1370 replies to this topic

[wxmx]

There's little indication of high latitude blocking, other than regional/transient/weak in at least 2/3 weeks... Polar night jet is in full force, and I see no forcing messing with it in the medium range.

OTOH, tropical forcing will become even less favorable, with a typical Niña setup, with +OLR anomalies in the C and W Pac and -OLR translating from the IO to around Indonesia...this will only help enhance the Aleutian ridge. Air masses source region will be mostly from the Pacific, and this setup usually chokes any kind of artic air intrusion, so even if it doesn't look like we will be immersed in a zonal flow regime, any amplification will lack artic cold air.

Whatever pattern change that might occur, it looks like it will happen after Dec 10th, not before.

[thunderbolt]

wxmx, on 18 November 2011 - 11:56 AM, said:

There's little indication of high latitude blocking, other than regional/transient/weak in at least 2/3 weeks... Polar night jet is in full force, and I see no forcing messing with it in the medium range.

OTOH, tropical forcing will become even less favorable, with a typical Niña setup, with +OLR anomalies in the C and W Pac and -OLR translating from the IO to around Indonesia...this will only help enhance the Aleutian ridge. Air masses source region will be mostly from the Pacific, and this setup usually chokes any kind of artic air intrusion, so even if it doesn't look like we will be immersed in a zonal flow regime, any amplification will lack artic cold air.

Whatever pattern change that might occur, it looks like it will happen after Dec 10th, not before.

so are you optamistic about patter change?

[am19psu]

wxmx, on 18 November 2011 - 11:56 AM, said:

There's little indication of high latitude blocking, other than regional/transient/weak in at least 2/3 weeks... Polar night jet is in full force, and I see no forcing messing with it in the medium range.

OTOH, tropical forcing will become even less favorable, with a typical Niña setup, with +OLR anomalies in the C and W Pac and -OLR translating from the IO to around Indonesia...this will only help enhance the Aleutian ridge. Air masses source region will be mostly from the Pacific, and this setup usually chokes any kind of artic air intrusion, so even if it doesn't look like we will be immersed in a zonal flow regime, any amplification will lack artic cold air.

Whatever pattern change that might occur, it looks like it will happen after Dec 10th, not before.

[CoastalWx]

The european models (both UK and EC) continue to shift the wave through P4-5 and into p6. That american models don't seem as bullish right now. IMO, I really would like to see a modest wave go into p6 and eventually 7 so that we can try to get some tropical forcing help, to dislodge the vortex up north. All the ensembles look somewhat better, but it still is no where near ideal, even at the end of their runs. Some runs show ridging into the GOA and western Canada. That's nice, but we still have lower heights across AK and the EC ensembles of troughing in the sw which will try and pump up the se ridge. Of course it doesn't mean some can sneak in 1 or 2 snow events, but the overall pattern still looks rather balmy for many in the east and southeast.


 EMON_phase_51m_small.gif   44.62K   1 downloads


 UKME_phase_23m_small.gif   28.86K   0 downloads

[CoastalWx]

On the EC ensembles, there does appear to be some split flow with weak ridging in western Canada and a trough in the sw. It may set up for a gradient pattern somewhere in the nrn US or southern Canada as colder air tries to come south, but the trough over the sw acts to pump up heights over the east.

[JBG]

uncle W, on 15 November 2011 - 09:14 AM, said:

this November reminds me of 1975 when we set the record for the warmest November at the time...It came after a brief cold shot minus the snow at the end of October...I had a handfull of analogs this year but only a few were mild into January with colder endings...1971 and 1974 were on the list and as of today they are my top two for now...1973 is not far behind...

All probably good analog as they were cold PDO phase La Ninas. And all depressing in varying degrees.

[Srain]

The medium range guidance continues to advertise a significant trough with a robust storm complex in the S Plains next weekend. While a lot of details remain to be seen, there does appear to be a cool down lurking in the medium range for the Great Plains Region. As yet another in a series of upper lows tap into some deep tropical moisture associated with the STJ and with a future Hurricane Kenneth in the EPAC added to the mix, there could be an active period to end the long Thanksgiving Holiday period for the Eastern 2/3rds of the CONUS...

Attached Files

•  11192011 Euro GFS Compare test8.gif   94.57K   0 downloads

[Hailstorm]

Those ECMWF medium-range maps also show the potential for an organized severe weather event for some parts of the Eastern US after Thanksgiving, given the strong temperature gradient in the mid-levels and low-levels combined with the tropical moisture and the deep trough.

