December 2016- End Of Year Forecast

General Weather Discussions and Analysis

Re: December 2016-Will the weather pattern change

Postby MontgomeryCoWx » Wed Nov 23, 2016 12:46 pm

Lord.... would like to see it more centered on Alaska but that will do as long as we don't have an overwhelmingly positive AO.
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Re: December 2016-Will the weather pattern change

Postby srainhoutx » Wed Nov 23, 2016 3:52 pm

The afternoon updated Climate Prediction Center Day 8+ Analogs as well as the temperature and precipitation outlook for days 6-10 suggest increasing moisture developing across the SE United States where they sorely need the rainfall to help with the ongoing wild fires. The pattern also suggests a fairly significant trough is anchored across the Central United States meaning unsettled weather is likely across our Region as well.
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Re: December 2016-Will the weather pattern change

Postby srainhoutx » Thu Nov 24, 2016 11:49 am

12Z GFS is suggesting a very intense cyclone developing to our WSW with a very deep trough digging well into Northern Mexico as we begin December. I see an intense 1054mb Greenland blocking Ridge developing and with a crashing Arctic Oscillation (AO) as well as a tanking Eastern Pacific Oscillation (EPO), the teleconnection indices continue to support increasing chances of a colder regime developing into December. We will need to monitor the trends as we progress further into December for the potential of steadily colder shots of Canadian air as well as an active stormy pattern across Texas.
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Re: December 2016-Will the weather pattern change

Postby srainhoutx » Sat Nov 26, 2016 11:52 am

The morning Updated CFSv2 Monthly Climate model that tends to have a warm bias continues to trend toward a much colder and somewhat 'wetter' December.

11262016 CFSv2 December CFSv2_NaT2m_20161126_201612.gif


11262016 CFSv2 CFSv2_NaPrec_20161126_201612.gif
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Re: December 2016-Will the weather pattern change

Postby srainhoutx » Sat Nov 26, 2016 4:04 pm

The afternoon ECMWF suggests a near 1050mb Arctic High dropping South across NW/W Canada in the extended range with an even stronger Arctic High moving out of Siberia into the Arctic Circle to follow. Even the GFS and Canadian models are 'sniffing' this Hemispheric Pattern change we equally strong Arctic Highs heading South.
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Re: December 2016-Will the weather pattern change

Postby unome » Mon Nov 28, 2016 6:42 am

QPF in early Dec starts off soggy for some in our area, albeit 6-7 days out from now

http://www.wpc.ncep.noaa.gov/index.php#page=qpf

http://www.wpc.ncep.noaa.gov/discussion ... isc=pmdepd
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Re: December 2016-Will the weather pattern change

Postby MontgomeryCoWx » Mon Nov 28, 2016 12:00 pm

12z GFS, Hour 204-384 looks cold. There's a stretch where we don't get out of the 30s in my neck of the woods.

Not that it won't be chilly before that timeframe, it will be colder than normal to normal from Wednesday onward.
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Re: December 2016-Will the weather pattern change

Postby MontgomeryCoWx » Mon Nov 28, 2016 3:51 pm

The GFS, Euro and CMC all agree that the first true Arctic plunge should happen around the 8th/9th timeframe.

From this Wednesday (11/30) onwards, we don't get warmer than the mid 60s in Montgomery County.
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Re: December 2016-Will the weather pattern change

Postby srainhoutx » Mon Nov 28, 2016 3:53 pm

The afternoon ensemble guidance suggests a very cold shot of Arctic air will continue building across the Western 2/3 rds of North America beginning this coming weekend. In fact some of the reliable computer models are suggesting temperatures across portions of Alaska and NW Canada may approach -70F for overnight lows around December 4th. Also the afternoon updated Climate Prediction Center Day 6 to 10 Day Outlook agrees with the possibility.

ecmwf-ens_T850a_namer_11 (1).png


gfs-ens_T850a_namer_41.png


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Re: December 2016- Cold/Rainy Weekend. Tracking Arctic Air

Postby srainhoutx » Tue Nov 29, 2016 3:37 am

Confidence is slowly increasing regarding the upcoming weekend, but there remains some uncertainty as to how quickly the cut off upper low over Northern Mexico ejects East. The ECMWF and its ensemble members remain progressive or faster moving this cold core upper low out of Mexico into Texas. The UKMET has joined the GFS/Canada model solutions suggesting a meandering slow moving upper low over Northern Mexico/Southern Arizona and Southern New Mexico and finally moving into West Texas about 24 hours slower than the ECMWF schemes.

