Central/Western Medium-Long Range Discussion

[1900hurricane]

Looks like a pretty pronounced split flow regime will likely establish itself for the first half of December, particularly for the second week. That week, medium-range guidance is placing a ridge over the northern part of the CONUS and into Canada on top of a trough in the Southwest. Looks like a pretty warm pattern with the potential for some good rain across the southern plains, although the European guidance is much less amplified with the southern stream.

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[jdrenken]

We have a strong GOA system within the 7 day range along with an east asia trough connection.  The models aren't going to be doing so well for the second week of December.

[1900hurricane]

Pretty good WPC Extended forecast discussion this morning talking about pattern change and the emergence of the Subtropical Jet.

 

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
155 AM EST TUE DEC 02 2014

VALID 12Z FRI DEC 05 2014 - 12Z TUE DEC 09 2014

...OVERVIEW/SENSIBLE WEATHER HIGHLIGHTS...
AN ACTIVE WEATHER PATTERN FOR THE WEST COAST AND WESTERN INTERIOR
THIS MEDIUM RANGE PERIOD...WITH AN INCREASED FREQUENCY OF PACIFIC
SHORTWAVE ENERGY DELIVERING PERIODS OF WIND AND PRECIPITATION.
DOWNSTREAM OF THE CONTINENTAL DIVIDE...A LOW-AMPLITUDE NORTHERN
STREAM FLOW SHOULD DELIVER OCCASIONAL...BUT BRIEF SURGES OF
COLD...CANADIAN AIR TO THE NORTHERN PLAINS...GREAT LAKES...AND NEW
ENGLAND DURING THE FIRST HALF OF THE FORECAST PERIOD. THE
LOW-AMPLITUDE NATURE OF THIS NORTHERN STREAM ENERGY IS EXPECTED TO
DELIVER PERIODS OF LIGHT PRECIPITATION FOR THE MIDWEST...OHIO
VALLEY AND MID-ATLANTIC STATES.

AFTER DAY 4...THE SOUTHERN BRANCH OF THE PACIFIC JET STREAM
BECOMES ACTIVE. MORE WIND THAN RAIN FOR THE DESERT SOUTHWEST---THE
WETTER PATTERN EMERGING DOWNSTREAM FOR TEXAS...THE SOUTHEAST AND
PIEDMONT.

...MODEL PREFERENCES/UNCERTAINTY ASSESSMENT...
THE FORECAST PHILOSOPHY REMAINS THE SAME...WITH THE 1/12Z
ECENS-GEFS AND NAEFS MAINTAINING A STEADY STREAM OF WESTERLIES
ALONG 40N LATITUDE FROM COAST TO COAST...AND A RATHER FAST-MOVING
BUT LOW-AMPLITUDE WAVE PATTERN DOWNSTREAM OF THE CONTINENTAL
DIVIDE. THE EAST CENTRAL PACIFIC CONTINUES TO PROJECT AN ACTIVE
SERIES OF CYCLONE MIGRATIONS FROM 170W TO 130W...AND WHAT IS
BECOMING MORE EVIDENT...IS THE LATITUDE FOR THE WAVE TRAIN
MIGRATION. TO ME---IT'S DISPLACED SOUTH OF A 'TYPICAL' LATE-AUTUMN
LATITUDE---CLOSER TO 40N-42N THAN 47N-48N ALONG 140W LONGITUDE. IF
THE ECENS MEAN IS ANY INDICATION OF WHAT CAN BE EXPECTED...ITS
1/12Z DETERMINISTIC RUN AND 250MB JET FORECAST SHOULD BE NOTED
FROM THE SOUTH COAST OF JAPAN TO 40N 140W BY THE END OF DAY 7.

