NYC/PHL December 24-27 Potential - Part 2

[tombo82685]

Let me continue.

What do I mean when I refer to incipient cyclogenesis?

Incipient cyclogenesis develops when an atmospheric disturbance develops over a baroclinic zone in the low levels. Mass divergence in the upper levels will incite low level convergence (this requires the level of non-divergence to be in between) since the atmosphere follows the laws of mass continuity. In other words, mass can not be destroyed or created. Upper level mass divergence incites incipient cyclogenesis over the baroclinic zone and cyclogenesis begins. Note in the early GFS runs this cyclogenesis altered the cold air advection pattern towards the East Coast as it developed a strong low level circulation (see above pictures). As I showed above, if the low level trajectory of the CAA is shifted eastward, where does the trough develop? Towards the EC, and the overall track is much farther N.

What we want is a PV that incites weak lower level cyclogenesis...just enough to enhance the low level cold air advection towards the GOM but not enough to shift it eastward before our trough develops and digs farther S.

wow, now i remember why i never pursued meteorology, good lord. Seriously your like a walking math/meteorology book, very impressive. I kind of get what your saying i might have to keep reading over it and look at the pics about 20 more times.

[baroclinic_instability]

ahhh, so when you get the upper level hgts that fall this induces cyclogenesis?

Well in a way. You need mass divergence aloft, in short, to develop sufficient cyclogenesis. Cyclogenesis itself is a weird beast and can be rather steady state or it can be positive feedback (self development). In either case, low level cold air advection will not only develop the trough farther south, it will enhance the low level baroclinic zone near the GOM...increasing the potential energy.

I remember the discussion from HPC which mentioned this. Basically, height differential thermal advection is the key to the phase and timing.

Exactly. We need the phase to happen at the exact right time to incite cyclogenesis at the right time so CAA is maximized towards the GOM without tracking too far eastward early on.

[baroclinic_instability]

Finally, to end the discussion for now, the 06Z NAM is not quite ideal yet because you can see the trough is already developing an east component.

Compare to the ECM which is still digging the trough into the GOM.

It all has to do with the CAA and incipient cyclogenesis. The ECM has the latest phase, and therefore it has the deepest CAA. This results in the cold air advection diving S and a much deeper solution. 6Z NAM is close but not quite there.

[tombo82685]

Finally, to end the discussion for now, the 06Z NAM is not quite ideal yet because you can see the trough is already developing an east component.

Compare to the ECM which is still digging the trough into the GOM.

It all has to do with the CAA and incipient cyclogenesis. The ECM has the latest phase, and therefore it has the deepest CAA. This results in the cold air advection diving S and a much deeper solution. 6Z NAM is close but not quite there.

that would come back to a stronger s/w. I f you have stronger s/w in the gom the hgts would be further south more towards the euro instead of bending east.

[tombo82685]

still vast differences between the euro and gfs at hr 57. euro/nam has a closed h5 low over tx, where the gfs isn't close

[baroclinic_instability]

that would come back to a stronger s/w. I f you have stronger s/w in the gom the hgts would be further south more towards the euro instead of bending east.

Yeah that too. The ECM, as you can see now, is literally the most ideal solution because it phases the latest, has the PV the farthest south, and it is just weak enough to enhance CAA without shifting trough development eastward. Also note all this needs to happen at the right time or things can go awry a number of ways. This truly is becoming a "thread the needle" event again...not as bad as the last potential storm, but a lot needs to happen the right way...hence the myriad of solutions in the ensembles.

[tombo82685]

nvm, gfs now closes off an h5 low at hr 63, while the 0z run wasn;t

[tombo82685]

slower with the s/w through 72..

[Ericjcrash]

slower with the s/w through 72..

This is what we need.....

[baroclinic_instability]

IOW it's all a matter of timing, and rather fine timing at that lol. BTW I love your use of the law of conservation of mass, but would just add that it can be converted to energy (which mass is just another form of.) Perhaps cyclogenesis includes a partial conversion also, which happens in many chemical and physical processes (though not to the extent that it happens in nuclear reactions.)

