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Jan 23/24 Major Coastal Storm Discussion


Zelocita Weather

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Well, the only thing I have to say about the NAM is that the precipitation depiction is what I have been talking about for a few days now.

 

The 300mb level jet will be so anomalous and expansive over the NE that I find it extremely hard to believe that we wont see a well-developed coma head when the coastal matures due to the amount of divergence aloft (Fig 1) and location of the 500mb low. In addition, the rapidly intensifying coastal will carry a large area of mid-level forcing that will also be extremely favorable for moderate to heavy precipitation over a rather expansive area.This should be a precip shield that is comparable to some of the more prolific Miller B and Miller C events for the Mid-Atlantic and Southern New England. Within this coma head, there should be at least one, if not two strong deformation bands that slowly drift from north to south. Those are the areas that could see elevated rates of 2-4"/hr with occasional Blizzard conditions. 

 

(Figure 1. 300mb heights/divergence courtesy of Doug S):

 

9d5721ff74fab9d97e91886a7fb6c3ac.png

 

We know that the precipitation shield should reach at least southern NY at this point, but now where do these bands set up? You tell me. I could see a band posting up near DC/Balt that moves up to Southern PA late Saturday morning into the afternoon, but the zone that is really a wildcard is without a doubt the NJ/NYC/LI/CT area. Since you have an insane easterly jet screaming in at around 85 knots @ 850mb, I could see how something tries to get going near Central NJ that eventually moves up to near TEB, but these details will not be ironed out until the snow is actually falling. I have to say that the NAM has had an area of prolific 700mb frontogenesis for quite a few cycles now that would be near ideal for the aforementioned banding to take place and really lay down some impressive snow numbers. This easterly fetch would also be carrying in moisture from a very warm Atlantic, which would further support heavy snow in this area. 

 

 

d2934f9f58723db68bc395ee37735e3c.png

 

The point to take away from this, is that despite all the model-watching and QPF analysis, these depictions WILL NOT be the final outcomes. Any shift with the general SLP placement will cause all of these incredibly complex meso-scale details to shift accordingly, so try not to grasp onto any solution too tight yet. 

 

The trends tonight look very good so far, and the new PARA SREF were similar to the OP SREF with most of the members leaning NW of the mean. I'm fairly confident we'll see another shift NORTH in the foreign guidance tonight, especially with the ECMWF, since most of its ensembles were more NW when compared to its final SLP track. Also, as we get closer to this event, look for the precipitation field to expand in aerial coverage and overall intensity. 

 

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As I been thinking all week this storm is looking very much like the Jan 1996 storm. Just the precip. Bands are slightly different. Look at the Kocin book.

I was there.

 

From p.599 while we wait for the GFS:

 

Medium-range model forecasts of this storm initially kept the region from new York City to Boston free of heavy snow... Within a day to two days prior to the onset of snow, many numerical models accurately predicted the strength and slow movement and related heavy precipitation of the storm.

 

Of course, the models are vastly improved since then. Still, some surprises are always possible (maybe not NAM-style ones, though).

 

All in all, I think the NYC area, including its suburbs remains in the hunt for a decent snowfall. In the next day or so, we'll see where things still stand.

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Well, the only thing I have to say about the NAM is that the precipitation depiction is what I have been talking about for a few days now.

 

The 300mb level jet will be so anomalous and expansive over the NE that I find it extremely hard to believe that we wont see a well-developed coma head when the coastal matures due to the amount of divergence aloft (Fig 1) and location of the 500mb low. In addition, the rapidly intensifying coastal will carry a large area of mid-level forcing that will also be extremely favorable for moderate to heavy precipitation over a rather expansive area.This should be a precip shield that is comparable to some of the more prolific Miller B and Miller C events for the Mid-Atlantic and Southern New England. Within this coma head, there should be at least one, if not two strong deformation bands that slowly drift from north to south. Those are the areas that could see elevated rates of 2-4"/hr with occasional Blizzard conditions. 

 

(Figure 1. 300mb heights/divergence courtesy of Doug S):

 

9d5721ff74fab9d97e91886a7fb6c3ac.png

 

We know that the precipitation shield should reach at least southern NY at this point, but now where do these bands set up? You tell me. I could see a band posting up near DC/Balt that moves up to Southern PA late Saturday morning into the afternoon, but the zone that is really a wildcard is without a doubt the NJ/NYC/LI/CT area. Since you have an insane easterly jet screaming in at around 85 knots @ 850mb, I could see how something tries to get going near Central NJ that eventually moves up to near TEB, but these details will not be ironed out until the snow is actually falling. I have to say that the NAM has had an area of prolific 700mb frontogenesis for quite a few cycles now that would be near ideal for the aforementioned banding to take place and really lay down some impressive snow numbers. This easterly fetch would also be carrying in moisture from a very warm Atlantic, which would further support heavy snow in this area. 

 

 

d2934f9f58723db68bc395ee37735e3c.png

 

The point to take away from this, is that despite all the model-watching and QPF analysis, these depictions WILL NOT be the final outcomes. Any shift with the general SLP placement will cause all of these incredibly complex meso-scale details to shift accordingly, so try not to grasp onto any solution too tight yet. 

 

The trends tonight look very good so far, and the new PARA SREF were similar to the OP SREF with most of the members leaning NW of the mean. I'm fairly confident we'll see another shift NORTH in the foreign guidance tonight, especially with the ECMWF, since most of its ensembles were more NW when compared to its final SLP track. Also, as we get closer to this event, look for the precipitation field to expand in aerial coverage and overall intensity. 

Very solid post. Hope you're right. Especially for northern sections, which are still especially sweating the small details. 

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For the record, I know nothing about weather (bachelor's degree in Social Work, and Master's in Education), but since I am headed to NYC tomorrow-Sunday, I stumbled over here and have been fascinated for the last two days with all of this information.  Most of these maps and half of what you all are saying make no sense to me, but I just can't stop following along with this!

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For the record, I know nothing about weather (bachelor's degree in Social Work, and Master's in Education), but since I am headed to NYC tomorrow-Sunday, I stumbled over here and have been fascinated for the last two days with all of this information. Most of these maps and half of what you all are saying make no sense to me, but I just can't stop following along with this!

If it makes you feel any better, I've been trying to follow for the past two years and I still feel like my pacifier is rolling around somewhere in the gutter while these winter-wizards wiggle their ears at me and speak in Chinese :). I've picked up a tremendous amount just reading, and yet, I'm still not even in nursery yet!

Sent from my XT1080 using Tapatalk

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Can someone explain the difference between the regular and 4k NAM? They seem a bit different with storm/precip position

Grid spacing (resolution). The NAM runs with 12 km grids (small resolution it uses to incorporate mesoscale features) where as the 4km uses a resolution of 4km. Ultra high resolution and used to pinpoint mesoscale banding and convective elements that the 12km Nam itself cannot see due to a lack of resolution .

Sent from my SAMSUNG-SM-N910A using Tapatalk

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