API 650 - addenda december 2005 , in it sparagraph 3.2.1-f defines TWO Wind forces acting SIMULTANEOUSLY on the tank:
One horizontal with a pressure of 18 lbf/ft2
and the OTHER, AN UP LIFT one ( new!!!) of 30 lb/ft2.

If this is true, in my opinion the overturning moment due to wind is really hudge,
yoy will end up almost for every case with anchor bolts to take care of this wind moment.
The wind moment could be apprixmated by:
Mw= 18*D*H + 0.0.785*(D^2) *(0.5*D)

for instance for a tank 60 ft diametere, you will get (from this up-lift pressure alone) a force equal to and the additional moment
= 644-E04 lb-ft..

I am compyling answers/ reactions and think to send an enquiry to API.

Meanwhile.. I am wondering..
My question..is How to calculate the overturning moment..