#794 Postby jinftl » Mon Jan 05, 2009 4:26 pm
What it comes down to as this….after a very exciting early winter, both in terms of model projections and actual weather reported across large (but not at all…i.e., most of florida), it has been a bit dull as of late for winter weather and weather enthusiasts in general…unless tracking record highs from Texas to the Northeast is an area of interest for someone. Now we are into the first week of January, approaching the climatological ‘peak of winter’ in the next few weeks, it is totally understandable that folks are anxious to see a pattern change to the level (or more extreme) than was seen 3 or 4 weeks ago.
What JB or the CPC (no denying the CPC 'called' December temps across the U.S.) or any source of forecasts that go beyond a week or 2 out may be best at doing is identify the beginning of an overall pattern change. But to draw specific temp and weather forecasts for a model run that is, say, 12 days out, has a huge margin of error with it. With hurricanes, we see the ‘cone of uncertainty’ that exists for any forecast going even just a few days out. What we don’t see, and need to factor in, is that if a forecasted arctic high pressure is 300 miles off the 12-day model forecast point even, that can lead to huge changes in who will or will not see an arctic outbreak. This is especially true as you move south in latitude through the U.S.
Just as it is generally easier to forecast the track of Cape Verde systems as they move from the Cape Verde Islands to the Caribbean (follow the ridge), these forecasts often become much more complicated as the storms approach mid-latitude locations where the interaction of complex environmental factors like ridges and troughs can lead to a wide range of solutions. The same is true on some level with arctic airmasses making their way into the Deep South. These airmasses may move with ease from Fairbanks south and east into Canada and even the Northern Plains, but as they move south, the path is not always as clearcut and successful. We saw this in December 2008 even, as the true arctic air could not make into deep into Florida or south Texas with any of its original vigor.
When things have been a bit dull, and let’s face it, there isn’t a huge window of opportunity ever for ‘true winter’ in the Deep South…and we are making our way through that window at something of a fair pace…it is much more interesting to ‘run’ with the most extreme model run, esp when it is far off in time and obviously can not be either refuted or confirmed. And without speculation, this wouldn’t be nearly as interesting a site. If we get in the 5-day window and NWS offices are clearly stating forecasts that show 0 deg in NYC and 20 in Atlanta and 40 in Miami….then we have an arctic outbreak on our hands, not an ‘all time’ outbreak, but quite possibly the coldest of the winter (but of course not every arctic outbreak means snow in the French Quarter…usually the coldest outbreaks sweep through and dry areas out). But this I have seen….we can only have so many ‘storms of the decade or century’ and ‘cold waves of the decade’ in any given season. ‘Duh’ I know….but sometimes needs to be stated.
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