A SECOND FEATURE OF THE PACIFIC---IS THE EARLY EMERGENCE OF THE
SUBTROPICAL JET...AND ACTIVE OVER NORTHERN MEXICO SO EARLY IN THE
LOW-SUN HALF OF THE YEAR. THIS IS USUALLY MORE A LATE JANUARY
THROUGH FEBRUARY OBSERVANCE. AND WITH THE DETERMINISTIC GUIDANCE
SUGGESTING NOTABLE INCREASES IN THE PACIFIC BRANCH OF A JET NEAR
25N...IN CLOSE PROXIMITY TO HAWAI'I NORTHEASTWARD INTO NORTHERN
MEXICO BY THE END OF DAY 7...AM THINKING THIS MEDIUM RANGE
FORECAST PERIOD IS TRYING TO TELL US SOMETHING---AND PERHAPS THE
PATTERN IS CHANGING IN EARNEST...WITH THE DOWNSTREAM EJECTION OF
THE CLOSED LOW OFF THE CALIFORNIA COAST SETTING THINGS INTO MOTION.

CANNOT RULE OUT THE 1/12Z DETERMINISTIC ECMWF---CANADIAN OR GFS AT
DAY 5---WHEN THE FOCUS TRANSITIONS FROM NORTHERN BRANCH TO
SOUTHERN BRANCH. TIMING THIS SEEMS LESS AN ISSUE. THE SOUTHERN
CURRENT BECOMES A PREVAILING AND DOMINANT FEATURE OF THE
UPPER-LEVEL FLOW PATTERN ACROSS THE SOUTHERN TIER STATES FOR THE
REMAINDER OF THE MEDIUM RANGE---AND PROBABLY BEYOND.

THERE ARE TWO POINTS OF CONTENTION BETWEEN THE DETERMINISTIC
GUIDANCE. EARLY IN THE PERIOD...DOES THE CLOSED LOW WEST OF
CALIFORNIA REMAIN INTACT OR SIMPLY SHEAR APART OVER THE DIVIDE?
THE SECOND POINT FOR CONTENTION...ONCE THE SOUTHERN JET MOVES INTO
THE SOUTHERN TIER STATES...DOES IT PHASE WITH THE NORTHERN
BRANCH...AND IF SO...AT WHAT LONGITUDE IN THE WESTERN ATLANTIC
WILL THE PHASING TAKE PLACE. WITH THE REMNANT CLOSED LOW NEEDING
TO MOVE THROUGH THE NORTHERN STREAM INITIALLY BEFORE A SOUTHERN
STREAM CAN FOLLOW IN BEHIND THE DEPARTING CUTOFF---AND TO ITS
SOUTH...A BLEND OF THE MEANS MIGHT BE THE WAY TO GO FOR DAYS 5-7.


IN THE PACIFIC...THE DETERMINISTIC GUIDANCE IS ESTABLISHING A
RATHER SOLID CONSENSUS WITH THE DEPTH AND BREATH OF THE 250MB JET
AXIS---ALONG AND SOUTH OF 40N LATITUDE. HERE...I THINK ALL THREE
MEANS WILL ALLOW THE MIGRATION OF A MODERATE MID-LEVEL TROUGH
ACROSS 30N-35N INVOF 120W (BETWEEN 6/00Z AND 7/12Z) SET THE
DOWNSTREAM PATTERN IN MOTION ACROSS THE SOUTHERN TIER.

VOJTESAK

[1900hurricane]

Eight or so days out looks fun. ECMWF has been really consistent showing a strong trough ejecting into the plains despite the range.

[Srain]

The 12Z guidance continues to advertise a very promising pattern from the West Coast into the Southern Rockies of New Mexico/Colorado into the Southern Plains. Higher elevation snows and even some potential for heavy elevated storms developing next weekend. In the cold sector, there is a snow and ice threat across the front range into W/NW Texas into portions of Oklahoma as the 5H low deepens. Depending on the eventual track, portions of Missouri into Arkansas may get into the winter weather side of this strong storm.

The pattern certainly appears to be transitioning toward a stormier/colder regime as we near the Christmas/New Year timeframe.

[Srain]

The GEFS as well as the CFS remain steady in suggesting a significant pattern change near the Christmas timeframe.

