2013 Fall Medium Range Discussion

[easternsnowman]

This is as bad as it gets for the east. There goes all our snowcover...nice solid 12" of snowpack. beautiful winter scenes and great skiing. soon to be ravaged. what a shame.

Let's get our spring now and hopefully by late march we'll have summer!

[am19psu]

Days 8-20 look quite cold for the CONUS as a whole, but mostly for the central CONUS, with possibly cross polar flow involved ...The E, and especially the NNE look warmish in this period. After that, my guess is for the mean trough to shift E.

 

Yup. Seems like a reasonable place to start. Kinda bearish on the MJO signals that Roundy is showing though. Been too strong and fast with MJO waves since the fall.

[baldereagle]

In a few more weeks and spring will be tantalizingly, temptingly beckoning the diehard midatlantic flock of snow geese......

[WEATHER53]

Man I thought KA was off deep end when he went +2ish for DC, and +5 for Jan and Feb but so far he has been closer than anyone.

[Srain]

Days 8-20 look quite cold for the CONUS as a whole, but mostly for the central CONUS, with possibly cross polar flow involved ...The E, and especially the NNE look warmish in this period. After that, my guess is for the mean trough to shift E.

 

 

 

 

[wxmx]

01022012 12Z Euro Ensembles 00zECMWFENS500mbHeightAnomalyNH240.gif

 

01022012 12Z GEFS 12zgfsensembles500mbHeightAnomalyNH240.gif

 

01022012 12Z GGEM 12zGGEMEnsembles500mbHeightAnomalyNH240.gif

 

Modeling this far out is quite on sync. Usually a good sign and confidence booster.

[tacoman25]

The 18z ensembles are much stronger/more amplified with the -EPO ridge, and sooner. Far more than any previous run.

[Isotherm]

The 18z ensembles are much stronger/more amplified with the -EPO ridge, and sooner. Far more than any previous run.

 

 

As we've discussed in the past, this is ultimately the key to getting severe and widespread cold into the US. We saw a -EPO burst in late December and we're seeing the effects right now, with arctic chill across New England and the Mid-west. However, heights are lowering rapidly in AK and thus the arctic air isn't pressing very far southward (will be confined to the nern tier as well).

 

Looks to me like this upcoming -EPO pulse will be more stable in that the mid level ridge doesn't simply pinch off, but maintains in a meridional N-S fashion up to the pole. I think we'll see the AO begin to trend back negative as well, in tandem with the EPO decline.

 

The EPO should be trending negative as the Eastern warm period is occurring next week. Consequently, the warm surge shouldn't be a long duration event as the north pacific is quickly reshuffling and will lower heights in the US thereafter. Probably an East Coast ridge hanging on a bit longer, but I don't think we're looking a prolonged major positive departures.

 

 

 

Then by the 12th the EPO ridging has extended to the pole and the AO is clearly negative.

 

 

[tacoman25]

Agreed, Isotherm, and look at what that small burst of -EPO produced over the past week...just imagine if the 18z solutions verify.

 

 

[donsutherland1]

At 6 am this morning, the temperature at Albany, NY was -3°. That's the first subzero low there since February 11, 2011. It likely marks the height of the current cooler period, as a period of moderation continues to lie ahead beginning in the next 5-7 days. With some of the guidance suggesting that the AO could head negative in the extended range (after going positive in the near-term) and the EPO could again become neutral or negative, the milder spell very likely does not mark the end of winter so to speak.

[donsutherland1]

This morning, the AO stood at +0.086. That ends a 39-day stretch during which the AO was negative. The ensemble guidance continues to indicate that blocking will likely redevelop in the extended range.

[Srain]

The medium range guidance continues to advertise a rather potent storm system crossing the Great Basin and across Texas next week. With the split zonal flow and a return flow off the Gulf becoming well established, concern grows that a significant severe episode may develop across the Southern Plains with higher elevation heavy snow fall depending on the eventual track of this storm. Many are traveling to Austin TX for the AMS National Meeting next week, so it is worth mentioning on our Main Page Medium Range Discussion thread.

 

 

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
102 AM EST THU JAN 03 2013

VALID 12Z SUN JAN 06 2013 - 12Z THU JAN 10 2013

...SOUTHERN STREAM EXPECTED TO BECOME AN ACTIVE WEATHER MAKER BY
MIDDLE OF NEXT WEEK...

