Winter 2014-2015 Pattern Discussion Thread III

[NCSNOW]

2 runs in a row from the can with big hit. Grit your spot on. Long ways to go watching how early next week shakes out.

[SnowGoose69]

2 runs in a row from the can with big hit. Grit your spot on. Long ways to go watching how early next week shakes out.

 

The Canadian has been hot lately, we'll see if that continues but its more or less had the last 2 events up in the Northeast with the other models playing catchup to it, it had the first system bombing to an extent into the Lakes and was suppressed with the clipper too, both verified.

[superjames1992]

2 runs in a row from the can with big hit. Grit your spot on. Long ways to go watching how early next week shakes out.

 

Kind of looks like ice to rain back to ice to me, though I'm not sure.  I don't have any text output and it's hard to tell with the color contouring I'm seeing whether it's just below or just above freezing.  There's a ton of precip as the coastal blows up, though. It ends up being a 1002 mb LP off of Cape Hatteras, which is a lot different than the other modeling.  It seems like the Canadian likes to overamp systems, though.

 

There's a HP that slides out as the storm starts and another one that slides in during the storm.  There's a lot of HPs in play with this one and none of them seem to be anchoring in on the modeling, so we might be in a situation where we either have cold filtering in or filtering out if we get a storm, and if it's as long-term as the Canadian shows, maybe both.  None of the HPs are necessarily classically-placed (they seem a little too far north to my layman eyes), but they're very strong, so they might do the trick.

 

I'm an overoptimistic weenie, but I think I like our chances of at least seeing a little frozen, even if it's very light.

[griteater]

sj - yeah, the Canadian brings the precip in on Sunday as ice, as sfc high is slipping off the mid-Atlantic coast.  Then the next high over the midwest doesn't work in as fast...so, it's a light icing event over to rain...with most of the precip in between the 2 highs.  It's a heavy precip producer again with a prolonged event

[griteater]

WPC leaning toward Euro ideas...

