Practical IFR advice

[RobertE]

My excuse for needing this is I live in the Bay Area of Northern Cal and the IMC we have here is pretty much either marine layer year round or status clouds filled with rain in the winter that are too cold to penetrate without fear of icing.  So I rarely get much experience beyond a few minutes penetrating the marine layer.

 

Last week I departed Wilmar, MN (yes, Weep No More did a great job) in drizzle.  It was too early for there to be any PIREPS and tops didn't show on Nexrad so I didn't know how high I'd have to go to get above.  I didn't want to drone on in the clouds for hours.  Anyway, I filed at 6K and by 5K was on top.  Which got me thinking. Is it reasonable to expect certain amounts of surface precipitation to be indicative of the thickness of the stratus cloud layer?  Is drizzle likely to be 3K thick, light rain 5K, moderate rain 10K and so on?  Even in asking the question I know that the amount of moisture held in a given cloud varies, so I know there must be variation.  But are there crude rules of thumb that are, typically, fairly predictive?

 

 

 

 

[ChrisH]

Area forecasts are a great way of getting a hint to cloud tops.

[Jim Peace]

You can always call a tower or the ARTCC on the ground via telephone and or RCO etc...and request a tops / flight conditions report.  They will just ask an airplane for one and give you a verbal.  Done it many times.

[John Pleisse]

One article I read some years back noted light rain would indicate tops at a minimum of 6,000. Have you messed with a Skew-T chart? All of my IMC was based on assurance of being on top. If I could be on top, I would go. The Skew-T charts were almost always correct. If they weren't (within a couple of thousand), it was an indication the wx was changing, to turn back or get a new plan going. PIREPS help.

[Danb]

Try weatheraero.com. Experimental. ADDS. Helpful for some Wx products...realistically preps are our best source but difficult to get when needed most....usairnet.com. Is a useful source also but not so with tops..

[Marauder]

Skew-Ts are the way to go to look for cloud tops (and layers). When I started working with them, there wasn't much training available to explain them. There are a few YouTube videos from Ed Williams and avwxworkshops that take some of the mystery out of them.

Prior to looking at them, I would use the area forecasts and look for PIREPS.

[Mooneymite]

Give and get pireps!

 

One peek is worth a thousand skew T's.

[midlifeflyer]

Skew-Ts are the way to go to look for cloud tops (and layers). When I started working with them, there wasn't much training available to explain them. There is a few YouTube videos from Ed Williams and avwxworkshops that take some of the mystery out of them.

Prior to looking at them, I would use the area forecasts and look for PIREPS.

 

Although nothing is truly stand-alone, the Skew-T is probably best tool for this purpose. While a primary purpose of the tool is the measurement of the potential for convective activity, at its simplest its a visual of where the temperature and dewpoint will converge and diverge, giving a very good estimation of cloud heights and layers. It's been fairly accurate when I've used it to get an idea whether, despite low ceilings, we will be en route in sunshine. 

 

I've very please to say that I converted Ed' excellent Skew-T presentation to video for YouTube:

Weather in the Vertical Part 1

Weather in the Vertical Part 2

[moodychief]

Skew-Ts truly changed my IFR planning and flying. Not only to know where to expect the tops but also to know where you can expect to be between layers and where the icing temps are most likely.

[Danb]

Now everyone has my attention,I have Ed's you tube's ready to study, in actuality if you are on a long cross country ie. excess of 750+miles, and you encounter Wx. Sat at 8500!ft. Mild rain, is there a way to ascertain tops not using potentially old(who knows when) preps. On another front do we all make pireps as we should? There should be a concerted effort and maybe Robert's original post for us to make it a point to provide pireps. This leads us in a different direction and Robert I'm not trying to ambush your question its a great one. It merely leads me to a petpieve on whether we are all doing our job as professional Mooney Pilots. Hopefully learning how to ascertain if Skew t's are easy it's another tool for our basket...

[Marauder]

Give and get pireps!

One peek is worth a thousand skew T's.

So true. I really wish ADS-B allowed us to send down PIREPs electronically instead of trying to verbally transmit it to Flight Service or squeeze it in with ATC.

[Robert C.]

Area forecasts are a great way of getting a hint to cloud tops.

 

+1

 

Interesting how few people know about this...until recently myself included. Of all people, it was the DPE who pointed it out to me when I fumbled the question on my oral. Now I religiously check it. Seems to give tops most of the time but not always.