[am19psu]

Another transient cool shot Mon-Wed next week for the East Coast. After that, MJO guidance would suggest that the warm pattern will continue for a while across the East. The new Euro ensembles show the MJO stalling near the P3/P4 border, but the statistical guidance from Paul Roundy shows the wave continuing as normal into P5/P6 by mid-December. All of those phases are generally warm ones for the EC in December.

[wxwatcher91]

am19psu, on 21 November 2011 - 07:17 AM, said:

Another transient cool shot Mon-Wed next week for the East Coast. After that, MJO guidance would suggest that the warm pattern will continue for a while across the East. The new Euro ensembles show the MJO stalling near the P3/P4 border, but the statistical guidance from Paul Roundy shows the wave continuing as normal into P5/P6 by mid-December. All of those phases are generally warm ones for the EC in December.

As the Euro started to let on last night, I think we'll see a more permanent trough set up over the center of the nation by no later than the 15th. Depending on synoptic specifics, this can offer some snow/ice possibilities for interior New England. The east will really get into the game by the end of the month, and into January

[Srain]

This could make for an interesting return home from the long Thanksgiving Holidays...

HPC Update:

12Z UPDATE... THE 12Z ECMWF HAS MADE A SIGNIFICANT TREND TOWARD
00Z-12Z RUNS OF THE GFS/UKMET/CANADIAN... NAMELY TRENDING FASTER
WITH THE INITIAL SRN STREAM TROF MOVING INTO THE SWRN STATES AND
THEN TOWARD A DEEP TROF/CLOSED LOW DEVELOPING OVER THE E-CNTRL
CONUS LATER IN THE PERIOD. THE 12Z GEFS MEAN IS NOW THE LONE
HOLDOUT IN SHOWING AN EVOLUTION REMOTELY CLOSE TO THE OLD 00Z
ECMWF. AS TIME PERMITTED THE FINAL FCST REFLECTS A PARTIAL
ADJUSTMENT TO ACCOUNT FOR INCREASED CLUSTERING OF OPERATIONAL
GUIDANCE... THOUGH NOT COMPLETELY DUE TO TYPICAL FCST ERRORS TO BE
EXPECTED BY DAY 7.


TROF ALOFT MOVING EWD FROM THE WEST COAST WILL BRING NEAR TO BELOW
NORMAL TEMPS AND AREAS OF PCPN TO THE WEST LATE THIS WEEK WITH A
WARMER/DRIER TREND DURING THE WEEKEND/EARLY NEXT WEEK AS A RIDGE
ALOFT BUILDS INTO THE SOUTHWEST. ALTHOUGH GUIDANCE IS NOT
UNANIMOUS... DURING THAT TIME PCPN WILL MOST LIKELY BE CONFINED TO
THE EXTREME NW. MEANWHILE OVER THE ERN HALF OF THE CONUS TEMPS
SHOULD TREND COOLER AFTER STARTING THE PERIOD ABOVE NORMAL... WITH
INCREASING PCPN CHANCES. THE CURRENT MOST LIKELY SCENARIO OVER
THE ERN HALF OF THE CONUS MID-LATE PERIOD WOULD BRING INCREASINGLY
UNSETTLED WEATHER OVER THIS REGION FROM THE WEEKEND INTO NEXT
WEEK... WITH WELL BELOW NORMAL TEMPS ALSO PSBL UNDER/W OF THE TROF
ALOFT. DEPENDING ON HOW THE TROF ALOFT EVOLVES... SOME LOCATIONS
MAY BE COLD ENOUGH TO SEE SOME SNOW. WITH ARRIVAL OF 12Z GUIDANCE
THE LOWER PROBABILITY SCENARIO OF A MORE PROGRESSIVE SYSTEM
FOLLOWED BY MODERATE TEMPS IS NOW MORE IN THE MINORITY THAN
BEFORE.

Attached Files

•  11212011 12Z Euro f168.gif   109.45K   0 downloads
•  11212011 12Z GFS f168.gif   104.42K   0 downloads
•  11212011 12Z Canadian f168.gif   111.09K   0 downloads

[am19psu]

So, snow for Madison or Pittsburgh next week? What a mess of a forecast this is going to be.