FEW CHANGES OVERALL TO THE FORECAST PHILOSOPHY FROM YESTERDAY. THE
MEDIUM RANGE FORECASTS AND SPLIT-FLOW PATTERN CONTINUES TO BE
HANDLED REASONABLY WELL. IN FACT...THE OPERATIONAL 2/12Z GFS AND
2/12Z ECMWF WERE PREFERRED 50/50 BLEND THROUGH DAY 5.

NORTHERN STREAM FLOW SHOULD REMAIN PROGRESSIVE WITH RESPECT TO THE
DEVELOPMENT OF SURFACE WAVES MIGRATING ACROSS SOUTHERN
CANADA...AND WITH A MODERATE 'KICKER' WAVE ENTERING THE PACIFIC
NORTHWEST ON DAY 6. THE 2/12Z ECMWF ENSEMBLE MEAN WAS A GOOD
APPROXIMATION OF THE OVERALL FLOW PATTERN...AND IN
PARTICULAR...WITH A SOUTHERN STREAM SYSTEM EJECTING OUT OF THE
SOUTHERN HIGH PLAINS FROM DAY 5 TO DAY 7. MEDIUM RANGE GRAPHICS
BEGIN TRACKING A MODERATE CYCLONE NORTHEASTWARD ACROSS THE
SOUTHERN ROCKIES AND SOUTH CENTRAL PLAINS BY DAY 6 AND INTO THE
MIDWEST ON DAY 7. THE ECMWF ENSEMBLES WERE GIVEN HIGHER WEIGHTING
(60%) FOR THE DAY 6-7 PERIOD TO MITIGATE THE TIMING DIFFERENCES
PRESENTED BY THE OPERATIONAL 12Z GFS/ECMWF.

ITS SOLUTION ALOFT (THE ECMWF ENSEMBLE MEAN) IS A GOOD MIDDLE
GROUND FOR THE PROGRESSION OF THE SOUTHERN STREAM SYSTEM...BEING
FASTER THAN THE PREVIOUS 2 OPERATIONAL EC RUNS (2/12Z-2/00Z)
ACROSS SOUTHERN CA/AZ AND A TAD SLOWER THAN THE PREVIOUS 2
OPERATIONAL GFS RUNS (2/12Z-3/00Z) ACROSS NM AND TX/OK. DID SEE
SOME MERIT IN USING THE 12Z OPERATIONAL GFS/ECMWF (20%/20%) FOR
DAY 6-7...TO HANDLE THE SURFACE DETAILS IN BOTH THE NORTHERN AND
SOUTHERN STREAM ACROSS NORTH AMERICA. THE 3/00Z GFS LOOKED TOO
FAST AND WAS A SOUTHERN OUTLIER BY LATE DAY 6 INTO DAY 7 ACROSS
NORTHERN TEXAS.

VOJTESAK
 

[okie333]

Unreal...

 

[pondo1000]

Unreal...

 

Unreal meaning what?

[am19psu]

Unreal meaning what?

 

Extremely -AO/+PNA forecasted by the GFS in 2 weeks

[BxEngine]

Extremely -AO/+PNA forecasted by the GFS in 2 weeks

Not sure if this is the appropriate spot to ask....but why does it seem that models sometimes seem to "rush" pattern changes? Is it just anecdotal? Or is there legitimacy to that?

[pondo1000]

Extremely -AO/+PNA forecasted by the GFS in 2 weeks

 

Thank you! That would be nice, but I guess we have to wait and see. That is a ways away

[am19psu]

Not sure if this is the appropriate spot to ask....but why does it seem that models sometimes seem to "rush" pattern changes? Is it just anecdotal? Or is there legitimacy to that?

 

It's definitely an appropriate spot, but I don't have a good answer. Hopefully Wes or dtk sees this and can do a better job illuminating.

[SnowNiner]

Unreal meaning what?

 

Do I read that right that the polar vortex is split up and it sets up a good chunk in south east canada?  It seems like the cold would be coming soon with that set up (if I'm reading it correctly). 

[Srain]

Looking stormy and cold across the West and Plains once we get beyond our brief warm up next week.

[Chinook]

Last 30 days SOI was -8.2, although the last 90 days averaged SOI was 0.0. It appears that in the atmosphere, December looked a bit more like El Nino. Of course, as water temperatures go, it seemed pretty close to neutral. I wonder if the subtropical jet was stronger than normal.