 

 

[Srain]

As Jeff alluded to late yesterday evening, the Global ensembles are in rather good agreement with the expected pattern change around the 20th of December. The ensembles are indicating a very active Southern Storm track with each storm assisting in buckling the jet stream pattern across North America that would tend to suggest that the stormy and progressively colder weather would develop across the Desert SW, Southern Rockies into the Southern Plains and on East. The longer range ensembles develop a West Coast Ridge easing the parade of storms currently affecting the W Coast but allow disturbances in the Eastern Pacific to track across Mexico, Texas and the Gulf Coast States before turning NE. The Polar jet should have embedded disturbances dropping S out of Canada and snow looks to begin building across the Plains lending to less and less airmass modification. This is a typical weak El Nino pattern and it appears we are well on the way to witnessing a big pattern shift that will bring a very active period that will last into the New Year.

 

 

 

 

 

 

 

 

[Srain]

The medium range pattern certainly looks very promising with at least 3 additional Southern tracking storms bringing beneficial moisture across California, the Desert SW, Southern Rockies into the Southern and Central Plains.

[Srain]

The over night ensembles continue to advertise an active Southern storm track with a strong storm signal late this week tracking across N Mexico into Texas and the Southern Plains. This storm looks to begin the process of ushering in a signicant pattern change that continues into the Christmas Holiday period.

The longer range guidance is suggesting the possibility of a NW Gulf Coastal low developing around the 24th +/- a day or two ushering much colder temperatures and additional Southern tracking storms as the polar jet buckles rather far S and a + PDO/+PNA/-EPO/-AO regime develops. The time frame into New Year looks cold and stormy from the Great Basin into the Plains.

[Srain]

The Day 11+ Analogs suggest cold air returns to the Great Basin and the Inter Mountain West and spreading into the Plains after Christmas.

 

[OKwx2K4]

Wow. What a difference a day makes. Looks very cold.

[1900hurricane]

Last couple of ECMWF runs have been trying to bring a huge piece of energy down in the west at the end of the forecast cycle. That might be something to watch coming up and could also be the harbinger of the oft-mentioned pattern change.

[OKwx2K4]

I hope so. This snowlessness is getting depressing.

[Srain]

The updated Day 11+ Analogs are beginning to show some memorable Winters. 1976 is back as well as 1989. We kept seeing those analog years showing up during the November cold spell if you recall.

 

 

[Srain]

The Day 11+ Analogs continue to advertise a big pattern change as we end December and head into the New Year.

 

 

 

[Kosmo Cramer]

looking forward to some snow tonight here in NE 

[Srain]

The Day 11+ analogs are bringing back some vivid memories of notable events for our Region.

[Srain]

Yet another day of very strong signals in the Day 11+ Analogs with below normal temperatures and above normal precipitation across the Inter Mountain West throughout the Plains.

[The Waterboy]

Steve,

I am a novice at best so I read mainly and post very little. No need to clutter up the threads with pointless chatter. But I do have a question if you have time to educate those of us who aren't experts.

What exactly are the Day 11+ Analogs? What data are they pulled from? And do you have a feel for how reliable the data is?

Thanks in advance for the lesson. I always enjoy your posts. They are informative with the facts and appear to be unbiased.

Thanks.

[Srain]

Steve,

I am a novice at best so I read mainly and post very little. No need to clutter up the threads with pointless chatter. But I do have a question if you have time to educate those of us who aren't experts.

What exactly are the Day 11+ Analogs? What data are they pulled from? And do you have a feel for how reliable the data is?

Thanks in advance for the lesson. I always enjoy your posts. They are informative with the facts and appear to be unbiased.

Thanks.

These are typically a forecaster adjusted blend of the Euro, GEFS and GEM 500mb ensembles and a blend of what the forecaster believes is the best fit for the pattern expects...

 

8-14 DAY OUTLOOK FOR DEC 27, 2014 - JAN 02, 2015 

THE ENSEMBLE MEAN PREDICTIONS OF THE 500-HPA HEIGHT PATTERN FOR THE WEEK-2 

PERIOD ARE IN FAIR AGREEMENT OVER NORTH AMERICA. A RIDGE IS PREDICTED OVER THE 

GULF OF ALASKA, ASSOCIATED WITH POSITIVE 500-HPA HEIGHT ANOMALIES OFF THE WEST 

COAST. A HIGH AMPLITUDE TROUGH IS ANTICIPATED OVER THE CENTRAL AND EASTERN 

CONUS, WITH NEGATIVE 500-HPA HEIGHT ANOMALIES ACROSS MOST OF THE CONUS. THE 

ENSEMBLE SPAGHETTI DIAGRAMS INDICATE MODERATE SPREAD ACROSS THE FORECAST 

DOMAIN.    

