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February 5th beefed up swfe thread-let's get some December 2007 juju,

weathafella

By weathafella,
in New England

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powderfreak

powderfreak

Posted
Posted

Well that is more because of the pattern shift, lol. And yes, I stand by that. :) congrats next week.

Haha I'm just joking...the law of averages says it has to snow more than 4" at a time at some point this winter, lol. Persistence forecasting says this becomes a cutter or south of the 00z GFS if the Debbie model has any say in it.

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Juliancolton

Juliancolton

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I tried starting a discussion on this in the NYC thread, but needless to say met. analysis there is a bit hard to come by. My main question is why this system seems so resistant to coastal cyclogenesis while the primary festers/fills. I know it happens a lot (cutters happen for a reason), but I've never stopped to figure out the mechanisms at play that distinguish a major redeveloper from a messy transfer. If I had to guess, I would say the ridge to the southeast is keeping the flow east of the relevant shortwave too confluent in the mid and upper levels, but I'd love a quick summary from someone who knows what they're talking about.

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CoastalWx

CoastalWx

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I tried starting a discussion on this in the NYC thread, but needless to say met. analysis there is a bit hard to come by. My main question is why this system seems so resistant to coastal cyclogenesis while the primary festers/fills. I know it happens a lot (cutters happen for a reason), but I've never stopped to figure out the mechanisms at play that distinguish a major redeveloper from a messy transfer. If I had to guess, I would say the ridge to the southeast is keeping the flow east of the relevant shortwave too confluent in the mid and upper levels, but I'd love a quick summary from someone who knows what they're talking about.

There actually is secondary redevelopment near CC on the GFS and Canadian. Basically the primary is rather strong and the S/W forcing is helping to sustain it until it weakens as it tracks over the mountains. Eventually the baroclinic zone along the east coast with the help of the S/W approaching the East coast helps spawn a new low which develops and moves near Cape Cod. If the parent S/W were further east, you would likely have more rapid cyclogenesis on the coast.

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Juliancolton

Juliancolton

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There actually is secondary redevelopment near CC on the GFS and Canadian. Basically the primary is rather strong and the S/W forcing is helping to sustain it until it weakens as it tracks over the mountains. Eventually the baroclinic zone along the east coast with the help of the S/W approaching the East coast helps spawn a new low which develops and moves near Cape Cod. If the parent S/W were further east, you would likely have more rapid cyclogenesis on the coast.

That makes sense, thanks. I guess I was overthinking it a bit. :) I assume a further east s/w would be facilitated by a less-pronounced negative tilt upstream.

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eduggs

eduggs

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That makes sense, thanks. I guess I was overthinking it a bit. :) I assume a further east s/w would be facilitated by a less-pronounced negative tilt upstream.

It almost all has to do with the upper levels.  Surface pressure decreases over a point when the mass of air on top of that point decreases.  Rising air motions cause a decrease in the mass of a column of air and therefore decrease the surface pressure.  So then you have to look for mechanisms that cause rising air motions.  The most obvious one is upper level divergence, when the upper level flow lines spread out or when the magnitude chances, e.g., jet streaks.  The other mechanism is positive vorticity advection.  When vorticity increases over a region, the upward vertical motion increases (explained by vorticity equation and other mathematical formulas etc).  By looking at the 500mb and 300mb charts around day 5, it looks like there isn't much upper level divergence or PVA along the east coast.  It's better to our west, which is why surface pressures are lower there.  As you mentioned before, the natural baroclinic environment along the east coast as well as frictional effects with mountain ranges promotes a minor surface pressure decrease along or just offshore.  But unless upper level support is favorable to enhance surface deepening (and also favorable for the filling of the primary - upper level convergence in the vicinity of the primary etc), transfer and deepening of any 2ndary low will be slow and weak.

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CoastalWx

CoastalWx

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That makes sense, thanks. I guess I was overthinking it a bit. :) I assume a further east s/w would be facilitated by a less-pronounced negative tilt upstream.

It pretty much fits a classic pattern with a strong S/W moving across the southwest US and no blocking. Classic. The SE ridge is enhanced thanks to the s/w pumping up heights as it moves across the south. What is left is figuring out the smaller details of storm track.

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ORH_wxman

ORH_wxman

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The 12z ECMWF continues to show a significant snow to sleet/ice event for interior SNE and over to rain along the coastal areas. Though even northern coastal areas around Boston and north shore could see a prolonged period of sleet and/or FZRA. It looks to be mostly snow in central and northern New England.

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Benchmarkbuoy

Benchmarkbuoy

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The 12z ECMWF continues to show a significant snow to sleet/ice event for interior SNE and over to rain along the coastal areas. Though even northern coastal areas around Boston and north shore could see a prolonged period of sleet and/or FZRA. It looks to be mostly snow in central and northern New England.

I always wonder what qualifies as "coast" when we are discussing rain/snow lines and storm track.  This term "coast" as well as "eastern Massachusetts" seem to mean different things to different people.  Perhaps that is because each storm is different and in some set ups coast in 5 miles from the ocean and in others "coast" is 30 miles from the ocean.  What are we thinking defines coast for this Wednesday event?  Thanks

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