[tacoman25]

The 12z Euro ensemble images aren't showing up on Alan's page. Anyone have them?

[wxmx]

We could start seeing 1060mb+ highs near AK and NW Canada in the long range models soon. The PV around HB and 560dm+ heights developing in AK are a recipe for severe arctic cold.

[SnowNiner]

We could start seeing 1060mb+ highs near AK and NW Canada in the long range models soon. The PV around HB and 560dm+ heights developing in AK are a recipe for severe arctic cold.

 

Does that placement of the PV and the ridging in Alaska have anything to do with the SSW? 

[wxmx]

Does that placement of the PV and the ridging in Alaska have anything to do with the SSW? 

 

Very probably, at least partially to a good degree.

[Srain]

A very active pattern continues to develop across the West and Plains during the medium/long range. A potent close core low will move inland along the Pacific Coast on Sunday setting the stage for a myriad of potential high impact weather events. There are both higher elevation snow and even a severe potential involved with this feature. Looking ahead to late next week, the ensembles suggest heights build over Alaska and the EPO transitions to strongly negative setting the stage for a stormy and colder regime across the West and the Plains.

 

 

 

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
940 AM EST FRI JAN 04 2013

VALID 12Z MON JAN 07 2013 - 12Z FRI JAN 11 2013

THE UPCOMING MEDIUM RANGE FORECAST CONTINUES TO FOCUS ON TWO
DOMINANT FEATURES ALOFT...A TROUGH OVER THE WEST AS OF EARLY MON
AND THEN EJECTING EWD THEREAFTER FOLLOWED BY A LARGER SCALE TROUGH
EXPECTED TO AMPLIFY INTO THE W-CENTRAL CONUS BY LATE NEXT WEEK.
INTERESTINGLY THERE IS GENERALLY GREATER SPREAD WITH DETAILS OF
THE INITIAL WRN TROUGH AND ASSOCIATED SENSIBLE WEATHER IMPACTS AS
THE FEATURE EJECTS OUT OF THE WEST...THAN WITH THE LATER-PERIOD
TROUGH THAT IN THE MEAN SHOULD SUPPORT A SURFACE FRONTAL SYSTEM
FROM THE GREAT LAKES SWWD INTO THE PLAINS BY DAY 7 FRI.

ALREADY AT THE START OF THE PERIOD THERE REMAINS SIGNIFICANT
DIFFERENCES FOR THE LEADING WRN TROUGH...WITH THESE DIFFS BECOMING
FURTHER MAGNIFIED WITH TIME.  SOLUTIONS RANGE FROM THE PAST FEW
ECMWF RUNS THAT TRACK A SLOW CUTOFF LOW NEAR THE WRN US-MEXICO
BORDER AND THEN NEWD INTO THE PLAINS TO THE UKMET THAT HAS OFFERED
A MORE NRN STREAM PHASED/PROGRESSIVE TROUGH. IN VARYING WAYS MOST
RECENT GFS AND CANADIAN RUNS HAVE BEEN PROGRESSIVE...BUT THE
LATEST 06 UTC GFS HAS SLOWED DOWN.  FROM A LONGER TERM PERSPECTIVE
ECMWF RUNS HAVE BEEN CONSISTENT WITH THEIR SEPARATED CLOSED LOW
ALBEIT WITH A MODESTLY FASTER TREND OVER THE PAST COUPLE OF
DAYS...WHILE A NUMBER OF GFS RUNS PRIOR TO 12 UTC YESTERDAY ALSO
HAD A SEPARATED CLOSED LOW. RECENT RUNS OF THE GEFS SHOWED SOME
FASTER TREND WITH THE SRN ENERGY...BUT NOT THE LATEST 00 UTC ECMWF
ENSEMBLE MEAN.

