Winter Flying 2008

tonycondon

tonycondon

Gastons CRO (Chief Dinner Reservation Officer)
Joined
Mar 9, 2005
Messages
15,454
Location
Wichita, KS
Display Name
Display name:
Tony
Its the most wonderful time of the year...

Mission: Pick up 1 and return to Ames, IA
Aircraft: Cessna 182RG with WAAS 430, 496, STEC autopilot.
Time: Leave Ames at 3:30 (2130Z) local for about a 5 hr round trip.

TAF for Des Moines is as follows:
FM082100 13014KT 6SM -DZ BR SCT009 BKN020
FM082300 11015KT 4SM -RA BR BKN009 OVC012
FM090400 05015KT 2SM RA SCT003 OVC006

Liquid precip is good. Clouds are lowish but still enough for the ILS.
Also good enough to file DSM as an alternate.

Champaign has much better weather:

FM081500 16015KT P6SM SCT050 OVC120
FM090400 17015KT P6SM VCSH OVC050

My first thought when i got the call was no way in hell, has to be
really icy up there. Checked out the forecast though, and it appears
not.

For the trip there:

attachment.php



and trip back:

attachment.php


So far so good, winds favor about 7000 on the way out and 4000 on the way back. My main concern at this point is that the freezing line is really not that far northwest of home for the return trip. If that front moves a little faster than forecast it would really screw things up. The sounding for Ames on return:

attachment.php




And thats where things get interesting. I thought I saw something about freezing rain in the NWS forecast, but it didnt really show up in the Terminals or Area Forecast. But that right there looks to me like a classic freezing rain profile, with temp/dewpoint > 0 aloft and freezing at the surface. That right there is no good batman. So I look back at the FIP forecast. Field elevation at home is 955 ft, btw.

attachment.php



There it is. that pretty much makes it an easy decision. This isnt even a FIKI trip.
 

Attachments

  • ice1.bmp
    2.9 MB · Views: 257
  • ice2.bmp
    2.9 MB · Views: 253
  • ice3.bmp
    2.9 MB · Views: 241
  • ice4.bmp
    2.9 MB · Views: 238
Love that potential for icing map at 1000 MSL. I'd have to dig tunnels to fly at 1000 MSL most places I go. :D
 
Tony, thanks for going over your thought process in this. Definitely helps someone like me.
 
Thanks for that Tony--this is the stuff I really need to learn--keep writing your go/no go decisions please :)
 
jesse said:
Thanks for that Tony--this is the stuff I really need to learn--keep writing your go/no go decisions please :)
Click to expand...

will do. interesting thing about this is that i actually caught that 1000 foot icing forecast as I was typing up this thread. By that point the guy in illinois had decided to find another way home or whatever, so i was not going either way.

We had several good threads last year with actual forecasts and discussion, im hoping to keeping that going
 
What I'm really curious about is...when is the last time you cleaned out your gmail inbox?!? :)
 
i have 7,271 MB (and counting), and i intend to use it!
 
tonycondon said:
i have 7,271 MB (and counting), and i intend to use it!
Click to expand...

I won't do a screen shot of mine. I have 853 in my inbox :blush: And amazingly I have 7,721 MB as well :smilewinkgrin:.

I'm not sure I understand the Skew T log. Can someone explain it in simpler terms?

Thanks,

Joyce
 
Sadly, there isn't much pilot-oriented Skew-T info out there. For basic info, search for "ruc soundings" and look on that page.

If you really want to know more than just the basics, I'd buy one of Scott's DVDs. Very much worth it.
 
yea Joyce, im no real expert on the Skew T's, but know the basics. Id recommend buying Scott Dennstaedt's CDs. His website is www.chesavtraining.com

The red line on the plot is temperature, and the blue line is dew point. Just a few reminders from basic weather theory.

temp = dew point = clouds (and possibly precipitation)

(temp = dew point) < 0 deg C can mean ice

oh and the diagonal red lines on the chart show lines of constant temperature. you can see lines for 0, +/-10, +/-20 deg C etc.

In that plot, there is an area where temp and dew point were equal (clouds, possibly precip) and the temps were above freezing. Flying in that area would probably be just fine wrt airframe ice, as long as those temps were accurate. However, notice how at lower altitudes, near the ground, the temp is below 0? That means that any precip that falls from those above freezing clouds will likely freeze when it hits the below freezing surface. Freezing Rain.

Theres about 10 million other little weather phenomenons that you can observe from the Skew T. I mostly have a basic understanding of how to find freezing rain, ice, and decent soaring conditions from them. Hopefully Scott will chime in to help us out.
 
Interesting Tony! I love these kinds of threads.
 
scott,

operationally speaking, is the non-classical supercooled liquid droplets that you mention the same as the laymans freezing rain?
 
jlwilson said:
II'm not sure I understand the Skew T log. Can someone explain it in simpler terms?
Click to expand...

See the July issue of AOPA PILOT magazine, page 107. Thomas Horne wrote a good column about Skew-T charts and how to use them in his monthly column, WX Watch: Skew-T Basics

Go to aopa.org and type "skew t" in the search box. Lots there.
 
Scott, thanks for the education. My brain is working on processing all of this. :)
 
Scott, thanks!

So in this case, it was case #1 with a warm nose, and freezing rain/drizzle at the surface. I guess i usually just look for the nose, and if i see that it triggers thought of freezing rain, regardless if the moisture source started out liquid or frozen.

I did notice that the forecasts updated to include freezing rain later on in the day. That made me very happy, as it verified my earlier thoughts on the matter.

We actually had spotty freezing rain earlier in the day than the METARs indicate, as early as 2230Z if i remember correctly. I had a student checking out in a Cherokee and as we got in the airplane he noticed a little precip. It was liquid during the runup, but when we went to take off it had frozen to the windscreen so i called for an abort to the takeoff. we then spent about an hour talking about symptoms, signs, and forecasts for freezing rain and ice in general.

As we were looking through the weather, we noted there was at least a 3 degC temp difference between Ames and Des Moines. I brought up the point to him that with frontal junk and winter weather, temps can change over short distances and the TAF really doesnt mean much away from the airport.
 
tonycondon said:
Its the most wonderful time of the year...
Click to expand...

It is, isn't it? I had a no go at Thanksgiving, but my decision was easier.

We flew to MEM thanksgiving morning, and at that time the progs and forcasts looked good for a Sunday afternoon return. After a good weekend of Elvis, the zoo, and Beale Street, it was time to go home. As some know, the southeast turned into an icebox that Sunday.

-Broad airmet over area telling of moderate ice between freeze level and 160.
-Freeze level ~2000agl across flight path area
-Ceilings ~1500agl across flight path area
-ADDS CIP/FIP icing tool indicates 50-75% chance of icing along route, and shows SLD at 030,050, and 070.

That was enough for me, I kept the rental car and made the 6 hrs drive home. Monday was to be an icy/snowy mess as well, so I decided on the drive. Went to work early Tuesday, left 3pm and drove back to MEM, grabbed a hotel for the night. Up at 4am CST, off MEM before sunrise, and had a beautiful clear ride home. I watched the sun rise with Elvis Blue Christmas coming thru the headsets and a 180kt ground speed. A just reward for having to drive. And, I made it to work by 9:30am EST that morning...
 
You must log in or register to reply here.
Back
Top