There are several things to take into consideration and to look for with East spikes if you want to guess it (on the fly) down to 10 minutes. In a nutshell though, if you are planning on riding an East wind (especially at the SW) after work (around 5 or 5:30) look at what the wind did the day before by checking iKitesurf for the previous day's wind.
If the day before the wind showed a spike around 5, odds are pretty good it's going to do it again. Plan accordingly. The safest thing to do is to just rig a 12 or 9 and just wait. It's not the time of year (yet) for the death spikes, but I personally make a habit of not rigging/riding UNTIL it picks up.
It usually blows til sunset, so what's the point of mowing the lawn in 11/12 knots just to get blasted off and have to re-rig? Let alone a true spike will do more than blow you off the water, it will also blow you across the road or loft you over a mangrove tree

Yesterday was just more of just an increased E as the wind came down from up high to down where we were as the land cooled off. I would have been surprised if it pulled a true spike from 12 to 35, that requires a whole different set of circumstances. I actually rigged my 12.5 because I was anticipating 18 to low 20's and wanted to test the top end on it (just got it )
If I think that pattern of extreme spikes is coming again, I will post warnings and hope you guys spread the word.
Last year was exceptionally unusual in the force and frequency of the spikes. Luckily, they showed an obvious pattern though, so we have a chance to not get caught off guard from them.