EXTENDED FORECAST DISCUSSIONNWS WEATHER PREDICTION CENTER COLLEGE PARK MD1233 AM EST WED JAN 07 2015VALID 12Z SAT JAN 10 2015 - 12Z WED JAN 14 2015...UNCERTAINTY ASSESSMENT/MODEL PREFERENCES...CONTINUE TO LIKE THE ECENS/ECMWF SOLUTION AND ITS SOUTHERN STREAMSOLUTION FOR THE GRADUAL SOUTH TO NORTH EROSION OF THEMODIFIED-ARCTIC SURFACE RIDGE---EAST OF THE MISSISSIPPI.LIKEWISE...WITH THE EMERGENCE OF MID-LEVEL ENERGY MIGRATION ACROSSTHE RIO GRANDE AND WESTERN GULF OF MEXICO. THERE IS SOME DEGREE OFVARIABILITY WITH TIMING OF INDIVIDUAL SHORTWAVES TRANSITING THEGULF OF MEXICO---BUT ESSENTIALLY---THE ECENS COULD BE FOLLOWED FORTHE ENTIRE DAY 4-7 PERIOD...FROM WEST COAST TO EAST COAST.THOUGHT THE MAIN REASON FOR THE VARIABILITY IN THE SOUTHERN STREAMWAS THE CURRENT NATURE/MOMENTUM OF THE WEAK/BENIGN UPPER-LEVEL LOWLOCATED INVOF 27N 120W. ITS PRESENCE...EVENTUAL BREAKDOWN...ANDMIGRATION INTO THE DOWNSTREAM FLOW OVER THE DESERT SOUTHWEST...RIOGRANDE...SOUTHERNMOST DIVIDE AND WEST TEXAS REGION HAS PROVIDEDTHE RUN-TO-RUN P-TYPE FORECAST CHALLENGE IN THE SOUTHERN PLAINS.IN GENERAL...THE WESTERN GULF OF MEXICO IS THE ONE REGION WHERE ANORTHWEST FLOW ALOFT AND NORTHERN STREAM 'SHEARING' INFLUENCE ISABSENT. AND THIS IS THE AREA WHERE THE DETERMINISTICGUIDANCE---THE 7/00Z DETERMINISTIC GFS INCLUDED---OFFER THE BESTPROSPECTS FOR LOW-LEVEL ORGANIZATION OF SOUTHERN STREAM ENERGYTHIS FORECAST PERIOD. AND ALTHOUGH...SOME RUNS LIKE THE IDEA OFTAKING SOUTHERN MID-LEVEL ENERGY NORTHEASTWARD INTO THELOWER-TO-MIDDLE MISSOURI VALLEY...THERE IS TOO MUCH NORTHWESTERLYSHEAR ALOFT AND DRY/MODIFIED-ARCTIC AIR TO GENERATE AND/ORMAINTAIN EVEN WEAK LOW-LEVEL CYCLOGENESIS. WITH THIS IN MIND---ADAY 4-5 FRONTAL PASSAGE (WPC GRAPHICS) WILL BE FOR THE MOST PARTDRY---BUT WILL ALLOW SOME COOLER AIR TO REINFORCE THE SURFACERIDGE DOWNSTREAM OVER THE NORTHEAST QUARTER OF THE NATION...THECENTRAL PLAINS AND REJUVENATE A LOCALIZED LAKE-EFFECT SNOW SHOWERPATTERN.THE MEDIUM RANGE FOCUS SHOULD REMAIN CENTERED IN THE WESTERN GULFOF MEXICO...AND FOR MORE THAN ONE MID-LEVEL IMPULSE TO BEGINMIGRATING NORTHWARD INTO THE COLD AIR. AND BEING A MEDIUM RANGEFORECAST...IT LEAVES SOME LEE-WAY FOR ADJUSTMENT FOR SOME WEAKERENERGY TO EJECT ATOP THE COLD AIRMASS AND SPREAD ACROSS THE OZARKSAND MID-MS AND LOWER OHIO VALLEYS. THE PRECIPITATION MIGHT BE ONTHE LIGHT SIDE...BUT COULD CAUSE TRAVEL ISSUES. OVERALL...THOUGHTTHE SCENARIO---A SLOWER 'FLUSH OUT' OF THE ARCTIC HIGH...WAS BESTSERVED BY THE ECENS/ECMWF IDEA....SENSIBLE WEATHER...BELOW NORMAL TEMPERATURES AND COLD HIGH PRESSURE CONTINUES ACROSSTHE NORTHEAST AND GREAT LAKES---WITH SNOWFALL POTENTIAL IN THELAKES AND FAVORED UPSLOPE TERRAIN.A BROAD-SCALE OVER-RUNNING PRECIPITATION PATTERN FOR PORTIONS OFTEXAS...SOUTHERN OKLAHOMA AND A LARGE EXPANSE OF THE GULF COASTAND INTERIOR SOUTHEAST BEGINS TO EMERGE DURING THIS MEDIUM RANGEPERIOD.VOJTESAK

[superjames1992]

sj - yeah, the Canadian brings the precip in on Sunday as ice, as sfc high is slipping off the mid-Atlantic coast.  Then the next high over the midwest doesn't work in as fast...so, it's a light icing event over to rain...with most of the precip in between the 2 highs.  It's a heavy precip producer again with a prolonged event

 

Yeah, I see now on Tropical Tidbits.  I was looking at WB (and initially Meteociel.fr) and WB's temperature contouring for the Canadian is awful since there's really no way to distinguish between 33/RN and 31/ZR (they look the same).  Looks like maybe a high-end advisory or low-end warning criteria event for the CAD-primed regions prior to the changeover?

 

Looks like it gets close to ZR towards the end of the storm, but not quite.

[griteater]

Para was a pretty good ice hit for typical NC/SC damming areas.  It has a 1051mb sfc high just north of NY state as precip is moving in Tues morning.

[superjames1992]

The Euro is a very cold rain. We've basically got 3+ different solutions right now with the GFS, Euro, and GGEM not even coming close on agreeing on timing, so we'll see.

[deltadog03]

on life support with this one folks.....

