Sorry I did not get back to you sooner, but to be perfectly honest, I was not too familiar with the term. It is possible I may have heard it referenced before, but it was not part of my formal training as a meteorologist and we have never had one up this way, so I was in the dark on the subject. I have done quite a bit of research on the internet to learn more and it looks as though the phenomena you describe was explained and named by Dr Fujita (of the same "F" scale tornado strength scale fame) back in 1955.
Anyway, during my research, it became evident pretty quickly as this is a phenomena that still lacks a full understanding as most of the research I found was severely lacking in detail and many links just led me to explanations that used the same exact wording and a few that the author seemed to try and give their own description that ended up being quite misguided.
So, in essence, a "wake low" is an area of low pressure that forms in the "wake" or just behind a complex of strong thunderstorms. The low forms due to a unique set of circumstances that I could give, but would not be understandable to someone without a formal background in meteorology. Safe to say though that these circumstances do not happen very often and thus wake lows do not happen very often. In any case, the low creates a fairly strong, but small area of low pressure. That low thus creates a strong pressure gradient that in turn creates the strong winds. The winds can blow at speeds of 50 mph+ for several hours, unlike those directly associated with the main complex of thunderstorms that typically blow for 30 minutes or less.
That was the down and dirty explanation and unfortunately I really cannot get much more detailed than that for two reasons. One, as mentioned, not a lot is known about these events and secondly, what is known is pretty technical meteorological stuff and to try and put it into a format that someone without a formal background in meteorology could understand would be a rather large undertaking on my part.
I can add that the reason this event was not in your forecast is that it involves thunderstorms and while we can predict the possibility of thunderstorms for a region, we cannot forecast all of the details such storms will produce. In addition, these events typically occur at a scale too small to be handled by the models and so the models are of no use when trying to forecast them. I would anticipate that as our knowledge of these events grows and technology improves, at least some forecasting skill will be able to be applied to them.
Here is a link to one of the sites that I found most informative during my research- if you want to read up on it some more:
Wake Low
-John
