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Bob Chill

December 2019 Med/Long Range Disco

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6 minutes ago, WxUSAF said:

Need some WAR or SE ridge during a big -EPO period or it’s just cold and dry. Take a look back at the pattern for last November’s early season snow. Big WAR, which is what brought the storm, but we had a good cold air source and so it snowed. Similar deals in 13-14 and 14-15. If it’s going to be a EPO dominated pattern, got to accept some cutters and cold/dry.

I realize about the WAR but before we enter prime climo an anti cyclone in the 50/50 spot usually hurts us more than helps especially with ssts still relatively warm. Now this look in another 3 weeks and we could probably get away with it. Love that Pac look tho.

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21 minutes ago, Bob Chill said:

Everything is right down the middle. Not bad enough to worry and not good enough to like it. lol. I'm not thinking we have much of a chance for the next 2 weeks unless something runs the gauntlet. Would be nice to get the atl & pac to play nice together this month. Sometime around the 24th-25th would be acceptable. 

I’m wondering how much this Pac puke can kick is due to the conflicting tropical forcing signals. Maybe Eps keeps expecting the MJO to get into torch phases (and maybe the “true” MJO wave is doing that) and so expects a Pac flood, but as we get closer in time, that Indian Ocean standing wave still ends up being the tail wagging the dog and the MJO forcing itself is overwhelmed. 

Either way, it’s probably having the net effect of turning what otherwise would be a December torch into a fairly seasonal week or two with low, but nonzero snow chances if we can time up some cold air and a southern wave. Certainly looks Nino-ish with active southern stream. I’m cautiously optimistic we get a fun event or two this month.

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7 minutes ago, WxUSAF said:

I’m wondering how much this Pac puke can kick is due to the conflicting tropical forcing signals. Maybe Eps keeps expecting the MJO to get into torch phases (and maybe the “true” MJO wave is doing that) and so expects a Pac flood, but as we get closer in time, that Indian Ocean standing wave still ends up being the tail wagging the dog and the MJO forcing itself is overwhelmed. 

Either way, it’s probably having the net effect of turning what otherwise would be a December torch into a fairly seasonal week or two with low, but nonzero snow chances if we can time up some cold air and a southern wave. Certainly looks Nino-ish with active southern stream. I’m cautiously optimistic we get a fun event or two this month.

I will say this...those sustained AN temp regime looks and blue balls over the N Pole keep getting pushed back and there is nary a sign of any SE ridge which many of the warm December forecasts were banking on. This cant be a bad thing as now the next 10 days look ok and takes us to almost mid December. It's a little premature for us to celebrate but many of those warm Dec forecasts may be quickly losing steam....no pun intended.

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Just now, WxUSAF said:

I’m wondering how much this Pac puke can kick is due to the conflicting tropical forcing signals. Maybe Eps keeps expecting the MJO to get into torch phases (and maybe the “true” MJO wave is doing that) and so expects a Pac flood, but as we get closer in time, that Indian Ocean standing wave still ends up being the tail wagging the dog and the MJO forcing itself is overwhelmed. 

Either way, it’s probably having the net effect of turning what otherwise would be a December torch into a fairly seasonal week or two with low, but nonzero snow chances if we can time up some cold air and a southern wave. Certainly looks Nino-ish with active southern stream. I’m cautiously optimistic we get a fun event or two this month.

No persistence to rely on yet in North America so our brains can't see through the computers. lol

Had a blocky pattern in general going for a few weeks that's evaporated and now looks like progressive is going to take over for the next few weeks. Both were modeled "ok" in the D10-15 range so we can prob trust the current d10-15 general pattern showing up. Which isn't very exciting but if anything (as you've already said), the big warning flags in the long range keep getting muted and delayed. Could be a clue that the general NA pattern has a tendency to be more amplified. 

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It has been a bit of a trend today for the D8-10 period.  GFS increases blocking again at 18z and shoves the Canadian vortex south into the N plains.  Looks to roll east from there.  Lets kick the closed low out of Cali and attack that arctic high!

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6 minutes ago, poolz1 said:

It has been a bit of a trend today for the D8-10 period.  GFS increases blocking again at 18z and shoves the Canadian vortex south into the N plains.  Looks to roll east from there.  Lets kick the closed low out of Cali and attack that arctic high!

A few interesting things to keep an eye on :

The mid month period when there are signs of a drop in the AO along with a +PNA interval. Some favorable action too from the strat may work its way down to a degree. 

Meanwhile, interesting progressions with the warming as it transpires in terms of the Canadian vortex and trop / strat vortex over Siberia/Scandy , as mentioned by Hugo. 

Also, the elongation and the movement of the trop vortex has my interest as well, in a backdrop favorable to keep the vortex perturbed.

Below are several relevant recent releases on the above.  

 

 

 

 

 

    

 

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A decent event appears near the end of the 18z GFS run... probably going to be our first real threat of the season if what the EPS/GEFS are suggesting that we have we actually have 

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9 minutes ago, yoda said:

A decent event appears near the end of the 18z GFS run... probably going to be our first real threat of the season if what the EPS/GEFS are suggesting that we have we actually have 

Feel like the Dec 11-12 time frame might need to be watched too. I like the end of the GFS run as well.  Looking forward to your first play by play of the season. ;)

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4 minutes ago, Scraff said:

Feel like the Dec 11-12 time frame might need to be watched too. I like the end of the GFS run as well.  Looking forward to your first play by play of the season. ;)

If we could get a wave along the tail end of the front that time could have potential. 18z teases that, but the wave is weak and sheared.