[deltadog03]

On a good note...I really think the EURO is about to have an AWESOME look by day 7-10

[griteater]

Euro splits the uprights moving a cold rain through the Carolinas on Monday in between the 2 surface highs - one off the NC Coast (which is farther south than the other models) and another 1040mb high over Nebraska.

 

Another shortwave is digging into the southwest

[deltadog03]

Grit, and others...hmmm..euro is gonna pull something here.....

[superjames1992]

Wow, the Euro looks like it might pop a fantasy storm on D8 or D9.

Looks like it might go Miller B to me. There wasn't even a storm on the 12z run aside from some thunderstorms in the Gulf.

EDIT: Inland runner.

[deltadog03]

yup inland runner, but still have at least something showing up in that range..hell, lets get to the arctic blast first..lol

[griteater]

Grit, and others...hmmm..euro is gonna pull something here.....

Wow, the Euro looks like it might pop a fantasy storm on D8 or D9.

Looks like it might go Miller B to me. There wasn't even a storm on the 12z run aside from some thunderstorms in the Gulf.

 

It's a sweet nino-like, split flow pattern, but cold air lacking out front.  Hard to get the cold air to press far enough south AND hold without the Atlantic side blocking.  Dr. No living like a king, at least tonight.

[deltadog03]

For real. Who pissed her off again? Lol

Sent from my iPhone using Tapatalk

[superjames1992]

Nice Polar Vortex Part 2 at the end of the Euro run.

[mackerel_sky]

6z gives light rain to most on Tuesday , yippee!

Maybe some ice in Person county! The wedge looks to build in the next day!

[calculus1]

The latest long-term AFD from GSP:

 

 

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
AS OF 315 AM WEDNESDAY...THE LATEST MODEL GUIDANCE AGREES THAT THE
EASTERN UPPER LONGWAVE TROF WILL LIFT NE...AS SPLIT FLOW ACRS THE
WESTERN STATES BECOMES MORE ACTIVE HEADING INTO THIS WEEKEND. A
SOUTHERN STREAM SHORTWAVE TROF WILL CROSS NORTHERN MEXICO...AND
LIKELY ACTIVATE AN INVERTED SFC WAVE INVOF THE NW GULF COAST REGION.
MEANWHILE...A SLOWLY MODIFYING CANADIAN AIR MASS WILL REMAIN ACRS
THE OHIO VALLEY AND MID ATLANTIC STATES...HELPING KEEP A SUPPLY OF
COOL/DRY AIR INTO THE AREA...POSSIBLY STARTING OUT AS A CLASSIC CAD
EVENT ON SATURDAY. THE 00Z OP MODELS ALL SEEM TO CONTINUE THE
DELAYED ONSET TRENDS ON POP...WITH THE AREA MORE LIKELY REMAINING
DRY UP THRU MOST OF THE DAY ON SUNDAY. BLENDING IN WITH THE PREV
FCST...I STILL HAVE POPS RAMPING UP ON SUNDAY TO CHC ACRS THE
SOUTHERN THIRD OF THE CWFA. TEMPS MAY SUPPORT FREEZING RAIN AT ONSET
SUNDAY...BUT THEN CHANCE OVER TO ALL RAIN...AS TEMPS WARM INTO THE
UPR 30S TO MID 40S. FROM THERE...CONFIDENCE IS LOWER ON WHAT THE
LLVL THERMAL PROFILES WILL BE LIKE ONCE BETTER FORCING AND MOISTURE
ARRIVE WITH THE SOUTHERN STREAM WAVE FROM SUNDAY NIGHT THRU TUESDAY.
THE GFS HAS A NOTABLE WINTRY MIX/FREEZING RAIN EVENT POSSIBLE FOR
THE NC ZONES...AS COLD AIR DAMMING STRENGTHENS. THE ECMWF AND CMC
HAVE MUCH WEAKER DAMMING...AND SUPPORT MAINLY AN ALL-RAIN EVENT.
CONFIDENCE IS STILL TOO LOW TO WARRANT A WINTRY PRECIP MENTION IN
THE HWO AT THIS TIME.

