Determining Icing Levels

M

meritflyer

Well-Known Member
What method do you use to determine icing levels? I typically use the winds aloft forecast.. Is there a better way?

Also, at 10,000' to figure out standard temperature, we'd decrease 15 degrees C by 2 degrees per 1000' correct?

Thanks all!
 
PIREP's are another great way to figure out where the ice is. Also, to be accurate you never know where the ice is until somebody see's it on their wing; until then you just have the potential for icing.
 
Winds aloft is good. Pireps are good. Also there is a forecast freezing level chart that can be found on most internet weather sites or from FSS.

A good rule of thumb for standard temp is Altitude x 2 minus 15.

Standard temp at 10,000msl is -5c. So 10 x 2 = 20. 20 - 15 = 5. negative 5, of course.
 
Keep in mind that those formulas for calculating the temperature at altitude are based on the "STANDARD DAY", and the rule of thumb that the altitude cools by 2 degress Celsius per 1000' is based on the STANDARD lapse rate.

So that means that using it to predict icing is probably not going to work...

You could fine tune it by using the temperature at field elevation today and applying standard lapse rate and that would probably get you a little closer, though. BTW, in Farenheit, the standard lapse rate is 3.6 degrees per 1000', in case you don't want to work metric.

So for example, if I live at 1200' and the temp when I take off is 90 degrees (F, of course). So the freezing level would be at 17,311' if the standard lapse rate applied.

here's the math:

90-32 (freezing temp)=58 degrees to cool

58 degrees to cool/3.6 degrees per 1000' =16.11111 or basically I have to climb from my present position by 16,111.11' feet to get to where it is 32 degrees (freezing).

1200' (where I'm starting from) +16,111.111= 17,311'
 
fish314 said:
Keep in mind that those formulas for calculating the temperature at altitude are based on the "STANDARD DAY", and the rule of thumb that the altitude cools by 2 degress Celsius per 1000' is based on the STANDARD lapse rate.

So that means that using it to predict icing is probably not going to work...
Click to expand...

The second part of his question asked for standard temp...not icing conditions.
 
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