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December 2020 General Discussions & Observations Thread


bluewave
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Good morning everyone, Tuesday Dec 1!  No topic yet... but the 5th-6th -possibly into early 7th, looks like a rain storm for most of the forum but may have a little ice for the nw edge of the forum I84 region, ending as an inch or two of snow, especially later Sunday the 6th. 

Overall a short wave dropping south in the Rockies this morning closes off and marches east this week, opening up a little over the Midwest then closing as it goes by LI Sunday with a surface low modeled-ensembled through PA-LI, intensifying as it moves to the northern New England coast late Sunday or Monday morning. NAEFS 52 member 500 MB heights are modeled to deepen 120 meters/24 hr period between the 5th-7th with the 500 MB vort max of the deepening 500MB system crossing NJ Sunday.  The 00z/1 EPS does not have this, leaving too much of the lead short wave behind in the sw USA. It could be right but I don't think so. I expect the future EPS to gravitate to the GEFS/NAEFS solution at 500 MB.  New 00z/1 RMOP not yet available to do a reality check.

So, despite the 06z/1 GFS OP run, I think this deserves some monitoring - just can't topic it yet due to less severity, wind and storm totals wise, than what occurred yesterday-Nov30. Snowfall, mainly nw edge of the forum---IF that far south.  I am looking at it carefully. As many will say, probably not much if anything wintry up there near I84 but I'm not so sure---certainly can see a period of hazardous minor ice or snow. 544A/1

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The first 8 days of December are averaging 45degs.(41/50).         Making it 40degs., or just Normal.       EURO is much colder for the period.      GFS has not been vaccinated yet.

54*(99%RH) here at 6am, overcast      50* by Noon.      49* by 12:30pm.      48* by 2pm.      47* by 2:30pm.     45* by 3pm.        42* by 7pm.      40* by 10pm.      39* by 10:30pm.

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4 minutes ago, bluewave said:

The Euro is really struggling with the split flow. Notice how much different the GFS and CMC are at day 10. Remember, the errors at day 7-10 often build into the day 11-15. 
 

AF426CA8-CC33-4642-B1D7-1D2C985E151B.thumb.png.254788816afd0d78bb7120e028c3d09b.png
AB23C108-E5CF-4527-8CEA-FD8BC00DA78C.thumb.png.97598cf34455d9b716f949c4bcb9119e.png

8A8A03C6-C6D5-428E-8C62-5E120A32E1F4.thumb.png.d36fe2c7dc6f925e6055b32c378755e0.png

Those are operational runs at day 10. They will always be changing. Use the ensembles that far out. 

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12 minutes ago, Allsnow said:

Those are operational runs at day 10. They will always be changing. Use the ensembles that far out. 

The OP GFS longer range has had less of a cold bias than the ensembles over SE Canada.  Sometimes, the lower resolution ensembles smooth out the ridge near the near the Northeast too much. Where the OP runs don’t.  

0BA859BB-4BC0-42E2-B5C6-34ED6B9D77E7.png.0be577217cc1667b1218dd0ee0a46374.png
11D5964B-530B-4912-8012-C9AE03C293A8.png.997b18e929023a8abfe3f3966c655f94.png

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5 minutes ago, bluewave said:

Those long range strat forecasts for change are very uncertain given how strong the PV has been.

So are day 10 operational models. They are always changing. So much for those Niña southeast ridge calls to start December 

 

Gef and eps continue to weaken the SPV by mid month. 

23652B11-231C-4C14-9265-A4FDB1DD7674.png

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6 minutes ago, Allsnow said:

So are day 10 operational models. They are always changing. So much for those Niña southeast ridge calls to start December 

 

Gef and eps continue to weaken the SPV by mid month. 

 

I was pointing out back in the October and early November threads how the atmosphere wasn’t showing the canonical La Niña patterns. We have been experiencing these more Niño-like +AAM spikes since the fall. So I mentioned that we may not follow  a typical La Niña November. This is much like the last few years with mismatched Niño and Niño-like influences at the same time. This is due to all the competing record equatorial and off equatorial SST warmth from the Indian Ocean into the Pacific.

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9 minutes ago, bluewave said:

I was pointing out back in the October and early November threads how the atmosphere wasn’t showing the canonical La Niña patterns. We have been experiencing these more Niño-like +AAM spikes since the fall. So I mentioned that we may not follow  a typical La Niña November. This is much like the last few years with mismatched Niño and Niño-like influences at the same time. This is due to all the competing record equatorial and off equatorial SST warmth from the Indian Ocean into the Pacific.

With those conflicting signals a wave 1 displacement of the SPV off the pole IMO will lead to a artic outbreak towards mid month. This is something that happen in 13/14 as punches were thrown at the vortex. I’m not calling for a 13/14 winter just that I expect colder air to come. This is supported by the eps and GEFS. 