Wonderful educational discussion, Im very glad I stayed up for this

Yes very true. For the most part, in analysis, the conservation of mass holds true. Cyclogenesis is a weird beast because, under the right conditions, kinetic energy of the flow can actually enhance the potential energy. This is where self development can happen.

[Inudaw]

This is what we need.....

Need that and the northern stream to nose dive in as per Euro... ;

[tombo82685]

hr 78 closed low over eastern tx north of hou...this looks a good bit better than 0z so far...s/w a good bit slower to

[tombo82685]

Need that and the northern stream to nose dive in as per Euro... ;

per my maps, its diving in faster 6z than 0z so far

[tombo82685]

hr 87 has a closed h5 low in sw la....s/w continues slower...northern stream dropping in good.

[tombo82685]

wow at how much slower this is than 0z, remarkable

[Ericjcrash]

per my maps, its diving in faster 6z than 0z so far

Yeah, the end result SHOULD be better, we shall see.

[tombo82685]

hr 93 h5 still closed barely tho in the gom....sub 1012 low has now formed over the gom

[Inudaw]

Even at 66 hours.. you can see how the southern short wave slows up and further south on the 6z..

6z

0z

[baroclinic_instability]

wow at how much slower this is than 0z, remarkable

All else equal, slower is definitely better.

[tombo82685]

hr 96 sub 1012 low 150 miles south of mobile al...

[Inudaw]

hr 96 sub 1012 low 150 miles south of mobile al...

Soo.. far...south... Not sure if it can recover from that far south on the 6z gfs... :X *is willing to eat my own words if it hooks hard north*

[baroclinic_instability]

Soo.. far...south... Not sure if it can recover from that far south on the 6z gfs... :X *is willing to eat my own words if it hooks hard north*

Wow the GFS almost misses the phase.

[tombo82685]

despite how much slower and closed low it still takes the same track....the northern stream must of slackened up cause the trof never really went neg tilt

[Inudaw]

despite how much slower and closed low it still takes the same track....the northern stream must of slackened up cause the trof never really went neg tilt

Yea northern stream did not continue to dive in per the Euro. x.x;

[Ericjcrash]

despite how much slower and closed low it still takes the same track....the northern stream must of slackened up cause the trof never really went neg tilt

Yea, but overall good run IMO. Slower is better.

[tombo82685]

deff a good tren there i would say of how much slower this was. If that h5 low was further north instead over the gulf of mex, would that of phased? Or do we need that northern stream to dig deeper

[Inudaw]

deff a good tren there i would say of how much slower this was. If that h5 low was further north instead over the gulf of mex, would that of phased? Or do we need that northern stream to dig deeper

I'd prefer the northern stream to dig deeper in the overall set up. Strangely the only model to dig the shortwave into the gulf that far sourth was the Nogaps.. and it missed the phase completely.. resulted in the northern stream forming a low pressure eventually way way way out in the Atlantic.

[atownwxwatcher]

Guys look how far south this dropped...could this be why it missed the phase?

00z 60

http://raleighwx.americanwx.com/models/gfs/00zgfs850mbTSLPp06060.gif

00z 54

http://raleighwx.americanwx.com/models/gfs/06zgfs850mbTSLPp06054.gif

That is a drastic drop south IMO in 6 hrs

[baroclinic_instability]

deff a good tren there i would say of how much slower this was. If that h5 low was further north instead over the gulf of mex, would that of phased? Or do we need that northern stream to dig deeper

GFS is getting close, that east coast vortex still has a negative influence though and it flattens the height field. No self development and no negative tilt early on. You need that for this thing to hook into the coast. Otherwise you get a UK solution. I have a feeling this will bomb but way off coast like the 0Z UK.

[tombo82685]

GFS is getting close, that east coast vortex still has a negative influence though and it flattens the height field. No self development and no negative tilt early on. You need that for this thing to hook into the coast. Otherwise you get a UK solution. I have a feeling this will bomb but way off coast like the 0Z UK.

that exactly what it did....alright im going to bed be back for the 12z