[Ellinwood]

am19psu, on 22 November 2011 - 08:11 AM, said:

So, snow for Madison or Pittsburgh next week? What a mess of a forecast this is going to be.

Anything past the end of the week is almost dartboard-worthy.

Euro's coming around to the GFS a bit WRT the cut-off low over the Midwest/TN Valley region. I imagine the Euro will get a decent grasp of it by tomorrow's 12z run, then the GFS will slowly move towards whatever solution the Euro gets.

-----

Also, for anyone who uses the EarthSat Models page, we have incorporated new maps for 10mb, 30mb and 50mb including heights, temps, anomalies and 12hr changes for both on all of our available models (only no 30mb stuff for the Canadian). These new maps will help out with some of the medium range and long range forecasting

[wxmx]

12z Euro is showing the first real artic shot entering the CONUS @day 10, thanks to a huge omega EPO ridge. Skeptical right now of course. Good news (for cold lovers), is that we're probably getting a somewhat favorable Pacific with an Aleutian low, but I'm not sure if it can pump the ridge to go all the way into the Artic circle.

[usedtobe]

wxmx, on 23 November 2011 - 02:33 PM, said:

12z Euro is showing the first real artic shot entering the CONUS @day 10, thanks to a huge omega EPO ridge. Skeptical right now of course. Good news (for cold lovers), is that we're probably getting a somewhat favorable Pacific with an Aleutian low, but I'm not sure if it can pump the ridge to go all the way into the Artic circle.

That's the way the pattern needs to change but it still aims the cold at the west and plains with the east probably warming back up until a major low goes into the great lakes and then somewhere off the east coast. That's probably gives up the 1st week of dec providing the euro amplification and pattern is right. That's a huge assumption as none of the models seem to be handling the longer ranges very well.

[wxmx]

usedtobe, on 23 November 2011 - 02:37 PM, said:

That's the way the pattern needs to change but it still aims the cold at the west and plains with the east probably warming back up until a major low goes into the great lakes and then somewhere off the east coast. That's probably gives up the 1st week of dec providing the euro amplification and pattern is right. That's a huge assumption as none of the models seem to be handling the longer ranges very well.

I agree, if verified, it would be a west of the Mississippi special. With no Atlantic blocking and a continuous ridging over the eastern third, pattern looks fickle and mediocre at best for that part of the CONUS. One more reason to be cautious about a real pattern change. Still, if it verified verbatim, that's a huge artic high showing up, and a modified version of it would probably slid east after freezing the plains.

[Ginx]

Jerry WXFella has been banging the 93/94 drum for a long time, seeing that evolution now.

[okie333]

wxmx, on 23 November 2011 - 02:47 PM, said:

I agree, if verified, it would be a west of the Mississippi special. With no Atlantic blocking and a continuous ridging over the eastern third, pattern looks fickle and mediocre at best for that part of the CONUS. One more reason to be cautious about a real pattern change. Still, if it verified verbatim, that's a huge artic high showing up, and a modified version of it would probably slid east after freezing the plains.

I'd be OK with it just "freezing the plains" lol

[SnowGoose69]

The pattern on the GFS runs in the medium longer range looks very December 2003 and 2004-2005 ish, that ridge or progressive flow that encompasses most of the country west of the Lakes and the trough which dips in and out of the NE and OH valley...interestingly enough this month has very much resembled November 2003 at least in terms of the temp departures, I know the hemispheric height pattern has not been exactly identical. December 2003 was not a very cold month at all but we lucked out in the NE with 2 snow events in a relatively so-so pattern otherwise. It wasn't til January the AO and NAO tanked. I know one of the Mets mentioned December 1988 as a match as well, there was a small pool of below normal departures in the rockies, but that month was mainly above for the West and Central and slightly below in the East, again with that shallow eastern trough and +AO and NAO.

[Srain]

usedtobe, on 23 November 2011 - 02:37 PM, said:

That's the way the pattern needs to change but it still aims the cold at the west and plains with the east probably warming back up until a major low goes into the great lakes and then somewhere off the east coast. That's probably gives up the 1st week of dec providing the euro amplification and pattern is right. That's a huge assumption as none of the models seem to be handling the longer ranges very well.

The 00Z Euro held sevre and does suggest the west and the plains will see the best shot for some very cold air to head S into the Great Basin. The GFS is not as amplified with the +PNA ridge. The euro would dump that cold air into Western Canada and points S that has been building for the last several weeks in Alaska during the first week of December. As you and others have stated, the models have struggled beyond the medium range.