868A5828-A09B-4892-BD44-2E384B423B93.png

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Of interest to me and for I84 northward winter weather interests. 

Note the side by side forecast for 00z/ 7 RMOP confidence (for Sunday evening).  Two things... heights are 60 meters or more deeper on the 1/00 run than that of 00z/30.

Two: vort max passage s of LI and likely triple point low s of LI... and position of the trough.  This increases my confidence on a sizable event and winter weather down very close to I84. 

 

added the 3rd frame...the side by side of the previous 11/30 cycle for the second frame, same time.  Now you can see. 

 

 

 

Screen_Shot_2020-12-01_at_7_29.02_AM.png

Screen_Shot_2020-12-01_at_7_29.22_AM.png

 

Screen_Shot_2020-12-01_at_7_30.34_AM.png

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29 minutes ago, MJO812 said:

Best looking pattern we ever had since a long time ago.  Hopefully it produces.

Looks good on those GFS ENS  long rang charts now that you posted at 324 hours but what will actually verify could be different. With this pattern change in progress it is now becoming difficult to even predict what is going to happen at the surface this coming weekend as the EURO and the GFS are completely at odds with one another within 5 days

prateptype_cat_ecmwf.conus.pnggfs_mslp_pcpn_frzn_us_19.png

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EURO is  0.3" snow and the GFS,CMC are 0.0" for the next 10 days.

GFS is blank till the 16th.      GFS has had a Trace or better on all these dates at one time or another......Dec. 02,05,07,10,13 now the 16th.   This is shotgun forecasting.   

When you start seeing a period with reliable consecutive sub-freezing High T's----then something may happen.

The GEFS doesn't even have a single BN 5-Day period showing.     I do think Tampa, Florida's feat of 32 straight months w/o a BN one, could end.      All 5-Day periods are BN in Florida.

Coney Island Polar Bear Club moving to Florida to demonstrate their superior abilities:    LOL

summaryCFSv2.NaT2mProb.202012.gif

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1 hour ago, jfklganyc said:

Cold air side, I am surprised nobody’s talking about most of the first week of December now running above normal. A change from just a few days ago

 

55F at 7 am. Doing yard work in shorts on 12/1

Coldest day here on Upton's forecast is next Monday with a high of 43-rest of the days are warmer.   Seasonable to slightly above

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Morning thoughts...

In the wake of yesterday's storm, it will be partly to mostly cloudy and cooler. Temperatures will hold steady or fall slowly. Likely high temperatures for the remainder of the day around the region  (from 8 am and afterward) include:

New York City (Central Park): 52°
Newark: 51°
Philadelphia: 48°

The first week of December will likely see the temperature average near or somewhat above normal.

30-Day Verification:

New York City (Central Park):
Average daily forecast: 58.0°
Average temperature: 59.1°
Average error: 1.9°

Newark:
Average daily forecast: 60.3°
Average temperature: 60.9°
Average error: 1.7°

Philadelphia:
Average daily forecast: 60.7°
Average temperature: 61.2°
Average error: 1.5°

 

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I corrected my prior RMOP post with adding the proper previous cycle forecast for 00z/7 as the 3rd frame. Now you can see the difference.   Also put it in here... 

 

Finally...here is the 06z/1 500 MB GEFS.  Pretty  confident membership on something sizable PA or NYS (upper low) for 00z/7.  Which is it?  north of us...probably,  but I think there will be a triple point low off NJ. 

Screen_Shot_2020-12-01_at_7_29.22_AM.png

Screen_Shot_2020-12-01_at_7_30.34_AM.png

Screen Shot 2020-12-01 at 9.13.42 AM.png

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6 minutes ago, wdrag said:

I corrected my prior RMOP post with adding the proper previous cycle forecast for 00z/7 as the 3rd frame. Now you can see the difference.   Also put it in here... 

 

Finally...here is the 06z/1 500 MB GEFS.  Pretty  confident membership on something sizable PA or NYS (upper low) for 00z/7.  Which is it?  north of us...probably,  but I think there will be a triple point low off NJ. 

Screen_Shot_2020-12-01_at_7_29.22_AM.png

Screen_Shot_2020-12-01_at_7_30.34_AM.png

Screen Shot 2020-12-01 at 9.13.42 AM.png

Potential for another wind event this weekend gotta see how it trends next few days 

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12 minutes ago, wdrag said:

I corrected my prior RMOP post with adding the proper previous cycle forecast for 00z/7 as the 3rd frame. Now you can see the difference.   Also put it in here... 

 

Finally...here is the 06z/1 500 MB GEFS.  Pretty  confident membership on something sizable PA or NYS (upper low) for 00z/7.  Which is it?  north of us...probably,  but I think there will be a triple point low off NJ. 

 

 

 

You are discounting the 0Z EURO solution for this weekend ?

prateptype_cat_ecmwf.conus.png

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