THAT 00 UTC ECMWF ENSEMBLE MEAN ALONG WITH THE COMPATABLE ECMWF
SEEMS TO CURRENTLY OFFER THE MOST APPEALING OPTION WITH GREATER
FLOW SEPARATION THAN THE ALTERNATE PROGRESSIVE CLUSTER OF
SOLUTIONS. HPC GUIDANCE HAS BEEN PRIMARILY DERIVED FROM A BLEND OF
THESE LESS PROGRESSIVE SOLUTIONS.  THIS BLEND OFFERS GOOD HPC
CONTINUITY AND SEEMS A GOOD FIT WITH RECENT FLOW HISTORY. MORE
IMPORTANTLY...LATEST WATER VAPOR IMAGERY LOOPS ACROSS THE ERN PAC
SEEMS TO CLEARLY FAVOR AMPLIFICATION INCLUDING SRN STREAM CLOSED
LOW FORMATION AND THESE TYPES OF FEATURES ARE RARELY VERY
PROGRESSIVE.  A LOOK AT ENSEMBLE PERTUBATIONS OVER THE FIRST 12-24
HOURS OF THE FORECAST CYCLE SHOWS ECMWF ENSEMBLE MEMBERS THAT ARE
SIGNIFICANTLY MORE AMPLIFIED THAN THOSE IN THE GEFS THAT SEEM IN
CONTRAST TO AFOREMENTIONED WATER VAPOR ANALYSIS.

ON THE OTHER HAND THERE IS BETTER THAN AVERAGE AGREEMENT WITH THE
TRAILING LARGER SCALE MID-UPPER LEVEL TROUGH FORECAST TO AMPLIFY
INTO THE WEST LATER NEXT WEEK.  LATEST ENSEMBLE MEANS AND NOW EVEN
GFS/ECMWF RUNS SEEM TO PROVIDE A REASONABLE AND POTENT COMPOSITE
SOLUTION...BUT HPC HAS UTILIZED A ECMWF/ECMWF ENSEMBLE MEAN BLEND
TO BETTER FIT A RECENT GUIDANCE TREND TOWARD ENHANCED
AMPLIFICATION.

SCHICHTEL

[usedtobe]

Here's today's D+11 CPC superensemble and temp composites for the analog dates at D+11 and D+13.  Note that the plains get a real arctic shot that slowly oozes eastward.

 

 

 

 

Now the temp composite for the D+11 day analogs.

 

 

Now the D+13 which would be equivalent to around Jan 17 or so.

By D+14 the cold air event gets to DC thugh the coldest still is in the plains and midwest.

[dtk]

It's definitely an appropriate spot, but I don't have a good answer. Hopefully Wes or dtk sees this and can do a better job illuminating.

 

I do not think I have a good answer for this, but I'll throw out some conjectures for fun.

 

For global NWP models in the 7+ day range (here I'm referring to both deterministic and ensemble), there is a transition from an initial value problem to a boundary problem (surface, external forcing, etc.), particularly as we still run these models uncoupled from the ocean/land [in contrast to the CFSv2 or Euro weekly/seasonal dynamic guidance, which are in fact fully coupled to ocean models....which has huge implications for the types of phenomena that can be predicted]. 

 

To account for this in the more NWP-type guidance, there is generally a relaxation of certain quantities back toward climatological states (particularly things like SST, surface conditions, etc.), which I suspect can trigger the atmospheric state back toward "preferred regimes". 

 

I will have to think about this some more, but the above is the thought that immediately comes to mind.

[donsutherland1]

Here's today's D+11 CPC superensemble and temp composites for the analog dates at D+11 and D+13.  Note that the plains get a real arctic shot that slowly oozes eastward.

 

 

 

Jan_4_500hgt_comp_sup814.gif

 

Now the temp composite for the D+11 day analogs.

 

 

Now the D+13 which would be equivalent to around Jan 17 or so.

Jan_4_analog_D13.gif

By D+14 the cold air event gets to DC thugh the coldest still is in the plains and midwest.

 

Great discussion, Wes.

 

I like the idea of the cold slowly oozing to the East. Some runs of the operational GFS have been more aggressive, but it seems that the guidance in the extended range is usually a little too quick when it comes to pattern changes.

 

Having said that, I continue to believe that the period of moderation that is coming up will be a temporary one. With a stronger signal for an EPO- and return to AO- in the extended range, I see little reason to change my thinking about the temporary nature of the returning milder pattern.

[wxmx]

Also, the MJO is unfavorable for the East now. I expect it to move toward more favorable phases in the last week of the month.

 

The GWO phase diagram is showing a low amplitude wave toward phase 4, which would favor a NE Pac ridge, which jointly with rising heights near the arctic, favor a full latitude ridge in that region, with a dipping EPO, that the models have been adamant with. Thus, my initial idea of a much colder CONUS for most of January, with the the possible exception near the east coast (which I expect to reverse by the end of the month) is looking good.