Attached Files

•  11242011 00Z Euro GFS Compare 500 mb test8.gif   89.73K   0 downloads

[SnowGoose69]

Srain, on 24 November 2011 - 06:36 AM, said:

The 00Z Euro held sevre and does suggest the west and the plains will see the best shot for some very cold air to head S into the Great Basin. The GFS is not as amplified with the +PNA ridge. The euro would dump that cold air into Western Canada and points S that has been building for the last several weeks in Alaska during the first week of December. As you and others have stated, the models have struggled beyond the medium range.

The Euro I believe is suffering from its SW U.S. bias through the long range, its been trying to dig systems too hard in that region and as a result has had more of a ridge in the East at times...this is one area in the medium to longer range the GFS often outperforms the Euro.

[Weathergun]

SnowGoose69, on 24 November 2011 - 08:04 AM, said:

The Euro I believe is suffering from its SW U.S. bias through the long range, its been trying to dig systems too hard in that region and as a result has had more of a ridge in the East at times...this is one area in the medium to longer range the GFS often outperforms the Euro.

Even if so, both models show the PNA ridge tilted somewhat NE to SW, and mostly over the Pacific, during this time frame. I don't think it would support a trough locking in over the East Coast,. Especially with no -NAO block.

[Srain]

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
303 AM EST SAT NOV 26 2011

VALID 12Z WED NOV 30 2011 - 12Z SAT DEC 03 2011

...WINTRY PATTERN FOR MUCH OF THE LOWER 48 THIS PERIOD...

AS WE HEAD INTO DECEMBER...TROUGHING ACROSS CENTRAL CANADA TEAMS
UP WITH RIDGING BUILDING ACROSS THE EASTERN PACIFIC JUST OFFSHORE
THE WEST COAST OF NORTH AMERICA SHOULD LEAD TO A POSITIVELY TILTED
TROUGH SPANNING THE CONTINENT FROM CENTRAL CANADA INTO THE WESTERN
UNITED STATES WITH HEIGHTS REBOUNDING ACROSS THE EAST. THE
GUIDANCE SHARES THESE IDEAS. DETAIL ISSUES CONTINUE TO ABOUND OUT
EAST...WHERE A COMPROMISE OF THE 00Z ECMWF/00Z UKMET MADE THE MOST
SENSE PER THE MODEL DIAGNOSTIC DISCUSSION /PMDHMD/. THIS
PREFERENCE WAS KEPT THROUGH LATE THURSDAY...THE END OF THE UKMET
RUN. THEREAFTER...THE 00Z GFS/00Z ECMWF WERE IN REASONABLE
AGREEMENT SO USED A COMPROMISE OF THOSE PIECES OF GUIDANCE LATE
THIS WEEK. THIS SET OF MODEL PREFERENCES MAINTAINED REASONABLE
CONTINUITY.

SNOW REMAINS POSSIBLE ACROSS THE EASTERN GREAT LAKES/UPPER OHIO
VALLEY EARLY ON WITHIN THE EASTERN CYCLONE COMMA HEAD UNTIL THE
SYSTEM EXITS INTO CANADA DURING THE DAY WEDNESDAY. IN ITS
WAKE...STRONG HIGH PRESSURE WEDGES INTO THE PLAINS WEDNESDAY
THROUGH FRIDAY WHICH SHOULD LEAD TO UPSLOPE SNOWS ACROSS MONTANA
AND WYOMING LATE WEDNESDAY INTO THURSDAY BEFORE THE HIGH MOVES OFF
TO THE SOUTHEAST AND WEAKENS. INCREASING HIGH PRESSURE ACROSS THE
INTERIOR WEST SHOULD LEAD TO OFFSHORE FLOW NEAR THE WEST COAST
BEGINNING THURSDAY AND CONTINUING INTO NEXT SATURDAY.
HOWEVER...NEAR THE CORE OF THE CLOSED LOW DROPPING THROUGH THE
WEST... MODERATE SNOWS ARE EXPECTED ACROSS THE GREAT
BASIN/SOUTHWEST/POSSIBLY THE SIERRA NEVADA LATE NEXT WEEK.
DEPENDING UPON HOW FAR EAST THE DEEP CYCLONE ACROSS THE WEST
TRACKS...SNOW IS ALSO A POSSIBILITY FROM THE BIG COUNTRY OF TEXAS
NORTHWARD TOWARDS THE OKLAHOMA PANHANDLE NEXT FRIDAY AND SATURDAY.
A FRONTAL SYSTEM CROSSING THE NORTHERN PLAINS/GREAT
LAKES/NORTHEAST SHOULD ALSO DROP SOME SNOW FROM THURSDAY INTO
SATURDAY.

