Weather question

C

CerroTorre

Pre-takeoff checklist
Joined
Nov 1, 2020
Messages
136
Display Name
Display name:
CerroTorre
Hi everybody, I’m in the process of dusting off the rust after a long time away, and I’m finding that some aspects of weather are just as confusing as they used to be... Hopefully somebody can spell it out for this aging brain...

So here’s a couple quote sfrom the Jeppesen PPL book I’m re-reading: “wind always shifts to the right in the northern hemisphere” and “When you are flying through a front at low to middle altitudes, you will always need to correct to the right in order to maintain your original ground track.”

Ok, when I plot out a frontal wind shift from SSW to WNW (as described in the textbook), and a northbound course across the front, that results in a correction to the LEFT. What am I getting wrong?

I know this may seem ridiculously specific, but something about wind behavior around Highs, Lows and fronts has ALWAYS been confusing - usually related to how it changes depending on specific location of the observer.

Anybody able to offer any clarification to the main question above?
 
I think of highs as air that is descending and pushing out of the center- moving clockwise.
I think of lows as air getting sucked into the center and moving counterclockwise. Wind correction has a lot to do with what direction you’re moving in relation to The center of that Airmass
 
For the first statement: Air masses that move in a N-S direction will deflect to the right in the northern hemisphere due to the Coriolis effect caused by the earth's rotation.

The second statement is less obviously clear. I would prefer understanding the underpinning rather than memorizing a rote solution. As you cross the frontal boundary, the winds will shift in a predictable fashion. Typically, when crossing a typical warm front S-N, the wind will shift from southerly to easterly. When crossing a cold front E-W, the wind will shift from southerly to westerly. The wind shifts correlate to the associated low pressure center driving the frontal boundary movement. You can figure out the effects on your ground track from there.
 
Thanks guys. I agree that understanding the underpinning concepts and mechanics is the goal. In the long run it’ll serve me better.

I just can’t make Jeppesen’s statement square up with what I understand about those mechanics. Which makes me question whether or not I actually understand the mechanics... :)

Thanks again for each of the thoughts. It all goes into the hopper...
 
I am a meteorologist, if you would like to message me. I can possibly explain whatever weather questions you have in easier to understand terms. Sadly.... most PPL content makes weather much more confusing than it really is....
 
I admit that I don't know as much about wind shifting as I should, but it appears to me part of the problem is what orientation you are flying in relation to the wind. Let's say that the wind is swirling in a clockwise direction. As you encounter it you could be entering a quartering headwind from the right front, that wind will push the airplane to the left, so you steer to the right to correct for it. If you were flying in the opposite direction the same wind would be a quartering tailwind from the left rear, that wind will push the airplane to the right, so you steer to the left to correct for it.
It's not just what the wind does, it's what the airplane does as it encounters it from various different directions.
 
Josh Jackson said:
I am a meteorologist, if you would like to message me. I can possibly explain whatever weather questions you have in easier to understand terms. Sadly.... most PPL content makes weather much more confusing than it really is....
Click to expand...

Welcome to the forum Josh. Always happy to see other Tucsonans here.
 
Timbeck2 said:
Welcome to the forum Josh. Always happy to see other Tucsonans here.
Click to expand...

Hey Tim, I know it was a while ago but we met last year at some point. Had to take a break from pursuing any physical flights, but spinning back up on the sim lately to try to knock out PPL this winter.
 
CerroTorre said:
Hi everybody, I’m in the process of dusting off the rust after a long time away, and I’m finding that some aspects of weather are just as confusing as they used to be... Hopefully somebody can spell it out for this aging brain...

So here’s a couple quote sfrom the Jeppesen PPL book I’m re-reading: “wind always shifts to the right in the northern hemisphere” and “When you are flying through a front at low to middle altitudes, you will always need to correct to the right in order to maintain your original ground track.”

Ok, when I plot out a frontal wind shift from SSW to WNW (as described in the textbook), and a northbound course across the front, that results in a correction to the LEFT. What am I getting wrong?

I know this may seem ridiculously specific, but something about wind behavior around Highs, Lows and fronts has ALWAYS been confusing - usually related to how it changes depending on specific location of the observer.

Anybody able to offer any clarification to the main question above?
Click to expand...


I think you completely understand the information the book is giving you. You are quoting "“wind always shifts to the right in the northern hemisphere” and “When you are flying through a front at low to middle altitudes, you will always need to correct to the right in order to maintain your original ground track.”" as if they are the same information. Wind "shifts" to the right in the northern hemisphere... this is correct... also if you were to fly perpendicular to any front, you would correct to the right. But the wind "shifting" to the right in the Northern Hemisphere is caused by the Coriolis effect and is actually referred to as "deflecting".

Does the textbook state that you are northbound through a warm front? this would cause your wind to go from SW to ESE, requiring a correction to the right. If you are flying southbound through a warm front, you go from ESE to SW, requiring a correction to the right. If you are flying westbound through a cold front, you shift from SW to NW, again requiring a correction to the right. If you are flying eastbound though a cold front, you go from NW to SW, requiring a correction to the right.

Its very difficult to notice a dramatic wind shift during a northbound transit through a cold front, unless you are hitting the trailing edge, which in that case, it would be a correction to the left.

Try not to get too wrapped up in the aviation weather for PPL. It is very basic and they do not overanalyze all of the situations, as weather can become extremely complex and confusing when you go down the rabbit hole.

I provide weather support for military pilots and even the "pros" get confused if you get too technical. KISS (Keep It Simple Stupid) and you cannot go wrong. Again, you understand the information, you just might be overanalyzing it.
 
Thanks Josh, my general tendency IS to overanalyze everything. Nailed it and guilty as charged. :) I agree it’s been the problem here. Your breakdown makes sense however. Although the wind shift directions you use are different than the text book...but again, that’s probably just me overthinking it.

All of this highlights, for me, the main challenge I recall from my PPL days - the difference between memorizing answers for a written and really understanding the material. The books almost make some of the learning process harder for someone who learns like myself.
 
Get a weather rock, it will be more accurate.

Just kidding, mostly.
 
PaulS said:
Get a weather rock, it will be more accurate.

Just kidding, mostly.
Click to expand...
lol.

I know right? I’ve seen weather rocks more accurate than the ECMWF or GFS for sure... :)
 
Methinks you are referring just to the change in wind correction as you cross a front. Either direction will cause a change in wind correction to the right:

Wind corr..png​
 
I can see how your chart sample will indicate a WCA to the right on a northbound track. Makes sense.

I got stuck on the specifics of the impacts of front passage as described in the Jeppesen PPL book I’m reading that seem to contradict the general theory and guidelines they also describe. Comes from maybe getting sucked into the weeds a bit ... combined with how much of these things depend on what specific reference point the author is using to describe a phenomenon. Northbound, southbound, aircraft, ground, NE of a low, SW of a hi, etc, etc.
 
CerroTorre said:
I can see how your chart sample will indicate a WCA to the right on a northbound track. Makes sense.
Click to expand...
Only the northbound track? You know the wind follows the isobars, don't you? In my sketch you can see going both north and south you have little WCA if north of the front, but you need to crab more right after crossing the front southbound, crab less when northbound.
 
Yes, I should have written that differently. But short answer is yes. Copy. :)
 
You must log in or register to reply here.
Back
Top