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NOGAPS and Dean
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I find it curious that the NOGAPS model just barely recognizes that Dean even exists and doesn't even havr Dean on its runs past 90 hours. I dont' have a whole lot of experience with these individual models, having just started to view them during last season (not much to go on there). Can someone explain why this sort of anomaly occurs? It just seems to really cast doubt on that model (at least in this situation) and its ability to forcast tropical cyclones. Or does NOGAPS know something that the others don't? Be as technical as you want to be...I can keep up!
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Re: NOGAPS and Dean
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First a gripe before another question in this same line.......the mods want us to post questions here instead of in the news talkback, but I am seeing that questions posted here just get ignored. This is NOT encouraging me to post questions here............
New Question: A lot is being made of the fact that the current long-range models on Dean are 'in good consensus' about his path 3-5 days out. I am wondering how much of that consensus is due to Dean's fast forward motion at this point. The slower a storm is moving, the wider the spread on the models and I would think that Dean HAS to slow down at some point or it will never make Cat 4 (I would think Cat 3 would be hard to achieve at 24mph!!). It has always seemed to me that most models don't predict these changes well even when they are predicting a slower forward speed. I guess what I am asking is, how much more spread the models would be if Dean's forward speed dropped to a more reasonable 14-16 mph. Right now, I am well outside the cone in the Tampa area, but now will be the time of what I call "cone creep". I am trying to gauge our level of safety here. This is important as I have my student returning on Monday and much to do this weekend.....
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Clark
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(Meteorologist)
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Thu Aug 16 2007 04:22 PM
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Re: NOGAPS and Dean
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The NOGAPS is a model that has not seen a lot of changes over the past few years, causing it to fall behind the times. I believe that it only has a resolution of 1 degree, or about 100km, which limits its ability to represent the inner cores of tropical cyclones.
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Clark
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(Meteorologist)
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Thu Aug 16 2007 04:26 PM
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Re: NOGAPS and Dean
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As for the forward speed question, generally when you have such a fast forward speed, the features that are steering the storms are pretty well established. It's not necessarily that there is little spread because of the fast forward speed; it's that there is little spread because of the persistence and intensity of the weather features that are causing that fast forward speed.
If the storm were moving slower, there could be the same spread or there could be more spread. It all depends on what the models are seeing as the factors that will influence the track. The storm would cover a smaller area of ocean in the same amount of time as if it were moving at 20+ mph, making that spread a bit smaller, but it could also be nearing the edge of a subtropical ridge, where track forecasts become a bit trickier.
Simply put, I'd say it's not the fast forward speed that results in those differences, but it can be used as a proxy to try to understand why differences in model spread may exist.
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Unregistered User
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(Unregistered)
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Thu Aug 16 2007 04:53 PM
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wind shear
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I'm just curious - I saw the Navy's wind shear predictions for the next few days, and it shows wind shear over Florida and the Yucatan/Mexican area, with a gap between the two. Wouldn't it be possible Dean would take the path of leas resistance and start heading for the panhandle?
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Clark
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(Meteorologist)
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Thu Aug 16 2007 06:17 PM
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Re: wind shear
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Not necessarily, and remember that things will evolve over time as well. Keep in mind that part of that "shear" could merely just be an outflow jet enhanced by Dean itself.
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