Attached Files

•  11262011 00Z Euro GFS Compare 500mb test8.gif   90.82K   2 downloads

[Srain]

While folks along the EC may not be too thrilled, there does appear to be some very chilly air heading S into the West and the Plains. A very deep H5 Low sinks S into Great Basin/N MX setting the stage for the first significant Winter Storm of the season, if the guidance is correct. We will see...

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
843 AM EST MON NOV 28 2011

VALID 12Z FRI DEC 02 2011 - 12Z MON DEC 05 2011

CURRENT GUIDANCE SHOWS REASONABLY GOOD AGREEMENT IN MAINTAINING A
POSITIVELY-TILTED LONGWAVE TROUGH FROM HUDSON BAY TOWARD THE FOUR
CORNERS REGION THROUGH THE MEDIUM RANGE PERIOD...WITH A
CORRESPONDING HIGH AMPLITUDE LONGWAVE RIDGE OVER THE NORTHEAST
PACIFIC...AND A SMALLER BUT STILL SIGNIFICANT RIDGE OVER THE
SOUTHEAST. TELECONNECTIONS WITH THE RIDGE OVER THE PACIFIC WHERE
ANOMALIES APPROACH 3 STANDARD DEVIATIONS ABOVE NORMAL AGREES WITH
THE PROJECTED TROUGH EXTENDING ACROSS THE FOUR CORNERS REGION AND
GENERALLY FAVORS BELOW NORMAL TEMPERATURES FOR MUCH OF THE ROCKIES
AND PLAINS.

CONCERNING THE DAY-TO-DAY DETAILS...THE STRONG FLOW CONSTITUTING
THE POLAR OR ARCTIC STREAM CROSSING THE NORTHERN CONUS...DUE IN
PART TO POTENTIAL INITIALIZATION ERRORS ORIGINATING FROM THE
HIGHER LATITUDES...CONTAINS AVERAGE TO BELOW AVERAGE
PREDICTABILITY AND IS SUPPORTED BY THE INCREASING SPREAD IN THE
GLOBAL ENSEMBLE MEMBERS. IN ADDITION....THIS NORTHERN STREAM FLOW
WILL DETERMINE THE TIMING AND TRAJECTORY OF THE UPPER LOW LEAVING
THE SOUTHWEST AROUND DAYS 4-5/FRI-SAT.

DETERMINISTIC AGREEMENT IS AVERAGE THROUGH DAY 4...WITH THE 00Z
GFS THEN ACCELERATING THE NORTHERN STREAM TROUGH OVER THE PLAINS
AHEAD OF THE MAJORITY OF GUIDANCE...GREATLY ALTERING THE SHORTWAVE
PATTERN EAST OF THE MISSISSIPPI RIVER. GIVEN THAT THE GFS IS ONLY
SUPPORTED BY ITS ENSEMBLE MEAN ALONG WITH THE GFS POSSIBLY
DISPLAYING A FAST BIAS AT LONGER RANGES...THIS SCENARIO IS
DISCOUNTED IN FAVOR OF THE ECMWF/UKMET/CANADIAN WHICH STRONGLY
AGREE ON A SLOWER AND GENERALLY DIFFERENT CONFIGURATION.

BEYOND DAY 5...THE MAIN ISSUE IS RESOLVING THE EVOLVING PATTERN
DOWNSTREAM OF THE AMPLIFYING RIDGE OVER THE NORTHERN PACIFIC.
GENERALLY SPEAKING...AN AMPLIFYING RIDGE IN THIS PROXIMITY FAVORS
THE POTENTIAL FOR CONSIDERABLE DIGGING OF DOWNSTREAM PERTURBATIONS
INTO TROUGHS OR POSSIBLY CLOSED LOWS ALONG WITH INTRUSIONS OF
POLAR OR ARCTIC AIRMASSES. TOTAL SOLUTION SPREAD IS QUITE LARGE
BEYOND DAY 5...BUT GIVEN THE ANTICIPATED LARGE-SCALE RIDGE A
SOLUTION SIMILAR TO THE 00Z ECMWF IS EXPECTED ALBEIT WITH
UNCERTAIN DETAILS. THUS...THE ECMWF WILL REMAIN THE FOUNDATION OF
THE UPDATED PRESSURES/FRONTS FOR ALL DAYS BUT WITH SLIGHTLY
GREATER BLENDING WITH ITS OWN ENSEMBLE MEAN BY THE END OF THE
PERIOD TO ADDRESS THE GROWING SPREAD AND UNCERTAINTY.

