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Pattern The Great December Dump

Keep in mind this is the FV3. We had this type of thing happen last year as well. Heck we had this happen last Saturday.


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FWIW, snow or not, I do believe a storm system is coming. Gfs/Euro both have them
 
By the looks of the 0z GEFS 500mb, the phase occurs over northern FL and the low continues to deepens off of the southeastern US coast. If it's cold enough, and if this is true of what the GEFS is showing, wrap around snow would be from northeastern/eastern AL, (possibly far west as Birmingham) all of northern GA, Upstate SC, Western NC and Central NC. It would be intense heavy snow bands too with that deepening low.500h_anom.conus.png

500h_anom.conus2.png
 
Good gawd, 0z GFS showing the low intensifying to a 978mb low off of the southeast coast! That's a CAT. 2 hurricane! :eek:

The low would need to close off sooner to allow snowfall further inland. Luckily, there is still time for this to trend better.

Baroclinic pressure =/= barotropic pressure.
 
Despite the Euro looking better, the EPS is about the same with the center of the low around Florida. We really need that energy on the Euro suite to be North. Way too suppressed.
 
The 0z EPS just took a big step towards the GEFS/GFS camp.

The differences between a massive snowstorm & no storm at all are actually pretty trivial given this is 7-8 days out. The latent heating contribution to this storm will be larger than usual which also makes these model forecasts highly dependent on each suite's convective parameterizations & thus adds another layer of uncertainty superimposed onto the fact that we're dealing w/ an upper low.

ecmwf-ens_z500a_us_fh192_trend (1).gif
 
Another paste bomb on the 6z gfs. Northern NC and VA special this run due to a more northern and inland track. I forgot how special a system can be when there is blocking and a phase!



snku_acc.us_ma.png
 
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Another paste bomb on the 6z gfs. Northern NC and VA special this run due to a more northern and inland track. I forgot how special a system can be when there is blocking and a phase!



snku_acc.us_ma.png


For an ideal hit in centered over NC, we want this upper low to track right over southern Georgia, it's a little too far north in this case and definitely favors the southern mid-Atlantic (Richmond, Roanoke, etc) verbatim. More than enough time to resolve little subtleties like this and determine if a storm will occur at all in the first place.

gfs_z500aNorm_eus_27.png
 
Euro needs to bite at it. Then a thread can be started


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Keep starting threads only to be let down. Models a week out have yet to verify. Until most of the models have something a thread shouldn't be started. Enough threads now. Hopefully it is legit but we have seen this over and over just like this past week rainmaker. Gfs and euro had me 10-12 inches of snow 8 days out. Not a flake all rain.
 
I’m definitely interested in what the UKMET will show over the next 48 hours. Sometimes it will lock on to a solution pretty early and not have the wild swings the GFS and Euro does in the 4-6 day range. Maybe that because it only runs twice a day with much less analysis by us, but I tend to give quite a bit of weight to the Ukie with these setups.
 
There are obviously some very distinct differences & in no way, shape, or form am I expecting a similar outcome (because that's crazy this far out) but seeing this huge Hudson Bay block, west coast trough coupled w/ a -NAO & +EPO w/ an upper low tracking near or just north of the Gulf coast certainly makes me think of the setup that led to the monster storm in late Feb 2004.

Point is, a pattern like this is capable of producing a really big storm if we get all our ducks in a row.

gfs-ens_z500a_namer_30.png
g20191215_0603_21535_1.png
 
From GSP


.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 230 AM EST Sunday: Upper level heights begin to rise as a
ridge axis develops west of the fcst area Wed. A stg subs zone will
encompass the region beginning Wed afternoon...which will allow a
1028 mb sfc high to transit the se/rn states into Fri. This setup
will return clearing skies and cooler max/min temps...altho near or
just below normal levels each day. By Fri night...a developing h5
trof will dig across the ern CONUS which will be a weather maker for
the FA into the weekend. Much uncertainty exists during this time
frame as the GFS and ECMWF models are at odds with the details of
the trof config. The GFS is developing a closed low within the trof
and diving it across GA/SC and off the Atl coast thru Sat...while
the ECMWF keeps a faster non/closed trof axis crossing the area with
limited coastal sfc low development. The GFS scenario would bring a
decent amt of wintry precip to the FA as colder air would have more
time to be advected south as the low deepens off the coast. The
latest ECMWF on the other hand keeps the better moisture axis over
the ern zones with a limited freezing sfc-layer potential. Its
interesting that the 00z ECMWF has trended more inline with the
colder and moister GFS soln...however this system will be monitored
over the upcoming week and much can change with the sensible weather
fcst. So for now...have a low-end chance sn or -ra/sn mix over the
northern zones Fri night with limited/nil snow accums.


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