Met question

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AirCanuck
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Met question

Post by AirCanuck » Thu Aug 23, 2018 7:58 am

I'm just gonna copy and paste this one because I've no idea what they're getting at:

you are at an airport which experiences the passage of a cold front in the early afternoon. Shortly afterwards, the clouds scatter out leaving a clear sky. During the next 12 hours, you would expect the temperature to:

a) decrease then increase slightly
b) steadily decrease
c) remain relatively constant
d) increase slightly then decrease

Answer is D... WHY?
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Jet Jockey
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Re: Met question

Post by Jet Jockey » Thu Aug 23, 2018 8:12 am

Well assuming there was only a few degrees of temperature between the air prior to the cold front's passage and the air behind it and with the cloud dissipating and sun coming out the air temperature should rise since it is the "early afternoon".

Once the sun goes down and the clear night becomes prevalent (no heat retention by the clouds) and in a colder air mass, the temperature should fall too.
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Ki-ll
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Re: Met question

Post by Ki-ll » Thu Aug 23, 2018 8:44 am

Surface temperature doesn’t follow the frontal passage immediately. So as mentioned above, the diurnal effects will prevail initially.
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AirCanuck
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Re: Met question

Post by AirCanuck » Thu Aug 23, 2018 10:33 am

I can't believe it is as simple as that but my buddy just said the same. Seems ridiculous!
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Anticyclone
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Re: Met question

Post by Anticyclone » Thu Aug 23, 2018 10:36 am

Yep.
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CpnCrunch
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Re: Met question

Post by CpnCrunch » Thu Aug 23, 2018 11:18 am

Dumb question.
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Jet Jockey
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Re: Met question

Post by Jet Jockey » Fri Aug 24, 2018 4:03 am

CpnCrunch wrote:
Thu Aug 23, 2018 11:18 am
Dumb question.
LOL.
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pelmet
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Re: Met question

Post by pelmet » Fri Aug 24, 2018 6:14 pm

And the answer is because...…

It clears up behind the cold front for an hour or two(warming things up slightly) and then clouds over(so it starts to cool down).
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pelmet
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Re: Met question

Post by pelmet » Wed Aug 29, 2018 8:42 pm

pelmet wrote:
Fri Aug 24, 2018 6:14 pm
And the answer is because...…

It clears up behind the cold front for an hour or two(warming things up slightly) and then clouds over(so it starts to cool down).
Remember....we pilots learn the very basics of a lot of things...electrical, powerplant, aerodynamics, met, etc. In reality all these things are a lot more complex than what we learn for the licence. But on occasion such as the question for the thread, it is digging a bit deeper and then you discover that a cold front is not just a cold front, there are different kinds of cold fronts just like we may explain the very basics of how to land an airplane to a non-pilot when there can be many different techniques and other bits of info that are occasionally used but not explained.....

"In the wake of the front, cold-air advection tends to promote currents of sinking air, which helps cause clouds to evaporate, promoting clearing or partially clearing skies. Cold fronts that promote currents of sinking air in their wakes are called katafronts. A katafront, by definition, is a front with sinking air currents on its cold side. Most cold fronts are katafronts."

"However, not all cold fronts behave this way. For particularly slow-moving cold fronts, it is possible to have rising air behind the surface front (along the upper-level frontal zone). Weather forecasters refer to any kind of surface front characterized by upward motion on its cold side as an anafront. Anafrontal cold fronts often have steady rain or snow that develops within the cold air behind the front."

"What to expect with a cold front...
(a) cold advection in its wake. Temperatures often fall after a cold front passes as a colder mass arrives (although this may not be the case in the warmer months, when solar heating during the day can overwhelm cold advection).

(d) sinking air and clearing skies behind the front, as long as it's a katafront (as most cold fronts are)."

https://www.e-education.psu.edu/meteo3/l7_p5.html

Maybe the answer I gave would be more correct in that it clears out then warms up due to daytime heating then cools off in the evening. And that is only sometimes but it is the only correct possibility of the four options.
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AirCanuck
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Re: Met question

Post by AirCanuck » Thu Aug 30, 2018 5:14 am

very interesting thanks for that one! I suspect this katafront causes the air to clear, daytime heating heats it up for a while, then as the cold air mass takes hold it cools down again
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