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Winter 2015-16

Mr Bob

By Mr Bob,
in Tennessee Valley

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Mr Bob

Mr Bob

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Temp wise, the 12z GFS has Knoxville topping out at 32 degrees Sunday afternoon, down to 8 then a high of 21 on Monday.  Down to 10 and a high of 25 Tuesday.  Down to 13 and finally back up to 32 by Wednesday.  Intredasting.

There is some "snow cover" effect in there which I would not expect with just a couple of inches but if the low does bomb out up the coast it will definitely be colder than what is currently forecast.

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ShawnEastTN

ShawnEastTN

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and this is why you don't get excited when both the parallel and regular gfs decide they want to "punk" you.  The Euro at 12z is night and day different.  

It seems maybe I say this every year but I don't recall such model variance this close to a potential event.  I tend to trust the euro, but i have a very hard time with that extreme suppression to Cuba essentially.  Just seems way overdone to me.   

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Carvers Gap

Carvers Gap

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John or Carvers, why don't you go ahead and pull the trigger on a short range thread.  I don't trust my mojo enough to do it.

 

12z Euro and Canadian seem way to suppressed.  I like the 12z, but hey...I wonder why!?  I am all for giving others a chance.  John1122 seems like a good choice...and heck, if you all are worried it won't pan out, just make it a short range thread.  We can put the medium and long range stuff in this one.  And for the record, it is not because the 12z non-American runs were non-supportive of the GFS.  I have been posting a lot lately and just want to give others a shot.  But if you need me to, I will.   Bout time for a Dr. No meme, Stove.

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Stovepipe

Stovepipe

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12z Euro and Canadian seem way to suppressed.  I like the 12z, but hey...I wonder why!?  I am all for giving others a chance.  John1122 seems like a good choice...and heck, if you all are worried it won't pan out, just make it a short range thread.  We can put the medium and long range stuff in this one.  And for the record, it is not because the 12z non-American runs were non-supportive of the GFS.  I have been posting a lot lately and just want to give others a shot.  But if you need me to, I will.   Bout time for a Dr. No meme, Stove.

 

I like the idea of a short range thread.  We can always start a specific event thread later if/when we have something really blowing up.

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Carvers Gap

Carvers Gap

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I like the idea of a short range thread.  We can always start a specific event thread later if/when we have something really blowing up.

 

Seems like I remember you had the idea one season, and I thought it worked really well.  Some reasonable differences in the medium and LR that should keep this thread going. 

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Carvers Gap

Carvers Gap

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Another good post from DonSutherland today.  Here is an excerpt...

 

However, if one looks out to the Pacific, some of the guidance is suggesting that the SOI will rebound to positive and possibly strongly positive values within 10 days. During strong or super El Niño events, that development can coincide with the development of strong ridging over some part of Ontario or Quebec.

 

The ECMWF ensembles and GFS ensembles are in agreement about the development of just such ridging during the 240-hour to 288-hour timeframe. If that occurs, what should have been the locking in of a colder pattern on account of the blocking—something I had expected—could wind up being a more variable pattern with shots of cold alternating with warmer conditions from the Plains States to the East. The Middle Atlantic region, New England, and Quebec might have the highest probability of seeing net warm anomalies in the extended range if such a pattern develops. This issue will need to be revisited in coming days.

 

Finally, on the stratospheric front, a strong Wave 2 pulse is likely to develop over the next 10-15 days. However, it’s far too soon to be sure whether the wave will have the amplitude necessary to trigger a sudden stratospheric warming event. The ECMWF argues against such an event through the next 10 days, but 10 days is beyond a reasonably accurate forecasting horizon. Such events are only forecast with reasonable accuracy within a few days of their onset, so aside from noting the forecast development of the wave, more data will be needed to reach any conclusions about the likelihood of such an event. The infrequency of such events—about one every two winters—argues for holding off on conclusions until more data is available.

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nrgjeff

nrgjeff

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I will refer to early or middle of next week (Jan 19-20) as the Tuesday WAA. Later Wednesday timing the boundary layer may warm up too much; so in the interest of optimism, I will call it Tuesday. 

 

Tuesday features a lingering surface ridge from here to our north, which would work to keep cold air in place. GFS likes bringing out a weaker wave faster on Tuesday, with more subtle WAA. GFS is favorable for snow, iff it held together. However the Euro and CMC go with slightly slower and more WAA as the surface ridge fades. I infer from them frozen to slop Tuesday night into Wednesday if anything. Yuck!

 

It does make sense that an earlier arrival would be with a more subtle wave moving faster in the flow. Little bigger wave would move slower, and arrive later perhaps warmer. Which model suite is right? Will it even hold together? Since Tuesday is not a dynamic WAA setup above the low levels, my wish-cast preference is for the faster weaker wave - but holding together. (edited for content after 12Z runs - concern about wave holding together)

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Jed33

Jed33

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Posted

Yeah Carvers, I was wondering the same thing. Granted, I don't know if it'll be a hurricane for too long of the trip toward Greenland, but it will most likely have some sort of impact on the block. I don't know if it'll be what we want to see or not. It could help, could definitely hurt if it displaces the block.