[carusoam]

We need a separate thread on the arts and sciences of Pireps...

Tops are nice to know.

Icing is 'mandatory'

Mike, are you with me? Could use a poll...

Best regards,

-a-

[Z W]

To answer your original question, no, I do not believe there is any direct correlation between level of precipitation and thickness of the cloud deck.  I've taken off into 500 ft ceilings, no rain, and not broken out until 9,000 ft.  I've also flown VFR in moderate precipitation where I can see blue sky in holes in the cloud deck above, probably 500-1000 ft thick.

 

You've gotten good advice on how to get an idea of cloud thickness.  I also like to open up the map on Garmin Pilot (used to do the same on Foreflight) and have it show ceiling heights for my entire route on the map.  That gives you a good idea of how widespread any low IFR conditions are, and whether you can plan to file and remain mostly under the cloud deck.  If the ceilings are too low for that, I look at the Area Forecast (not the TAFs) and file above the forecasted tops.  If I can get a tops PIREP that is recent I consider that much better than the Area forecast.

 

All of that being said, if it's just clouds and light or moderate rain, it should not be a big deal to you if you get it slightly wrong and end up getting some actual time.  It's good practice, and as far as I've found, practice is the only way to get comfortable with it.  I try to do that sometimes on flights with high ceilings, so I know an approach won't be required, and I can always descend down out of the clouds if needed.

 

Stay away from ice, and anything red on NEXRAD, and you should have a safe flight.

[Bob_Belville]

With NEXRAD, Stormscope, and George, I don't mind at all spending en-route time in clouds but it can be tough on old paint, particularly leading edges, and props blades.

[kmyfm20s]

Just down loaded the app skewtlogpro. Pretty cool!

[jlunseth]

There is another way to actually see and calculate cloud tops, in addition to Skew T, which is a great tool.  If you go to aviationweather.gov and pull up the infrared map, you will see the temps of the tops as colors along the route of flight.  If you see a cold spot of say, -20 (there is a scale at the bottom of the chart), and the ground temp at that location or near it is 0, then there is a 20 degree difference between the top and the ground.  Divide by two per thousand feet for the average lapse rate, and the top is at 10,000 or close to it.  The Adds Flight Path Tool on the website is also useful and among other things has the ability to show at what altitudes icing is likely to be present along the route of flight.. 

 

But the SkewT app is the best, that is what I use.  It won't show intensity though.

[kortopates]

I do that as well, (use the IR sat picture), but rather than estimate altitude via the adiabatic lapse rate (which really varies between dry and wet anyway) go to winds forecast to get accurate altitude vs temperature - fast and accurate estimate.

Sent from my iPhone using Tapatalk

[jlunseth]

Yes, I agree, the lapse rate varies.  I have not tried the winds forecast, will take a look. 

[Piloto]

XM\WX shows cloud tops. I have used and found to be very useful. Specially when it shows your proximity to clear of clouds. It shows this even in the absence of radar returns, pretty impressive. They use satellite data since it shows the tops even over the Bahamas.

 

José  

[midlifeflyer]

But the SkewT app is the best, that is what I use.  It won't show intensity though.

 

I think it does, at least for those who know enough about interpreting the information the Skew-T provides. It  measures the degree of atmospheric instability and different levels and those are related to storm intensity as well as icing potential.

[kmyfm20s]

Great web planner, you can enter your route.

http://skewt.meteor.com

[Robert C.]

Very cool, thanks for sharing.

[midlifeflyer]

I think it does, at least for those who know enough about interpreting the information the Skew-T provides. It  measures the degree of atmospheric instability and different levels and those are related to storm intensity as well as icing potential.

I think I made a mistake on this. The Skew T does show the information.

 

But jlunseth was talking abou the app and at least the last time I looked, the SkewTLogPro app did not show the curve representing the dry/then wet adiabatic cooling rate of a hypothetical lifted parcel. That's the one (the black line in the diagram below) that, when compared with the actual temperature indicates atmospheric stability or instability. That was one of the reasons I didn't get the app and prefer to rely on the NOAA's javascript version at http://rucsoundings.noaa.gov/gwt/ 

[gsengle]

No one has mentioned the flight path app at weather.aero (experimental adds) - under desktop apps.  put in your flight path, and it shows you a cross section of the atmosphere per their super computer models.  switch over to relative humidity, and where it drops off, you're out of the clouds.  humidity needs to be near 100% to have clouds.

 

g