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The assuming we don't _______ thread


aldie 22

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Very good consensus on the 18Z Ensembles. 8/12 showing a similar solution for 132 hrs out is amazing.

This could be a long-duration event if it evolves as advertized by the GFS. (assuming we don't end up dryslotting)

Good game...let's play it...the assume game

Assuming we don't dryslot

Assuming we don't mix

Ok everyone add your favorites

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Good game...let's play it...the assume game

Assuming we don't dryslot

Assuming we don't mix

Ok everyone add your favorites

Assuming we aren't fringed.

Assuming we stay all snow

Assuming the warm ocean next to us

Assuming our astronimically parched soil

Assuming our south of 40N latitude

Assuming the snow falls at night

Assuming the snow doesn't graupel on us

Assuming the mountains dont suck up the moisture

Assuming no one is travelling over Christmas

Assuming the tropical forcing is minimal

Assuming its a strong Nina

Assuming it turns out to be a Nino-like strong Nina

Assuming it turns out to be a Nino-like strong Nina with blocking

Assuming the moon alignment with Jupiter doesn't pull the storm to the lakes.

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Excellent...other people add your favorites

if the snow falls in the early evening, the ground will likely be warm from the sunlight, hence little or no accumulations can be expected at night

of course, snowfall during daylight hours will be cut back dramatically as I believe the Moon is out this week, so you got that on top of the sun angle eating away

its almost not worth having the snow fall...how many days till' spring?

but what's it matter, may as well be spring out there now

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Hi all -

The flow beneath extensive high latitude -AO/-NAO attributed blocking is complex, with multi-nodal SPV connecting a general band of negative geopotential anomalies along 45-55 W in the means. At any given time a more intermediate and/or southern stream S/W will tend to cut underneath, threatening a phase and deeper cyclogenesis, but this is inherently a stochastic affair in the models as this recent event certainly pointed out.

Firstly regarding the nearer term: there is still some potential remaining that the [now] early to midweek system will affect some portion of southern and eastern New England. Here are the issues with this event:

The low-level baroclinic axis is suppressed unusually far east and south along and off the eastern seaboard. This combined with [likely] convective feedback processing in the models is causing surface depictions across multiple guidance types to be displaced east and or south of the better theoretical position beneath superior deep layer forcing. The main jet axis leaves the NJ Coast with its left and right entrance regions nosing out over waters south of Long Island

Resized to 98% (was 904 x 508) - Click image to enlargepost-904-0-47348400-1292694759.jpg

as the above annotated images show. There could be an error that we have not collectively been discussing. Moreover, looking out to 72 hours and beyond, we see that the NAM model is attempting to perhaps correct for this [error] by anchoring a deep layer, deep vortex concatenated under the U/A closed low, while the original low it was developing amid the convective mass is attempting to escape and shear eastward - a condition that looks more +NAO than -NAO, so is not very well teleconnection supported.

Last night's runs unilaterally showed forsaking those governing dynamics for convection out over the outer Gulf Stream and west Atlantic Basin, keying in on any one of the resulting convective induced vorticity maxima and using it to mechanize a deep gale quite far displaced east from the better divergence aloft. I don't believe that is right. I would be more willing to go with convection streaking out and perhaps robbing cyclogenesis farther NW over actually having a main show low event deep southeast where the thermal gradient is weak and there is an absence of frontal slopes to force synoptic scale lift; jet interaction/cross-sectional analysis would not support.

That said, if there are some mechanical processes not readily observable in these prognostics they may turn up with some other analysis.

I see some chance that a stronger low may anchor in farther W, and that there would be some retrograde motion into eastern areas of New England with some snow. For now, will leave it at that.

On to next weekend:

This event has more teleconnector-related intuitive support for actually having a chance to happen than the nearer term. Both the CDC and CPC are showing a relaxation of the NAO, supplying a less suppressed/negative wave interference on the means.

Resized to 88% (was 1006 x 369) - Click image to enlargepost-904-0-12745000-1292697090.jpg

The PNA is what is more intriguing however, showing a lot of members clustered enough for a concerted rise from a long standing -negative phase state; hence enters the modal shift of the PNA. However long lasting aside, one that recovers almost 2 full SD, it would be hard to perceive that can occur without at last altering the characteristic of the flow amid the Pacific relay into North America. As certain scientist have shown statistically, particularly during modal periods of the PNA during cold season, large synoptic scale precipitation events are favored. The reasons for that on a more physical level are pretty obvious, in that when the modal intervals are taking place, this means large scale mixing of differentiable air masses taking place, hence instability at large scales leads to storm development.

Resized to 88% (was 1006 x 369) - Click image to enlargepost-904-0-12745000-1292697090.jpg

3.5 days from now the CPC intensely clustered members have a PNA that starts concertedly rising out through D10. This centers wonderfully on next weekend's shortening of the L/W lengths.

Lastly, the MJO was decaying out of Phase 5 and through 6 over the last week. Incidently this was not a statistical fit for EC storms. But, it is appearing to re-strengthen entering Phase 7, and that should time for late Phase 7 and early 8 by next weekend, which statistically IS a good fit. I don't have a lot of experience using the MJO for single planetary events - and I don't think it should. Nonetheless, the numbers still fall out that way and Phase 8 and 1 tend to own the lion's share of coincident EC events.

John

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