THERE ARE ENHANCED PROBABILITIES FOR NEAR- TO ABOVE-NORMAL TEMPERATURES FOR THE 

CALIFORNIA COAST, AHEAD OF THE RIDGE OFF THE WEST COAST. BELOW-NORMAL 

TEMPERATURES ARE FAVORED FOR MUCH OF THE NORTHERN, CENTRAL AND EASTERN CONUS 

DUE TO ANOMALOUS NORTHERLY FLOW. THERE ARE ENHANCED PROBABILITIES FOR NEAR- TO 

ABOVE-NORMAL TEMPERATURES FOR ALASKA, ALEUTIANS AND THE PANHANDLE RELATED TO 

THE SOUTHWESTERLY WINDS, EAST OF THE SURFACE LOW PRESSURE OVER THE BERING SEA.  

BELOW-MEDIAN PRECIPITATION IS FAVORED FOR THE WESTERN CONUS IN ASSOCIATION WITH 

THE FORECAST RIDGE OFF THE WEST COAST. THERE ARE ENHANCED PROBABILITIES OF 

NEAR- TO BELOW-MEDIAN PRECIPITATION FOR THE MIDDLE MISSISSIPPI VALLEY 

CONSISTENT WITH THE BIAS CORRECTED PRECIPITATION FROM THE ECMWF ENSEMBLES AND 

GFS ENSEMBLES. NEAR- TO ABOVE-MEDIAN PRECIPITATION IS FAVORED FOR THE NORTHERN 

ROCKIES, THE GREAT PLAINS, IN ASSOCIATION WITH EXPECTED UP-SLOPE FLOW OVER THE 

SURFACE. ABOVE-MEDIAN PRECIPITATION IS ALSO FAVORED FOR THE SOUTHEASTERN CONUS 

AND NEW ENGLAND, AHEAD OF THE TROUGH. THERE ARE ENHANCED PROBABILITIES OF NEAR- 

TO ABOVE-MEDIAN PRECIPITATION FOR WEST ALASKA AND THE ALEUTIANS. 

THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 20% OF TODAY'S 0Z GFS ENSEMBLE 

MEAN CENTERED ON DAY 11, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 

11, 20% OF YESTERDAY'S GFS SUPERENSEMBLE MEAN CENTERED ON DAY 10, 20% OF 

TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11, AND 20% OF YESTERDAY'S 

12Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 10 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 OUT OF 5, DUE 

TO FAIR MODEL AGREEMENT WITH SOME DISAGREEMENT BETWEEN TOOLS FROM THE ECMWF AND 

GEFS ENSEMBLES ACROSS THE EASTERN CONUS.

FORECASTER: QIN GINGER ZHANG

 

[Srain]

The afternoon Updated CPC Day 8+ Analogs and Discussions prove interesting as we begin to get closer to the end of December and early January for our Region. Of interest is the noisy sub tropical jet in place after the cold air arrives particularly for portions of Central and Eastern Texas extending into portions of Louisiana. The guidance is attempting to develop a Coastal wave New Years Eve after the cold air is entrenched across the Southern Plains/Southern Rockies/Texas and portions of Louisiana.
 

 

 

PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST MON DECEMBER 22 2014

6-10 DAY OUTLOOK FOR DEC 28, 2014 - JAN 01, 2015

TODAYS MODEL SOLUTIONS ARE IN GOOD AGREEMENT ACROSS THE WESTERN CONUS AND 
ALASKA. THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEANS FEATURE A TROUGH OVER THE 
BERING SEA, A RIDGE ACROSS THE NORTHEAST PACIFIC, AND A TROUGH EXTENDING FROM 
HUDSON BAY SOUTHWEST TO THE SOUTHERN ROCKIES. THE 0Z CANADIAN ENSEMBLE MEAN IS 
DISMISSED AS AN OUTLIER SOLUTION DUE TO ITS MUCH DIFFERENT FORECAST ACROSS THE 
NORTH PACIFIC. POOR MODEL CONTINUITY EXISTS EAST OF THE ROCKIES WITH TODAY'S 0Z 
ECMWF ENSEMBLE MEAN INDICATING MUCH HIGHER 500-HPA HEIGHTS ALONG THE GULF COAST 
AND EASTERN CONUS COMPARED TO ITS MODEL RUN FROM YESTERDAY. SPREAD IS 
RELATIVELY SMALL AMONG TODAY'S 0Z ECMWF ENSEMBLE MEMBERS AND SUPPORTS THE 0Z 
ECMWF ENSEMBLE MEAN SOLUTION EAST OF THE ROCKIES. TELECONNECTIONS UPON A 
POSITIVE 500-HPA ANOMALY CENTER WEST OF BRITISH COLUMBIA (50N 135W), PREDICTED 
BY ALL MODEL SOLUTIONS, SUPPORTS THE ORIENTATION OF A POSITIVELY TILTED 
LONGWAVE TROUGH DEPICTED BY THE 0Z ECMWF ENSEMBLE MEAN AND THE FLOW DOWNSTREAM 
OVER THE EASTERN CONUS. THEREFORE, THE 500-HPA MANUAL BLEND IS WEIGHTED MOST 
HEAVILY WITH THE 0Z ECMWF ENSEMBLE MEAN BUT FORECAST CONFIDENCE IS REDUCED DUE 
TO POOR MODEL CONTINUITY. TODAY'S HIGH RESOLUTION 12Z GFS MODEL IS IN 
REASONABLY GOOD AGREEMENT WITH THE 0Z ECMWF ENSEMBLE MEAN.

THE COVERAGE OF BELOW-NORMAL TEMPERATURES ACROSS THE SOUTHEASTERN CONUS, ON 
YESTERDAY'S TEMPERATURE OUTLOOK, IS REDUCED DUE TO HIGHER 500-HPA HEIGHTS 
PREDICTED BY THE PREFERRED 0Z ECMWF ENSEMBLE MEAN. MEANWHILE, FORECAST 
CONFIDENCE ACROSS THE WESTERN AND CENTRAL CONUS IS ABOVE-AVERAGE AS A 1044-HPA 
SURFACE HIGH IS EXPECTED TO BUILD SOUTH FROM CANADA ON DAYS 6 AND 7. 
TEMPERATURES ARE FORECAST TO AVERAGE AS MUCH AS 20 DEGREES F BELOW-NORMAL 
ACROSS THE NORTHERN/CENTRAL PLAINS BY DAY 7. BELOW-NORMAL TEMPERATURES ARE 
FAVORED FOR MOST OF THE WESTERN/CENTRAL CONUS DUE TO THE ANOMALOUS COLD 
PREDICTED EARLY IN THIS PERIOD. 

ABOVE-MEDIAN PRECIPITATION IS FAVORED ALONG THE TRACK OF A SHORTWAVE TROUGH ON 
DAY 6. THAT SHORTWAVE TROUGH IS EXPECTED TO MOVE NORTHEAST FROM THE LOWER 
MISSISSIPPI VALLEY TO NEW ENGLAND. SOUTHWEST FLOW ALOFT TILTS THE ODDS TOWARDS 
ABOVE-MEDIAN PRECIPITATION ACROSS CENTRAL AND EASTERN TEXAS. A BUILDING 
SUBTROPICAL RIDGE INCREASES CHANCES FOR BELOW-MEDIAN PRECIPITATION ACROSS SOUTH 
FLORIDA, WHILE THE AMPLIFIED RIDGE CENTERED OVER THE NORTHEAST PACIFIC IS 
LIKELY TO SUPPRESS PRECIPITATION ALONG THE WEST COAST. 

ANOMALOUS SOUTHERLY FLOW, EAST OF THE TROUGH OVER THE BERING SEA, INCREASES 
CHANCES FOR ABOVE-NORMAL TEMPERATURES AND ABOVE-MEDIAN PRECIPITATION FOR MUCH 
OF ALASKA. 

TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 10% OF TODAY'S 0Z GFS ENSEMBLE MEAN 
CENTERED ON DAY 8, 10% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 8, AND 
80% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 8 
 

MODEL OF THE DAY: 0Z ECMWF ENSEMBLE MEAN 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: BELOW AVERAGE, 2 OUT OF 5, DUE TO 
POOR MODEL CONTINUITY AND LARGE DIFFERENCES AMONG THE ENSEMBLE MEANS ACROSS THE 
EASTERN CONUS.
 

[Srain]

The Updated CPC Day 8+ and Day 11+ Analogs and Prognostic Discussions suggest our Region will experience the coldest weather as we end 2014 and begin 2015...

 

PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK, MD
300 PM EST TUE DECEMBER 23 2014

6-10 DAY OUTLOOK FOR DEC 29, 2014 - JAN 02, 2015

TODAYS MODEL SOLUTIONS REMAIN IN GOOD AGREEMENT ACROSS THE WESTERN CONUS AND 
ALASKA. THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEANS FEATURE A TROUGH OVER THE 
BERING SEA, A RIDGE ACROSS THE NORTHEAST PACIFIC, AND A 500-HPA TROUGH 
EXTENDING FROM HUDSON BAY SOUTHWEST TO THE SOUTHERN ROCKIES. THE HIGH 
RESOLUTION MODEL RUNS ARE INCLUDED IN THE 500-HPA MANUAL BLEND AS THESE 
SOLUTIONS CONSISTENTLY INDICATE A CLOSED 500-HPA LOW OVER THE DESERT SOUTHWEST. 
HOWEVER, THE 12Z GFS IS MORE PROGRESSIVE WITH THE TROUGH. THE 0Z CANADIAN 
ENSEMBLE MEAN IS LIKELY AN OUTLIER SINCE ITS SOLUTION DOES NOT DEPICT THE 
POSITIVELY TROUGH OVER THE LOWER 48. MODEL AGREEMENT IMPROVED AMONG TODAY'S 
ODEL SOLUTIONS ACROSS THE EASTERN CONUS.

THE HIGH RESOLUTION 6Z GFS AND 0Z ECMWF MODEL RUNS INDICATE A 1048 TO 1052-HPA 
SURFACE HIGH BUILDING SOUTH FROM THE CANADIAN PRAIRIES INTO THE ROCKIES EARLY 
IN THE PERIOD. TEMPERATURES ARE FORECAST TO AVERAGE AS MUCH AS 20 DEGREES F 
BELOW-NORMAL ACROSS THE ROCKIES AND HIGH PLAINS ON DAYS 6 AND 7. BELOW-NORMAL 
TEMPERATURES ARE LIKELY FOR MUCH OF THE WESTERN AND CENTRAL CONUS DUE TO THE 
ANOMALOUS TROUGH. TEMPERATURE GUIDANCE IS IN BETTER AGREEMENT TODAY WITH NEAR 
TO BELOW-NORMAL TEMPERATURES FAVORED FOR THE NORTHEAST, WHILE A SUBTROPICAL 
RIDGE FAVORS ABOVE-NORMAL TEMPERATURES ACROSS THE FLORIDA PENINSULA.  

SOUTHWEST FLOW ALOFT INCREASES CHANCES FOR ABOVE-MEDIAN PRECIPITATION ACROSS 
THE GULF COAST STATES NORTHEAST TO SOUTHERN NEW ENGLAND. THE HIGH RESOLUTION 
MODELS ARE IN GOOD AGREEMENT WITH MORE THAN ONE INCH OF RAINFALL OCCURRING 
ALONG THE CENTRAL GULF COAST WHERE THE HIGHEST PROBABILITIES FOR ABOVE-MEDIAN 
PRECIPITATION ARE FORECAST. UPSLOPE FLOW TILTS THE ODDS TOWARDS ABOVE-MEDIAN 
PRECIPITATION ACROSS THE SOUTHERN HIGH PLAINS. LITTLE OR NO RAINFALL IS 
EXPECTED ACROSS SOUTH FLORIDA WHERE BELOW-MEDIAN PRECIPITATION IS FAVORED. A 
DRY SIGNAL AMONG PRECIPITATION IS STRONGEST ACROSS THE PACIFIC NORTHWEST AND 
NORTHERN CALIFORNIA, ASSOCIATED WITH THE RIDGE OVER THE NORTHEAST PACIFIC AND 
ANOMALOUS OFFSHORE FLOW.  

