W/V divided by TAS (in miles per minute) = Max drift. So at 90 KTAS with a 30 knot wind, max drift is 30/1.5 = 20 deg. Now apply the relevant 'clock factor' to your track; if the wind is 15 deg off, use 1/4 of max drift, if it's 30 deg off use 1/2 max drift, if it's 45 deg off use 3/4 of it and if it's 60 deg or more, use all of it. Thus if you're on a track of 360 at 90 KTAS and the W/V is 330/30, your max drift is 20 deg. The wind is 30 off, so use half of max drift and make your heading 350 deg.
Similarly, your groundspeed is affected by a wind at 90-30 deg off, i.e more or less all of the wind. So use 90-30, i.e. 60 Kts as your estimated groundspeed.
(Dalton values would be a hdg of 350.4 deg and a GS of 64 kts, so it's close enough for visual navigation backed up by pre-planned visual fixes - and anyway, who said the weather-guesser was 100% right in the first place!)
PS - Sorry, newguy, guess we both replied at the same time!!
[ 06 October 2001: Message edited by: BEagle ]