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December 27/28 Storm Threat


Baroclinic Zone

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I think what is helping is the interaction with our S/W tomorrow andf the PV lobe north of Maine.Notice how they form a closed H5 contour which helps keep the flow underneath more zonal.

post-33-0-46462600-1356364808_thumb.gif

post-33-0-15885800-1356364814_thumb.gif

I hate to say it ... well, scratch that, I love to say it, because it's a point I've hammered over the years and wish to keep on hammering until people start showing a modicum evidence that they consider this when they look at middle to extended range charts during a low meridional flow (meaning S/Ws the move more through the Pacific open waters as opposed to taking the more circuitous route over a large eastern Pac/western North American ridge arc).

Notice how the dynamics of the governing wave are nosing over land from 00z initialization and onward? This happens so often I can't count! We have this like "unmanned fire-hosing" of solutions spraying all over the board among the various models, and no sooner does the wave come over land and it "appears" (albeit tentative right now) there a converging underway - or at least less dischord. I believe data assimilation, although very slick, still improving, and much more useful than allowing holes in the grid, still is not perfect, and doesn't compare to actual sonde data in the grids.

btjm -

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Based on current modeling, this looks very similar to the Christmas 2002 event. I'm just not so sure SW CT can get in on the really heavy snow though.

I loved that storm. Somewhere, I have a video out my kitchen door (before we added our family room addition) showing it ripping (for Bob) snow while my relatives were hemming and hawing over whether to leave earlier or later.

I suggested earlier, lol...

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The ULL keeps digging more ENE which is helping keeping the low from gaining much latitude.

Yeah! This trend over the last 12 hours has been awesome. Re-intensifying the mid level low and vort max south of Long Island ... if this trend continues, I could see this being a major hit along and north of Rt 2 ... and further east in MA and NH than some might think right now.

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Trends are great. At this point the Freeport option has legs because I doubt that far north has tainting issues but at ths rate I may be able to find a place 30 minutes away..lol.

Gfs takes care of most of us on the front end and keeps folks in the 495 belt and north all frozen.

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I'm waaaay behind, but I just saw the 06z GFS 500mb and surface panel synoptic evolution and was pretty agog!

Also, the latter system going to 553mb S of NS on D9 panel is alarming considering that for that time range, you are talking about nano correction to get that back on the NE Coast...

Later on I hope to be agog with eggnog

Merry Christmas Tip

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The GFS actually tracks the 850low over the Cape and the 700 low over SE MA...normally that would be a great snow track for a chunk of SNE, but because those lows gained a lot of laittude first before trekking ENE near the south coast...we end up with the snow being a bit further north than usual.

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Yeah, a little better than earlier progs though. Looks like quite a wintry deal for your WFO.

Probably the best storm at the WFO since Thanksgiving 2011, and I'll be heavy, heavy margaritas on the beach.

I'm a little surprised that even the 12z GFS is showing that funky looking mid level drying up this way. I guess it's trying to inject a little dry air aloft from that high to the north.

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The GFS actually tracks the 850low over the Cape and the 700 low over SE MA...normally that would be a great snow track for a chunk of SNE, but because those lows gained a lot of laittude first before trekking ENE near the south coast...we end up with the snow being a bit further north than usual.

78hr 850mb low is actually just south of LI, then scoots right over the Cape.

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The GFS actually tracks the 850low over the Cape and the 700 low over SE MA...normally that would be a great snow track for a chunk of SNE, but because those lows gained a lot of laittude first before trekking ENE near the south coast...we end up with the snow being a bit further north than usual.

You must be feeling more confident of 25 miles from the shore staying all frozen
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12z NCEP ensemble EOFs

EOF_4fig_NCEP.gif

Focus on EOF1 ... first of all, the greatest amount of variance explained ... and secondly the SLP pattern is one that we're interested in --> related to the longitude of the track ... a positive EOF1 is exhibited by ensemble members on the eastern side of guidance.

So now look at the sensitivity in the 500mb heights over the next 24 hours. Notice that the greatest sensitivity is actually not over the northeast in the confluence zone as one might expect, but is over the Southeast and Gulf. I think this is related to the idea of compression, and how much shortwaves are allowed to amplify in the flow ... lower heights over Florida allow shortwaves (such as our Christmas system) to dig freely for much longer before nonlinear terms grow leading to cyclonic wave breaking.

SEN_1_NCEP_Z500_0-1day.gif

Sam, on the EOF1, you said a positive EOF would be members on the eastern side of guidance, but looking at that..it looks like the + values are NW of the mean MSLP. I must be missing something.

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I wonder if those are being affected by the issues going on with the ARW members. Essentially, there is a problem with incorrectly not assigning pytpe to frozen or freezing precip. And the ARW members are dragging down the means of snowfall and rates (ZR too). If that's the case, these probs would probably be even higher if it weren't for the low balled totals from the ARW runs.

I've noticed that as well but wasn't sure if it was must me being a weenie or legit. Thanks for the clarifications.

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Sam, on the EOF1, you said a positive EOF would be members on the eastern side of guidance, but looking at that..it looks like the + values are NW of the mean MSLP. I must be missing something.

That first image shows the SLP pattern (anomaly from the ensemble mean) described by a positive EOF1 ... a negative EOF1 would have the opposite pattern.

So this image of a positive EOF1 indicates lower pressures to the east and higher pressures to the west ... low pressure east of the ensemble mean.

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