The calm wind runways are the 17/18s. These are used when winds are less than 5kts.
Now, our general rule of thumb is not to change the airport to north ops until the METAR updates a second time so we are not flipping back and forth, unless of course the change is so extreme that we have to. So like last night it was backwards for a little while because the winds were shifty due to the storm. Also we have to take into consideration how DAL is affected, b/c we don't want them running opposite, and yes there are times when the winds are reversed between the two.
95% of the time it is an easy call, but, especially during storm season, that other 5% is a real pain.
We like south ops because the majority of the flights arrive from north of the airport.
Andrew Podner, WWA1662
Command Captain
VP - Hub Operations - N. America, West
ZME ATM, I1 Controller/Instructor
Monster Driver - EHAM/NZAA