TAF interpretation

[gregc]

looking a a bit more detail interpreting a TAF

KTTN 231131Z 2312/2412 26008KT P6SM OVC040
FM231500 25012G18KT P6SM SCT250
FM232200 27005KT P6SM SKC
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does this mean 18 kt gusts (abruptly) starting at 1500 and ending at 2200, building starting at 1500 and diminishing thru 2200, or some combination?

i've attached an image showing wx conditions that illustrate an abrupt change in gusts (orange). is this typical?

greg

 

[poadeleted20]

does this mean 18 kt gusts (abruptly) starting at 1500 and ending at 2200, building starting at 1500 and diminishing thru 2200, or some combination?

It's saying that the prevailing wind will be 260/8 from the beginning of the period through 1400, 250/12G18 from 1500 to 2200, and then 270/5 from 2200 to the end of the forecast period (1200 the next day). Obviously, it's not going to be an instantaneous ("abrupt" change"), but those are the prevailing winds during those periods. Personally, I'd expect the buildup to start about 1500, but not to reach those values for a while, and then the dropoff to begin so it reaches the lower level by 2200, but that's just guesswork.

i've attached an image showing wx conditions that illustrate an abrupt change in gusts (orange). is this typical?

Those are typical for frontal passages and things like that. However, changes due to the diurnal cycle tend to be more gradual.

 

[gregc]

thanks for the explanation
very helpful