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16 minutes ago, Scraff said:

Feel like the Dec 11-12 time frame might need to be watched too. I like the end of the GFS run as well.  Looking forward to your first play by play of the season. ;)

Just be patient. Even though it looks like we go back to bn temps after a nice warm day or 2 next week, pulling an event out of the progressive flow with no block requires a lot of little things to work out. Most importantly tight spacing... Each airmass capable of producing snow will only be in a good spot for 2-3 days tops. Miss that window and the next event is likely rain. 

It does look like we're moving back into the game mid/late next week. Would be nice if the +pna pattern hangs on for 1-2 weeks so we can get more than one isolated chance at threading the needle 

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14 minutes ago, Scraff said:

Feel like the Dec 11-12 time frame might need to be watched too. I like the end of the GFS run as well.  Looking forward to your first play by play of the season. ;)

Bank on it.  8 am flight to Key West on the 12th for a Friday the 13th birthday weekend. 

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14 minutes ago, WxUSAF said:

If we could get a wave along the tail end of the front that time could have potential. 18z teases that, but the wave is weak and sheared.

18z gefs actually supports the ops idea.

gfs-ens_z500a_us_49.png

gfs-ens_apcpn24_us_46.png

Unusual to see qpf panels like this 300 hours out.

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What a nice stretch of cold per latest Gefs . This is the Ensemble Metrogram for temps...this is a solid 7 day stretch through the end of the run . Yes this is Carroll county airport but for a mean its impressive.  I'm sure there are colder members in the mix . I'll take my chances if verbatim we had 7 days of cold enough air over us or nearby to score a frozen event . Hopefully this is a trend .:D

Build it... ( The Cold ) 

And they ...( Storms ) will come 

 

 

PhotoPictureResizer_191202_194941656_crop_1233x1910.jpg

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@frd  Some positive signs amongst the muddy waters, imo.  The propensity for HLB so far has been decent.  Nothing sustained.....yet.  Aleutian low seems to want to keep forming. No shortage of closed lows traversing the country.  No red flags with the strat and if anything signs are positive.  I know others have mentioned the MJO and the struggle models are having with it.  I think once we get to mid Dec we will see the MJO stopping its flirt with phase 3 and circle back to 8/1.   +IOD is coming down but SSTs still showing it plainly...it will have its say.

Feeling pretty positive about late Dec and Jan....Though, I feel pretty positive every time before I play golf.  Not so much once back to the clubhouse!

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17 minutes ago, psuhoffman said:

0z gfs has a happy ending 

Really think that time period (Dec 16-19) is going to be our first real threat around here

ETA: Actually, is it just me... or did the 00z GFS OP run at the end look like a train of threats headed our direction? 

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EPS is now fairly strongly picking up on the possibility of a deep dropping PV as well as the potential for a significant cold shot. Below is the run over run changes being seen. Note that we see a significant change in the heights. This is representative of the EPS  now seeing lower pressures associated with the pv much farther south then previous runs.

epsheightschange.gif.450f3771a05ccc262b76149d50234982.gif

 

Thus we are seeing very significant run over run changes with the 850 temps which are also indicative of a deeper dropping pv.

eps850tempchange.gif.13a0db8ab0597457068154e0106cf08e.gif

 

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30 minutes ago, midatlanticweather said:

HM Tweets again reinforcing what is being discussed

 

 

 

Excellent animation by Hugo regarding the upcoming wave break in the North Atlantic. Gives more support to something near mid month. The evolution of any -NAO is still key to an any snow possibilities down our way. By this time we are deeper in December, will be interesting to see what transpires in the NAO domain the second and third weeks of December. Maybe the block times perfectly with some over-running moisture to our South, as signs are for an active STJ this month. 

 

Also,  note the changes here beyond December 7 th :

 

00Z GEFS 1.0° 100 hPa 60°N tercile categories

The tercile-category anomaly of the lower-stratospheric polar vortex, defined by the 100 hPa 60°N zonal-mean zonal wind, has been used as a diagnostic for the behaviour in the ‘coupling layer’ between the stratosphere and troposphere, i.e. the level in the stratosphere where circulation anomalies are important for influencing tropospheric weather regimes (e.g. Charlton-Perez et al. 2018, Lee et al. 2019). The chart below shows the percent of GEFS members in each tercile anomaly category, based on daily 1979-2018 ERA-5 climatology.

Weak = lower tercile; neutral = middle tercile; strong = upper tercile.

U100-60 GEFS terciles

 

 

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Most excellent ! 

I totally agree, minute details in weather do matter, that is what makes this hobby so enjoyable.    Next, I need snow, a lot of it please. I want to dust off the snowshoes. :sled:

 

 

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More on the possible NAO block from HM and his  general thoughts about December. 

Great job so far Anthony ! Colder risks seem to be gaining traction lately.  

 

 

 

 

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That post by Webb is a prime example of why trusting ensembles right now past D10 is risky.  In 4 days it goes from CONUS torch/Pac flood to a nasty Arctic outbreak.  

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