[franklin NCwx]

Euro ensembles and GFS ensembles still bullish on a coastal system day 7-8.

[BullCityWx]

Euro ensembles and GFS ensembles still bullish on a coastal system day 7-8.

 

Control was really close to a snow event around hour 200 or so. 

[metwannabe]

Euro ensembles and GFS ensembles still bullish on a coastal system day 7-8.

Yes they are but the airmass is so marginal it would be nice to have a fresh supply of cold air

[burgertime]

I said it before with indices and the look at 5h that coastal storm is probably our best bet for winter weather around here. I'm starting to get worried that after this big cool down we might go back to just a plain boring pattern where we are seasonal at best. Hopefully the OP Euro is on to something with another PV coming down. If we get on repeat with those winter weather will happen at some point as one PV drop will be timed with some sort of energy. 

[packbacker]

Euro ensembles and GFS ensembles still bullish on a coastal system day 7-8.

That is interesting...the pattern is still so progressive, which actually could help us.

It's good to see the OP EURO where its at and the ENS mean where it's at. The members look good too, no cutters.

[SnowNiner]

That is interesting...the pattern is still so progressive, which actually could help us.

It's good to see the OP EURO where its at and the ENS mean where it's at. The members look good too, no cutters.

 

 

Yeah, this looks very nice.  I like the placement of the ridge/trough better than it's been.  It's a bit further west.  It looks more like it could pop a gulf storm right in the right place.  It's progressive after this but it looks pretty good. 

 

[Cold Rain]

5 maps at 144 hr.  First, here is the 0z GFS.  The blue X in the upper left is a northern stream shortwave near Maine, behind which a strong 1040 mb high pressure is building in (upper right) over the Lakes and into the NE.  You'll also notice the surface ridging (wedging) building down east of the Apps (lower right).  Also notice the upper level flow, as indicated by the green arrow in the upper left.  It is out of the SW.  The point of that is to show that there is a long SW fetch with embedded pieces of energy.  You think the model understands the exact timing and strength of those at this lead?  We've also seen these impulses overperform this year.  Even jshetley has to acknowledge the abundance of precipitation events in this "nina-like" pattern.  I have also highlighted the moisture field in the lower left to show where precipitation could be falling.

 

I would argue that given the setup in this depiction, precipitation would be under-modeled and the strength of the cold air damming would be also under-modeled.  The timing of the cold + precipitation works out well.  This looks like a frozen-freezing precipitation scenario, as modeled...for many:

 

 

Here is the 6z GFS.  It also shows the shortwave in the northern stream in roughly the same position as the 0z.  It appears less consolidated.  A strong 1040 mb high is building in, but not quite yet in damming position.  Therefore, you see less of a damming signature.  Also, moisture is a bit less.  This could be due to the flatter west-east flow (upper left) or the model just not seeing a piece of energy in the southern stream well.

 

This depiction looks like a rain to ice setup, maybe starting out frozen for NW areas:

 

 

Next up, we have the 0z CMC.  The northern stream shortwave appears to be a tick north of the GFS solutions, which takes the confluence zone a tick north, which keeps the high pressure zone a tick north.  You still see some wedging though, in the upper right.  The high is again strong at 1040 mb.  This model wants to spin up a low along the coast, which, if correct, could inject warmer air into the mid layers, as the model is showing. There is a nice moisture fetch and of course, a more robust precipitation response.

 

Unfortunately, it appears to be rain for many, with perhaps some ice in the NW zones.  Is this solution right?  I prefer a more strung out system than a strengthening low, at this point.  Anyway, subtle differences with the northern stream wave have an impact on how and when the high builds in:

 

 

Next is the 0z Navgem.  The northern stream wave looks fairly robust, but it's timing is just a bit slower.  Thus, strong HP is still back west a bit.  The southern stream moisture fetch looks pretty good, though the precipitation output is meager on this panel.  The timing of both the cold and the moisture influx is a bit slower on this model, but it is very possible, again, for the model to be keying in on the wrong piece of energy or under-modeling the precip.  A winter storm is not out of the question, according to this model:

 

 

Finally, we have the 0z Euro at 144. The Doc.  The King.  The crème de la crème.  This model shows a broader confluence zone back west, which keeps the high from building in quickly.  This allows plenty of moisture to flow in ahead of the high.  The high is also weaker at 1036 mb, compared to the rest of the models, which are all consistently at 1040 mb at this time frame.  The northern stream wave tracks NE, causing the high to build eventually transition NE instead of east and south.  The King suggests rain.

