LEM, perhaps I read too much into the question, but I assumed that beast was asking about takeoff alternates.
In Australia you must if the departure aerodrome is closed for arrivals (i.e.fog) you must provide for an alternate within 60 minutes.
For the purposes of the Australian calculations (which I accept is not necessarily the country that Beast was asking about) the "60 minutes" is determined using the calculation that determines the 60 minutes speed/range for ETOPS. The logic being that 60 minutes is 60 minutes regardless of whether it is ETOPS or not.
So this all being the case the aim is to get as big a distance as possible to maximise the operational possibilities, in some cases you may not have an airport within 280 nm and in some cases this may prevent you from departing. The bigger the distance the more potential airports that can be used as a takeoff alternate.
To do this the calculation as others have said is quite complicated and needs to be done and published in an ops manual, not done on the day, which means that it does NOT vary with the conditions. Remember this is a number for planning purposes and may bear no relation to what you may fly on the day.
If it DID vary with the day, you may have a situation where you could depart on one day and carry airport X as a takeoff alternate, but on the next day, because the aeroplane is heavier or whatever, you may not be able to depart carrying exactly the same airport.
Logically having 2 figures for 60 mins S/E (i.e. an ETOPS figure and a NON-ETOPS figure) doesn't make sense to me because a flight is either ETOPS or not. If it is not it has aerodromes within 60 minutes - if that makes sense...
Let's assume a 1000 foot rate after cleanup.
Let's also assume a cruise altitude of 10000feet.
LEM - I don't think that you would cruise a 737 at 10000', around the mid 20's perhaps.