To further complicate the sensible weather forecast is the Coastal low/trough scenario depicted by the model solutions along the South Texas Coast moving NE toward the Upper Texas Coast Saturday night into Sunday, possibly extending into early Monday. Brisk chilly NE winds at the surface suggest colder temperatures in the mid to upper 40's inland with 50's near the Coast with over running precipitation increasing as the Coastal low/trough develops. There is growing concern for some elevated thunderstorms lending to the potential of a heavy rainfall event, depending on where the Coastal low/trough develops and just how quickly the cold core upper low ejects from Northern Mexico into Texas. To further complicate the sensible weather forecast is the possibility of some phasing with another storm system further North across the Great Plains which appears to have some very cold air associated with it.

Another feature to watch much further NW across Alaska and NW Canada is the arrival of the first Arctic Outbreak we have seen in a couple of years. The reliable computer models are suggesting 2 meter temperatures may plummet to near -50F with even some locations in Eastern Alaska and NW Canada approaching near -70F for overnight lows next Sunday into next Tuesday. Arctic air appears to be on the move South next week into the Rockies and the Great Plains. We will monitor that feature as it gets a bit closer.

ecmwf-ens_T850a_namer_11 (2).png


For now, attention turns to the weekend and what appears to be a raw and wet pattern as Winter returns to Texas. Stay tuned!

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
134 AM EST TUE NOV 29 2016

VALID 12Z FRI DEC 02 2016 - 12Z TUE DEC 06 2016

...INCREASING CONFIDENCE OF HEAVY RAINFALL THIS WEEKEND ACROSS THE
WESTERN/CENTRAL GULF COAST...

...MODEL EVALUATION/PREFERENCES...

THE MAJOR FORECAST CHALLENGE WILL BE THE EVOLUTION OF A FORECAST
CLOSED LOW OVER THE SOUTHWEST US THIS WEEKEND. A SHORTWAVE IS
FORECAST TO AMPLIFY AND FORM A CUTOFF LOW ON FRIDAY SOMEWHERE
ACROSS SOUTHERN AZ/NM OR NORTHERN MEXICO. SPREAD INCREASES
DRAMATICALLY WITH RESPECT TO THIS FEATURE AFTER THE CUTOFF FORMS,
WITH THE 12Z ECMWF/UKMET SUGGESTING A MORE PROGRESSIVE EASTWARD
MOTION...WHICH PROVIDES A SECOND RUN OF A FASTER SOLUTION IN BOTH
MODELS.

THE 18Z GFS/12Z CMC AS WELL AS THE 18Z GEFS MEAN/12Z CMCE MEAN ALL
SUGGEST A MUCH SLOWER PROGRESSION, KEEPING THE CUTOFF ACROSS
NORTHERN MEXICO OR WEST TX THROUGH SUNDAY. THE GFS HAS SHOWN A
MODERATE TO HIGH LEVEL OF RUN-TO-RUN CONSISTENCY WITH RESPECT TO
THIS SLOWER PROGRESSION OF THE CUTOFF. THERE IS GOOD AGREEMENT
AMONG THE GFS AND ITS ENSEMBLE MEAN...AS THERE IS AMONG THE ECMWF
AND ITS ENSEMBLE MEAN...SO ITS HARD TO IDENTIFY AN INTERMEDIATE
SOLUTION (I.E. BLENDING SUCH DISPARATE FORECASTS WOULD LOOK
UNREALISTIC IN IDENTIFYING THE LOWS AND FRONTS).

A BLEND OF THE 12Z ECMWF ENSEMBLE MEAN AND 12Z OPERATIONAL ECMWF
WAS USED...WITH MORE WEIGHTING TOWARDS THE MEAN SOLUTION GIVEN THE
LARGE ENVELOPE OF POSSIBILITIES.
SUPPORT WAS GIVEN BY RUN TO RUN CONTINUITY IN THE ECMWF FROM LAST
NIGHT IN MOVING THE SOUTHWEST CLOSED LOW EAST FASTER, PLUS THE 12Z
UKMET 500 MB WAVE PATTERN SHOWING ABOVE AVERAGE AGREEMENT WITH THE
ECMWF IN PHASING THE SOUTHERN STREAM ENERGY WITH THE NORTHERN
STREAM WAVE CROSSING FROM THE PLAINS AND UPPER MS VALLEY. FINALLY
THE VAST MAJORITY OF ECMWF ENSEMBLE MEMBERS HAVE THE MORE
PROGRESSIVE CLOSED LOW/TROUGH FORECAST. THE 00Z UKMET SLOWED DOWN
THE PROGRESSION OF THE CLOSED LOW...AND CLUSTERS WELL NOW WITH THE
00Z GFS..SO CONFIDENCE IN ANY ONE SOLUTION REMAINS LOW.