 

 

In summary, as you can see, all of the models have similar features in similar places at similar times.  But the slight differences in location, timing, and trajectory mean a great deal to the final outcome.  A winter storm is most certainly on the table at this point.  So is a rain storm.  The keys to remember are:

 

1)  Models almost always underestimate CAD at this lead.  If there is CAD from that strong of a high pressure, it will be colder than currently shown.

 

2)  The southern stream's precipitation producing efficiency has been under-modeled many times this season.  I expect dry conditions to be the least likely outcome here.

 

3)  It always comes down to timing.  This isn't the best pattern for a winter storm.  But it's a workable one.  If the northern stream can press a bit, like the GFS shows, wedging should be strong.  Timing of southern stream impulses, which may not even be on the grid yet, is always difficult for models at this lead.

 

Here's how I would rate chances for the possible outcomes:

 

Dry: 10%

All rain:  25%

Major winter storm (mostly frozen for CAD zones and just outside of CAD zones): 25%

Minor winter storm (mix of rain and frozen for CAD zones, maybe extending just south and east):  40%

 

I would favor CAD and adjacent areas for either rain to ice or ice to rain, depending on the exact timing.  But I do expect someone to see some winter weather by the time all is said and done.

 

 

 

[packbacker]

Yeah, this looks very nice.  I like the placement of the ridge/trough better than it's been.  It's a bit further west.  It looks more like it could pop a gulf storm right in the right place.  It's progressive after this but it looks pretty good. 

 

 

Agreed, the past few runs of the EPS the ridge is getting taller, a tick further west and the EC trough is in a good spot and is getting a touch sharper.  

[packbacker]

 

1)  Models almost always underestimate CAD at this lead.  If there is CAD from that strong of a high pressure, it will be colder than currently shown.

 

2)  The southern stream's precipitation producing efficiency has been under-modeled many times this season.  I expect dry conditions to be the least likely outcome here.

 

3)  It always comes down to timing.  This isn't the best pattern for a winter storm.  But it's a workable one.  If the northern stream can press a bit, like the GFS shows, wedging should be strong.  Timing of southern stream impulses, which may not even be on the grid yet, is always difficult for models at this lead.

 

Here's how I would rate chances for the possible outcomes:

 

Dry: 10%

All rain:  25%

Major winter storm (mostly frozen for CAD zones and just outside of CAD zones): 25%

Minor winter storm (mix of rain and frozen for CAD zones, maybe extending just south and east):  40%

 

I would favor CAD and adjacent areas for either rain to ice or ice to rain, depending on the exact timing.  But I do expect someone to see some winter weather by the time all is said and done.

 

Great writeup, be nice to sneak a little ice next week, but I don't get overly pumped  up about freezing rain.

 

This is looking nice, be nice if the other models followed suit.

[burgertime]

OK preface with it's the 12z NAM at hour 84...but just look at the 5h map and you can see a lot of chunks of energy in the flow. I'm with you CR it would be foolish to jump on any one solution right now. I think we are more likely to end up with some kind of ZR or frozen drizzle over rain/dry but that's just a feeling right now. 

[Cold Rain]

That MJO diagram looks nice.  But yeah, I'd love to see some other models jump on.  GFS takes it around the horn.  The Euro, which had it hanging in phase 5, now moves it to phase 6 and into the COD.  That's progress, I guess.

 

Where we continue to falter is with blocking.  We have no signal for that...STILL.  The AO and NAO are strongly positive and are forest to fall to neutral, at best.  We need a reshuffling there, big time.