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February 15-MOrch possible wintry threats


tombo82685

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This has been a great period of time to see the lag effects from the Tropical Forcing end of things and stratospheric end of things on the NAO (which is why predicting the NAO is tough since it relies on lag effects of multiple variables). Both factors have promoted cyclonic wave breaking off the North American Coast now for the last week or so and that should continue through next week. Overtime, these CWB anomalies push the jet toward the equator and enhance easterly anomalies across the North Atlantic (all of which is tied into the AAM propagation too). This has been correlated to lead to a -NAO period during the winter season and it is interesting to see this show up on the data.

Why trust it now?

1. The stratospheric setup in the lowest layers continues to remain favorable, not a deterrent.

2. The AAM state is also favorable

3. A 2 week period of CWB off the N.A. coast

4. Favorable MJO propagation but will it speed off into unfavorable territory?

5. Already a positive anomaly up there, just displaced too far east

Everyone should read this post very carefully. This is what medium range forecasting is all about folks.

 

Oh, and #climo

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12z GFS still appears to be focusing on the northern stream s/w.  Not seeing improvement in that regard.  Could be right idk... but if it is focusing on the wrong one, forecasts will drastically change by what I would think would be tomorrow 12z since the energy in the Gulf of Alaska is coming onshore today and will have been on land long enough to be adequately sampled.

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Everyone should read this post very carefully. This is what medium range forecasting is all about folks.

 

Oh, and #climo

Lol thanks Adam. The way the AO/NAO are behaving, I wonder if we continue the snow potential into early March, despite the increasingly bad Pacific. Then maybe the bad Pacific/warmth finally sets in full force mid-March before maybe a cool shot or something just after equinox with 1 last shot of the white stuff.

The refusal of the different players to align will probably keep these snow events sub KU levels in our area from 2/20-3/10 but the NAO can always make things interesting down our way (not just New England).

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Next week, on the modeling, is almost like last week if you think of things in a very general sense:

1. Prior waves help carve out a "-NAO look" with a 50-50 low and confluence/building high from Canada (last week, this slowly came to realization on the NWP as we got closer).

2. Next Pacific wave is plowing in and amplifying into the SW USA (but models show very little run-to-run consistency here with this, as you would expect at this range).

3. Possible northern stream s/w influence but active southern stream to bring the storm threat.

Definitely not the same thing of course as 2/5-10 but similar.

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The last 3 Marches haven't been like climo. March is i believe a snowier month than december. Lately the month has torched. So on torch, we drop the t for m and make it morch for march.

 

Long term Philly period of record DEC (3.8") & MAR (3.6") are nearly identical however the recent 1981-2010 mean has DEC (3.6") now ahead of MAR (2.8").

 

PHL hasn't recorded double digit MAR snow since 1993, looking forward to the 1991-2020 mean the disparity only continues to grow.

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Anyone see this on the NAM for Friday night? What does it think it's seeing? 

 

nam_namer_063_precip_p12.gif

Jaimie, honestly, the nam seriously needs to be blown up and reassembled again. It has been horrid this whole winter. When the hpc throws out statements on not using it, their are issues. Fwiw, it's probably developing something on the arctic front. There is a decent s/w associated with it that some of the models have bringing a period of lgt precip. HM also has mentioned it to.

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Jaimie, honestly, the nam seriously needs to be blown up and reassembled again. It has been horrid this whole winter. When the hpc throws out statements on not using it, their are issues. Fwiw, it's probably developing something on the arctic front. There is a decent s/w associated with it that some of the models have bringing a period of lgt precip. HM also has mentioned it to.

I figured it was an overexaggeration of what HM mentioned before. 

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Maybe it's the weenie inside me, but i would not be surprised if that next tues/wed storm continues to trend colder. The look on the gfs ensembles does not scream cutter to me with that -nao and 50-50 low  and the ridge placement out west. The only thing that could muck it up is it seems like there may be a northern stream disturbance and if that passes to our north that would warm us up.

 

f120.gif

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Jaimie, honestly, the nam seriously needs to be blown up and reassembled again. It has been horrid this whole winter. When the hpc throws out statements on not using it, their are issues. Fwiw, it's probably developing something on the arctic front. There is a decent s/w associated with it that some of the models have bringing a period of lgt precip. HM also has mentioned it to.

Tombo, the sonofabitch went and doubled down on the crazy on the 0Z run, nailing us and hard.

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Here's the sounding @ hour 60 when the GFS brings in precip.

thats plenty cold. AS long as the LP takes a GFS like track, it would be plenty cold. The NAM tracks the low to our west and warms 925- surface.

9ysy6u9a.jpg

INteresting to see the total totals around 50. Convective snow? looks high fluff ( strictlyt GFS 0z run here)

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