IN ADDITION TO BELOW NORMAL TEMPERATURES FOR MUCH OF THE
ROCKIES/PLAINS THROUGH THE PERIOD... CORRESPONDINGLY WARM AREAS
ARE ANTICIPATED OVER PARTS OF THE PACIFIC NORTHWEST BENEATH THE
EASTERN EDGE OF THE LONGWAVE RIDGE...AND ACROSS MUCH OF THE
EAST/SOUTHEAST WHICH WILL REMAIN BENEATH A BROAD BUT WEAKER RIDGE
THAN OVER THE PACIFIC. FINALLY...SIGNIFICANT SNOWS ARE EXPECTED
ACROSS THE CENTRAL/SOUTHERN ROCKIES DAYS 3/4 DUE TO THE UPPER
LOW...WITH A LARGER SHIELD OF PRECIPITATION DEVELOPING ACROSS
PARTS OF THE PLAINS/MISSISSIPPI VALLEY DAY 5 BEYOND AS MORE
ABUNDANT MOISTURE INTERACTS WITH THE EJECTING LOW.

[thebigrombalski]

we are moving from bendy tree season, to bendy jet stream season...imagine the Jet stream as a rollercoaster track...i'd probably pee my pants dropping out of the rockies and rounding the bend in NX/TX

[am19psu]

If we can get a phase between the ejecting cutoff low in the SW and the northern stream shortwave, there is going to be a significant system in the Plains/MW next week. Lots of baroclinic energy available for a rapid cyclogenesis.

[Thundersnow12]

am19psu, on 28 November 2011 - 09:52 AM, said:

If we can get a phase between the ejecting cutoff low in the SW and the northern stream shortwave, there is going to be a significant system in the Plains/MW next week. Lots of baroclinic energy available for a rapid cyclogenesis.

Gotta love the differences between the 12z runs of the NAM and GFS...NAM doesn't cut off the southern wave but ejects it into the plains with a decent snow event where the GFS cuts it off and there is an attempt at a better phase on this run but not major.

[am19psu]

Thundersnow12, on 28 November 2011 - 11:51 AM, said:

Gotta love the differences between the 12z runs of the NAM and GFS...NAM doesn't cut off the southern wave but ejects it into the plains with a decent snow event where the GFS cuts it off and there is an attempt at a better phase on this run but not major.

I get in trouble with this sometimes, but I feel pretty confident if the phase shows up in the mid-levels as depicted in the GFS, you're going to get a lot stronger surface deepening than what the GFS is showing. Non-hydrostatic pressure falls would be through the roof in that scenario.

[tacoman25]

Looks like the first true Arctic blast of the season coming to the CONUS this weekend/early next week. -18C into MN by hour 150 on latest GFS.

[Thundersnow12]

am19psu, on 28 November 2011 - 12:04 PM, said:

I get in trouble with this sometimes, but I feel pretty confident if the phase shows up in the mid-levels as depicted in the GFS, you're going to get a lot stronger surface deepening than what the GFS is showing. Non-hydrostatic pressure falls would be through the roof in that scenario.

0z GFS with a better phase and overall better snow event

[am19psu]

Thundersnow12, on 29 November 2011 - 01:05 AM, said:

0z GFS with a better phase and overall better snow event

Yeah, but it's still not all the way there, with mid-level trough remaining positively tilted and open. The Euro really holds back the southern stream, which will limit the potential, too, if that solution verifies. There is still a chance for a big event if everything comes together, but I'm not holding my breath right now.

[Srain]

am19psu, on 29 November 2011 - 08:08 AM, said:

Yeah, but it's still not all the way there, with mid-level trough remaining positively tilted and open. The Euro really holds back the southern stream, which will limit the potential, too, if that solution verifies. There is still a chance for a big event if everything comes together, but I'm not holding my breath right now.

