12z/18z 12/01 model runs thread:

[RNS]

This afternoon/s run of the GFS appears to be much more in line with what is actually taking place with regard to the overall pattern. remember its the driving patternt hat makes the storm...so if we can accurately make an assessment of the pattern late this week and this weekend...i have strong confidence that this storm will fall right into place with the ideas we are about to outline:

the following figures depict GFS 500 hPa heights and vorticity 84-156 hours:

84hr:



90hr:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_090s.gif

96hr:



102hr:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_102s.gif

108hr:



114hr:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_114s.gif

120hr:



126hr:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_126s.gif

132hr:



138hr:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_138s.gif

144hr:



150hr:

http://www.nco.ncep.noaa.gov/pmb/nwprod ... 0_150s.gif

156hr:



First off...i like the way the GFS is trending...though it still has a long way to go before coming around to the EC solution from last night which at the point i think is the closest to correct of all the other models.

anyway...the GFS digs the PJ s/w into the central plains at the beginning of the period (84hrs) however this time keeps it as an open wave...or IOW doesn/t close it off. We also notice the 50/50 low and deep trough centered near newfoundland...with height rises (indicative of blocking and a developing negative NAO) nosing in from the northeast. There also appears to be the development of the PNA ridge across western north america (notice the strong riding in the western part of the country)... anchored by a deep low pressure center in the gulf of AK.

the development of the PNA ridge in the western part of the country argues for the PJ s/w in question to dig more as it heads southeast in response to the amplification back to the west...all the while the deep trough and 50/50 low near newfoundland says that the trough associated wth the digging s/w should tilt positive...promoting less in the way of height rises ahead of it as low pressure closes off...thus a colder pattern across the northeast.

the confluent flow and height rises in back of the 50/50 low would promote the development of surface high pressure across northern new england and southeast quebec province helping to keep the cold air in place across the eastern US. in such a situation...strong cold air damming usually develops along the eastern side of the appalachains...and the models typically have a VERY hard time seeing this. since surface low pressure cant go through a cold tounge like that east of the mountains...it/s forced to the coast (where the thermal gradient is best)...and thus the reason why systems transfer to the coast. this is no exception.

the GFS is beginning to pick up on this though IMO has the 500 hPa closed low TOO far west with not enough of a positive tilt given the strong 50/50 low. at 108hrs the GFS has the H5 low centered almost directly over Cincinnati which is too far to the west and goes hand in hand with the GFS bias of overdoing the strength of the polar jet. therefore my adjustment to the GFS would be for the closed low to be located over Southwest Virginia...within a more positively tilted trough.

Then we have the 12Z NOGAPS...or in summary not much better.

500 hPa heights and vorticity 84-144hrs:

84hr:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 00&tau=084

96hr:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 00&tau=096

108hr:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 00&tau=108

120hr:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 00&tau=120

132hr:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 00&tau=132

144hr:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 00&tau=144

The NOGAPS cold bias takes center stage here...at 84hrs the NOGAPS begins to phase the digging PJ energy with the STJ s/w as strong height rises develop across the western part of the country indicative of an amplyfing PNA ridge...this the PJ s/w is allowed to dig much further and grab the STJ s/w in an effort to phase.

in any event the NOGAPS splits the PJ s/w as once piece of it remains locked up in canada and the second piece phases with the STJ s/w therefore forming a closed H5 low over the boot heel of MO by 108 hrs as the trough maintains a strongly positive tilt. notice also the weaker height rises taking place to the east of the system.

up until this point the NOGAPS has a fairly decent look to it...however it buries the closed low too far to the southwest over Arkansas...Louisiana and Mississippi...and proceeds to cut it off as the main westerly flow splits away to the northeast. and secondly the NOGAPS is much too fast in getting rid of the deep trough centered near newfoundland...at the beginning of the period in question it has the feature centered very far back to the west...however is faster in getting rid of it than any other model.

by 144 hours the NOGAPS has a huge cutoff low sitting over moblie alabama and a zonal flow overtop dispersing the cold air. IMO NOT HAPPENING. that solution is almost as bad as last nights 0z run where it completely failed to phase the two features.

below are the complete set of model analysis paramaters at 144 hrs...incase somebody needs a good laugh:

https://www.fnmoc.navy.mil/CGI/PUBLIC/w ... 2003120112

the UKMET is much more in line with the ideas expresed by last nights EC:

http://meteocentre.com/animate.php?lang ... 12Z%20ANIM

notice low pressure at 996mb off the just off the coast of north carolina...

[JCT777]

This sounds very interesting. I want to believe there will be a low off the NC coast. Maybe I will just take a wait and see attitude instead of simply writing off the possibility of a snow and/or ice event.

[RNS]

more likely than not there will be