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jaxjagman

jaxjagman

Posted
Posted

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1203 AM EST FRI JAN 15 2016

VALID 12Z MON JAN 18 2016 - 12Z FRI JAN 22 2016

PATTERN OVERVIEW...

THE PATTERN IS EXPECTED TO REMAIN PROGRESSIVE THROUGH THE END OF
NEXT WEEK...WITH THE FLOW LARGELY COMPRISED OF 2 OR MORE STREAMS
OF LOW AMPLITUDE AND SHORT WAVELENGTH. SOME GROWTH IN
AMPLITUDE...POSSIBLY PHASING...IS GENERALLY AGREED UPON BY THE
GUIDANCE TO DEVELOP NEAR OR EAST OF THE PLAINS/LWR MS VALLEY BY
DAY 6/THU...WHICH COULD RESULT IN A SIGNIFICANT LOW CROSSING THE
SOUTHEAST AROUND DAY 7/FRI. ALSO GENERALLY AGREED UPON BY THE
GUIDANCE IS A LONGWAVE TROUGH REACHING THE WEST COAST BY
FRI...WITH MORE HEAVY PRECIPITATION LIKELY FOR CALIFORNIA.

MODEL PREFERENCES AND CONFIDENCE...

MODEL CHOICES ARE LARGELY DECIDED UPON BY THE GREATEST CLUSTERING
OF SOLUTIONS...
PARTICULARLY THE ENSEMBLE MEANS...WHICH SHOW GOOD AGREEMENT
THROUGH THE ENTIRE PERIOD. THUS...A BLEND OF THE ENSEMBLE MEANS
FORMS THE BASIS FOR THE FORECAST. MIXED IN EARLY IN THE PERIOD IS
ABOUT 50 PERCENT OF THE 18Z GFS/12Z ECMWF WHEN THEY SUFFICIENTLY
AGREE WITH EACH OTHER AND THE ENSEMBLES. HOWEVER...THESE SOLUTIONS
DIVERGE QUICKLY BY DAY 4. THUS...THEIR USE IS QUICKLY
DROPPED...WHICH IS CONSISTENT WITH RECENT MODEL PERFORMANCES THAT
SHOW DETERMINISTIC SKILL FALLING QUICKLY AROUND DAY 4. CONFIDENCE
IS ABOUT AVERAGE THROUGH DAY 3...THEN BELOW AVERAGE FROM DAY 4
BEYOND.

SENSIBLE WEATHER HIGHLIGHTS...

THE WEST COAST...PARTICULARLY CALIFORNIA...WILL LIKELY RECEIVE
PERIODS OF HEAVY PRECIPITATION THROUGH THE PERIOD...INCLUDING MON
AS THE LEADING EDGE OF ANOTHER SIGNIFICANT TROUGH MOVES
ASHORE...AND AGAIN THU/FRI...AS AN EVEN STRONGER TROUGH NEARS THE
REGION. MULTI-DAY MODEL QPFS FOR EACH OF THESE EVENTS FOR
CALIFORNIA AND PARTS OF THE PACIFIC NORTHWEST INCLUDE 1 TO 2
INCHES OF LIQUID EQUIVALENT...WITH HIGHER AMOUNTS MORE THAN LIKELY
ACROSS THE HIGHER ELEVATIONS OF THE COASTAL
RANGES/CASCADES/SIERRAS IF THE MODELS ARE CLOSE TO CORRECT.

FARTHER EAST...COLD AND OCCASIONALLY BLUSTERY CONDITIONS WILL
PREVAIL FROM THE NORTHERN PLAINS ACROSS THE GREAT LAKES WITH SOME
LAKE EFFECT SNOWS LIKELY AS WELL. FROM THE S. PLAINS TOWARD THE
GULF COAST...MODELS ARE SUGGESTING A LOW TO MODERATE PROBABILITY
OF 2 SEPARATE LOWS CONSOLIDATING OR PERHAPS PHASING NEAR THE
CENTRAL OR EASTERN GULF COAST BY THU/FRI...POSSIBLY ALLOWING AN
EXPANDING SWATH OF PRECIPITATION TO DEVELOP. IF PHASING OCCURS AND
THE NORTHERN STREAM IS ABLE TO TRANSPORT SUFFICIENTLY COLD AIR
SOUTHWARD TOWARD THE LOW...WINTRY PRECIPITATION COULD EFFECT AREAS
FROM PARTS OF THE MIDDLE/LOWER MS VALLEY/TN VALLEY/S.
APPALACHIANS/SOUTHEAST BY THE END OF NEXT WEEK. IT IS WORTH
MONITORING THIS PARTICULAR SYSTEM OVER THE NEXT FEW DAYS AS THE
SPLIT FLOW PATTERN IS SUPPORTING LIMITED PREDICTABILITY AND
SHORTER LEAD TIMES ON THE DETERMINISTIC SCALE AT THIS TIME.

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