These pesky cut off upper lows are a headache to forecast. It is interesting that this pattern has been around for a while now with troughing to the W and ridging to the E. Sort of an IMBY post, but we're going to end November with 4.70 inches of rain at IAH with near normal temps (or slightly below) and who would have thought that in a La Nina Pattern, albeit weak.

HPC Morning Update:


A STRONG POSITIVE MID-LEVEL HEIGHT ANOMALY ACROSS THE NORTHEASTERN
PACIFIC WILL WORK IN CONJUNCTION WITH A WEAKER NEGATIVE MID-LEVEL
HEIGHT ANOMALY ACROSS HUDSON BAY TO HELP MAINTAIN A
POSITIVELY-TILTED LONGWAVE WAVE TROUGH EXTENDING FROM HUDSON BAY
TOWARD THE FOUR CORNERS REGION THROUGH THE MEDIUM RANGE PERIOD.
MODEL TRENDS...WHICH HAVE BEEN TOWARD GREATER REINFORCEMENT OF THE
BASE OF THE TROUGH...AND CLUSTERING OF 00Z GUIDANCE FAVOR
DISCOUNTING THE MORE PROGRESSIVE 00Z GFS. 0OTHERWISE...THE 00Z
UKMET/CANADIAN/ECMWF WERE IN REASONABLY GOOD AGREEMENT THROUGH DAY
5 BEFORE MORE TYPICAL TIMING/STRENGTH DIFFERENCES BECOME MORE
APPARENT. THUS...THE UPDATED PRESSURES/FRONTS WILL BE CONSTRUCTED
USING NON-NCEP GUIDANCE FOR THIS CYCLE...WITH GREATER EMPHASIS
TOWARD DETERMINISTIC SOLUTIONS THROUGH DAY 4 BEFORE TRANSITIONING
TOWARD ENSEMBLE MEAN GUIDANCE FOR DAYS 5-7.

GIVEN ANTICIPATION FOR REINFORCING THE TROUGH EARLY IN THE PERIOD
ALONG WITH MUCH LARGER SOLUTION SPREAD DEPICTED BY 00Z ENSEMBLE
MEMBER SPAGHETTI DIAGRAMS...CONFIDENCE IS MUCH LESS THAN WOULD
OTHERWISE BE SUGGESTED BY JUST CONSIDERING DETERMINISTIC GUIDANCE.
DAYS 3/4 ARE AVERAGE...DAYS 5-7 BELOW AVERAGE. REGARDING SENSIBLE
WEATHER...BELOW NORMAL TEMPERATURES AND WINTER PRECIPITATION ARE
EXPECTED FROM THE SOUTHERN/CENTRAL ROCKIES TOWARD THE GREAT
LAKES...WHILE A WARMING TREND SHOULD COMMENCE ALONG THE EAST COAST
DAYS 5-7. A NARROW REGION OF NEAR TO SLIGHTLY ABOVE NORMAL
TEMPERATURES SHOULD ALSO PERSIST ACROSS THE PACIFIC NORTHWEST.

[CoastalWx]

The 11-15 day euro ensembles try to get a little more NATL ridging going. Heights lowered a bit near and just south of AK, but heights also increased in the west. It means areas in the Mid Atlantic cooled off a bit after the 10th.

Overall the ridge in the GOA does retrograde a good amount, but the difference seemed to be the Atlantic. Not sure how stable this change is so we'll have to see what future models do...but it is possible to have these NATL ridges. It's not a -NAO by any means, but it helps to push down the se ridge just a bit.

[CT Blizz]

Pattern change is on it's way..for some at least. Noyes all over it.

http://t.co/D3PWcrlY

[wxmx]

CT Blizz, on 29 November 2011 - 12:54 PM, said:

Pattern change is on it's way..for some at least. Noyes all over it.

http://t.co/D3PWcrlY

Not sure what he describes qualifies as a pattern change...regionally probably, and even then, it will be from Above Normal to just near Normal for the Northeast... The big picture, ie. main synoptic features, will remain there with small changes, AO/NAO will remain mostly positive for at least 10-15 days, the Pacific ridge will probably retrograde a bit, and the PV will remain near the Hudson Bay or just N, not a very cold setup for most of the CONUS. The big story, cold wise, next 5-7 days will be in the C/S Rockies and C/S Plains, then the MW and part of the Northeast maybe.