IN THE NORTHEAST...THE MODELS ARE IN GENERALLY GOOD AGREEMENT ON A
CUTOFF LOW CENTERED OVER SOUTHEASTERN ONTARIO ON DAY 3 (FRI 02
DEC), WHICH WILL BE IN THE PROCESS OF OPENING INTO A SHORTWAVE AS
IT BEGINS TO MOVE MORE QUICKLY EAST ACROSS THE NORTHEAST ON FRI.
THE ASSOCIATED SFC LOW PRESSURE SYSTEM WILL MOVE QUICKLY EAST AWAY
FROM NEW ENGLAND ON FRI.

OUT WEST..THE MEAN EAST PACIFIC TROUGH DRIFTS EAST WITH
TIME...WITH NEGATIVE HEIGHT ANOMALIES DEVELOPING AS THE TROUGH
CROSSES THE GREAT BASIN EARLY NEXT WEEK. AMPLIFICATION IS EXPECTED
DOWN STREAM FROM THE AMPLIFYING NORTHEAST PACIFIC RIDGE BY THE
MIDDLE OF NEXT WEEK.


...WEATHER HIGHLIGHTS/THREATS...

THERE IS POTENTIAL FOR HEAVY RAINFALL THIS WEEKEND ACROSS PORTIONS
OF THE UPPER TEXAS AND LA GULF COASTS...WITH STRONG MOISTURE
INFLUXES AND INCREASES IN AVAILABLE MOISTURE ALONG WITH LIFT OVER
A FRONTAL ZONE IN THE AREA. THE SLOWER GFS/CANADIAN GLOBAL CLOSED
LOW PROGRESSIONS WOULD DELAY THE TIMING. THERE IS POTENTIAL FOR
WIDESPREAD RAIN ACROSS THE PARCHED SOUTHEAST ONCE THE WAVE CROSSES
THE REGION.

WITH THE FRONTAL WAVE IN NORTHERN NEW ENGLAND...SNOW IS EXPECTED
IN NORTHERN MAINE THU AND TAPERING AS THE WAVE DEPARTS FRI.
EXPECT VALLEY RAIN AND MOUNTAIN SNOW TO SPREAD INTO THE PAC NW BY
SATURDAY AS A PACIFIC SFC FRONT MOVES INLAND...WITH SNOW
CONTINUING IN THE PAC NW AND NORTHERN ROCKIES SUN AS MOIST ONSHORE
FLOW CONTINUES UNDERNEATH A STRONG WEST-EAST UPPER LEVEL JET.

ANOMALOUSLY LOW HEIGHTS WILL PROMOTE BELOW AVERAGE TEMPERATURES
ACROSS MUCH OF THE SOUTHERN PLAINS SAT INTO SUN WITH THE
COMBINATION OF CLOUDS AND COLD ADVECTION.
LIKEWISE...COLD ANOMALIES DEVELOP WITH LOWERING HEIGHTS AND THE
ARRIVAL OF PRECIP OVER THE WEEKEND.

HIGH PRESSURE BUILDING DOWN THE LEE SIDE OF THE CANADIAN ROCKIES
SUPPORTS THE FIRST ARCTIC OUTBREAK OF THE SEASON DEVELOPING AND
MOVING SOUTH INTO MT AROUND THE MIDDLE OF NEXT WEEK...SO TEMPS
COULD DROP TO DOUBLE DIGITS BELOW NORMAL ON TUE 06 DEC IN MT IF
THIS OCCURS. LOWERING HEIGHTS IN THE GREAT BASIN AND INTERMOUNTAIN
WEST SUPPORTS TEMPS DROPPING BELOW NORMAL ACROSS ID/UT/WY AS WELL
BY TUE 06 DEC.

PETERSEN
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