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Jan 25/26 Storm Threat...(Part 3)


Marion_NC_WX

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There seems to be a variety of perspectives on (and frequent misapplication of) model trends and seasonal trends of late.

Model Trends: Some have referred to a model trending warmer or colder or westward or eastward than it's previous run (I've been guilty of that too). While that technically may be true, it offers little value to forecasting, other than to correctly say that there is greater uncertainty in the situation. For this type of observation to be useful in trying to ascertain the details of a complex situation, you should observe both the trend of the elements in the model against itself over several run cycles and/or the trend in elements of the model against the trends of the same elements in other models.

For example: "The 0Z Ukie shifts east compared to it's 12Z run" tells you very little, unless other models are and/or have been doing the same. But, if it shifts east again on the next 0Z run, then you have a potentially useful trend. In the case of our storm, it went west. So it was west, went east, and went west again. Another good example is the high pressure in the northeast. Originally, most models were very slow in moving that feature out to sea. Over several run cycles, they moved it out with more haste. That's an example of a useful trend in which there was good consensus.

Seasonal Trends: There are plenty of examples of comments like, "Things have trended east all season, so I'm not buying a westward track." Or, "High pressure has stayed locked in place longer than the models have shown all season, so I think it's gonna hang on longer this time too." That is a faulty conclusion and will most likely lead one down a road of misery and disappointment. Playing the seasonal trend card without analyzing and comparing the current pattern to the seasonal pattern to date is a mistake.

For example: The seasonal trend so far has been for storms to not really cut inland too much. Also, it has seemed that confluence has remained in the NE a bit longer than the models suggested, thus far. Therefore, it might be easy to apply those things to the current situation. But by examining the pattern and realizing that up until just recently, we've had major blocking, an element missing in our current pattern, the application of the seasonal trend to those components is in error. Blocking suppresses and slows the pattern. High pressure can remain favorably located longer and storms can better avoid cutting too far inland.

The bottom line is, look at the pattern we're in before employing a seasonal trend which might have been specific to a different pattern. And make sure to examine a model elements against several runs of itself and other models before declaring a trend. Doing otherwise will likely lead to erroneous conclusions.

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Looks like the GFS may be going the way of the NAM tonight.

It's definitely looking that way early on...1009 mb surface low just off the Louisiana Coast at 60 hours...

EDIT: one difference I do see in the GFS (vs NAM) is no weak low in Southern Canada and somewhat better freezing line out ahead of the system.

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This thing bombs out big time! @ 90hr. GFS

All so a repost of yesterdays play by play for the storm.

FROM FRIDAY

<li style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">Okay, I giving a play by play from now till the storm

1.) Tonight the Euro takes our hope away for the storm!

2.) Tomorrow the GFS, NAM take way our storm. GFS( took it away one run earlier)

3.) Sunday GFS starts to trend back to a storm but not so big, with the NAM to follow.

4.) Early in the wee morning hours of Monday the EURO, GFS are hinting this thing is going to be a major hit.

5.) Monday evening we start to get some people putting out amounts and lots are Happy and Few no so much.

6.) Tuesday it starts snowing and those who are getting snow are as happy as a cheshire cat.

7.) Wed. we add up the snow totals and find the winners and losers. At the same time we are already on the look out for then next storm.

8.) WED., Thurs those who got a foot plus of snow want more and those who got nothing want more!<li>

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it looks to me basing this only on the 850 line that around hky and morganton into the mountains it switches over to about .50-.75 of snow after about .50-.75 of rain so but with there being so a warm nose it may be rain or sleet pretty strong 850 low as well.

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This model run is trying it dang-est to produce a big time snow for the Mountains and maybe Foothills (West of HWY 321)...

at hour 84 even with the surface low placement not the best, you got the best lift coming into Western North Carolina, a 500mb and 850mb track just under the mountains and the freezing line trying to wedge along the escarpment.

All of the dynamics in play will be occuring during the overnight hours Tuesday into Wednesday.

If we're gonna get somebody a snowstorm out of this, it will have to be with the dynamics at the perfect time of the day.

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