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Jan 20-22 Threat Potential Part 2


am19psu

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According to the NAM, on Thursday @ 12 noon the 540 line is north of PA?

D

That's the 5400 h5 line, but to save space, it is measured in 540*DM*. Your thinking critical thickness 540 line which is on a different map. Hope this helps

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Did this same thing virtually yesterday at 00z to come back more NW the next run...

Would expect this to come back once again NW at 18 Z...

What has more merit though, 0z/12z runs or the 6z and 18z??? Seems to me the 0 and 12z runs match up well with the euro.?seeing as that the southern stream is coming into play later in the game, the northern s/w flexes it's muscles longer. Hence a colder, " drier" solution

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not when Rainshadow posted verification scores, shows how overdone NAM qpf has been this winter.

well... I agree that this might be the case, but it might be more pronounced in a system that is already bombing out while moving through our area.. The NAM QPF distribution isn't giving me a sense that these totals are too outlandish.. If I saw this surface depiction and upper level and it was trying to produce 6-12 inches, I'd be a little weary.

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Precip shield on the NAM looks disorganized (lack of banding for our area) with generally light to moderate snows. I doubt we get more than 0.25-0.35 QPF but with good ratios of 12-1 or even 14-1 3-5" still looks pretty good. Someone would probably end up with 7" locally if a heavier band were to setup. The flip flopping of the model runs (especially less than 72 hrs out) has been something awfull this winter. With the last system if I remember correctly, it was the 06z NAM runs that kept showing the largest QPF followed by a major shift on the next run. Yesterday we saw that from 12z to 18z.

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Precip shield on the NAM looks disorganized (lack of banding for our area) with generally light to moderate snows. I doubt we get more than 0.25-0.35 QPF but with good ratios of 12-1 or even 14-1 3-5" still looks pretty good. Someone would probably end up with 7" locally if a heavier band were to setup. The flip flopping of the model runs (especially less than 72 hrs out) has been something awfull this winter. With the last system if I remember correctly, it was the 06z NAM runs that kept showing the largest QPF followed by a major shift on the next run. Yesterday we saw that from 12z to 18z.

Euro and GFS, the 2 best models, have been very consistent with this light snow event. Never trust the NAM outside of 24 hours, for QPF.

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Euro and GFS, the 2 best models, have been very consistent with this light snow event. Never trust the NAM outside of 24 hours, for QPF.

Yes your right about the GFS and Euro (for this event) but with the last few events the GFS has been horrible. In fact the GFS op was in many cases much further east and OTS than its own esemble means. I would say the overall confidence in particular model this winter has been below average. If anything, the EC and GFS ensemble means seem to be the most accurate so far. If we can get some development a tad further SW and if the trough could go negative a tad sooner we would be in business like the 1/18 12z nam indicated.

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What has more merit though, 0z/12z runs or the 6z and 18z??? Seems to me the 0 and 12z runs match up well with the euro.?seeing as that the southern stream is coming into play later in the game, the northern s/w flexes it's muscles longer. Hence a colder, " drier" solution

What has more merit? IMO where the greatest thermal Gradient would actually be...majority of your storms this winter if not all..have tried to develop to far east..to only get tugged back more NW at the end...its the timing differences right now.. If you go back and look at hours 36 on the 6 Z NAM to 30 hrs on the 12 Z..You will see the 12 Z is slower and or further south at that time compared to its previous run, which effects the ending downstream result.

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12z NAM text for NYC crew:

NYC: .30" - temps in the upper 20's

LGA: .30" - temps in the upper 20's

JFK: .29" - temps from 30-31.5

EWR: .33" - temps in the upper 20's

With those temps in the city area, ratios will not be that high. I would go with 9-11 to 1 ratios or 2.5"-3.5"

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