Go/No-Go 4.25.08

[CJones]

Some guys were wanting to go fly somewhere for dinner tonight just to go burn some gas. TAF said 5000' broken till 7pm when it drops to 2500' broken, vis remains >6. I said someone could fly out VFR, and I could file IFR to get back to AMW if necessary. Well, the latest TAF has that ceiling dropping lower than expected, and the winds are howling, so I'm gonna cast my vote for 'no-go' for this type of 'fun' trip.

BUT... While poking around with the current forecasts, pastcasts, etc. I thought I would play with SkewT and try to figure out how that thing really works along with the ADDS Flight Path Tool.

After looking at things, I really don't want to go 'play' tonight, but what would you say if you are coming in from the south, trying to get back in to AMW. Would you stop short for the night, or would you feel OK coming in for the approach? Why or why not? Of course some of you will say "Someone said ice, so I said NO." That's fine. What about the folks that weigh all options and take an educated (however slight) risk? Why or why not?

If I'm reading the SkewT correctly, the bases should be around 2250 ft (temp/dewpoint within 3* of each other) with tops around 5000'. This jives with METAR at AMW at the time (2200OVC) and PIREP SW of our area of tops at 6000'. Also, ice would start around 2000' (if in clouds) due to temp = 32F and lower above. Am I reading this correctly? Any other less 'general' knowledge that can be taken from this?

 

[gibbons]

Chris,

The way I see it there are plenty of opportunities to fly in challenging weather without turning a "just for fun" trip into a lot of work. If I'm going on a fun trip and the weather doesn't look fun, I don't go.

 

[CJones]

Chris,

The way I see it there are plenty of opportunities to fly in challenging weather without turning a "just for fun" trip into a lot of work. If I'm going on a fun trip and the weather doesn't look fun, I don't go.

Exactly, this is a definite no-go for me. When I have that much stuff to worry about, it defeats the purpose of trying to take a "fun" trip. I'm really just posting this as something to talk about. We haven't beat this dead horse enough just yet.

 

[Rudy]

Chris,
Nice to see a Skew-T on here, I deal with them a lot in forecasting, and they are a great tool.
I havent posted in awhile, but had to post something when I saw the Skew-T on here.
Best,

 

[TangoWhiskey]

When Scott D. gets here, the beating of the horse shall begin. I think your analysis of the SkewT-logP was accurate. What was driving this weather? A front? What was going on in the upper atmosphere? Were the conditions expected to move through fast, or linger? And then, looking back on it (perhaps tomorrow), did what you expect actually occur?

I love these "weather analysis with actual data" threads; I learn a lot from them.

 

[CJones]

Chris,
Nice to see a Skew-T on here, I deal with them a lot in forecasting, and they are a great tool.
I havent posted in awhile, but had to post something when I saw the Skew-T on here.
Best,

Yeah, you're professionally trained on this stuff. Enlighten us!

If you think THIS is a good one, read this: http://www.pilotsofamerica.com/forum/showthread.php?t=19154

When Scott D. gets here, the beating of the horse shall begin. I think your analysis of the SkewT-logP was accurate. What was driving this weather? A front? What was going on in the upper atmosphere? Were the conditions expected to move through fast, or linger? And then, looking back on it (perhaps tomorrow), did what you expect actually occur?

I love these "weather analysis with actual data" threads; I learn a lot from them.

All of this is following a strong cold front that pushed through around 3am this morning, firing off strong t-storms and plummeting temps down 30 degrees from what they were this time yesterday.

Looks like a strong jetstream at FL310-330 is hitting us from the arctic before pushing back up north.

The latest TAF has clouds lifting by late tonight (0700Z):

KDSM 252320Z 260024 28024G33KT P6SM OVC025
FM0700 26015KT P6SM SCT025
FM1400 28018G28KT P6SM SCT250
FM2300 30012KT P6SM BKN250

I love this type of stuff too, Troy, which is why I thought it would be good idea to take opportunity of (hopefully) the last icing scenario of the season.

 

[Rudy]

Yeah, you're professionally trained on this stuff. Enlighten us!

It seems like you have it figured out pretty well, If you have any questions I would be glad to help in any way I can.

 

[tonycondon]

Interesting you should ask Chris. As you now know, I was up flying in the stuff when you posted. The soundings were a tad off, and of course were on the chilly side. Here's what I saw preflight:

For a 4 PM (2100Z) departure. Yes Scott, I remember to post the Op20 this time From my analysis the very tops of the clouds may be right at freezing but then it should be clear above. I could see sun poking through holes in the overcast so was pretty confident that it was in fact clear above. It was nice to see warm air above AND below the possible freezing level, so my PP student and I launched on an instrument lesson.

The largest extent of icing probability forecast for the time was at 4000 feet, and then it was a small chance, with a 15-25% probability of Trace ice. Once again, above and below was in the clear. It really didnt seem to me like there would be ice, however:

As we climbed out, temps were fine and water was running back on all surfaces. Between 4 and 5000 however, we started to freeze in some areas. it was interesting. the inside of the struts froze but the outsides still had water on them. windscreen stayed wet the whole time. We were coming up on the tops so we kept climbing and got out on top where the ice quickly melted. Temps at 6000 were around +6 degC. Reported the light clear icing to FSS and Approach and did our instrument lesson on top.

TNU UA /OV TNU315015 /TM 2120 /FL060 /TP C172 /SK OVCUNKN-TOP050 /TA 02 /IC LGT CLR 040-050

When we were done we requested a descent to ames that would get us through the icing layer quickly and picked up very little. Bases were at 3000 and it melted off in +4 degC air on our way back to the airport.

This was definitely one of those days where as the sun set the temps shifted left significantly and you would want to be out of the clouds ASAP. I was happy that it didnt take much convincing to the Mason City bound fellow in the Archer to just go VFR underneath.

 

[Rudy]

Heres the front that came through earlier on high res. satellite.

Not really that relevant to the post, but i just hand to nerd out a little more, haha

 

[sba55]

AMW looks ok to me for right now. Most of the >light icing is to the north. If I could be on top for most of the flight, I'd fly in from the south.

-Felix