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March 6-8th Ocean Storm Discussion Part III


Baroclinic Zone

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Yes oceanstwx I mean hpc is bullish (and I shld have clarified) wrt to that area wrt big snowfall numbers. To show 70 percent of 8 inch snows and 20 percent of 24 inch snows in some of same areas show they are thinkin this cld be a biggie. I mean they even have probs for 30 + (which is rare to see probs) for, so in that sense they are bullish or at least respecting models and 850 and 250 mb anomalies.

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SREF’s somewhat similar, south a bit with the heaviest of the QPF, but also jacked numbers up a bit, so about the same overall, still 1.25”+ for here. They also like the trough scenario, it’s a 48 hour period of light to moderate snow here, probably hits 6” when alls said and done due to cold temps, although probably not the 9” that we would need for 24 hour warning criteria. Overall still very nice though.

-skisheep

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SREFs really are like watching yesterdays news guys.  They're so heavily based in NAM type nonsense they're going to lag.

 

This run of the NAM should be much more useful, it's faster in the south, digging better, it's finally coming to the party with it's Sunday best on.  Will probably face plant somewhere around 36 hours but I'm glad to see this idea go bye bye (no phase)

 

This should also be good news for those of us that watch TV, as we should see the related products come around and maybe get some actual forecasts for snow this evening on TV..

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Yes oceanstwx I mean hpc is bullish (and I shld have clarified) wrt to that area wrt big snowfall numbers. To show 70 percent of 8 inch snows and 20 percent of 24 inch snows in some of same areas show they are thinkin this cld be a biggie. I mean they even have probs for 30 + (which is rare to see probs) for, so in that sense they are bullish or at least respecting models and 850 and 250 mb anomalies.

 

 

Those probabilities are experimental. Plenty of science involved, but can suffer from a few members skewing the mean, just like all ensembles. Here is the HPC write up on how they are created:

 

 

The operational WPC Winter Weather Desk (WWD) creates 24-h forecasts of snowfall and freezing rain accumulations for each of three consecutive 24-h periods (days) extending 72 hours into the future. These products are shared with the NWS Weather Forecast Offices (WFO) in a collaborative process resulting in refinement of the accumulation forecasts. After the 24-h snowfall and freezing rain accumulation forecasts are finalized, the WWD issues its public products: a limited suite of probabilistic winter weather forecasts. These probabilistic forecasts are computed based on the deterministic accumulation forecasts combined with ensemble information (see below) and are manually edited by the WWD forecaster. The probabilistic forecasts found here on the WPC PWPF page are also based on the deterministic WWD accumulation forecasts, but are generated totally automatically using an ensemble of model forecasts along with the WWD forecasts. The automatic nature of this product generation allows a much more extensive set of displays of probabilities for snowfall or freezing rain exceeding a number of thresholds and accumulations of snowfall or freezing rain for various percentile levels.

 
The automatic processing also allows the generation of probabilistic winter precipitation forecasts for 48-h intervals based on 48-h accumulations obtained by adding two 24-h accumulations together. The same method used to compute the 24-h probabilistic products is applied to the 48-h intervals ending at 48 and 72 hours after the initial time.
 
A multi-model ensemble is utilized to create a distribution of values around the WPC accumulation at each grid point. The typical constituency of this ensemble is as follows:
 
21 NCEP Short-Range Ensemble Forecast (SREF) members

1 NCEP North American Mesoscale (NAM) 12Z (day) or 00Z (night) operational run

1 NCEP Global Forecast System (GFS) 12Z (day) or 00Z (night) operational run

1 European Center for Medium-Range Weather Forecasts (ECMWF) latest operational run

1 Canadian Model (CMC) latest operational run

1 ECMWF latest ensemble mean

1 NCEP Global Ensemble Forecast System (GEFS) latest ensemble mean (6-h SLRs)

1 GEFS latest ensemble mean (24-h mean SLR)

___

28 Total members

The GFS based forecast and the SREF (because there are so many of them) to an extent are really going to juice the probabilities.

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Failboat storm up here barring a Flutie hail mary.

 

AWT

 

 

I'm surprised at how cold the Euro is. I hope its not being too cold...like it was in the 2/27 event

 

That has to be a concern after the last storm

 

Whenever DC is in the game, we're usually smoking cirrus up this way.

 

Just like 2010

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NAM going to do the full monty this run.  Makes me think the CMC may be about to leap too, RGEM/NAM were both mishandling (apparently) the energy coming into MN later today.

 

GFS/Euro were different.

 

1 flag.   NAM is speeding that ULL out.  Seems odd in this block, but has to be watched.  That's how Andy's UKMET hosed us and not in a good way.

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NAM going to do the full monty this run.  Makes me think the CMC may be about to leap too, RGEM/NAM were both mishandling (apparently) the energy coming into MN later today.

 

GFS/Euro were different.

 

1 flag.   NAM is speeding that ULL out.  Seems odd in this block, but has to be watched.  That's how Andy's UKMET hosed us and not in a good way.

I mentioned that a few days ago and have been following these trends when comaring really any of the models,  esp. the operational NAM and the SREFS since they're cousins.   The weenie arw camp was consistently quicker and further n with the ULL, and jmo it was partly because the block was a little weaker and further NE.  Or perhaps,  the energy was ejecting a little quicker in advance.

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