SURFACE LOW PRESSURE OVER THE BERING SEA COUPLED WITH RIDGING OVER THE 
NORTHEAST PACIFIC ENHANCE ODDS FOR ABOVE-NORMAL TEMPERATURES AND ABOVE-MEDIAN 
PRECIPITATION ACROSS ALASKA. 

TODAY'S OFFICIAL 500-HPA BLEND CONSISTS OF 15% OF TODAY'S 0Z GFS ENSEMBLE MEAN 
CENTERED ON DAY 8, 15% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 8, 10% 
OF TODAY'S OPERATIONAL 0Z GFS CENTERED ON DAY 8, 10% OF TODAY'S OPERATIONAL 6Z 
GFS CENTERED ON DAY 8, 40% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 
8, AND 10% OF TODAY'S OPERATIONAL 0Z ECMWF CENTERED ON DAY 8 
 

MODEL OF THE DAY: 0Z ECMWF ENSEMBLE MEAN 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: AVERAGE, 4 OUT OF 5, DUE TO 
IMPROVED MODEL AGREEMENT ACROSS THE EASTERN CONUS AMONG THE 0Z/6Z GFS AND 0Z 
ECMWF ENSEMBLE MEANS AND TEMPERATURE GUIDANCE.

8-14 DAY OUTLOOK FOR DEC 31, 2014 - JAN 06, 2015 

THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEANS FEATURE A RIDGE EXTENDING FROM THE 
NORTHEAST PACIFIC NORTH TO ALASKA, A POSITIVELY TILTED TROUGH OVER THE 
WEST-CENTRAL CONUS, AND A SUBTROPICAL RIDGE CENTERED ACROSS THE BAHAMAS AND 
CUBA. SPREAD AMONG THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEMBERS IS MODERATE TO 
LARGE WITH THE POSITION AND AMPLITUDE OF THE RIDGE (TROUGH) OVER THE NORTHEAST 
PACIFIC (WEST-CENTRAL CONUS). 

TEMPERATURE TOOLS ARE IN REASONABLY GOOD AGREEMENT BUT LOWER PROBABILITIES, 
COMPARED TO THE 6-10 DAY OUTLOOK, REFLECT THE LARGER SPREAD AMONG ENSEMBLE 
MEMBERS. THE UPPER-LEVEL TROUGH FAVORS BELOW NORMAL TEMPERATURES ACROSS THE 
SOUTHWEST, CENTRAL/SOUTHERN ROCKIES, CENTRAL/SOUTHERN PLAINS, AND MIDWEST. 
BELOW-NORMAL TEMPERATURES FORECAST FOR THE PACIFIC NORTHWEST ARE DUE TO 
ANOMALOUS COLD EARLY IN WEEK-2, WHILE A WARMING TREND IS EXPECTED ACROSS 
CALIFORNIA. TEMPERATURES ARE EXPECTED TO BE CLOSE TO AVERAGE FOR MUCH OF THE 
EAST COAST. 

A FRONT IS EXPECTED TO STALL EARLY IN WEEK-2 AND INCREASE CHANCES FOR 
ABOVE-MEDIAN PRECIPITATION ACROSS THE GULF COAST STATES NORTHEAST TO SOUTHERN 
NEW ENGLAND. SOUTHEAST FLOW TILTS THE ODDS TOWARDS ABOVE-MEDIAN PRECIPITATION 
ACROSS THE RIO GRANDE VALLEY. BELOW-MEDIAN PRECIPITATION IS EXPECTED TO PERSIST 
ALONG THE WEST COAST DUE TO UPPER-LEVEL RIDGING. ALTHOUGH BELOW-MEDIAN 
PRECIPITATION IS FAVORED FOR THE NORTHERN/CENTRAL HIGH PLAINS, THE POTENTIAL 
THAT UPSLOPE FLOW RETURNS LATER IN WEEK-2 LIMITS THE PROBABILITY.  

