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ronjon wrote:The first shot of cold air for Florida will come Thursday night. Looks like it will be cold but not bitterly so. It also looks to be a fairly brief shot. However, after the weekend, the long range GFS shows another strong front a week later and then a final stronger blast in early February. The last blast shows the -10 deg C line at 850 mb down into the FL panhandle. If this were to pan out, we would be seeing a major freeze in the state.
As long as the pattern isn't too warm, one or more of the GFS runs seemingly shows a major freeze well down into FL about every other day or so in the winter especially out in the 11-15 day range, which obviously almost never verifies since MAJOR freezes occur no more often than a good number of years apart on average. Why does the GFS show these freezes so often? Because of a very strong cold bias, which increases further out in forecast time. The number of false alarms is astoundingly high on this model and has been since 2001, when the model was cooled to reduce the number of false modeled tropical cyclones. My recommendation is to never assume anything extremely cold on these 11-15 day GFS maps will verify accurately since they almost never do. Instead, I would monitor anything real cold that appears as early as, say, ~day 6-7, and starts to appear on virtually all models with similar intensity near day 6-7. Then I'd see if it steadily progresses.
Attached is a chart (see top one, which is for N Hemisphere) which displays model biases over the last 30 days (this chart has shown the GFS to have a strong cold bias every day I've seen it since 2001)(GFS' black line is well below the neutral line):
. Does not get much better than this compared to what the rest of the Country is dealing with. 
