TCU, +TSRA and all of that good stuff.

One thing that is changing is that more and more of us FLIB's have NEXRAD in the aircraft and so have our own independently derived ideas about how we need to respond to that nasty yellow and red stuff looming down-track. (Have a look HERE for my own take on onboard NEXRAD.)

My question: What are your thoughts on how you folks "behind the radar" and us folks driving the airplanes can most effectively work together to keep the traffic moving and keep us out of Big Trouble?

Compared to NEXRAD, how good are you at "seeing" the weather? Are you assuming that we "know what we are getting into"? How annoying is it to you when we ask for "20 degrees right to avoid buildups"? If we want to try lower to stay visual, can you advise us about MVA's and such? What's the general feeling around your facility about how to keep the spam-cans out of convective trouble (assuming you ever even think about it)?

I look forward to your advice.


Exogenous said...

Good stuff. Is that on-board radar or Nexrad?

deltamike172 said...

The screen depicted is from the MD80, so it would be on board radar from the nose cone. That is WAAAAY better than anything we display, both in detail and in timeliness. Approach has more intensity options than Center, and may be more accurate, but Center's weather radar is delayed upwards of 5 -7 minutes. The older version of our precip radar is from the actual traffic radar, and I sometimes overlap (most controllers hate the clutter) to get a better idea where the heavy stuff is RIGHT NOW.

We don't have a problem with pilots deviating, per se. If you give us a heads up, that helps, of course. If we ask you "how long on that deviation", we generally want the worst case scenario. If you deviate longer than you claim to want if we ask, we may have to scramble to coordinate with other sectors. In most cases, the holes are obvious and there is a conga line through it.

I wish I knew more about how pilots figure out what they can go through and what they need to go around. I try to let pilots know what altitude I'm going to descend them to so they can maybe figure out how far to deviate, since the cloud is probably fatter at the bottom. Maybe I'm just wasting my breath.


Frank Van Haste said...


Re: "I wish I knew more about how pilots figure out what they can go through and what they need to go around."

Not sure how you can calibrate this with what you see on your equipment, but here's my idea from the left seat of a Cessna 182...

The "green returns" are no problem at all. The "yellow returns" can get a little bumpy but I've never actually been uncomfortable going through them. I will do what I need to so I avoid the "red returns". In my mind green = light, yellow = moderate and red = heavy precip.

Regardless of the intensity of returns, I won't go near any cell that indicates lightning is present.

Even in the absence of precipitation returns, I'll ask for a deviation if the cumulus tops are rising a couple thousand feet above me, as I figure the updrafts inside that convection machine are likely to get my attention. I'll probably ask to go around something that your friend with the MD-80 will push right through.

That's just one private pilot's rough idea of operational issues. YMMV.


deltamike172 said...

We don't depict "Light" precip, only moderate, heavy and "extreme" (aka, its pouring, I guess). We scan different altitudes, and its not uncommon to display extreme, but pilots go right through since that precip is actually much lower than their altitude.

So, if you decide you're going around something, how far around are you going to go? Do you just avoid the actual displayed color, or do you need/desire/want to miss the worst stuff by xx miles? Airline pilots feel free to step in on this one, as well....

Frank Van Haste said...


Speaking just for myself, I'm going to take a couple of things into account as I plan my response to the weather. First, there is the known latency of the NEXRAD display. Like your Center radar, the image can be 7 to 10+ minutes out of date. If the wx is pretty static I can just react to what I see, but if the cells are fast movers I have to project their positions. If possible I am going to deviate to pass upwind of the displayed position.

Second, if lightning is present I don't want to shake hands with the stuff...and if it's a really tall one or part of an organized line, I will be trying for 15 or 20 miles. In contrast the usual summer popcorn can be kept fairly close provided that visual contact is maintained. Not going to trust the NEXRAD images for that dance.

So, to summarize, if it's just rain I want to deviate to avoid the heavy (red) echoes, with an allowance for the latency. For the boomers I want a few miles (5?) clearance for air-mass cells and lots of miles for squall lines or mesoscale supercells.

Again, my $0.02, YMMV.


Anonymous said...


Challenger/GIII driver's two cents~ Depends on the severity of what the radar is showing, ride reports and the most important of all....what our eyes see. If we see building CU, lightning, or heavy rain shafts, we don't penetrate if traffic/airspace allows. Most companies require 20 mile deviations around SEVERE complexes and we also try and not deviate around the downwind side of any storm (turbulence/hail possibilities). Radar wise...just because something is being painted green or yellow doesn't mean the ride will be acceptable. Of course anything red, forget it. Again, the eyes don't lie. Looking out the window, working the radar, getting PIREPS and a little bit of luck should keep the ride "safe".

Senior Captain said...

That radar image looks like what I imagine I'd have seen on my last flight if I had radar!