THE TROUGH OVER THE BERING SEA INCREASES CHANCES FOR ABOVE-NORMAL TEMPERATURES 
AND ABOVE-MEDIAN PRECIPITATION ACROSS ALASKA. TODAY'S ENSEMBLE MEANS INDICATE A 
RIDGE STRENGTHENING ACROSS ALASKA WHICH COULD EVENTUALLY RESULT IN DRIER 
CONDITIONS LATER IN WEEK-2. 

THE OFFICIAL 8-14 DAY HEIGHT PROG CONSISTS OF: 20% OF TODAY'S 0Z GFS ENSEMBLE 
MEAN CENTERED ON DAY 11, 20% OF TODAY'S 6Z GFS ENSEMBLE MEAN CENTERED ON DAY 
11, AND 60% OF TODAY'S 0Z EUROPEAN ENSEMBLE MEAN CENTERED ON DAY 11 


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: AVERAGE, 3 OUT OF 5, DUE TO 
GOOD AGREEMENT AMONG THE 0Z/6Z GFS AND 0Z ECMWF ENSEMBLE MEANS OFFSET BY 
MODERATE TO LARGE SPREAD AMONG THE GFS AND ECMWF ENSEMBLE MEMBERS. 

FORECASTER: BRAD PUGH

 

 

 

 

[Srain]

The December 25th CPC Day 8+ Analogs suggests the coldest weather will remain entrenched across our Region. Temperature anomalies could range in the -25 to -35 range with the best chance of above normal precipitation across the Rockies and along the NW Gulf Coast into Louisiana.

[Srain]

While our East Coast friends can only dream of some distant cold pattern that seems to be a mirage, our Region continues to benefit from the current pattern and that looks to continue into the extended Range.

 

 

 

 

[Srain]

CPC updated Day 8+ Analogs...

 

[andyhb]

Despite poor model performance as of late, I have a bit of a feeling that something may be coming down the track here as we pass mid month. Shorter range guidance has been consistent in developing another strong N Pacific jet extension (developing in association with the strong ULL currently over northeast Asia), which then progresses and develops into a strong Aleutian low, which pumps the heights in the west and torches western Canada in some solutions, which also blocks cross polar flow from developing.

 

Obviously going further out is getting conjecture-heavy, but the breakdown/progression of said ridge eastward would likely open the door for the jet energy associated with the Aleutian low to move into the Gulf of Alaska and possibly open the door for a western trough/eastern ridge configuration to develop (probably transient as well). As long as the pattern doesn't become significantly blocked up, and with a persistent +NAO and lack of a strong -AO this seems somewhat likely at least over North America, a warming trend seems possible from mid month into the third week of the month, along with a storm or two developing out of the aforementioned western trough (obviously sensible wx impacts are nonsense to consider at this point, but I'm sure most can figure out what such a configuration may lead to).

 

We'll see how this plays out in coming days. I wouldn't call it a forecast per say, more of a pattern recognition observation based on what similar progressions have developed into recently. This is of course rendered more volatile by the aforementioned problems with guidance recently, although large scale synoptic features seem to be relatively consistent across the suite currently at least in the earlier going over the west/central Pacific.

[andyhb]

Looking at that call looks pretty bleak right now as far as verification and current model guidance. Looks like we did/will have some warming mid-month, but the +PDO-enhanced +PNA ridge and eventual -EPO looks to dominate rather than the Aleutian Low sliding eastward, as seems to have been the overarching pattern over the past year and a half...sigh.

 

Seems foolish to ever go against it these days.

[Jebman]

I have a question concerning the weak El Nino.

 

This upcoming spring and summer, what effect on South Central Texas weather will the weak Nino have? Will it bring more chances for rain this summer? Will it cool the weather in Austin down any in summer? I ask because I will be down there April thru late summer. Thanks.

[andyhb]

Latest Euro weeklies are pretty "wow" through much of April.

[icebreaker5221]

Latest Euro weeklies are pretty "wow" through much of April.

 

I haven't seen them; why are they "wow"?